Snow Melt Systems
Remake batch 26: rewritten from scratch under the authoring cheatsheet with datasheet constraints; neighbors re-pointed to the new scope boundaries; the electrical code is now the adopted-electrical-code project fact
Showing changes from Rev 2
to Rev 3
in Snow Melt Systems.
---
title: Snow Melt Systems
category: Mechanical / Piping & Pumps
−toc_depth: 3
description: >
− When to use: Embedded radiant snow and ice melting in outdoor hardscape — walkways, entry plazas,
− ramps, accessible routes, vehicular drives, aprons, and loading-dock approaches — using either
− hydronic glycol loops in PEX/PE-RT tubing or electric resistance cable/mat, with automatic
− snow/pavement sensing controls, in cold-climate commercial, institutional, healthcare,
− transportation, and high-end residential site work.
− Not intended for: Roof, gutter, and downspout deicing (see sync/gutters-and-downspouts and
− electric heat tape under NEC Article 426 Exposed); in-building hydronic distribution to reach the
− manifold (sync/hydronic-piping); the heating plant — boilers, heat exchangers, pumps, expansion
− tanks (sync/hydronic-piping, sync/hydronic-specialties); glycol loop flushing and commissioning
− chemistry (sync/hydronic-cleaning-and-flushing); pipe freeze-protection heat tracing
− (sync/electric-heat-tracing); the concrete flatwork containing the elements (sync/concrete-paving);
− and the below-slab vapor retarder (sync/vapor-barriers-under-slab).
+ When to use: Embedded radiant snow and ice melting in outdoor hardscape: walks, plazas, entrance aprons, exterior stairs and ramps, accessible routes, drives, loading dock approaches, and parking aprons, heated by hydronic tubing carrying an inhibited glycol solution or by electric heating cable or mat cast into concrete, placed in asphalt, or set beneath unit pavers. Covers the snow melting class and the design surface heat flux as the design basis, the slab-side hydronic circuit (tubing, spacing, circuit hydraulics, glycol type and concentration for the snow melt loop, and the manifolds), the electric heating element under NFPA 70 Article 426 with its ground-fault protection of equipment, the automatic and manual controls with their sensors, setpoints, and idle mode, the insulation beneath the heated pavement, embedment depth and attachment, testing before, during, and after the pavement is placed, and the record drawing of the circuit layout.
+
+ Not intended for: De-icing cable on roofs, in gutters, and in downspouts, and trace heating of piping and vessels (see [[sync/electric-heat-tracing]]); the heating plant that supplies a hydronic circuit, namely boilers (see [[sync/boilers]]), heat exchangers (see [[sync/heat-exchangers]]), circulating pumps (see [[sync/hvac-pumps]]), and expansion tanks and air separators (see [[sync/expansion-tanks-and-air-separators]]); the distribution piping between the plant and the snow melt manifold, with its joints and pressure test (see [[sync/hydronic-piping]]); balancing valves, strainers, and the glycol makeup package (see [[sync/hydronic-specialties]]); cleaning, flushing, passivation, and the initial glycol charge of the loop (see [[sync/hydronic-cleaning-and-flushing]]); interior radiant floor heating (see [[sync/radiant-heating-and-cooling-panels]]); the concrete pavement (see [[sync/concrete-paving]]), the asphalt pavement (see [[sync/asphalt-paving]]), and the permeable paver section (see [[sync/permeable-paving]]) that carry the embedded elements; branch circuit conductors and raceways (see [[sync/conductors-and-cables]] and [[sync/raceways-and-conduit]]) and the panelboard that supplies them (see [[sync/panelboards]]); the building automation system that supervises the controller (see [[sync/building-automation-system]]); firestopping of penetrations into the building (see [[sync/firestopping]]); and functional performance testing under the commissioning plan (see [[sync/commissioning]]).
---
# Scope {toc}
−## This Standard covers the design, specification, and installation of embedded radiant snow and ice melting systems in outdoor hardscape surfaces, including pedestrian walkways, entry plazas, ramps, accessible routes, vehicular drives and aprons, and loading-dock approaches. {note}
+## Boundary of Work {toc}
−## Two technology types are covered: hydronic systems that circulate a glycol/water mixture through embedded PEX or PE-RT tubing connected to a dedicated heating plant or the building hydronic system, and electric resistance systems that use embedded heating cable or factory-wired heating mats. {note}
+### This standard governs the elements that heat an outdoor pavement from within: the hydronic tubing or the electric heating cable or mat embedded in it, the manifolds or the power connections at its edge, the sensors and the controller that decide when it runs, the insulation beneath it, and the tests that prove the embedded element before the pavement closes over it. It begins at the manifold connections or the junction boxes at the pavement edge and ends at the finished surface. {note}
−## Also covered are automatic snow and pavement sensing controls with manual override, glycol fill and make-up provisions, heat exchangers where the loop connects to the main building system, circuit manifolds, and slab expansion provisions at the heated assembly. {note}
+### The surfaces in scope are walks, plazas, entrance aprons, exterior stairs and ramps, accessible routes, drives, loading dock approaches, and parking aprons, whether finished in cast-in-place concrete, asphalt, or unit pavers over a concrete or aggregate base. {note}
−## This Standard applies to new construction and renovation in cold-climate regions where ice and snow accumulation on pedestrian or vehicular surfaces poses a safety risk or an operational requirement. {note}
+### A snow melt element is the one part of a pavement that cannot be reached after the pavement is placed. Every other defect in a hardscape is repaired by cutting out a panel; a tube or cable that was crushed by a vibrator, nicked by a saw, or never tested is found in the first storm and is repaired by removing the pavement. The weight this standard gives to layout, attachment, cover, and testing before placement follows from that. {note}
−## The following are outside this Standard and are governed elsewhere: {note}
+### The plant that supplies a hydronic circuit, the piping that reaches the manifold, the electrical distribution that reaches the junction box, and the pavement itself are each governed by their own standard. This standard states what it needs from each at the boundary and does not restate them. {note}
−- Roof, gutter, and downspout snow/ice removal and deicing heat tape — see [[sync/gutters-and-downspouts]] for drainage context; exposed roof/gutter electric heat under NEC Article 426 is a distinct trade scope.
−- Hydronic distribution piping routed inside the building to reach a snow melt manifold — material, joining, pressure class, and main-system distribution belong to [[sync/hydronic-piping]].
−- The primary hydronic heating plant — boilers, heat exchangers, pumps, and expansion tanks — that supplies the snow melt circuit — see [[sync/hydronic-piping]] and [[sync/hydronic-specialties]].
−- Flushing, chemical treatment, and commissioning of the glycol loop — see [[sync/hydronic-cleaning-and-flushing]].
−- Electric heat tracing for freeze protection of water supply or drain piping — see [[sync/electric-heat-tracing]].
−- Concrete flatwork mix design, finish, and jointing of the slabs that contain the tubing or cable — see [[sync/concrete-paving]].
−- The below-slab vapor retarder under the heated slab assembly — see [[sync/vapor-barriers-under-slab]].
+- De-icing cable on roofs, in gutters, and in downspouts, and trace heating of piping and vessels: [[sync/electric-heat-tracing]].
+- Boilers, heat exchangers, circulating pumps, and expansion tanks and air separators of the hydronic plant: [[sync/boilers]], [[sync/heat-exchangers]], [[sync/hvac-pumps]], and [[sync/expansion-tanks-and-air-separators]].
+- The distribution piping between the plant and the snow melt manifold, its joints, and its pressure test: [[sync/hydronic-piping]].
+- Balancing valves, strainers, and the glycol makeup package: [[sync/hydronic-specialties]].
+- Cleaning, flushing, passivation, and the initial glycol charge of the loop: [[sync/hydronic-cleaning-and-flushing]].
+- Interior radiant floor heating: [[sync/radiant-heating-and-cooling-panels]].
+- The concrete pavement, its mixture, jointing, finishing, and curing: [[sync/concrete-paving]]; the asphalt pavement: [[sync/asphalt-paving]]; the permeable paver section: [[sync/permeable-paving]].
+- Branch circuit conductors and raceways to the junction boxes, and the panelboard that supplies them: [[sync/conductors-and-cables]], [[sync/raceways-and-conduit]], and [[sync/panelboards]].
+- The building automation system that supervises the snow melt controller: [[sync/building-automation-system]].
+- Firestopping where tubing, leads, or conduit enter the building through a rated assembly: [[sync/firestopping]].
+- Functional performance testing under the commissioning plan: [[sync/commissioning]].
−## A snow melt system is a life-safety and operational asset, not a comfort amenity; once tubing or cable is encased in concrete or asphalt it cannot be repaired, so design coordination, embedded-element protection, and pre-pour testing carry unusual weight in this scope. {note}
+### The extent of each heated area, the circuit boundaries, and the locations of the manifolds and junction boxes shall be as indicated on [[drawing: the snow melt plan]].
+### The pavement in which the elements of each heated area are embedded shall be as indicated on [[drawing: the civil paving plans and sections]].
+
+## Terms Used in This Standard {toc}
+
+### The following terms carry the meanings given here throughout this standard: {note}
+
+- Snow melting class: the performance classification of ASHRAE Handbook, HVAC Applications, Snow Melting and Freeze Protection, from Class I, which allows snow to accumulate on the surface during a storm and melts it afterward, through Class II, which keeps the surface passable with some accumulation during heavy snowfall, to Class III, which keeps the surface free of snow and ice throughout the storm
+- Snow-free area ratio: the fraction of the heated surface kept free of snow during the design storm, which the handbook fixes at 0 for Class I, 0.5 for Class II, and 1.0 for Class III
+- Design frequency: the percentage of the annual snowfall hours at the design station during which the design heat flux is not exceeded
+- Design surface heat flux: the heat delivered at the pavement surface, in Btu/h·ft², that the snow melting class and the design frequency require at the design station, before the losses from the back and edges of the pavement are added
+- Idle mode: operation of the system between storms at a reduced output that holds the pavement at a set temperature so that melting begins without a cold start
+- After-run: continued operation after the sensor reports the surface dry or the precipitation ended, so that meltwater evaporates rather than refreezing
+- Ground-fault protection of equipment: a residual-current trip that de-energizes a circuit when the leakage current reaches the setting, intended to protect the heating element and the pavement, and distinct from the personnel protection of a ground-fault circuit interrupter
+
# Referenced Standards {toc}
…2 unchanged lines
## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−## The adopted edition of the National Electrical Code varies by jurisdiction; the Contractor shall confirm the locally adopted NEC cycle before sizing electrical work. {note}
−
| Standard | Title |
|----------|-------|
−| NFPA 70 (NEC) Article 426 | Fixed Outdoor Electric Deicing and Snow-Melting Equipment |
−| NFPA 70 (NEC) 426.20 | Embedded Deicing and Snow-Melting Equipment — Installation |
−| NFPA 70 (NEC) 426.28 | Ground-Fault Protection of Equipment |
−| NFPA 70 (NEC) 210.20 | Branch-Circuit Ratings — Overcurrent Protection and Continuous Loads |
−| ASHRAE Handbook — HVAC Applications, Ch. 51 (2023) | Snow Melting and Freeze Protection |
+| ASHRAE Handbook, HVAC Applications | Snow Melting and Freeze Protection |
+| NFPA 70 | National Electrical Code (Article 426, Fixed Outdoor Electric Deicing and Snow-Melting Equipment) |
+| UL 515 | Electrical Resistance Trace Heating for Commercial Applications |
+| UL 1673 | Electric Space Heating Cables |
+| IEEE 515.1 | Testing, Design, Installation, and Maintenance of Electrical Resistance Trace Heating for Commercial Applications |
+| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
| ASTM F876 | Crosslinked Polyethylene (PEX) Tubing |
| ASTM F877 | Crosslinked Polyethylene (PEX) Hot- and Cold-Water Distribution Systems |
−| ASTM F2623 | Polyethylene of Raised Temperature (PE-RT) SDR-9 Tubing |
−| ASTM E814 | Fire Tests of Penetration Firestop Systems |
−| UL 515 | Electric Resistance Heat Tracing for Commercial and Industrial Applications |
−| UL 1673 | Electric Floor Heating Cables |
+| ASTM F2623 | Polyethylene of Raised Temperature (PE-RT) SDR 9 Tubing |
+| ASTM F1960 | Cold Expansion Fittings with PEX Reinforcing Rings for Use with Crosslinked Polyethylene (PEX) Tubing |
+| ASTM F1807 | Metal Insert Fittings Utilizing a Copper Crimp Ring for SDR9 Crosslinked Polyethylene (PEX) Tubing and SDR9 Polyethylene of Raised Temperature (PE-RT) Tubing |
+| ASTM C578 | Rigid, Cellular Polystyrene Thermal Insulation |
+| ASTM D3321 | Use of the Refractometer for Field Test Determination of the Glycol-Base Concentration of Engine Coolant |
+| ASTM D1177 | Freezing Point of Aqueous Engine Coolants |
# Submittals {toc}
−## Action Submittals {note}
+## Action Submittals {toc}
−### The Contractor shall submit the following action submittals for review before fabrication or installation:
+### The Contractor shall submit the following for the Engineer of Record's review and return before any tubing, heating cable, mat, manifold, or controller is ordered:
−- Product data for tubing or heating cable/mat, manifolds, controls, sensors, glycol heat-transfer fluid, and insulation.
−- Shop drawings showing the tubing or cable layout, circuit boundaries, on-center spacing, manifold and sensor locations, slab edge and under-slab insulation extent, and expansion-joint and saw-cut joint locations overlaid on the snow melt layout.
−- Heat-load calculations per ASHRAE Handbook — HVAC Applications Chapter 51, identifying the design climate class, design surface output, and the resulting tubing spacing or watt density.
−- For electric systems, branch-circuit and panel schedules showing connected load, continuous-load sizing at 125%, and GFPE provisions.
−- For hydronic systems, the glycol type, concentration, and design freeze point, with the make-up, air-separation, and expansion provisions.
+- Product data for the tubing or the heating cable or mat, the manifolds or the power connection kits, the controller, the sensors, the insulation, and the heat transfer fluid, each with its listing or its product standard conformance
+- A heat flux calculation for each heated area, stating the snow melting class, the design frequency, the design station and its weather data, the resulting design surface heat flux, the back and edge loss allowance, and the installed output
+- For a hydronic system, a circuit schedule listing every circuit with its length, its design flow, its pressure drop, and its manifold connection, with the supply temperature, the temperature drop, and the glycol type and concentration the schedule assumes
+- For an electric system, a circuit schedule listing every heating circuit with its element type, its length or its mat dimensions, its supply voltage, its rated wattage and amperage, its branch circuit, and the ground-fault protection device that serves it
+- Shop drawings showing the layout of every circuit to scale, the spacing, the depth below the finished surface, the manifold, junction box, and sensor locations, the insulation extent, and every pavement joint overlaid on the layout, with each joint crossing detailed
+- The controller sequence of operation, with the activation, after-run, idle, and high limit setpoints the controller will be shipped with, and the points exposed to the building automation system
+- For a hydronic system, the freeze point of the glycol solution at the selected concentration, from the fluid supplier's published table
+- The qualifications of the installer and, for an electric system, of the electrician who will make the connections
```datasheet
−label: Action Submittals
+label: Action Submittals Required
type: checkbox
options:
− - Product data (tubing/cable, manifold, controls, sensors, fluid, insulation)
− - Shop drawings (layout, spacing, manifold/sensor locations, joints overlaid)
− - Heat-load calculations (ASHRAE Ch. 51, climate class, output)
− - Electric branch-circuit and panel schedules (continuous load, GFPE)
− - Hydronic glycol type/concentration and make-up/expansion provisions
−default: []
+ - "Product data with listings"
+ - "Heat flux calculation per heated area"
+ - "Hydronic circuit schedule"
+ - "Electric circuit schedule"
+ - "Circuit layout shop drawings with joints overlaid"
+ - "Controller sequence of operation and setpoints"
+ - "Glycol freeze point at the selected concentration"
+ - "Installer and electrician qualifications"
+default:
+ - "Product data with listings"
+ - "Heat flux calculation per heated area"
+ - "Hydronic circuit schedule"
+ - "Electric circuit schedule"
+ - "Circuit layout shop drawings with joints overlaid"
+ - "Controller sequence of operation and setpoints"
+ - "Glycol freeze point at the selected concentration"
+ - "Installer and electrician qualifications"
+constraint: all_of
```
−## Closeout Submittals {note}
+### No embedded element shall be placed in a pavement until the shop drawings for that heated area have been returned by the Engineer of Record.
−### The Contractor shall submit the following closeout submittals before final acceptance:
+### The shop drawing with the joints overlaid is the submittal that prevents the common failure. A contraction joint sawn across a tube cuts it, an isolation joint that a cable bridges without a sleeve shears it when the panels move, and neither is visible once the pavement is finished. The overlay is where those crossings are found while the layout can still be moved. {note}
−- Record drawings showing the as-installed tubing/cable routing, circuit identification, and sensor and manifold locations.
−- Documented results of the pre-pour pressure test (hydronic) or insulation-resistance test (electric), including the test held through the concrete placement.
−- Operation and maintenance manuals covering the control sequence, setpoints, glycol service, and seasonal startup/shutdown.
−- Manufacturer warranty documents for tubing/cable, controls, and heat-transfer fluid.
+## Closeout Submittals {toc}
+### The Contractor shall submit the following before the work of this standard is accepted:
+
+- Record drawings of each heated area, dimensioned from fixed site features, showing the as-installed route of every circuit, its identification, the depth below the finished surface, and the manifold, junction box, splice, and sensor locations
+- A photographic record of every heated area taken after the elements were secured and before the pavement was placed, with a dimensioned reference in each frame
+- The pressure test record for each hydronic circuit, or the insulation resistance and element resistance record for each electric circuit, at each stage this standard requires
+- The functional test record
+- Operation and maintenance data, including the sequence of operation, the setpoints as left, the glycol type, concentration, and freeze point, and the seasonal startup and shutdown procedure
+- Warranty documentation for the embedded elements, the controller, and the sensors
+
```datasheet
−label: Closeout Submittals
+label: Closeout Submittals Required
type: checkbox
options:
− - Record drawings (as-installed routing, circuit IDs, sensor/manifold locations)
− - Pressure / insulation-resistance test records (through concrete placement)
− - Operation and maintenance manuals (sequence, setpoints, glycol service)
− - Manufacturer warranty documents
−default: []
+ - "Record drawings of each heated area"
+ - "Photographic record before pavement placement"
+ - "Pressure test or insulation resistance records at each stage"
+ - "Functional test record"
+ - "Operation and maintenance data"
+ - "Warranty documentation"
+default:
+ - "Record drawings of each heated area"
+ - "Photographic record before pavement placement"
+ - "Pressure test or insulation resistance records at each stage"
+ - "Functional test record"
+ - "Operation and maintenance data"
+ - "Warranty documentation"
+constraint: all_of
```
−## Informational Submittals {note}
+### The record drawing and the photographs are the only map of an element that no one will see again. A future core, a bollard footing, a sign post, or a utility repair in a heated pavement is located against them, and a pavement without them is a pavement no one can safely cut. {note}
−### The Contractor shall submit the following informational submittals:
+# Quality Assurance {toc}
−- Manufacturer installation instructions for the embedded elements and the substrate-specific listing where asphalt is used.
−- Qualification statements for the installer and, for electric systems, the licensed electrician of record.
+## Installer Qualifications {toc}
−```datasheet
−label: Informational Submittals
−type: checkbox
−options:
− - Manufacturer installation instructions (and asphalt listing if applicable)
− - Installer and electrician qualification statements
−default: []
−```
+### Hydronic tubing, manifolds, and the circuit connections shall be installed by an installer trained by the tubing manufacturer for embedded snow melt installation, who shall submit the manufacturer's current training certificate.
−# Quality Assurance {toc}
+### Electric heating cable and mats shall be laid out and secured by the installer and shall be connected, tested, and energized by an electrician licensed in the jurisdiction, working to the manufacturer's installation instructions.
−## Installer Qualifications {note}
+### The installer shall have installed not less than three embedded snow melt systems of the selected heat source within the preceding five years, and shall submit those project references on request.
−### Hydronic tubing loops shall be installed by an installer trained and certified by the tubing or manifold manufacturer for embedded snow melt installation.
+### Where the parties disagree whether a reference project is comparable, the Engineer of Record shall make the initial determination.
−### Electric heating cable and mat circuits shall be terminated and connected by a licensed electrician working under the manufacturer's installation instructions.
+## Product Conformance and Listing {toc}
−## Source Quality {note}
+### PEX tubing shall conform to ASTM F876 and ASTM F877, and PE-RT tubing shall conform to ASTM F2623, each marked by the manufacturer with the standard, the size, the pressure and temperature rating, and the oxygen barrier where one is furnished.
−### Heating cable and mats shall be listed under UL 1673 for embedded floor/pavement heating, or under UL 515 where supplied as heat-tracing-listed snow melt cable.
+### Electric heating cable and mats shall be listed by a nationally recognized testing laboratory for embedded deicing and snow melting use under UL 515 or UL 1673 as applicable to the product, and the listing shall name the pavement material in which the product is embedded.
−### Where electric heating elements are installed in asphalt, the elements shall be listed by the manufacturer for asphalt embedment; cable not listed for asphalt shall not be used in asphalt.
+### Electric heating elements embedded in asphalt shall be listed for asphalt embedment at the placement temperature of the asphalt, and an element not so listed shall not be placed in asphalt.
−### PEX tubing shall comply with ASTM F876 and ASTM F877; PE-RT tubing shall comply with ASTM F2623.
+### Every electric heating element, power connection kit, splice kit, end seal, and controller in a heating circuit shall be a component of one manufacturer's listed system.
−## Pre-Pour Coordination {note}
+### The electric installation shall comply with [[parameter: adopted-electrical-code]] and with the amendments of the Authority Having Jurisdiction, and shall be made available for the inspections that authority requires.
−### A pre-pour coordination meeting between the snow melt installer, the concrete contractor, the electrical contractor (for electric systems), and the Engineer of Record shall be held before concrete placement.
+### The listing is what proves the element survives the pavement. An asphalt lift is placed at a temperature that softens the insulation on a cable listed only for concrete, and a mat whose listing names concrete has not been evaluated for the compaction loads of a paver bed. The listing names the material because the material is the test condition. {note}
−### Saw-cut and expansion-joint locations shall be reviewed against the tubing or cable layout at the coordination meeting; no joint shall be cut where it crosses an embedded loop or cable run.
+## Pre-Placement Conference {toc}
−# Environmental and Service Conditions {toc}
+### Before the elements of any heated area are laid out, the Contractor shall convene a conference attended by the snow melt installer, the pavement contractor, the electrician where the system is electric, the mechanical contractor where the system is hydronic, and the Engineer of Record.
−## Design Climate Class {note}
+### The conference agenda shall cover the circuit layout against the pavement joint plan, the depth below the finished surface and how it will be held during placement, the attachment method, the pavement placement method and the equipment that will run over the elements, the hold points at which the Engineer of Record is notified, and the test required at each stage.
−### The snow melt design shall be based on the ASHRAE climate class appropriate to the local snowfall intensity, wind exposure, and the surface's priority of service. {note}
+### The decisions settled at the conference shall be recorded in the minutes and shall be incorporated into the shop drawings before layout begins.
−### Class I covers light snowfall and lower-priority surfaces; Class II covers moderate snowfall and standard commercial surfaces; Class III covers heavy snowfall, wind-exposed sites, and critical surfaces such as hospital entrances and accessible ramps. {note}
+# Design Basis {toc}
−### The ASHRAE design climate class shall be specified for the system, based on the snowfall severity and the priority of the surfaces served.
+## Heat Source {toc}
+### The heat source of each snow melt system shall be as indicated in the datasheet.
+
```datasheet
−label: ASHRAE design climate class
+label: Heat Source
type: radio
options:
− - Class I — light snowfall, lower priority
− - Class II — moderate snowfall, standard commercial
− - Class III — heavy snowfall / wind-exposed / critical
−default: Class II — moderate snowfall, standard commercial
+ - "Hydronic, glycol solution in embedded tubing"
+ - "Electric, resistance heating cable or mat"
```
−## Surface Priority {note}
+### No heat source is the norm across projects, because the answer follows the plant and the area. A hydronic system has a higher first cost in tubing, manifolds, and the plant that serves it, and a lower operating cost wherever a fuel-fired or waste-heat source is available, and it is the usual choice for a large area on a site that already has a hydronic plant or where one is being installed. An electric system has a lower first cost, no plant, no fluid, and no freezing risk when it is off, and a higher operating cost at any electricity price above the cost of fuel heat, and it draws a connected load that a large area can push past the available service. It is the usual choice for a small area, for a site without a hydronic plant, and for a retrofit where tubing cannot be run back to a plant. {note}
−### Accessible routes, ramps, and the primary egress path from a building entrance shall be designed to the highest surface priority on the project, because residual ice on these surfaces presents a direct life-safety hazard.
+## Snow Melting Class {toc}
+### The snow melting class of each heated area shall be as indicated in the datasheet.
+
```datasheet
−label: Surface priority of the heated area
−type: radio
+label: Snow Melting Class
+type: select
options:
− - Critical (hospital entry, accessible ramp, primary egress)
− - Standard commercial (walkways, plaza, entry apron)
− - Low priority (secondary walks, residential)
−default: Standard commercial (walkways, plaza, entry apron)
+ - "Class I"
+ - "Class II"
+ - "Class III"
```
−## Design Surface Output {note}
+### The class sets the snow-free area ratio and, with the design frequency, the design heat flux, so it is the first design decision and the one the output follows from. Class I, with a snow-free area ratio of 0, lets snow accumulate during the storm and melts it afterward, at the lowest output and the lowest operating cost, and suits a surface that can be closed during a storm. Class II, with a ratio of 0.5, keeps the surface passable during all but the heaviest snowfall at a moderate output, and suits walks, plazas, and drives that are in use through a storm. Class III, with a ratio of 1.0, keeps the surface free of snow and ice throughout the storm at the highest output, and suits a surface where any accumulation is a hazard or a stoppage: an emergency entrance, an accessible ramp, a loading dock on a slope, a helipad approach. No class is the norm across projects, because the same project often holds a Class III ramp beside a Class II walk. {note}
−### The design surface output shall be calculated per ASHRAE Handbook — HVAC Applications Chapter 51 for the selected climate class, not assumed from a default watt density. {note}
+### The design frequency of each heated area shall be as indicated in the datasheet.
−### For hydronic systems, surface output typically ranges from 80 to 125 Btu/hr·ft² for Class I, 125 to 200 Btu/hr·ft² for Class II, and 200 to 250 Btu/hr·ft² for Class III; commercial walks in Zones 4 to 6 commonly fall at 100 to 125 Btu/hr·ft². {note}
−
−### The hydronic design surface output shall be specified in Btu/hr·ft², consistent with the ASHRAE design climate class selected for the system.
−
```datasheet
−label: Hydronic design surface output
+label: Design Frequency
type: range
−unit: Btu/hr·ft²
−min: 80
−max: 250
−step: 5
−default: 125
+unit: '%'
+min: 75
+max: 99
+setpoints: [75, 90, 95, 98, 99]
+constraint: min
```
−### For electric systems, pavement watt density typically ranges from 30 to 50 W/ft²; 40 W/ft² (≈136 Btu/hr·ft²) is the common commercial pavement value in Zones 4 to 6. {note}
+### The design frequency is the share of the snowfall hours in the handbook record for which the installed output is enough. A system designed to 75 percent is undersized in one snowfall hour in four, which is acceptable where the surface can wait out a heavy storm; a system designed to 99 percent is sized for the storm of the record and runs at a fraction of its capacity in every other one. The output difference between the two is often a factor of two, and the frequency is chosen with the class because a Class III surface at a low frequency is not Class III in the storm that matters. {note}
−### Electric watt density shall not exceed 1,300 W/m² (≈121 W/ft²) per NEC 426.20; typical design values are well below this ceiling.
+## Design Surface Heat Flux {toc}
+### The design surface heat flux of each heated area shall be the value indicated in the datasheet, calculated in accordance with ASHRAE Handbook, HVAC Applications, Snow Melting and Freeze Protection.
+
```datasheet
−label: Electric design watt density
+label: Design Surface Heat Flux
type: range
−unit: W/ft²
−min: 30
−max: 50
−step: 1
−default: 40
+unit: Btu/h·ft²
+min: 50
+max: 400
+step: 5
+derived: "the snow melting class, the design frequency, and the ASHRAE Handbook design data for the snow melting station nearest the site"
+default: derived
+constraint: min
```
−# System Type {toc}
+### The surface flux follows from the class, the frequency, and the station, so it is derived rather than chosen. The handbook tabulates, for each listed station and each class, the surface flux not exceeded at each frequency, and a calculation from the local snowfall rate, air temperature, wind speed, and humidity gives the same answer for a site that is not listed. The value is the flux at the surface; the installed output of the tubing or the cable is that flux plus the losses from the back and the edges of the pavement, which depend on the insulation selected under this standard. {note}
−## Hydronic and electric systems trade differently across plant availability, operating cost, installation complexity, and scale; the choice shall be made with the mechanical and electrical engineers of record before the system is sized. {note}
+### The installed output of each heated area shall be not less than the design surface heat flux plus the back and edge losses calculated for the pavement section and the insulation selected, and the calculation shall state the loss allowance used.
−## Hydronic systems suit larger areas and projects with an available heat source, and spread the energy demand across a fuel-fired or central plant; electric systems suit smaller areas, retrofits, and projects without a hydronic plant, at the cost of high continuous electrical demand. {note}
+### Where the heat source is electric, the installed watt density shall be the installed output converted at 3.412 Btu/h per watt, and shall not exceed 120 W/ft² of heated area, the limit of NFPA 70 426.20(A).
−## The snow melt technology type shall be specified as hydronic or electric, based on the area served and the availability of a hydronic heat source.
+### Where the heat source is hydronic, the tubing spacing, the depth below the finished surface, the supply temperature, and the circuit flow shall together deliver the installed output at the design surface temperature, as shown in the heat flux calculation.
+# Hydronic Circuit {toc}
+
+## Requirements in this section apply where the heat source selected under Design Basis is hydronic. {note}
+
+## Tubing {toc}
+
+### The tubing material shall be as indicated in the datasheet.
+
```datasheet
−label: Snow melt technology type
−type: radio
+label: Tubing Material
+type: select
options:
− - Hydronic — glycol loop in embedded tubing
− - Electric — resistance heating cable
− - Electric — factory-assembled heating mat
−default: Hydronic — glycol loop in embedded tubing
+ - "PEX-a"
+ - "PEX-b"
+ - "PEX-c"
+ - "PE-RT"
```
−## Heat Source (Hydronic) {note}
+### The three PEX types differ in the crosslinking process and in the result. PEX-a is crosslinked in the melt and is the most flexible of the four, bends to the tightest radius, recovers from a kink when heated, and is joined by cold expansion fittings under ASTM F1960; it carries the highest price. PEX-b is crosslinked after extrusion by moisture cure, is stiffer, is joined by crimp or clamp fittings under ASTM F1807, and costs less. PEX-c is crosslinked by electron beam and sits between the two in flexibility and price. PE-RT is not crosslinked, is as flexible as PEX-b, can be joined by heat fusion, and is rated under ASTM F2623 for the temperature and pressure of a snow melt circuit. No material is the norm across projects, because the choice turns on the fitting system the manifold uses and on the bend radius the layout needs at the circuit ends. {note}
−### Where a hydronic system connects to the main building hydronic system, a heat exchanger shall isolate the glycol snow melt loop from the building water side so glycol cannot migrate into potable or building heating water.
+### Tubing shall be furnished with an oxygen diffusion barrier as indicated in the datasheet.
```datasheet
−label: Hydronic heat source
+label: Oxygen Diffusion Barrier
type: radio
options:
− - Dedicated boiler or water heater for snow melt
− - Heat exchanger off the main building hydronic system
− - Standalone electric boiler package
−default: Heat exchanger off the main building hydronic system
+ - "Barrier tubing"
+ - "Non-barrier tubing"
+default: "Barrier tubing"
```
−# Hydronic Components {toc}
+### Oxygen diffuses through the wall of an unbarriered polyolefin tube and into the fluid, where it corrodes every ferrous component in the loop: the pump volute, the expansion tank, the heat exchanger shell, the manifold where it is steel. A barrier layer in the tube wall stops that, and nearly every snow melt circuit is connected to a plant that contains ferrous parts, which is why barrier tubing is the default. Non-barrier tubing is chosen where the whole loop, plant included, is non-ferrous or where the fluid treatment program under [[sync/hvac-water-treatment]] is designed to scavenge the oxygen. {note}
−## Tubing {note}
+### The tubing nominal size shall be as indicated in the datasheet.
−### Embedded hydronic tubing shall be PEX-a, PEX-b, or PE-RT rated for the design supply temperature and working pressure, supplied in continuous lengths without buried joints within a circuit.
−
−### No mechanical joint, coupling, or fitting shall be embedded in the slab within a snow melt circuit; circuits shall run continuous from supply manifold to return manifold.
−
```datasheet
−label: Hydronic tubing material
−type: radio
−options:
− - PEX-a (ASTM F876/F877)
− - PEX-b (ASTM F876/F877)
− - PE-RT (ASTM F2623)
−default: PEX-a (ASTM F876/F877)
+label: Tubing Nominal Size
+type: range
+unit: in
+min: 0.5
+max: 1
+setpoints: [0.5, 0.625, 0.75, 1]
+constraint: exact
```
+### The tubing spacing on centers shall be as indicated in the datasheet.
+
```datasheet
−label: Tubing nominal diameter
−type: radio
−options:
− - 1/2 in
− - 5/8 in
−default: 5/8 in
+label: Tubing Spacing on Centers
+type: range
+unit: in
+min: 4
+max: 12
+setpoints: [4, 6, 8, 9, 10, 12]
+constraint: exact
```
−## Tubing Spacing {note}
+### Size and spacing are selected together with the supply temperature and the depth, and the heat flux calculation is where the combination is proved. A larger tube carries more flow at the same pressure drop and allows a longer circuit and a smaller manifold, and costs more per foot; a smaller tube bends more easily at the circuit ends. Closer spacing delivers more output at a given supply temperature and evens the surface temperature between the tubes, at more tube per square foot; wider spacing suits a low output class and a deeper embedment, where the pavement spreads the heat before it reaches the surface. Neither value has a norm across projects. {note}
−### On-center tubing spacing shall be selected for the surface priority: 6 in OC for critical surfaces, 9 in OC for standard commercial surfaces, and 12 in OC for low-priority or residential surfaces.
+### Each circuit shall be one continuous length of tubing from the supply manifold to the return manifold, and no fitting, coupling, or splice shall be embedded in the pavement.
−```datasheet
−label: Tubing on-center spacing
−type: radio
−options:
− - 6 in OC (critical / hospital / ramp)
− - 9 in OC (standard commercial)
− - 12 in OC (residential / low priority)
−default: 9 in OC (standard commercial)
−```
+### Where a tube is damaged before the pavement is placed, the circuit shall be replaced in its entirety, and the damaged tube shall not be repaired with an embedded coupling.
−## Circuit Length {note}
+### Tubing shall be rated by its manufacturer for continuous service at the design supply temperature and the system working pressure, and for the glycol type and concentration selected under Heat Transfer Fluid.
−### Hydronic circuit length shall be limited so that circuit pressure drop stays below 4 ft H₂O per 100 ft, which generally caps a 1/2 in circuit near 300 ft and a 5/8 in circuit near 400 to 500 ft.
+## Circuit Hydraulics {toc}
−### Circuits served from a common manifold shall be reverse-return or balanced with manifold balancing valves so that flow is distributed evenly across loops of unequal length.
+### The circuit length shall not exceed the value indicated in the datasheet.
```datasheet
−label: Maximum circuit length
+label: Circuit Length
type: range
unit: ft
−min: 200
−max: 500
−step: 25
−default: 300
+min: 150
+max: 700
+setpoints: [150, 200, 250, 300, 350, 400, 500, 600, 700]
+derived: "the tubing nominal size, the design flow per circuit, and the circuit pressure drop limit stated in the heat flux calculation"
+default: derived
+constraint: max
```
−## Supply Temperature and Delta-T {note}
+### Circuits served from one manifold shall be of lengths within 10 percent of one another, or shall be balanced at the manifold so that each circuit receives its design flow.
−### The hydronic loop shall be designed for a supply temperature of 120°F to 140°F with a circuit temperature drop of 20°F to 30°F; a 130°F supply with a 110°F return is the typical commercial default.
+### The circuit length is a consequence of the tube size and the flow the output demands, which is why it is derived. A circuit that is too long for its tube either starves at the design flow or needs a pump head the plant was not sized for, and a manifold that serves circuits of unequal length delivers most of the flow to the shortest unless each is balanced. Keeping the circuits on a manifold within a narrow band of length is what makes the balancing valves able to even the flow without throttling one circuit to a trickle. {note}
+### The design supply temperature of each system shall be as indicated in the datasheet.
+
```datasheet
−label: Design supply temperature
+label: Design Supply Temperature
type: range
unit: °F
−min: 120
−max: 140
+min: 90
+max: 160
step: 5
−default: 130
+drawing_ref: "the snow melt system schedule on the mechanical drawings"
+default: deferred
+constraint: exact
```
+### The design circuit temperature drop of each system shall be as indicated in the datasheet.
+
```datasheet
−label: Design circuit delta-T
+label: Design Circuit Temperature Drop
type: range
unit: °F
−min: 20
−max: 30
+min: 10
+max: 40
step: 5
−default: 20
+drawing_ref: "the snow melt system schedule on the mechanical drawings"
+default: deferred
+constraint: exact
```
−## Heat-Transfer Fluid {note}
+### The supply temperature and the temperature drop are system-sized quantities that the mechanical engineer sets with the plant, the tube spacing, and the depth, and they sit on the schedule beside the flow and the head the plant has to deliver. A high supply temperature lets wider spacing or deeper embedment reach the output, and is limited by the tube rating and by the thermal stress it puts into the pavement; a large temperature drop reduces the flow and the pump but leaves the return end of each circuit cooler than the supply end, which shows as a strip that melts last. {note}
−### Propylene glycol shall be used where system runoff can contact food-preparation areas, landscaping, or stormwater that drains to sensitive receiving waters; ethylene glycol is more efficient but toxic and shall be used only where project conditions specifically justify it and runoff exposure is controlled.
+## Heat Transfer Fluid {toc}
−### The glycol concentration shall be selected for the design freeze point: 30% propylene glycol provides protection to about −15°F and is the typical North American default, while 40% is required for design conditions at or below −20°F.
+### The glycol type of the snow melt loop shall be as indicated in the datasheet.
```datasheet
−label: Heat-transfer fluid type
+label: Glycol Type
type: radio
options:
− - Propylene glycol (lower toxicity)
− - Ethylene glycol (higher performance, toxic)
−default: Propylene glycol (lower toxicity)
+ - "Inhibited propylene glycol"
+ - "Inhibited ethylene glycol"
+default: "Inhibited propylene glycol"
```
+### Propylene glycol is the default because a snow melt loop lies under a surface that people, pets, and stormwater cross, and a leak from it reaches the ground. Propylene glycol is of low toxicity and is the fluid most jurisdictions accept near a storm inlet or a planting bed; it is more viscous than ethylene glycol at the same freeze point, so it carries more pumping power and a lower heat transfer coefficient. Ethylene glycol transfers heat better and pumps more easily, and is toxic if ingested, so it is chosen where the loop is isolated from the ground and from any potable connection and the Owner accepts the handling requirements. {note}
+
+### The glycol concentration by volume of the snow melt loop shall be as indicated in the datasheet.
+
```datasheet
−label: Glycol concentration (by volume)
+label: Glycol Concentration by Volume
type: range
−unit: "%"
−min: 25
−max: 50
+unit: '%'
+min: 30
+max: 60
step: 5
−default: 30
+derived: "the freeze protection required at [[parameter: site-ambient-temperature-minimum]], from the fluid supplier's published freeze point table"
+default: derived
+constraint: exact
```
−## Make-Up, Air Separation, and Expansion {note}
+### The concentration follows from the site's minimum temperature and the fluid supplier's table, so it is derived rather than chosen. A snow melt loop is unlike a building loop in that it sits idle in a pavement at the outdoor temperature for days at a time, so it is protected to the freeze point, at which no ice crystals form, rather than to the burst point, at which slush is tolerated, because slush in a tube under a pavement blocks the circuit at the moment the system is called on. Each additional five percent of glycol lowers the heat transfer and raises the pumping power, which is why the concentration is taken from the table rather than rounded up. {note}
−### The hydronic loop shall include a glycol make-up/fill provision, an air separator, and an expansion tank sized for the system fluid volume; snow melt loops hold large fluid volumes and omitting these provisions causes air-binding and startup failures.
+### The glycol shall be an inhibited formulation intended for closed hydronic service, and uninhibited or automotive glycol shall not be used.
−### A means of purging air from each circuit, such as manifold purge and isolation valves, shall be provided so that each loop can be individually filled and bled.
+### Where the snow melt loop is served from a hydronic system that does not itself carry the glycol solution selected here, a heat exchanger furnished under [[sync/heat-exchangers]] shall separate the two fluids, and the glycol type and concentration selected here shall apply to the snow melt side only.
−## Manifold {note}
+### The initial glycol charge, the verification of the concentration by refractometer under ASTM D3321, and the freeze point under ASTM D1177 shall be performed under [[sync/hydronic-cleaning-and-flushing]] against the type and concentration selected here.
−### The circuit manifold shall include balancing valves, flow indication, and purge/isolation valves for each loop, and shall be located in a heated interior space or an accessible vault at the slab edge. {note}
+## Manifolds {toc}
−### Where the manifold is in an unheated exterior vault, the supply and return piping between the building and the manifold shall be routed through conditioned space or heat-traced so the glycol cannot freeze in the connecting piping.
+### The manifold location shall be as indicated in the datasheet.
```datasheet
−label: Manifold location
−type: radio
+label: Manifold Location
+type: select
options:
− - Heated interior space
− - Accessible exterior vault at slab edge
−default: Heated interior space
+ - "Heated space within the building"
+ - "Below-grade vault at the pavement edge"
+ - "Above-grade insulated enclosure at the pavement edge"
```
−# Electric Components {toc}
+### A manifold inside the building is protected from freezing, flooding, and traffic and is reached from the mechanical room, and it needs the supply and return legs of every circuit to run back through the wall, which lengthens each circuit by the distance from the pavement to the manifold and fixes the circuit count the wall penetration can carry. A below-grade vault at the pavement edge keeps the circuits short and the manifold out of sight, and it sits at the outdoor temperature, collects water unless it drains, and is reached through a lid that must carry the traffic over it. An above-grade enclosure is reached without lifting a lid and stays above the water, and it stands in the hardscape where it is seen and struck. No location is the norm across projects. {note}
−## Heating Element Form Factor {note}
+### Each manifold shall be furnished with the accessories indicated in the datasheet.
−### Single-conductor heating cable is field-cut to length and laid at a calculated spacing; twin-conductor cable and factory-assembled mats carry a fixed watt density and are installed by cut-and-turn at the rated spacing. {note}
+```datasheet
+label: Manifold Accessories
+type: checkbox
+options:
+ - "Isolation valve on each circuit supply and return"
+ - "Balancing valve with flow indicator on each circuit"
+ - "Purge and drain valve on each manifold"
+ - "Manual air vent on each manifold"
+ - "Supply and return thermometers"
+ - "Supply and return pressure gauges"
+default:
+ - "Isolation valve on each circuit supply and return"
+ - "Balancing valve with flow indicator on each circuit"
+ - "Purge and drain valve on each manifold"
+ - "Manual air vent on each manifold"
+ - "Supply and return thermometers"
+constraint: all_of
+```
−### The electric heating element form factor shall be specified, selecting field-cut single-conductor cable or a fixed-spacing twin-conductor cable or factory-assembled mat.
+### The isolation valves are what let a circuit be found and shut off when it leaks, the balancing valves are what even the flow across circuits of unequal length, and the purge valves are what let each circuit be filled and bled on its own; without them a manifold of ten circuits is filled by chasing air from one circuit into the next. The thermometers show the operator whether the loop is delivering the design temperature drop, which is the one reading that distinguishes a plant problem from a circuit problem. {note}
+### Manifolds shall be of brass, stainless steel, or an engineered polymer rated by the manufacturer for the glycol type and concentration selected and for the design supply temperature, and shall have circuit connections of the fitting system the tubing manufacturer lists for the tubing selected.
+
+### Where a manifold is in a vault or an enclosure at the pavement edge, the vault or enclosure shall drain to daylight or to a storm connection, shall be insulated on every face, and shall have a lid or door rated for the traffic over it.
+
+### Where a manifold is outside the building, the supply and return piping between the building and the manifold shall be insulated and shall carry the glycol solution selected under this standard, so that no water-filled section lies outdoors.
+
+### Each circuit shall be tagged at the manifold with the circuit identification shown on the record drawings.
+
+# Electric Heating Elements {toc}
+
+## Requirements in this section apply where the heat source selected under Design Basis is electric. {note}
+
+## Heating Element Form {toc}
+
+### The heating element form shall be as indicated in the datasheet.
+
```datasheet
−label: Electric heating element form factor
−type: radio
+label: Heating Element Form
+type: select
options:
− - Single-conductor heating cable (field-cut)
− - Twin-conductor constant-wattage cable (field-spaced)
− - Factory-assembled heating mat (fixed spacing)
−default: Twin-conductor constant-wattage cable (field-spaced)
+ - "Single-conductor constant-wattage cable, cut to a designed length"
+ - "Twin-conductor constant-wattage cable, fixed output per foot"
+ - "Self-regulating parallel-resistance cable"
+ - "Mineral-insulated metal-sheathed cable, factory terminated"
+ - "Factory-assembled mat with cable at a fixed spacing"
```
−## Cable Spacing and Cover {note}
+### A single-conductor constant-wattage cable is a series resistor whose output depends on its length, so each circuit is cut to the length the design calls for and both ends return to the junction box; it gives the designer the most freedom and the installer the most to get wrong. A twin-conductor cable has both conductors in one jacket, delivers a fixed output per foot at its rated voltage, and terminates at one end, which simplifies the layout. A self-regulating cable reduces its output as it warms, which limits the slab temperature and lets the cable be overlapped, at a higher cost per foot and a startup inrush the circuit has to carry. A mineral-insulated cable has a metal sheath and is rated for the highest asphalt placement temperatures and for direct burial, and it is factory terminated to length and cannot be cut in the field. A mat carries cable pre-spaced on a mesh and is unrolled over the area, which is the fastest installation on a regular shape and the hardest to fit around an obstruction. No form is the norm across projects. {note}
−### Adjacent cable runs shall be spaced not less than 25 mm (≈1 in) apart per NEC 426.20(B).
+### Each heating cable or mat shall be marked by its manufacturer at the intervals its listing requires with the product identification, the rated voltage, and the rated output per foot or per square foot.
−### Minimum cover over embedded electric heating cable shall be 1.5 in of concrete or 3 in of asphalt, measured from the top of the cable to the finished surface.
+### Heating cable shall not be cut, shortened, or spliced in the field except as the manufacturer's listing permits, and the resistance of each cut-to-length circuit shall be verified against the design value before the cable is secured.
+### Adjacent runs of heating cable shall be spaced not less than 1 in on centers, and a cable shall not cross or overlap itself unless the listing permits it.
+
+## Electrical Supply and Protection {toc}
+
+### The supply voltage of the heating circuits shall be as indicated in the datasheet.
+
```datasheet
−label: Minimum cover over heating cable
−type: radio
−options:
− - 1.5 in concrete
− - 3 in asphalt
−default: 1.5 in concrete
+label: Heating Circuit Supply Voltage
+type: range
+unit: V
+min: 120
+max: 600
+setpoints: [120, 208, 240, 277, 347, 480, 600]
+drawing_ref: "the panel schedules on the electrical drawings"
+default: deferred
+constraint: exact
```
−## Branch Circuits and Overcurrent {note}
+### Snow melt heating circuits shall be treated as continuous loads, and the branch circuit conductors and the overcurrent device shall be rated for not less than 125 percent of the connected load.
−### Snow melt loads shall be classified as continuous loads; branch-circuit conductors and the overcurrent protective device shall be rated at not less than 125% of the connected load per NEC 210.20.
+### Each branch circuit supplying embedded snow melt equipment shall be provided with ground-fault protection of equipment in accordance with NFPA 70 426.28, with a trip setting of 30 mA unless the heating element manufacturer's listing requires a different setting.
−### The connected electrical demand of the snow melt system shall be confirmed against the available service and panel capacity before the system is sized, because a large heated area at 40 W/ft² can draw several hundred amperes.
+### Ground-fault protection of equipment is set at 30 mA, not the 5 mA of personnel protection, because a long embedded heating cable has a capacitive leakage that trips a 5 mA device on a dry day. A 30 mA trip still opens the circuit when the insulation on a cable in the pavement breaks down, which is the fault the protection exists to catch before the cable burns open and the pavement is cut to find it. {note}
−## Ground-Fault Protection {note}
+### Each snow melt system shall have a disconnecting means in accordance with NFPA 70 426.50 that opens every ungrounded conductor of the heating circuits and the controller, located within sight of the controller or lockable in the open position.
−### Each fixed outdoor electric snow melt circuit shall be protected by ground-fault protection of equipment (GFPE) set at 30 mA per NEC 426.28.
+### Caution markings identifying the presence of embedded electric snow melting equipment shall be posted in accordance with NFPA 70 426.13 at the controller and at each junction box at the pavement edge.
−### GFPE at 30 mA is equipment protection against heating-element faults in the pavement, not the 5 mA personnel-protection threshold of a GFCI; on large systems, GFPE panels selected to resist nuisance tripping should be specified. {note}
+### The connected load of each electric snow melt system shall be confirmed against the service and panelboard capacity shown on the electrical drawings before the heating elements are ordered, and the Contractor shall report any shortfall to the Engineer of Record in writing.
+### A heated area at the watt density Class II or III demands draws a load that is easy to underestimate: a few thousand square feet at the upper end of the common density range is a load in the hundreds of amperes, running through the night of a storm. The confirmation is required before ordering because a shortfall found after the cable is in the pavement is corrected by a service upgrade. {note}
+
+## Cold Leads and Connections {toc}
+
+### Each heating circuit shall terminate in a factory-made or listed field-assembled power connection with nonheating cold leads, and the transition from the heating section to the cold lead shall be located within the pavement where the listing requires it or in the junction box where the listing permits it.
+
+### Cold leads shall leave the pavement in a raceway in accordance with NFPA 70 426.22, bushed at the pavement end, sized for the leads it carries, and routed to a junction box at the pavement edge, and the raceway from the junction box onward shall be furnished under [[sync/raceways-and-conduit]].
+
+### Junction boxes serving embedded heating circuits shall be located above the finished grade or in a listed enclosure where their location is below it, and shall be accessible without removing pavement.
+
+### No splice in a heating cable shall be embedded in the pavement unless it is made with the manufacturer's listed splice kit for embedded service and its location is recorded on the record drawings.
+
+### Where a heating element or its cold leads cross a pavement expansion or isolation joint, the crossing shall be made with the slack, the sleeve, or the loop the manufacturer's instructions require so that the joint movement is not carried by the element.
+
+### The equipment grounding conductor of each heating circuit shall be connected to the metal sheath or braid of the heating element at each power connection, and the sheath or braid shall be continuous through every splice.
+
# Controls {toc}
−## The control strategy shall be selected for the surface priority: fully automatic control with a pavement temperature/moisture sensor and an aerial ambient sensor is appropriate for critical and standard commercial surfaces, while semi-automatic or manual-only control may be acceptable on low-priority surfaces.
+## Control Type {toc}
+### The control type of each snow melt system shall be as indicated in the datasheet.
+
```datasheet
−label: Control strategy
−type: radio
+label: Control Type
+type: select
options:
− - Fully automatic (pavement + aerial sensor)
− - Semi-automatic (manual enable, auto shutoff)
− - Manual only
−default: Fully automatic (pavement + aerial sensor)
+ - "Manual switch with run timer"
+ - "Aerial snow sensor"
+ - "Pavement-mounted snow and ice sensor"
+ - "Aerial and pavement-mounted sensors in combination"
+ - "Building automation system initiation with a pavement-mounted sensor"
```
−## Sensing {note}
+### A manual switch with a run timer costs the least and starts the system only when someone decides to, which on an unstaffed site means after the snow is on the ground. An aerial sensor on a pole or a roof detects precipitation and air temperature and starts the system as the snow begins to fall, before it reaches the pavement, and it cannot see drifting snow, blown snow, or meltwater that refreezes on the surface. A pavement-mounted sensor reads the surface temperature and the moisture on it, so it responds to whatever is on the pavement from any source and holds the system on until the surface is dry, and it starts only once moisture reaches the sensor. The combination starts on the aerial sensor and runs on the pavement sensor, which is the earliest start and the surest finish, at the cost of two sensors and the wiring to both. Initiation from the building automation system puts the start decision in the operator's hands or the system's weather feed with the pavement sensor to confirm the condition, and suits a campus that already supervises its snow operations. No type is the norm across projects. {note}
−### An automatic system shall include a pavement-mounted sensor that measures surface temperature and detects moisture, and an aerial sensor that detects ambient precipitation, so the system runs only when snow or ice is actually present.
+### Where a pavement-mounted sensor is selected, the sensor shall be set in the pavement at the location indicated on [[drawing: the snow melt plan]], flush with the finished surface, in a heated area away from the pavement edge, from drains, and from any place where snow is plowed or stored.
−### Sensors shall be located in a representative heated zone away from artificial heat sources, drainage paths, and snow-storage piles so the reading reflects true pavement conditions.
+### Where an aerial sensor is selected, the sensor shall be mounted where it is exposed to falling precipitation, clear of roof overhangs, exhaust discharges, and tree cover, at the location indicated on [[drawing: the snow melt plan]].
−## Activation Setpoint {note}
+### A sensor that reads the wrong place runs the system for the wrong reason. A pavement sensor at a drain reads wet long after the surface is dry, one at the edge reads the unheated ground, and one under a snow pile reads a storm that ended a week ago. The location is a design decision because the sensor is the only thing the controller knows about the pavement. {note}
−### The system shall activate when the pavement surface temperature is at or below 38°F with precipitation detected; the activation setpoint shall be field-adjustable at the control panel.
+## Setpoints and Sequence {toc}
+### The controller shall start the system when the sensor reports moisture and the pavement or air temperature is at or below the activation temperature indicated in the datasheet, and the activation temperature shall be adjustable at the controller.
+
```datasheet
−label: Pavement activation setpoint
+label: Activation Temperature
type: range
unit: °F
−min: 34
−max: 42
+min: 32
+max: 45
step: 1
default: 38
+constraint: exact
```
−## Post-Precipitation Soak {note}
+### The controller shall continue heating after the sensor reports the surface dry or the precipitation ended for the after-run period indicated in the datasheet, and the period shall be adjustable at the controller.
−### The control sequence shall continue heating for a soak period after precipitation stops so that residual melt water evaporates instead of re-freezing; a system that shuts off immediately leaves wet pavement that ices over.
−
−### The post-precipitation soak time shall be field-adjustable; 30 minutes is the typical starting point for walkways and 60 minutes for ramps.
−
```datasheet
−label: Post-precipitation soak — walkways
+label: After-Run Period
type: range
unit: min
−min: 15
−max: 60
−step: 15
−default: 30
+min: 0
+max: 240
+setpoints: [0, 15, 30, 60, 90, 120, 180, 240]
+constraint: exact
```
+### An activation temperature a few degrees above freezing starts the system while the surface is still above the freeze point so that the first snow lands on a warm pavement, and 38°F is the setting controllers are shipped with and the one nearly every project keeps. The after-run has no norm because it depends on the surface: a sloped drive that drains dries in minutes, and a flat plaza with a sensor at its high point holds meltwater in its low corners for an hour after the sensor reads dry, and that water is the ice the system was built to prevent. {note}
+
+### The idle mode of each system shall be as indicated in the datasheet.
+
```datasheet
−label: Post-precipitation soak — ramps
+label: Idle Mode
+type: radio
+options:
+ - "No idle mode, cold start on each call"
+ - "Idle at a pavement temperature setpoint"
+ - "Idle at a pavement temperature setpoint with outdoor temperature reset"
+```
+
+### A system that starts cold heats the whole mass of the pavement from the outdoor temperature before the surface reaches the melting point, which on a thick slab in deep cold takes hours, during which the snow accumulates; it uses no energy between storms. Idling holds the pavement at a setpoint near freezing between storms so that melting begins within minutes of the call, at an idle energy use that over a season can exceed the energy used for melting. Outdoor reset lowers the idle setpoint as the outdoor temperature rises so that the pavement is held only as warm as the next storm needs, which recovers part of that idle energy. Class III surfaces are usually idled because the response time is the point of the class; Class I surfaces usually are not. No mode is the norm across projects. {note}
+
+### Where an idle mode is selected, the idle pavement temperature setpoint shall be as indicated in the datasheet and shall be adjustable at the controller.
+
+```datasheet
+label: Idle Pavement Temperature Setpoint
type: range
−unit: min
−min: 30
−max: 90
−step: 15
−default: 60
+unit: °F
+min: 20
+max: 38
+step: 1
+constraint: exact
```
−## Idling and Freeze Protection (Hydronic) {note}
+### Where an idle mode is selected, the controller shall hold the idle setpoint by cycling the heating circuits or by resetting the supply temperature of a hydronic system, and shall not idle a hydronic system by stopping the circulating pump while the plant remains on.
−### The control sequence shall distinguish a snow-melt mode from a freeze-protection (idling) mode and shall define the setpoints and outdoor-reset strategy for each, so the glycol loop does not freeze when the system is off in deep cold.
+### The controller shall stop heating when the pavement sensor reads a high limit adjustable between 40°F and 60°F, and shall restart when the reading falls below the limit, so that the pavement is not heated beyond the melting condition during a storm.
−### A freeze-protection mode shall maintain a minimum slab or fluid temperature during extreme cold even when no precipitation is detected, where the design relies on idling to avoid a cold-start of a large fluid volume.
+### The controller shall be furnished with the features indicated in the datasheet.
```datasheet
−label: Operating modes provided
+label: Controller Features
type: checkbox
options:
− - Automatic snow-melt on precipitation
− - Idling / freeze-protection mode
− - Manual override (timed run)
+ - "Manual override with a timed run"
+ - "Remote start input from the building automation system"
+ - "Status and alarm contacts to the building automation system"
+ - "Networked interface to the building automation system"
+ - "Ground-fault trip alarm contact"
+ - "Sensor failure alarm with fail-safe operation"
+ - "Run-time and energy logging"
default:
− - Automatic snow-melt on precipitation
− - Manual override (timed run)
+ - "Manual override with a timed run"
+ - "Status and alarm contacts to the building automation system"
+ - "Sensor failure alarm with fail-safe operation"
+constraint: all_of
```
−# Slab Insulation {toc}
+### Where a sensor failure alarm is selected, the controller shall respond to a failed sensor by the fail-safe operation indicated in the datasheet.
−## Under-slab and perimeter insulation is the single most common value-engineering deletion in snow melt design; without it, heat is lost downward, the surface cannot reach design output, and operating cost rises sharply. {note}
+```datasheet
+label: Sensor Failure Response
+type: radio
+options:
+ - "Run on the remaining sensor or the air temperature alone"
+ - "Stop and alarm"
+```
−## Slab edge (perimeter) insulation shall be provided at not less than R-10 (≈2 in extruded polystyrene), extending down the slab edge to a depth of at least 24 in.
+### The points the controller exposes to the building automation system shall be integrated under [[sync/building-automation-system]], and the controller shall be furnished with the interface that standard selects for the project.
−## Under-slab insulation shall be provided at not less than R-5 where the heated slab is on grade.
+### For a hydronic system, the controller shall interlock with the plant under [[sync/boilers]] and [[sync/hvac-pumps]] so that the circulating pump runs whenever heat is called and the plant delivers the design supply temperature on a call from the snow melt controller.
+## Control Panel Enclosure {toc}
+
+### The controller enclosure shall be rated under NEMA 250 as indicated in the datasheet.
+
```datasheet
−label: Slab edge insulation
+label: Controller Enclosure Rating
+type: select
+options:
+ - "NEMA Type 1"
+ - "NEMA Type 3R"
+ - "NEMA Type 4"
+ - "NEMA Type 4X"
+ - "NEMA Type 12"
+```
+
+### The controller of a hydronic system usually sits in the mechanical room beside the plant, and the controller of an electric system is as often mounted outdoors near the junction boxes as it is in the electrical room, so no rating is the norm across projects. Type 1 is the indoor dry-location enclosure; Type 3R sheds rain and is the outdoor minimum; Type 4 resists hose-directed water for a location that is washed down; Type 4X adds corrosion resistance for a location exposed to deicing salt spray; Type 12 excludes dust and dripping oil in an industrial interior. {note}
+
+### Controllers and ground-fault protection equipment installed outdoors shall be rated NEMA Type 3R or better.
+
+### Controllers installed where deicing salt spray or a washdown reaches them shall be rated NEMA Type 4X.
+
+# Pavement Assembly and Embedment {toc}
+
+## Insulation Beneath the Heated Pavement {toc}
+
+### Insulation beneath the heated pavement shall have the thermal resistance indicated in the datasheet.
+
+```datasheet
+label: Insulation Thermal Resistance Beneath the Pavement
type: range
−unit: R-value
−min: 10
+unit: 'h·ft²·°F/Btu'
+min: 0
max: 20
−step: 1
−default: 10
+setpoints: [0, 5, 7.5, 10, 15, 20]
+constraint: min
```
+### Heat that leaves the bottom of a heated pavement warms the ground, and without insulation that loss is a large share of the installed output in the first hours of a call and a smaller but continuous share of an idled system. An insulation board under the pavement cuts the back loss and shortens the response time, and it costs the board, the labor, and a pavement section that is deeper by the board thickness, and it has to carry the pavement loads without crushing. A value of zero is a real selection on a Class I surface that melts after the storm, where the response time does not matter and the ground beneath acts as a heat store that returns part of the loss. No value is the norm across projects. {note}
+
+### Where insulation is selected, the insulation board shall be polystyrene conforming to ASTM C578 of the type indicated in the datasheet.
+
```datasheet
−label: Under-slab insulation (on grade)
+label: Insulation Board Type
+type: select
+options:
+ - "ASTM C578 Type X, 15 psi"
+ - "ASTM C578 Type IV, 25 psi"
+ - "ASTM C578 Type VI, 40 psi"
+ - "ASTM C578 Type VII, 60 psi"
+ - "ASTM C578 Type V, 100 psi"
+derived: "the design loading of the pavement section on the civil paving plans"
+default: derived
+```
+
+### Edge insulation at the heated pavement shall be as indicated in the datasheet.
+
+```datasheet
+label: Edge Insulation
+type: radio
+options:
+ - "None"
+ - "Vertical board of the same type and thermal resistance as the insulation beneath the pavement, at every edge not abutting a heated area"
+```
+
+### An exposed pavement edge, a curb, or a building wall draws heat sideways out of the heated panel and shows as a strip along the edge that melts last. Edge insulation stops that where the edge abuts unheated ground or an unheated slab, and it is omitted where the edge abuts another heated area or where the layout places the first tube or cable run close enough to the edge to carry the loss. {note}
+
+### Insulation shall be placed on the prepared base, with the joints between boards butted tight, and the embedded elements shall be secured above it on the reinforcement, the rails, or the mesh and not pinned through it.
+
+## Embedment Depth and Attachment {toc}
+
+### The depth of hydronic tubing below the finished surface, measured to the top of the tube, shall be as indicated in the datasheet.
+
+```datasheet
+label: Hydronic Tubing Depth Below the Finished Surface
type: range
−unit: R-value
−min: 5
−max: 15
−step: 1
−default: 5
+unit: in
+min: 1.5
+max: 4
+step: 0.5
+constraint: exact
```
−# Slab Coordination {toc}
+### The depth of electric heating elements below the finished surface, measured to the top of the element, shall be as indicated in the datasheet, and shall be not less than the cover the element's listing requires for the pavement material.
−## Concrete Cover {note}
+```datasheet
+label: Electric Heating Element Depth Below the Finished Surface
+type: range
+unit: in
+min: 1.5
+max: 4
+step: 0.5
+constraint: exact
+```
−### Hydronic tubing shall have at least 2 in of concrete cover over the top of the tube; less than 2 in of cover at tubing locations risks cracking under load.
+### Depth trades response against protection. An element close to the surface heats the surface quickly at a low supply temperature or watt density and sits within reach of a contraction joint saw cut and of the surface loads; an element set deeper is protected by the pavement above it and heats the surface slowly, through more mass, at a higher output. The depth is also what the installer has to hold during placement, and a depth the reinforcement does not naturally give is a depth that needs chairs or rails to hold. Neither value has a norm across projects. {note}
−### The minimum cover over embedded elements shall be coordinated with the concrete contractor before placement so that reinforcement, tubing/cable, and finished grade are all reconciled.
+### Embedded elements shall be secured to the reinforcement, to manufacturer-supplied rails or tracks, or to a carrier mesh at intervals not exceeding the manufacturer's published spacing and not exceeding 3 ft on straight runs and 1 ft at bends, so that the element holds its position and depth through placement.
−## Expansion and Joints {note}
+### Where tubing or cable is secured to reinforcement, the ties shall be of a material and form that does not cut or abrade the element, and wire ties shall be twisted away from the element.
−### Provisions shall be made for thermal movement of the tubing where it crosses slab expansion joints, such as a protective sleeve so the tube is not sheared or abraded at the joint.
+### The pavement contractor shall hold the depth below the finished surface by the method agreed at the pre-placement conference, and shall not raise or lower the element to suit the screed.
−### Tubing and cable shall not pass through a saw-cut control joint; loops shall be laid out so that planned saw cuts fall between runs.
+### The embedded elements shall be laid out so that no contraction joint is sawn over a tube or a cable, and the joint plan under [[sync/concrete-paving]] shall be reconciled with the circuit layout on the shop drawings before layout begins.
−## Penetrations and Transitions {note}
+### Where a tube crosses a pavement expansion or isolation joint, the tube shall pass through a sleeve of a length not less than 12 in centered on the joint, and the tube shall be dropped below the joint depth so that the saw cut of an adjacent contraction joint cannot reach it.
−### Where snow melt tubing or conduit penetrates a fire-rated assembly at a building transition, the penetration shall be firestopped with a system tested to ASTM E814 for the rated assembly.
+### Where tubing or cold leads pass from the pavement into the building, the penetration shall be sleeved, and where it passes through a rated assembly it shall be firestopped under [[sync/firestopping]].
−### Locations, routing, extents, and arrangement of the heated areas, manifolds, and sensors shall be as shown on the drawings. [[drawing: snow melt plan]] {note}
+### Where the pavement is unit pavers, the embedded elements shall be placed in the concrete base beneath the setting bed or in the setting bed itself as the element's listing or the tubing manufacturer's instructions permit, and the pavers shall be set without impact over the elements.
+### Where the pavement is asphalt, the asphalt shall be placed at a temperature not exceeding the rating of the element's listing, the elements shall be covered by hand-placed material before the paver or roller runs over them, and no vibratory compaction shall be used over the elements until the lift above them is in place.
+
# Testing {toc}
−## Hydronic Pressure Test {note}
+## Hydronic Tubing Pressure Test {toc}
−### The embedded hydronic tubing shall be hydrostatically tested before concrete placement; once the tubing is encased there is no repair option, so the pre-pour test is a mandatory hold point.
+### Each hydronic circuit shall be pressure tested from the manifold before the pavement is placed, and the test pressure shall be held through the placement and until the pavement has been finished and is no longer being worked.
−### The hydrostatic test shall be held at 1.5× the design working pressure, not less than 100 psig, for 30 minutes with no pressure drop, and the tubing shall remain pressurized through the concrete placement so that a tube damaged during the pour is revealed immediately.
+### The pressure test shall be made with the medium indicated in the datasheet.
```datasheet
−label: Hydrostatic test pressure
+label: Pressure Test Medium
+type: radio
+options:
+ - "Compressed air or nitrogen"
+ - "Water"
+ - "Glycol solution at the selected concentration"
+```
+
+### Air or nitrogen is the usual medium on a snow melt circuit because the test is made outdoors, often in freezing weather, and a water-filled circuit that is left under test overnight freezes and bursts the tube the test was meant to prove; air shows a leak as a pressure drop and shows its location poorly. Water shows a leak where it is and reads a pressure drop with less sensitivity to temperature, and it suits a test made in warm weather on a circuit that will be drained or charged immediately after. Testing with the glycol solution proves the circuit and charges it in one operation, and it puts the fluid in the tube before the pavement is placed, where a tube damaged during placement spills it into the base. No medium is the norm across projects. {note}
+
+### The test pressure shall be not less than the value indicated in the datasheet and not less than 1.5 times the system working pressure.
+
+```datasheet
+label: Tubing Test Pressure
type: range
unit: psig
−min: 100
+min: 40
max: 150
−step: 5
−default: 100
+setpoints: [40, 50, 60, 75, 80, 100, 125, 150]
+constraint: min
```
+### The test pressure shall be held with no pressure drop, after allowance for temperature change, for not less than the period indicated in the datasheet before the pavement is placed.
+
```datasheet
−label: Hydrostatic hold time
+label: Tubing Test Hold Period Before Placement
type: range
−unit: min
−min: 30
−max: 60
−step: 15
−default: 30
+unit: h
+min: 1
+max: 72
+setpoints: [1, 2, 4, 8, 24, 48, 72]
+constraint: min
```
−## Electric Insulation-Resistance Test {note}
+### A gauge readable from outside the pavement shall remain on each manifold throughout placement, and the pressure shall be read and recorded before placement begins, at intervals not exceeding one hour during placement, and after finishing is complete.
−### Each electric heating circuit shall be insulation-resistance (megohmmeter) tested at 500 V DC before, during, and after concrete placement, with a minimum acceptable reading of 1 MΩ or the manufacturer's stated minimum, whichever is greater.
+### Where the pressure falls during placement, placement over the affected circuit shall stop until the leak is located and the circuit is replaced or the Engineer of Record directs otherwise in writing, and the cost of the delay and the replacement shall be borne by the Contractor.
−### Test readings shall be recorded at each stage so that damage occurring during the pour can be isolated to the placement step.
+### The test record for each circuit shall state the medium, the pressure, the ambient temperature, the start and end times, and each reading taken during placement, and shall be signed by the installer and by the pavement contractor.
+## Electric Insulation Resistance Test {toc}
+
+### Each electric heating circuit shall be tested for insulation resistance between the heating conductors and the sheath or braid, and for element resistance between the conductors, on receipt, after the element is secured and before the pavement is placed, after the pavement is placed, and before the circuit is energized.
+
+### The insulation resistance test voltage shall be as indicated in the datasheet, and shall not exceed the voltage the element manufacturer permits.
+
```datasheet
−label: Insulation-resistance test voltage
−type: radio
−options:
− - 500 V DC (standard; most pavement heating cable)
− - 1000 V DC (manufacturer-stated minimum where higher rating required)
−default: 500 V DC (standard; most pavement heating cable)
+label: Insulation Resistance Test Voltage
+type: range
+unit: V DC
+min: 500
+max: 2500
+setpoints: [500, 1000, 2500]
+constraint: exact
```
+### The insulation resistance of each circuit at each test shall be not less than the value indicated in the datasheet or the element manufacturer's published minimum, whichever is greater.
+
```datasheet
−label: Minimum insulation resistance
+label: Insulation Resistance
type: range
unit: MΩ
min: 1
−max: 100
−step: 1
−default: 1
+max: 1000
+setpoints: [1, 5, 10, 20, 50, 100, 500, 1000]
+default: 20
+constraint: min
```
−## Functional Test {note}
+### The element resistance of each circuit shall be within the tolerance the manufacturer publishes of the design value, and shall not change between successive tests by more than that tolerance.
−### After concrete has cured, the complete system shall be functionally tested to confirm that the control sequence activates the heating elements on a simulated precipitation/cold signal, that all circuits energize or circulate, and that the post-precipitation soak and override functions operate as specified.
+### A reading that falls between the test before placement and the test after it is the signature of a cable damaged by the pavement work, and the stage at which it fell is what tells the Contractor where to look. The test before energizing catches the moisture that entered a connection during the weeks the circuit sat waiting for the pavement to cure. The 20 MΩ default is the minimum IEEE 515.1 sets for a commercial heat tracing circuit, and a manufacturer's higher published minimum governs where one is stated. {note}
+### A circuit whose insulation resistance or element resistance fails at the test before placement shall be replaced before placement, and a circuit that fails at a later test shall be reported to the Engineer of Record, who shall determine whether the circuit is repaired through the pavement, replaced, or abandoned and replaced by an adjacent circuit, with the cost borne by the Contractor.
+
+### The test record for each circuit shall state the test voltage, the readings at each stage, the ambient conditions, and the instrument used, and shall be signed by the electrician.
+
+## Functional Test {toc}
+
+### After the pavement has cured and before the first heating season, the Contractor shall operate each system through a complete cycle, by simulating the sensor conditions at the controller, and shall demonstrate that each circuit flows or draws its rated current, that the activation, after-run, idle, and high limit functions operate at their setpoints, that the manual override runs the system for its timed period, and that the alarm and status contacts report to the building automation system.
+
+### For a hydronic system, the flow in each circuit shall be read at the manifold and balanced to the circuit schedule, and the supply and return temperatures shall be recorded with the system at the design supply temperature.
+
+### For an electric system, the current of each heating circuit shall be measured at the controller and recorded against the rated current, and the ground-fault protection shall be tripped by its test function and reset.
+
+### The functional test shall be witnessed by the Engineer of Record or the commissioning authority where one is engaged, and the record shall be delivered with the closeout submittals.
+
+### Functional performance testing of the system under the commissioning plan, where the project is commissioned, shall be performed under [[sync/commissioning]] after the functional test of this standard is complete.
+
# Installation {toc}
−## The system shall be installed in accordance with the manufacturer's written installation instructions, the approved shop drawings, NEC Article 426 for electric work, and ASHRAE Handbook — HVAC Applications Chapter 51 for design intent.
+## Placement Sequence {toc}
−## Embedded elements shall be secured to the reinforcement or carrier mesh at the spacing shown so they do not float or displace during concrete placement.
+### The embedded elements shall be laid out on the prepared base or on the insulation, secured, tested, photographed, and released by the Engineer of Record before the pavement is placed, and the pavement contractor shall not begin placement over a heated area until that release is given.
−## Protection During Placement {note}
+### Placement over the embedded elements shall be from outside the heated area or from boards or mats that spread the load, and no wheeled equipment, chute, or pump hose shall rest on the elements.
−### The Contractor shall protect embedded tubing and cable from damage during reinforcement placement, traffic, and concrete vibration, and shall not allow vibrators or tools to contact the elements directly. {note}
+### Concrete shall be consolidated over the elements by means that do not contact them, and internal vibrators shall not be inserted at an element.
−### Embedded elements damaged before or during placement shall be repaired only by methods permitted by the manufacturer, or the affected circuit shall be replaced; a damaged circuit shall not be encased.
+### An element damaged during placement shall be exposed, replaced for its full circuit length or repaired by the manufacturer's listed method where the listing permits an embedded repair, retested, and recorded on the record drawings, and the pavement over it shall be replaced to match the adjacent work at the Contractor's cost.
−## Asphalt Substrates {note}
+### The elements are the only part of the pavement that is finished before the pavement is started, and every trade that follows works over them. Naming the release as a hold point and the pavement contractor as the party who does not start without it is what keeps the pour from being the first time the two trades talk. {note}
−### Where electric elements are installed in asphalt, the elements and the placement temperature shall comply with the manufacturer's asphalt listing so that paving heat does not damage the cable insulation.
+## Record Drawings {toc}
+### Before the pavement is placed, the Contractor shall measure the location of every circuit, manifold, junction box, splice, and sensor from fixed site features, and shall record the depth below the finished surface, and those measurements shall be the basis of the record drawings.
+
+### The record drawings shall be delivered as a dimensioned plan of each heated area at a scale that shows the individual runs, and a reduced copy shall be mounted in a frame at the controller.
+
# Delivery, Storage, and Handling {toc}
−## Tubing, cable, and mats shall be delivered in the manufacturer's original packaging and stored protected from sunlight, physical damage, and contamination until installation. {note}
+## Tubing, heating cable, and mats shall be delivered in the manufacturer's packaging, stored off the ground and out of direct sunlight, and protected from crushing, abrasion, and the heat of other site work until they are laid out.
−## Heating cable and mats shall be inspected and insulation-resistance tested on receipt and again immediately before installation, and any element failing the test shall be rejected. {note}
+## Tubing shall not be exposed to sunlight for longer than the manufacturer's published limit before it is covered by the pavement, and tubing that has exceeded the limit shall not be installed.
−## Glycol heat-transfer fluid shall be stored in sealed containers and protected from freezing and contamination before charging the loop.
+## Heating cable and mats shall be tested for insulation resistance on receipt, and an element that fails the test on receipt shall be rejected and returned.
+## Glycol shall be stored in sealed containers protected from freezing and contamination until it is charged under [[sync/hydronic-cleaning-and-flushing]].
+
# Warranty {toc}
−## The manufacturer's standard warranty shall be provided for the embedded tubing or heating cable, the controls, and the heat-transfer fluid.
+## The Contractor shall warrant the embedded elements and their connections against leakage, open circuit, and loss of insulation resistance, and the controller and sensors against failure to operate as specified, for the period indicated in the datasheet, measured from the date of substantial completion.
−## The installer shall warrant the installation, including embedded-element integrity and system operation, for not less than the project's standard warranty period from the date of substantial completion.
−
```datasheet
−label: Installer workmanship warranty period
+label: Snow Melt System Warranty Period
type: range
unit: years
min: 1
−max: 5
−step: 1
−default: 1
+max: 25
+setpoints: [1, 2, 3, 5, 10, 20, 25]
+constraint: min
```
+## Where the contract General Conditions specify a longer warranty period than the datasheet, the longer period shall govern.
+
+## A failure of an embedded element within the warranty period shall be corrected by the Contractor at no cost to the Owner, including locating the failure, removing and replacing the pavement over it to match the adjacent work, the glycol lost, and the restoration of any finish, planting, or site feature disturbed to reach it.
+
+## Where the parties disagree whether a failure arose from the element, its installation, or from later work by others in the pavement, the Engineer of Record shall make the initial determination, and the record drawings shall be the evidence of where the elements were.
+
+## The unassigned cost in a snow melt warranty is the pavement. The tube or the cable is a few dollars a foot, and the slab over it is what a warranty argument is about, which is why the pavement is named here and why the record drawings are named as the evidence. {note}
+
# Spare Parts {toc}
−## Spare control components — pavement and aerial sensors and any consumable control modules — should be provided so a sensor failure does not disable the system during a storm event.
+## The Contractor shall furnish the spare parts indicated in the datasheet, delivered to the Owner with the closeout submittals.
```datasheet
−label: Spare parts furnished
+label: Spare Parts Furnished
type: checkbox
options:
− - Spare pavement sensor
− - Spare aerial (ambient) sensor
− - Glycol make-up supply (hydronic)
− - Spare GFPE module (electric)
+ - "One pavement-mounted sensor of each type installed"
+ - "One aerial sensor of each type installed"
+ - "One ground-fault protection module of each type installed"
+ - "Glycol concentrate for one makeup of the loop"
+ - "One power connection kit and one end seal of each type installed"
default:
− - Spare pavement sensor
− - Spare aerial (ambient) sensor
+ - "One pavement-mounted sensor of each type installed"
+constraint: all_of
```
+
+## A pavement sensor is the part that fails first, by physical damage from a plow blade or by water entry at its lead, and it fails during a storm. A spare on the shelf is what lets the Owner's staff restore the system the same day instead of waiting for a part in the week the pavement is iced. {note}