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Appendix C: Troubleshooting Tips For Reliable Electrical Heat Trace Performance
Troubleshooting Tips
Troubleshooting tips are provided here as a beginning point in correcting start-up issues and clearing out alarm and trip
events.
High Temperature Reading/Alarm
The following summarizes some of the possible causes and solutions for heat tracing high temperature alarms.
Possible Cause
Recommended Solutions
Temperature of product in process
line is above alarm set point or the
expected reading due to events other
than heat tracing—high processing
temperatures, steam-outs, etc.
Let process return to normal condition or adjust alarm set point (if
approved by project engineer) to allow for this processing condition.
High alarm setting programmed or
expected reading did not consider
natural temperature overshoot
associated with the control scheme.
Move control set point down to allow for overshoot or raise the high
temperature alarm set point (if approved by project engineer). It may also
be possible to decrease the control band on the control circuit or adjust the
type of control from on-off to proportional.
Improperly located RTD sensor.
Is the RTD sensor installed next to a heated tank or a steam jacketed pump
that might cause a higher than expected reading? Is the RTD sensor on the
heater itself? Move the RTD sensor to location more representative of the
majority of the piping. Is the sensor location representative for properly
controlling under all flow scenarios? Review location of the RTD(s) with
respect to the known process flow patterns which occur and change as
appropriate.
Wrong insulation size, type, or
thickness on all of the line being
traced.
Measure circumference of insulation, divide by π, and compare to
insulation diameter charts for proper over sizing. Check insulation type and
thickness against design specification. Replace insulation or review system
design for alternate operating possibilities.
Wrong insulation size, type, or
thickness on part of the line being
traced.
The insulation system should be as specified in the design for the entire
circuit being traced. Having a lower heat loss on one part of the circuit and
higher heat loss insulation on the other part of the circuit (perhaps where
the RTD sensor is) will result in the better insulated line being too hot. Redo
the insulation to assure uniformity and consistency.
Damaged RTD temperature sensor.
Disconnect RTD sensor and measure resistance. Compare to resistance
tables for corresponding value of temperature. Compare to pipe or
equipment temperature known by another probe or sensor. If different, the
RTD sensor may need replacement.
Heat tracing over designed in heat
output and or/ due to cable availability
or natural design selections available.
This can result in higher than expected
temperatures due to overshoot
(especially when used with on-off
control mode). This can also occur in
an ambient sensing control modes.
Review design as well as installation instructions. Check heat tracing
for presence of proper current. Since replacing the circuit may not be a
desirable option here, the first approach should be to adjust the control
method which the TraceNet control system has been configured in.
Heat tracing circuits are mis-wired
such that the RTD for circuit 1 is
controlling circuit 2, etc.
Trace and recheck field and panel wiring. Use circuit "turn-on " and
"turn-off" technique or disconnect RTD’s one at a time to see if the proper
RTD failure alarm occurs on the right circuit. Let process return to normal
condition or adjust alarm set point (if approved by project engineer) to
allow for this processing condition.
