Although the best brands of heat trace cable are extremely durable and can protect homes and businesses for decades, there may still be occasional glitches that cause hiccups in heat cable systems.
One of the most common problems is when a circuit breaker (ground fault protection device) trips. This type of fault occurs when the circuit is overloaded. A circuit breaker that does not trip can lead to short circuits. Short circuits can be dangerous to you and your property.
There are two different ways in which a circuit breaker may trip. The circuit may trip immediately as the system is powered up. Or the circuit may trip after a few seconds of the system operating.
Knowing when the circuit trips is important in properly fixing the problem.
Immediate Circuit Trips
A circuit trip that happens immediately upon power-up of the system is most often due to a short circuit to the ground fault somewhere in the cable system.
Any troubleshooting for this type of circuit trip should include a megger test. A megger test is a method of testing to help verify the condition of electrical insulation. This test will isolate potential faults to the ground by testing the insulation resistance of both the power wires and the cable.
The megger test will also help identify if the insulation resistance is at or above the manufacturer’s recommended minimum. If that minimum is not being met, you will need to take further action by following these three steps:
1. Check to verify that the heat cable’s conductive core material is not in contact with any type of metal in the system.
The conductive core needs to be isolated from all metal parts. This includes the metal grounding braid and the metal parts of the junction box.
To complete this check, you’ll need to inspect all splices, junction boxes, power connections, and end seals for any contact between the conductive core materials and metal components.
Make sure that the end seals and junction boxes are dry as you run through the check. Megger tests can fail if the end seals or junction boxes are wet.
Suppose you find an area where the conductive core is in contact with metal. In that case, you’ll need to make the necessary repairs until the insulation resistance meets or exceeds the manufacturer’s minimum requirement.
2. Conduct Independent Megger Tests
If you conclude that the conductive core is not in contact with any metal parts and the insulation resistance is still below what it should be, some independent megger tests will be necessary.
For these independent tests, you’ll need to isolate each section of heat cable in your system. Then, run tests on each one. Doing so can help identify if there is any specific area of physical damage that may be causing the conductive core to short out.
On any sections of the cable that test low, you’ll want to check the piping systems for any apparent damage. If you don’t see any clear signs of damage, you may want to remove and replace the section(s) that are testing low.
Once you are able to remove and replace the problem area, conduct a megger test on the new section of cable to be sure that it is good.
3. Test the Power Wiring
If each section of heat cable passes its megger test, run a megger test on the power wiring between the heat cable panel and the junction box. If you discover that this wiring has a short, it will be necessary to remove it and replace it with some new wire.
Slightly Delayed Circuit Trips
Circuit trips that occur a few seconds after the system is powered-up typically point to an issue with the start-up current. A few different things may cause a problem with the start-up current.
1. The start-up temperature is lower than it should be.
Often, heat cable circuits need to be started at a specific temperature for freeze protection.
To determine if this is the cause, you’ll need to find out the manufacturer’s maximum circuit length recommendation for your start-up temperature. Then compare this with the actual installed circuit length.
If the ambient temperature is lower than the necessary start-up temperature for the cable, the breaker will experience a nuisance trip until the cable is warm enough to perform correctly.
You can temporarily solve this by turning the circuit breaker on and off until the heat cable warms up. But, you’ll need to look into a permanent solution. This leads us to our next possible cause.
2. The length of the circuit is too long for the size of the breaker.
Suppose the start-up temperature, along with the breaker sizing, matches up with the manufacturer’s recommendations. In that case, your next step is to check that the cable length you have installed is within the maximum circuit length limits.
If the circuit length exceeds the maximum length for the start-up temperature and breaker size, as recommended by the manufacturer, the circuit length will need to be shortened.
The circuit length can be shortened by dividing the circuit section to create two or more circuits that comply with the manufacturer’s recommended length, start-up temperature, and breaker size.
3. The third possibility is that the trip level for the ground fault may be set too low.
The panel for the heat cable may have adjustable ground-fault-current detection that needs to be set to a specific minimum. If the settings are below the specified threshold, you may experience nuisance tripping on longer sections of circuits. If adjustments need to be made for the trip level, make sure that the settings are within the safety guideline for the specific home or property and verify that the settings align with local codes. Whether your heat cable system is used in pipes or for your roof, it’s important to keep it running correctly to avoid ice dams, frozen pipes, etc. If the obvious problems aren’t fixing your ground fault issues, make sure to call in a licensed professional who has experience with heat trace tape/cable and electrical work to help you get your system operating again.