Symptoms
Probable Causes
Correction
Power output appears correct but pipe
temperatures are below design value.
Insulation is wet.
Remove and replace it with dry insulation,
and secure proper weatherproofing.
Insufficient heating cable was used
on valves, supports, and other heat
sinks.
Splice in additional heating cable but do
not go over maximum circuit length.
Thermostat was set incorrectly.
Reset thermostat.
Improper thermal design.
Check with the local or factory
representativefordesignconditions;
modify as recommended.
Power output is zero or appears low.
Low or no input voltage.
Repair electrical supply lines and
equipment.
Circuit is shorter than the design
shows, due to splices or tees not
being connected, or the heating
cable having been severed.
Check routing and length of heating cable
(use “as builts”). Connect splices or tees,
locate and replace the damaged heating
cables, then recheck the power.
Improper connection causing a
high-resistance connection.
Recrimp with the correct procedure.
Tighten set screws on terminal block.
Control thermostat is wired in
normally open position.
Rewire in the normally closed position.
Pipe is at an elevated temperature.
Reduce pipe temperature. Check the pipe
temperature. Verify the power output of
heating cable. See note below for method.
Heating cable has been exposed to
excessive moisture or chemicals.
Replace damaged heating cable. Check
the pipe temperature. Verify the power
output of heating cable. See note below for
method.
Heating cable has been exposed to
excessive temperatures.
Same as above.
Note
: The power output is temperature-sensitive and requires a special procedure to determine its value:
1. Check the pipe temperature under the thermal insulation at several locations.
2. Power the heating cable and allow it to stabilize for 10 minutes, then measure current and voltage at the junction box.
3. Calculate the power (watts/ft) of the heating cable by multiplying the current by the voltage and dividing by the actual
circuit length.
Current (A) x Voltage (Vac)
Length (ft)
Power (watts/ft) =
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