1 Scope
NOTE This standard governs the design basis, products, controls, testing, and installation of electrical resistance trace heating applied to piping, valves, vessels, and tanks. (1.1)
NOTE Electric heat tracing supplies heat to a pipe or vessel to replace heat lost through its insulation, holding the contents at or above a target temperature when the surrounding ambient would otherwise let them cool or freeze. (1.2)
NOTE The three governing applications -- freeze protection, process temperature maintenance, and roof and gutter de-icing -- each impose different output, control, and temperature-class requirements, and the selected application drives nearly every other decision in this standard. (1.3)
NOTE Trace heating output is meaningless without the matching insulation system; the cable wattage, the insulation material, and the insulation thickness are a single coupled design and shall be specified and verified together. (1.4)
1.4.1The Contractor shall furnish and install a complete trace heating system including heating cable, power connection kits, splice and tee kits, end seals, controls, ground-fault equipment protection, and identification labeling.
1.4.2All heating cable, accessories, and controls within a single circuit shall be products of one manufacturer's listed system.
1.4.3Pipe insulation, jacketing, and weather barrier required over traced piping are specified in Mechanical Insulation and are coordinated with, but not furnished under, this standard. 2 Referenced Standards
NOTE The publications listed below are referenced in this standard; the edition in force is the one adopted by the authority having jurisdiction unless a specific edition is stated. (2.1)
| Standard |
Title |
| IEEE 515 |
Standard for the Testing, Design, Installation, and Maintenance of Electrical Resistance Trace Heating for Industrial Applications |
| IEEE 515.1 |
Standard for the Testing, Design, Installation, and Maintenance of Electrical Resistance Trace Heating for Commercial Applications |
| NFPA 70 (Article 427) |
National Electrical Code — Fixed Electric Heating Equipment for Pipelines and Vessels |
| NFPA 70 (Articles 500–516) |
National Electrical Code — Hazardous (Classified) Locations |
| NFPA 70E |
Standard for Electrical Safety in the Workplace |
| UL 515 |
Standard for Electrical Resistance Trace Heating for Commercial Applications |
| UL 515A |
Outline of Investigation for Electrical Resistance Trace Heating and Associated Controls for Use in Sprinkler and Standpipe Systems |
| IEC/IEEE 60079-30-1 |
Explosive Atmospheres — Electrical Resistance Trace Heating — Part 1: General and Testing Requirements |
| IEC 60079-30-2 |
Explosive Atmospheres — Electrical Resistance Trace Heating — Part 2: Application Guide |
| ASHRAE 90.1 |
Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings |
3 Definitions
NOTE The following terms are used throughout this standard: (3.1)
- Self-regulating cable is a parallel heating cable whose conductive polymer core increases its resistance as it warms, so output falls automatically as the pipe heats and rises as it cools, making the cable inherently fail-safe against overheating and allowing it to be overlapped without burnout.
- Constant-wattage (zone) cable is a parallel heating cable that delivers a fixed output per unit length largely independent of temperature, suiting long uniform runs but offering no self-limiting protection.
- Series-resistance cable is a single heating conductor energized as one long circuit, used on large industrial runs where the circuit length is fixed by design.
- Mineral-insulated (MI) cable is a metal-sheathed cable with magnesium-oxide insulation rated to the highest sheath temperatures, factory-terminated to length, and not field-cuttable.
- Maintain temperature is the target temperature the system holds at the pipe or fluid under the minimum design ambient.
- T-class (temperature class, T1 through T6) is the maximum sheath or surface temperature a heater may reach, used to confirm it cannot ignite a surrounding explosive atmosphere.
- Ground-fault equipment protection (GFEP) is a residual-current trip function, typically set at 30 mA, that de-energizes a circuit on insulation breakdown to protect equipment, distinct from the 5 mA ground-fault protection intended for personnel.
4 Submittals
NOTE Action submittals establish that the proposed system meets the design basis before fabrication and ordering. (4.1)
4.1.1The Contractor shall submit the following action submittals for review:
- Product data for heating cable, power connection, splice, tee, and end-seal kits, controls, and GFEP devices
- Heat-loss calculations and cable output selection for each circuit, referencing pipe size, maintain temperature, minimum ambient, and insulation system
- Circuit schedule listing each circuit's cable type, output, voltage, length, breaker size, and control device
- Maximum circuit length and cold-start inrush data with the proposed breaker trip curve
- T-class and area-classification listing documentation for every circuit in a classified location
- Shop drawings showing cable routing, power and end-of-circuit locations, splice and tee locations, and control sensor locations
- Wiring diagrams for control panels, GFEP devices, and monitoring interfaces
☑ Product data -- cable, kits, controls, GFEP
☑ Heat-loss and cable output calculations
☑ Circuit schedule
☐ Maximum circuit length and inrush data
☐ Classified-location listing and T-class documentation
☑ Shop drawings -- routing and component locations
☐ Control and GFEP wiring diagrams
NOTE Informational submittals demonstrate qualifications and listings without being a condition of fabrication. (4.2)
4.2.1The Contractor shall submit the following informational submittals:
- Manufacturer's installation and design qualification of the installing firm
- Product listing certificates (UL, FM, or equivalent NRTL) for each cable and accessory
- Manufacturer's printed installation, splicing, and end-seal instructions
☑ Installer qualification
☑ Product listing certificates
☑ Manufacturer installation instructions
NOTE Closeout submittals document the as-installed system and its commissioning results. (4.3)
4.3.1The Contractor shall submit the following closeout submittals:
- As-built circuit schedule and routing drawings reflecting field changes
- Insulation-resistance (megger) test records for every circuit
- Continuity and GFEP functional test records
- Energy-compliance documentation per ASHRAE 90.1, including control setpoints
- Operation and maintenance manuals and warranty documentation
☑ As-built circuit schedule and drawings
☑ Insulation-resistance test records
☑ Continuity and GFEP functional test records
☐ ASHRAE 90.1 energy-compliance documentation
☑ Operation and maintenance manuals and warranty
5 Quality Assurance
NOTE A trace heating system that is correctly designed but poorly installed fails the same way as an undersized one; qualification of the installer and the products is therefore part of the design basis. (5.1)
5.1.1The heating cable manufacturer shall be a firm regularly engaged in the production of listed trace heating systems.
5.1.2The installing firm shall be trained and qualified by the heating cable manufacturer in the splicing, termination, and testing of the proposed system.
5.1.3Every heating cable and every accessory shall be listed by a nationally recognized testing laboratory for its application and location.
5.1.4Heating cable installed in a hazardous (classified) location shall be listed for the applicable class, division or zone, and gas or dust group of that location.
5.1.5The maximum sheath temperature of any cable in a classified location shall not exceed the temperature class required for that location.
6 Environmental and Service Conditions
NOTE The design ambient is the lowest temperature the system must perform at, not the average winter temperature; sizing to an average leaves circuits short on the coldest nights, which is when they are needed. (6.1)
6.1.1The minimum design ambient temperature shall be the basis for heat-loss calculation and cable output selection.
NOTE The maintain temperature is the lowest temperature the system holds at the pipe under the minimum design ambient. (6.1.2)
6.1.3Freeze protection shall maintain the pipe contents at or above the freeze-protection setpoint under the minimum design ambient.
● Freeze protection
○ Process temperature maintenance
○ Roof and gutter de-icing
6.1.4Wind increases convective heat loss from insulated pipe; exposed outdoor runs shall include a wind-speed allowance in the heat-loss calculation.
6.1.5The maximum exposure temperature is the highest temperature the de-energized cable will see, set by process upsets, steam-out, or solar gain, and it shall not exceed the cable's rated exposure temperature.
7 Area Classification
NOTE Specifying a general-purpose cable in a classified area is a code violation and an ignition hazard; the area classification governs the cable and every accessory in the circuit, not just the controller. (7.1)
7.1.1The area classification of each circuit shall be established from the project hazardous-area drawings.
7.1.2Cable and accessories in an ordinary (unclassified) location shall be listed for general-purpose use.
7.1.3Cable and accessories in a classified location shall be listed to the requirements for explosive atmospheres and marked with the applicable temperature class.
● Ordinary (unclassified)
○ Class I Division 2 / Zone 2
○ Class I Division 1 / Zone 1
○ Class II Division 2 (dust)
○ T1 (450 °C)
○ T2 (300 °C)
● T3 (200 °C)
○ T4 (135 °C)
○ T5 (100 °C)
○ T6 (85 °C)
8 Heating Cable
NOTE The cable technology is the first product decision and it constrains output range, maximum exposure temperature, maximum circuit length, and field workability. (8.1)
NOTE The technologies differ in where they fit: (8.1.1)
- Self-regulating parallel cable is the default for freeze protection and moderate process maintenance because its output falls as the pipe warms, it cannot overheat on overlap, and it tolerates being cut to length in the field.
- Constant-wattage (zone) cable suits long uniform runs where a fixed output per unit length is acceptable, but it offers no self-limiting and shall not be overlapped.
- Mineral-insulated cable is used where sheath temperatures exceed the polymer range or where maximum ruggedness is required, and because it is factory-terminated to length it cannot be field-cut.
8.1.2The Contractor shall furnish the heating cable technology selected for each circuit.
● Self-regulating parallel
○ Constant-wattage (zone) parallel
○ Series-resistance
○ Mineral-insulated (MI)
8.1.3The rated power output shall be selected from the heat-loss calculation for the pipe size, maintain temperature, minimum ambient, and insulation system, and undersizing the output is a critical error that the calculation exists to prevent.
NOTE The supply voltage governs the maximum circuit length and the conductor losses; higher voltage allows longer circuits but raises the cold-start inrush that the breaker must tolerate. (8.1.4)
8.1.5The Contractor shall energize each circuit at the supply voltage shown for that circuit.
○ 120 V 1Φ
○ 208 V 1Φ
● 240 V 1Φ
○ 277 V 1Φ
○ 480 V 1Φ
NOTE The cable jacket shall be selected for the chemical and thermal exposure of its location. (8.1.6)
8.1.7General-purpose runs shall use a polyolefin outer jacket.
8.1.8Runs exposed to chemicals, high temperature, or organic corrosives shall use a fluoropolymer outer jacket.
8.1.9Runs requiring grounding continuity or mechanical protection shall include a metallic braid, and runs subject to impact shall include a metal armor overjacket.
● Polyolefin
○ Fluoropolymer (FEP)
○ UV-stabilized polyolefin (outdoor de-icing)
○ Tinned-copper braid
● Tinned-copper braid with polyolefin overjacket
○ Tinned-copper braid with fluoropolymer overjacket
○ Metal armor overjacket
NOTE A continuous metallic braid is required by NEC Article 427 to provide an equipment grounding path along the cable and to serve as the reference for ground-fault sensing; it shall not be omitted. (8.1.10)
9 Maximum Circuit Length and Overcurrent Protection
NOTE Self-regulating cable draws a large cold-start inrush current at low ambient because the cold core is at its lowest resistance; if the breaker trips on that inrush, the circuit never starts, so the breaker must be coordinated with the inrush, not just the steady-state load. (9.1)
9.1.1The maximum circuit length shall not exceed the manufacturer's published maximum for the selected cable, voltage, and minimum start-up temperature.
9.1.2The branch-circuit breaker shall be sized for the cold-start inrush current and shall use a trip characteristic that tolerates that inrush without nuisance tripping.
○ Standard thermal-magnetic (inverse time)
● High-magnetic / time-delay (Type D equivalent)
9.1.3Each heating circuit shall be supplied from a dedicated branch circuit and shall not share a neutral or overcurrent device with non-tracing loads.
10 Ground-Fault Equipment Protection
NOTE NEC Article 427.22 requires ground-fault equipment protection on each trace heating branch circuit because insulation breakdown in a wet, energized cable is the dominant failure mode and must de-energize the circuit before the fault propagates. (10.1)
NOTE The 30 mA equipment-protection trip level is deliberately higher than the 5 mA personnel-protection level; specifying 5 mA produces constant nuisance trips on long circuits whose distributed capacitance leaks more than 5 mA at energization. (10.1.1)
10.1.2Each heating circuit shall be protected by a listed ground-fault equipment-protection device.
10.1.3The ground-fault equipment-protection trip level shall be set for equipment protection, not personnel protection.
10.1.4A circuit whose distributed leakage approaches the trip level shall be subdivided into shorter circuits rather than raising the trip level above the equipment-protection range.
11 Controls
NOTE The control strategy sets how accurately the system holds temperature and how much energy it wastes; ambient sensing is the simplest and least precise, while electronic sensing of the pipe is the most accurate and most efficient. (11.1)
NOTE The strategies trade precision against cost: (11.1.1)
- Ambient-sensing control energizes the circuit below a set air temperature and suits straightforward freeze protection where the pipe temperature need not be held precisely.
- Line- or pipe-sensing control senses the pipe or fluid temperature directly and suits process maintenance and critical freeze protection.
- Electronic control with an RTD probe gives the most accurate temperature hold, the greatest energy savings, and an interface to the building automation or SCADA system.
11.1.2The Contractor shall furnish the control strategy selected for each circuit or group of circuits.
● Ambient-sensing thermostat
○ Line/pipe-sensing thermostat
○ Electronic controller with RTD sensing
11.1.3A single thermostat cannot correctly control branches with different heat-loss characteristics; each major application or branch shall have independent control and independent ground-fault equipment protection.
11.1.4Control enclosures installed outdoors or in wet locations shall be rated NEMA 4X.
● NEMA 4X
○ NEMA 4
○ NEMA 7 (classified location)
11.1.5The control setpoint shall be field-set to the maintain temperature and recorded on the as-built circuit schedule.
11.1.6The responsibility for furnishing and setting thermostats and controllers shall be assigned in the circuit schedule so that control does not fall between the cable and the controls scopes.
12 Monitoring
NOTE Basic systems annunciate only on a ground-fault trip, which means a cable that has stopped heating for any other reason goes unnoticed until the pipe freezes; current monitoring detects that loss of heat before the failure. (12.1)
12.1.1The level of monitoring shall be selected for the criticality of the traced service.
● GFEP trip indication only
○ Per-circuit current and ground-fault monitoring
○ Per-circuit monitoring with BAS/SCADA interface
12.1.2A heat trace monitoring panel, where provided, shall measure per-circuit current and ground-fault leakage and shall annunciate loss of continuity.
12.1.3Where a building automation or SCADA interface is required, the monitoring panel shall provide digital output for each circuit's alarm state.
13 Components and Accessories
NOTE Accessories are manufacturer-specific; a splice, end seal, or power connection from a different manufacturer voids the cable listing and is a leading source of field failures and requests for information. (13.1)
13.1.1All power connection, splice, tee, and end-seal kits shall be from the same listed system as the heating cable.
NOTE Every heating cable terminus shall be sealed with a factory-listed end seal; an unsealed end admits moisture and is the leading cause of insulation-resistance failure and ground-fault nuisance tripping. (13.1.2)
13.1.3A listed end seal shall be installed at the end of every heating cable run.
13.1.4A listed power connection kit shall be installed at the supply end of each circuit.
13.1.5A listed splice or tee kit shall be installed wherever heating cable sections are joined.
● Listed end-seal kit
○ Lighted end-seal kit
● NEMA 4X
○ NEMA 4
○ NEMA 7 (classified location)
14 Pipe and Material Compatibility
NOTE A high-temperature cable energized at low ambient can drive its surface above the service temperature of a plastic pipe, softening or failing the pipe; the cable surface temperature shall be verified against the pipe rating, not assumed safe. (14.1)
14.1.1The maximum cable surface temperature shall not exceed the service temperature rating of the pipe material it is applied to.
14.1.2High-temperature self-regulating or constant-wattage cable shall not be applied to CPVC, PEX, or other thermoplastic pipe without confirming the cable surface temperature stays within the pipe rating.
● Carbon steel
○ Stainless steel
○ Copper
○ CPVC
○ PEX
15 Roof and Gutter De-Icing
NOTE De-icing cable manages meltwater so it drains instead of refreezing into ice dams at the eave; it is a drainage path, not a way to keep the whole roof clear of snow. (15.1)
15.1.1Roof and gutter de-icing cable shall be listed to IEEE 515.1 and UL 515 for that application.
15.1.2Roof and gutter de-icing cable shall have a UV-stabilized jacket suitable for continuous outdoor exposure.
15.1.3De-icing cable shall be controlled by an automatic ambient- or moisture-sensing control so it operates only during icing conditions, as required for energy compliance.
15.1.4Cable routing in valleys, gutters, downspouts, and at the eave edge shall follow roof de-icing layout. 16 Energy Compliance
NOTE ASHRAE 90.1 treats electric trace heating as an energy use to be minimized; it permits freeze protection only where no cost-effective alternative exists and requires automatic control so cable does not run when it is not needed. (16.1)
16.1.1Every heating circuit shall be controlled automatically; no circuit shall be left energized continuously without temperature or moisture control.
16.1.2Roof and gutter de-icing wattage shall not exceed the limits established by the adopted energy code for that application.
16.1.3Energy-compliance documentation, including the insulation system and control setpoints used for the trace heating design, shall be provided as a closeout submittal.
17 Identification and Labeling
NOTE NEC Article 427.13 requires warning labels because the heating cable is hidden under insulation and is invisible to anyone working on the pipe; without the label requirement in the specification, field crews do not install them and the system fails inspection. (17.1)
17.1.1A caution label identifying the presence of electric heat tracing shall be applied to the pipe insulation jacket at intervals and at every point of access.
17.1.2Each caution label shall identify the circuit voltage and the location of the controlling ground-fault protection panel.
17.1.3The presence of heat tracing shall be marked on the outer insulation jacket so it is visible before the insulation is opened.
18 Testing
NOTE Insulation-resistance (megger) testing finds a cable damaged in handling or installation before it is energized; energizing a damaged circuit destroys the cable and can trip the ground-fault device immediately, so this test is the gate to energization, not an afterthought. (18.1)
18.1.1The Contractor shall perform an insulation-resistance test on each circuit before energization and again after installation of the pipe insulation.
18.1.2Polymer-insulated cable shall be insulation-resistance tested at 2500 Vdc between the heating conductor and the metallic braid.
18.1.3Mineral-insulated cable shall be insulation-resistance tested at the test voltage specified by the cable manufacturer.
18.1.4The measured insulation resistance of each circuit shall meet or exceed the minimum value specified by the manufacturer.
18.1.5A circuit that fails the insulation-resistance test shall not be energized until the fault is located and corrected.
18.1.6The Contractor shall verify continuity of each heating circuit and of the cable braid grounding path.
18.1.7The Contractor shall functionally test each ground-fault equipment-protection device by injecting a test fault and confirming the circuit de-energizes at the set trip level.
18.1.8All test results shall be recorded by circuit and submitted as a closeout deliverable.
19 Installation
NOTE Heat tracing is installed on the bare pipe before the insulation subcontractor closes it in; if the sequence and the overlap at valves and flanges are not explicit in the specification, the trades collide and cable gets crushed or left out at the fittings. (19.1)
19.1.1The installation sequence and the division of responsibility between the cable installer and the insulation subcontractor shall be defined before either trade begins.
19.1.2Heating cable shall be installed only after the pipe pressure test is complete and accepted.
19.1.3Heating cable shall be attached to the pipe with manufacturer-listed fastening tape or cable ties at the intervals given in the manufacturer's instructions.
19.1.4Heating cable shall not be installed in a manner that exceeds its minimum bend radius.
19.1.5Additional cable length shall be applied at valves, flanges, pipe supports, and instruments to replace their added heat loss, in accordance with the manufacturer's heat-sink allowances.
● Single straight run
○ Multiple straight runs
○ Spiral wrap
19.1.6Self-regulating cable may be overlapped on itself at heat sinks; constant-wattage and series-resistance cable shall not be overlapped.
19.1.7The point of power connection, the end-of-circuit location, and the splice and tee locations shall be installed per heat trace circuit layout. 19.1.8Control and sensor probes shall be located on the pipe at the position shown so they sense the controlling temperature rather than a local hot or cold spot, per control sensor locations. 19.1.9No section of pipe insulation shall be installed over a heating circuit that has not passed its pre-insulation insulation-resistance test.
19.1.10The insulation, jacketing, and weather barrier installed over the traced pipe shall comply with Mechanical Insulation and shall maintain a continuous weather seal so the cable stays dry. 20 Delivery, Storage, and Handling
NOTE Heating cable is a polymer-and-metal assembly that is damaged by crushing, sharp bends, and prolonged sunlight; cable damaged before installation fails its insulation-resistance test or fails in service, so it shall be protected from receipt to energization. (20.1)
20.1.1Heating cable shall be delivered on the original reels or in the original packaging with the manufacturer's markings legible.
20.1.2Heating cable and accessories shall be stored indoors, dry, and protected from physical damage and ultraviolet exposure until installation.
20.1.3Cable ends shall be kept sealed against moisture from delivery until the listed end seal or power connection is installed.
20.1.4Damaged cable shall be rejected and shall not be repaired by splicing outside the manufacturer's listed methods.
21 Warranty
21.1The Contractor shall warrant the complete trace heating system against defects in materials and workmanship for the warranty period.
● 1 year
○ 2 years
○ 5 years
21.1.1The heating cable manufacturer's warranty for the cable and accessories shall be assigned to the Owner at closeout.
22 Spare Parts
NOTE Trace heating accessories are manufacturer-specific and not stocked locally, so a future repair without spares means an extended outage on the traced service; a small spare stock keeps the system maintainable. (22.1)
22.1.1The Contractor shall furnish spare power connection, splice, and end-seal kits matching the installed system.
025
Default: 10 percent of installed quantity
22.1.2The Contractor shall furnish spare heating cable of each installed type for future repairs.