Troubleshooting Electric Heat Tracing Systems
The following information is intended to assist in troubleshooting electric heat tracing systems. The
primary objective is to provide an enhanced understanding of the elements of a successful heat tracing
installation. Of these elements, one of the most important is the thermal insulation.
Before calling the heat tracing vendor, make a visual inspection of the installation; perhaps the thermal
insulation is wet, damaged or missing. Also consider the possibility that repairs or maintenance of in-line
or nearby equipment may have resulted in damage to the heat tracing equipment. These are common
causes of tracing problems which are often overlooked. Other possible causes are listed below with their
symptoms and remedies.
If an electric heat tracing circuit is suspected to be damaged, a dielectric insulation resistance (megger)
test should be performed using a 2500 Vdc megohmmeter for polymer-insulated heating cables or 1000
Vdc for MI cable. Periodic testing with accurate records will establish a “normal” range of operation (refer
to the Inspection Report Form on page 3). Dielectric insulation resistance readings which deviate from
the normal range can quickly reveal a damaged circuit.
Please select from the symptoms below:
| Symptom |
Possible Cause |
Remedy |
|
| I. No heat/no current |
A. Loss of power (voltage) |
A. Restore power to tracing circuit (check circuit breaker and
electrical connections). Poorly made terminations can cause EPD-type
breakers to trip unexpectedly |
| |
B. Controller setpoint too low |
B. Adjust setpoint |
| |
C. High temperature limit switch activated |
C. May require manual reset to reenable heat tracing circuit |
| |
D. “Open” series heating circuit |
D. Repair or replace circuit 1 |
| |
E. Controller failure |
E. Repair sensor or controller 2 |
| |
|
|
| Symptom |
Possible Cause |
Remedy |
|
| II. Low system temperature |
A. Controller setpoint too low |
A. Adjust setpoint |
| |
B. Temperature sensor located too close to heating cable or other
heat source; may be accompanied by excessive cycling of control relays/
contacts |
B. Relocate sensor |
| |
C. Insulation material and/or thickness different than designed |
C. Replace insulation; increase insulation thickness (if dry);
consider increasing voltage for higher cable output 3 |
| |
D. Ambient temperature lower than designed |
D. Install higher output heating cable; increase insulation
thickness; raise voltage 3 |
| |
E. Low voltage (check at power connection point) |
E. Adjust voltage to meet design requirements 3 |
| |
|
|
| Symptom |
Possible Cause |
Remedy |
|
| III. Low temperature in sections |
A. Wet, damaged or missing insulation |
A. Repair or replace insulation and jacket |
| |
B. Parallel heating cable; open element or damaged matrix |
B. Repair or replace; splice kits are available from cable
manufacturer |
| |
C. Heat sinks (valves, pumps, pipe supports, etc.) |
C. Insulate heat sinks or increase amount of tracing on heat sinks |
| |
D. Significant changes in elevation along length of the heat-traced
pipe |
D. Consider dividing heating circuit into separate, independently
controlled segments |
| |
|
|
| Symptom |
Possible Cause |
Remedy |
|
| IV. High system temperature |
A. Controller “on” continuously |
A. Adjust setpoint or replace sensor2 |
| |
B. Controller failed with contacts closed |
B. Replace sensor or controller2 |
| |
C. Sensor located on uninsulated pipe or too close to heat sink |
C. Relocate sensor to an area representative of conditions along entire pipe length |
| |
D. Backup heating circuit controller “on” continuously |
D. Adjust setpoint or replace backup controller |
| |
|
|
| Symptom |
Possible Cause |
Remedy |
|
| V. Excessive cycling |
A. Temperature sensor located too
close to heating cable or other heat
source; may be accompanied by
low system temperature |
A. Relocate sensor |
| |
B. Ambient temperature near controller
setpoint |
B. Temporarily alter controller setpoint |
| |
C. Connected voltage too high |
C. Lower voltage |
| |
D. Heating cable output too high
(overdesign) |
D. Install lower output heating cable or
lower voltage |
| |
E. Controller differential too narrow |
E. Widen differential or replace controller
to avoid premature contact
failure |
| |
|
|
| Symptom |
Possible Cause |
Remedy |
|
| VI. Temperature variations
from setpoint along
pipeline |
A. Unanticipated flow patterns or
process operating temperatures |
A. Redistribute heating circuits to accommodate
existing flow patterns;
confirm process conditions |
| |
B. Inconsistent cable installation along
pipeline |
B. Check method of cable installation,
especially at heat sinks |
| |
C. Inconsistent cable performance |
C. Compare calculated watts/foot
[(volts x amps) ÷ length] for the
measured pipe temperature with
designed cable output for the same
temperature; regional damage to
parallel cable can cause partial
failure |
| |
|
|
Notes . . .
1. Flexible, plastic-jacketed heating cables may be field-spliced; MI cables usually require replacement.
2. Mechanical thermostat sensors cannot be repaired or replaced; RTD or thermocouple sensors can be replaced. Some controllers have replaceable
contacts/relays or may require a manual reset if a “trip-off” condition on the heating circuit was detected.
3. The operation of most electric heat tracing cables is dramatically affected by changes in the supply voltage. Before making any changes, consult the
cable manufacturer with information on the alternate voltages available. Otherwise, cable failure and/or an electrical safety hazard may result in
some situations.