Choose heat trace cable by the pipe material, diameter, insulation, lowest expected temperature, and available voltage. Then size the cable length and select the power connection, end seal, and electrical protection to suit.
Length alone is not enough. A cable can reach the end of the pipe and still provide too little heat or exceed the circuit's electrical limits.
For the wider winter checklist, including outdoor plumbing and cold-snap preparation, see this guide to preventing frozen pipes.
What Heat Trace Cable Does and Where You Need It
Heat trace cable runs against the outside of a water pipe to help keep the water inside from freezing. It is also sold as heat tape for water pipes or pipe heating cable.
The cable adds heat; insulation slows heat loss. Both matter. Insulation alone cannot keep stagnant water above freezing indefinitely when the surrounding temperature stays below freezing. Heat trace also needs power, so an outage can leave the pipe without active protection.
Exposed water lines, service entries, and well supply lines can need active protection. Pipes in unheated spaces may also be vulnerable. The location matters: a cable intended for an outdoor pipe is not automatically suitable indoors, inside a water pipe, or below ground.
Sump discharge lines need separate consideration. Their hoses, drainage conditions, and periods without water may fall outside a supply-pipe cable's permitted applications.
If the line is already frozen, check for leaks or visible damage before attempting to thaw it. For professional equipment options, see this guide to choosing a pipe thawing machine. Heat trace is primarily for preventing freezing; thawing an existing blockage requires a suitable method for the pipe and its condition.
Self-Regulating vs Constant-Wattage Heat Trace
Self-regulating cable changes its heat output along its length as temperatures change. Colder sections produce more heat; warmer sections reduce output. This helps a cable respond to sections of pipe with different exposure.
Constant-wattage cable supplies a nominally fixed heat output while energized. Its control requirements and installation limits depend on the product.
Technology and installation rules are separate decisions. Some self-regulating cables permit overlap, but routing limits still apply. Some parallel-resistance constant-wattage systems can be cut and terminated in the field. The product's instructions determine what is permitted.
Factory-Assembled or Cut-to-Length Cable
A factory-assembled cable comes with its heating section and connections already prepared. Select the correct heating length before buying. Do not shorten a factory assembly unless its instructions expressly permit it.
Bulk cable allows an installer to prepare a suitable length with approved power connections and end seals. It still has a maximum permitted run and circuit load.
This distinction matters with King products: the SRP installation manual prohibits cutting or altering the assembly, even though the cable is self-regulating.
Choosing Watts Per Foot and Voltage
The right output depends on how much heat the protected pipe loses. To read a cable selection chart:
- Choose the chart for the pipe material: metal or plastic.
- Find the pipe diameter and the lowest air temperature the system must handle.
- Match the insulation material and thickness to the chart's conditions.
- Read the required watts per foot and number of cable runs.
- Check maximum cable length and electrical loading separately.
This is how King's bulk SR selection tables are organized. Another cable family may use a different method. If the pipe or conditions fall outside the chart, ask for a system design rather than guessing the next wattage.
Check Pipe Material, Diameter and Insulation
Identify the pipe material and diameter before selecting cable. Metal and plastic pipe can need different outputs and methods of distributing heat. A general plastic-pipe description does not establish suitability for every plastic material.
Inspect the insulation, too. Gaps, wet wrapping and uncovered fittings can leave the installation performing differently from the chart's insulated-pipe design.
Where aluminum tape is required, it can help distribute heat as well as secure the cable. Use the specified tape and arrangement; ordinary electrical tape is not an automatic substitute.
Match Output to the Lowest Expected Temperature
Use the lowest air temperature the system is designed to withstand, rather than an average winter temperature. This is the minimum design temperature used in the selection chart.
King's bulk SR range includes 3, 5, 8 and 10 W/ft pipe ratings, measured at 50Ā°F (10Ā°C). Those numbers identify output under stated conditions, not a universal outdoor temperature limit. Pipe ratings also differ from roof and gutter deicing ratings.
Avoid choosing a higher wattage simply because it sounds safer. The design must suit the pipe, insulation and cable temperature limits. Depending on the system, the answer may be a different output, additional cable runs or a revised insulation arrangement.
Match the Cable to 120V or 240V Power
Choose a cable and connection system that matches the available supply. A 120V plug kit cannot power a 240V cable.
Higher voltage does not automatically reduce the electricity bill. A system drawing 500W uses 0.5 kWh in an hour whether it operates at 120V or 240V. The current differs, but equal power over equal time means equal energy use.
Measure the Route and Check Cold-Start Limits
Measure the pipe route and allow for fittings, supports, branches, and connections. Valves and exposed supports can draw heat away from the pipe, so they may need extra cable. These areas are often called heat sinks. Use the cable's allowances to calculate the total heating length.
Also distinguish a bulk reel from an installed run. A 500-foot reel does not mean all 500 feet can operate as one circuit.
Self-regulating cable can draw more current when cold. The permitted circuit length therefore depends on startup temperature and the electrical arrangement, as well as the cable model. Use the applicable King circuit-design tables, and have the installer confirm the limits for the supplied cable and kit.
Before ordering, gather:
- Pipe material, diameter, and protected length.
- Valves, supports, branches and other fittings.
- Insulation material and thickness.
- Minimum design temperature and installation location.
- Available voltage and power-connection location.
- Exact cable, connection kit, and control requirements.
How to Install Heat Trace Cable on a Water Pipe
Use the instructions supplied with the exact cable and kit, together with your local electrical code. The steps below explain the sequence. King requires a qualified licensed electrical contractor for installation and service of its bulk SR cable and accessories; hardwired connections and circuit requirements also need a qualified electrician.
1. Confirm the Cable Is Approved for the Location
Match the product's permitted applications to the full pipe route, including wet areas, building entries, and concealed sections.
For example, the King SRK00 instructions restrict indoor and concealed routing. A pipe-freeze-protection description does not authorize running the cable through a wall or beneath a floor.
2. Finish and Inspect the Pipework
Complete the pipe installation and required testing first. Check for leaks, rough edges, and other conditions that could damage the cable.
Isolate the electrical supply before installation. Inspect the cable and accessories, then record the required initial electrical tests for later comparison. Do not install or energize damaged cable.
3. Route and Secure the Cable
Follow the cable's straight-run or wrapping layout. For example, King's SR instructions place a straight run on the lower half of the pipe, at roughly the 4 or 8 o'clock position when viewed from the end. When two runs are required, they use both positions.
Keep the cable against the pipe and secure it with the attachment materials listed in its instructions. Route the extra length around valves and supports as designed. Protect the jacket from sharp edges, crushing and tight bends, and never energize cable on the reel.
4. Complete Connections and Fit the Controls
Use power, splice and end-termination kits approved for that cable. Keep cable ends and connection components dry during installation.
Position the sensor so it measures the intended air or pipe temperature. A pipe sensor heated directly by the cable can give a misleading reading. Use the controller's placement instructions; dimensions for another product may not apply.
5. Add the Specified Insulation and Weather Protection
Cover the pipe-and-cable arrangement with the insulation material and thickness used in the design. Carry the coverage around fittings and add the required outer weather protection.
Use insulation permitted for that cable. Foam and fiberglass are not interchangeable simply because they fit around the pipe.
6. Test, Label and Record the Installation
Complete the required electrical and operating checks before relying on the system. Add warning labels and retain the model details, circuit information, and test results.
A light on a plug confirms only what that indicator is designed to show. It does not prove that every section of pipe is adequately protected.
Check the System Before Winter
Look for damaged cable, loose connections, water entry, and missing or wet insulation. Arrange the testing specified for the system, and investigate protective-device trips before resetting them.
Compare new test readings with the installation records. A change can help the technician identify a developing problem before cold weather exposes it.
Heat Trace Cable and Installation Components
Choose a factory assembly for a fixed heating length or bulk cable for a professionally prepared installation. Then match the power connection and controls to the supply voltage. In both cases, select wattage from the pipe's heat-loss requirements.
King Preassembled 120V Heating Cable
The King preassembled 120V heating cable suits a permitted application where a factory heating length fits the route. It avoids preparing bulk-cable power and end terminations on site. Measure both the heating route and the reach to a suitable outlet: the SRP instructions prohibit an extension cord.
King 120V Bulk Cable and SRK08 Connection Kit
Choose King 120V 5 W/ft bulk cable when the selection chart calls for that output and the installation needs cable cut and terminated on site. This arrangement requires professional preparation of the power connection and end seal.
The compatible SRK08 plug-in connection kit includes an end seal. The kit is rated for 120V only and 15A, with 5mA GFCI protection for selected SR cables. Its rating does not remove the need to check cold-start and circuit-length limits.
King 240V Bulk Cable and a Hardwired Connection
Use King 240V 5 W/ft bulk cable where the design calls for that output and a suitable 240V supply is available. This is a separate electrical arrangement from the 120V SRK08 plug kit.
A hardwired arrangement may use the King SRK00 pipe-mount power connection kit. Confirm the required enclosure, supply protection, and complete component list before installation. A connection kit alone is not the whole electrical system.
End Seals and Temperature Controls
The King SRK12 end seal kit is a separate termination option for compatible cable. Check what comes with the selected power kit before ordering an additional seal.
Include compatible temperature controls with a King SR installation. One option is the King PYRO FPC freeze-protection controller. Select the correct voltage version and load capacity, then position its sensor to measure the intended air or pipe temperature. The FPC-02 power box requires indoor wall mounting and installation by a qualified electrician.
How Much Does Heat Trace Cost to Run?
Running cost depends on actual power consumption, operating hours, and the electricity rate:
Energy in kWh = average watts Ć hours Ć· 1,000
Cost = kWh Ć electricity rate
For example, suppose 50 feet of cable averages 5 W/ft while energized:
- Average load: 50 Ć 5 = 250W.
- Running continuously for 30 days: 250 Ć 720 Ć· 1,000 = 180 kWh.
- At an illustrative rate of CAD $0.15/kWh: 180 Ć $0.15 = CAD $27.
This is a worked example, not a forecast for a particular King cable. Self-regulating output changes with temperature, so the rated W/ft is not necessarily the average throughout the month.
A suitable controller can switch heating off when it is unnecessary. Self-regulation alone reduces output without necessarily switching the circuit off. Actual savings depend on the installation and operating conditions.
Heat Trace for Roofs and Gutters
Some cable systems are approved for both pipe protection and roof or gutter deicing. Check the exact model; the applications use different ratings, layouts and installation accessories.
A cable attached to a pipe beneath insulation is a different installation from one routed across a roof and through a downspout. Follow the deicing instructions for roof clips, transitions and electrical connections rather than adapting the pipe layout.
With the pipe details and required output in hand, compare heat trace cables and installation accessories to assemble the system.
Frequently Asked Questions
Does Heat Trace Cable Need Insulation Over It?
Yes. The pipe-protection systems discussed here require insulation as part of the design. Use the permitted material and thickness for the pipe and lowest expected temperature, with weather protection where required.
Can Self-Regulating Heat Trace Overlap Itself?
Only when the product's instructions allow it. King SR permits overlap; other cables may have different restrictions. Damaged cable must not be energized.
How Much Does Heat Trace Cost to Run?
Multiply actual average watts by operating hours, divide by 1,000, then multiply by your electricity rate. Temperature and controls affect self-regulating cable consumption.
Do I Need a GFCI for Heat Trace?
Use the ground-fault protection specified for the cable system and local electrical requirements. Personnel GFCI and equipment protection are different; a qualified electrician should confirm the required arrangement. King's SRK08 kit includes 5mA GFCI protection.