Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Snow Melt Systems
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### 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.
−### 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. {note}
+### 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.
### PEX tubing shall comply with ASTM F876 and ASTM F877; PE-RT tubing shall comply with ASTM F2623.
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### 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.
−### 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. {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.
# Environmental and Service Conditions {toc}
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### 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}
+### The ASHRAE design climate class shall be specified for the system, based on the snowfall severity and the priority of the surfaces served.
+
```datasheet
label: ASHRAE design climate class
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## Surface Priority {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. {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.
```datasheet
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### 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
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### 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}
+### 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.
+
```datasheet
label: Electric design watt density
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```
−### 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.
−
# System Type {toc}
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## 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}
+## 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.
+
```datasheet
label: Snow melt technology type
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## Heat Source (Hydronic) {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. {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.
```datasheet
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## Tubing {note}
−### 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. {note}
+### 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.
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## Tubing Spacing {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. {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.
```datasheet
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## Circuit Length {note}
−### 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. {note}
+### 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.
### 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.
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## Supply Temperature and Delta-T {note}
−### 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. {note}
+### 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.
```datasheet
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## Heat-Transfer Fluid {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. {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.
−### 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. {note}
+### 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.
```datasheet
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## Make-Up, Air Separation, and Expansion {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. {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.
### 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.
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### 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}
−### 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. {note}
+### 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.
```datasheet
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### 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}
+### 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.
+
```datasheet
label: Electric heating element form factor
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### Adjacent cable runs shall be spaced not less than 25 mm (≈1 in) apart per NEC 426.20(B).
−### 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. {note}
+### 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.
```datasheet
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### 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.
−### 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. {note}
+### 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 {note}
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# 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. {note}
+## 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.
```datasheet
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### 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.
−### 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. {note}
+### 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.
## Activation Setpoint {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. {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.
```datasheet
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## Post-Precipitation Soak {note}
−### 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. {note}
+### 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. {note}
+### The post-precipitation soak time shall be field-adjustable; 30 minutes is the typical starting point for walkways and 60 minutes for ramps.
```datasheet
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## Idling and Freeze Protection (Hydronic) {note}
−### 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. {note}
+### 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.
### 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.
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## 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.
−## Under-slab insulation shall be provided at not less than R-5 where the heated slab is on grade. {note}
+## Under-slab insulation shall be provided at not less than R-5 where the heated slab is on grade.
```datasheet
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## Concrete Cover {note}
−### 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. {note}
+### 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.
### 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.
## Expansion and Joints {note}
−### 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. {note}
+### 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.
### 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.
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## Hydronic Pressure Test {note}
−### 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. {note}
+### 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.
### 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.
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## Electric Insulation-Resistance Test {note}
−### 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. {note}
+### 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.
### Test readings shall be recorded at each stage so that damage occurring during the pour can be isolated to the placement step.
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# Installation {toc}
−## General {note}
+## 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.
−### 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.
+## 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.
−### 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.
−
## Protection During Placement {note}
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## Asphalt Substrates {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. {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.
# Delivery, Storage, and Handling {toc}
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## 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}
−## Glycol heat-transfer fluid shall be stored in sealed containers and protected from freezing and contamination before charging the loop. {note}
+## Glycol heat-transfer fluid shall be stored in sealed containers and protected from freezing and contamination before charging the loop.
# Warranty {toc}
−## The manufacturer's standard warranty shall be provided for the embedded tubing or heating cable, the controls, and the heat-transfer fluid. {note}
+## The manufacturer's standard warranty shall be provided for the embedded tubing or heating cable, the controls, and the heat-transfer fluid.
−## 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. {note}
+## 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
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# 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. {note}
+## 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.
```datasheet
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- Spare aerial (ambient) sensor
```