Heat tracing systems are essential for maintaining the integrity and functionality of pipelines, tanks, and equipment in various industries. However, even though the equipment is designed and manufactured to be robust, problems can still crop up like any electrical system. As such, you must understand how to address some of the typical issues associated with heat tracing systems, determine the root cause, and take appropriate corrective actions. Let us share how you can keep your heat tracing system running smoothly.

Learn More: Electric Heat Tracing: Understanding The Proper Installation Procedures

 Common problems plaguing heat trace systems

Issue #1: Circuit breaker trips

Circuit breaker trips usually occur in two ways – the circuit trips after a few seconds of operation, or the circuit trips immediately upon power-up. Observing the trip time can reveal clues that help inform the troubleshooting process. If it is the latter, the problem may stem from the heat tracing cable, the power connection, or the power wiring.

We always recommend performing a megger check, which tests the insulation resistance of both the cable and power wires to isolate potential faults to ground, when troubleshooting the system. Firstly, isolate the heat tracing cable from the power wiring in the cable power connection box before testing the heat tracing cable between the buss wire and braid. This check should help ensure that the insulation resistance meets or exceeds the manufacturer’s recommended minimum. 

If the insulation resistance does not meet or exceed the manufacturer’s recommended minimum, here is what to do:

Step 1: Check all end seals, power connections, splices, and tee boxes to ensure that the conductive core material is isolated from the metal grounding braid or other metal parts of the junction box. Perform the necessary repairs and re-run megger checks until the insulation resistance is above the recommended minimum requirement if there is contact. Ensure all connections are dry during the checking of junction boxes and end seals, as the presence of moisture can cause the megger test to fail. 

Step 2: Isolate each piece of heat tracing cable on the circuit and run a megger check on each independently if no metal braiding or parts are in contact with the conductive core and the insulation resistance is still below requirement. Doing so can help identify any damage to the heat tracing cable that is causing the problem. 

Inspect the piping system for signs of damage on the sections that test low. We suggest removing and replacing the section of cables that test low if you cannot identify any obvious signs of damage. Longer sections can be segregated and tested independently to isolate the fault. Once the issue is identified, remove the problematic section and replace it with new heat tracing cables. Subsequently, verify the heat tracing cable is functioning perfectly by conducting a megger test.

Step 3: If the heat tracing cable sections test okay, proceed to conduct another megger check on the power wiring running from the cable junction box back to the heat tracing panel, as the issue could stem from the wiring. Replace the power wiring with a brand-new wire if there is a short. 

Conversely, the problem may lie with the startup current generated by self-regulating heat tracing cables if the circuit trips after a few seconds of operation. Possible causes include:

• The startup temperature is lower than the designated startup temperature
• The circuit length is too long for the size of the breaker;
• The ground fault current trip level is set too low (if it is adjustable);

Check the manufacturer’s maximum circuit length recommendation and the circuit breaker rating for your startup temperature versus the installed length. Usually, the cable circuits must be started at a fixed temperature for freeze protection. If the heat tracing cable is run to its maximum circuit length for a startup temperature of 40°F but the ambient temperature is actually lower, the breaker will experience a nuisance trip until the cable’s conductive core is warm enough to draw acceptable current to the breaker. To resolve this issue, cycle the circuit breaker on and off until the heat tracing cable warms up. 

Conversely, inspect the installed cable length and ensure it complies with the maximum circuit length limits if the breaker sizing and startup temperatures conform the the manufacturer’s recommendation. Divide the circuit into multiple shorter circuits satisfying the run length, breaker size, and startup temperature specifications if it is too long.

If the cause does not lie with the above two issues, inspect the adjustable ground fault current detection and ensure it is set to a minimum of 30 mA. Any setting below this threshold can cause nuisance tripping on longer circuit runs. Additionally, please ensure the setting conforms to local codes and is within safety guidelines.

Issue #2: Circuit temperatures are too low

Circuit temperatures may be too low when:

• A process controller setpoint or heat trace thermostat is not correct;
• A heat trace thermostat is not wired correctly;
• A heat tracing cable is not connected to the power;
• A heat tracing cable is connected to the wrong voltage;
• A temperature sensor is placed incorrectly;
• A temperature sensor is wired incorrectly;
• The amount of cable used is insufficient to offset the heat sinks in the system.

You can take the following steps to determine the root cause of the low temperature:

Step 1: Inspect the process control system and heat trace thermostat to ensure they are set to the desired pipe temperature.

Step 2: Ensure the heat trace thermostat is wired to close upon achieving the setpoint. Additionally, check that the device is wired from the common terminal to the normally closed position for freeze-protection applications.

Step 3: Test the power in the cable end seal and cable power connection box to double-check that the heat tracing cable is connected to power. The voltage reading should be relatively similar for both ends of each circuit. A drop in voltage is expected over a long run of cable; the amount varies according to cable type and manufacturer. So, refer to the documentation for reference. However, at least one of the cable buss wires could be damaged and need replacing if the inspection shows 120 V at the start of the cable run and 0 V at the end.

Step 4: Ensure the heat tracing cable is connected to the correct voltage by checking the voltage and comparing it to the measured values in the design documents. For instance, a 240 V cable powered at 120 V will not maintain the correct pipe temperature. You can make adjustments accordingly to resolve any voltage issues.

Step 5: Ensure ambient sensors are installed away from heat sources, such as steam traps and sunny areas. Instead, they should be located on the coldest, most exposed part of the application. Furthermore, line sensors should be located at least 90 degrees (on the pipe) away from the heat tracing cable so that pipe temperature – not cable-sheath temperature – is measured. These temperature sensors should also be placed at the coldest expected end of the heat tracing line and away from large heat sinks. 

Step 6: Inspect the wiring of the temperature sensors and ensure they adhere to the manufacturer’s instructions. Wiring a three or four-wire system incorrectly can cause your system to turn off at a temperature that should call for heat.

Step 7: Evaluate all large heat sinks, such as pass-throughs in walls, pumps, valves, and other obstacles, to ensure they have adequate heat tracing cable to maintain pipe temperature. Always follow the manufacturer’s recommendations regarding any required extra cable at these heat sinks, pipe shoes, and supports. 

Issue #3: Circuit temperatures are too high

Circuit temperatures may be too high due to:

• Incorrect setpoint on the process controller or thermostat;
• Incorrect location of the temperature sensor;
• Incorrect wiring of the temperature sensor;
• A faulty thermostat

Inspect the heat trace thermostat or process controller setpoint and check that it is set to the desired pipe temperature and that the temperature sensor is installed in the correct location. For process applications, we recommend using independent temperature sensors for each flow path and pipe size, as utilising the same sensor for multiple pipe diameters and flow paths can overheat smaller or low-flow pipes. Temperature sensors also must be wired according to the manufacturer’s instructions to ensure proper operation.

Do not neglect to check the thermostat to ensure it is not subjected to excessive electrical current or heat. These operating conditions can cause the internal switch to close permanently. As a result, the system will call for heat regardless of the thermostat setpoint. Additionally, always inspect the thermostat and replace it if it is faulty.

We hope what we shared covers the basics and can help you understand what your heat tracing service provider should look for when addressing your specific system faults. Remember, heat tracing system servicing should only be carried out by trained and qualified professionals to ensure personnel safety and the protection of equipment. 

For all your heat tracing needs, look no further than Supermec. We carry an extensive selection of heat trace products, including Raychem heat trace termination kits, Raychem heat tape, and glass tape for heat trace. Visit our website today to browse our comprehensive catalogue.