48
Self-regulating or power limiting heater
may be operating in its cold start regime.
When reading current on one of these
type heaters, it is necessary to read
the current at steady state. One
may have to wait as long as 5
minutes for heater steady state
values. After five minutes the current
value will continue to drop as the
pipe or equipment begins to warm.
Heater circuit may be longer than
anticipated in the design stage.
Verify installed length (if possible)
and if different review design. If
length is different but performance-
wise the “as built” design is
acceptable, initiate “as built” drawing
change and change controller high
current setting.
Wrong heater wattage or heater resistance
may be installed.
Check heater set tags or markings on
heater cable against installation
drawings. As an additional check,
disconnect heater from power and
measure DC resistance.
Heat tracing may be powered on wrong
voltage.
Recheck heater supply voltage.
Current sensing circuitry may have
encountered a problem.
Use a different current clamp type
meter which is known to be
accurate and do a comparative
reading. Investigate current
measurement circuitry further. Note
that one should only read heater
currents when the heater is 100% on.
Field heater wiring is improperly labeled
and/or connected such that the heater and
the circuit number are not matched.
Trace out the circuit wiring from the
field back into the panel and
subsequently to the controller.
Wherever possible, turn the circuit
“off” and “on” and watch for an
appropriate response. If this is the
problem, redo the wiring.
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