Test Procedures
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1 De-energize the circuit.
2 Disconnect the thermostat or controller if installed.
3 Disconnect bus wires from terminal block, if installed.
4 Set test voltage at 0 Vdc.
5 Connect the negative (–) lead to the heating cable
metallic braid.
6 Connect the positive (+) lead to both heating cable bus
wires simultaneously.
7 Turn on the megohmmeter and set the voltage to
500 Vdc; apply the voltage for 1 minute. The meter
needle should stop moving. Rapid deflection indicates
a short. Record the insulation resistance value in the
Inspection Record.
8 Repeat Steps 4–7 at 1000 and 2500 Vdc.
9 Turn off the megohmmeter.
10 If the megohmmeter does not self-discharge,
discharge phase connection to ground with a suitable
grounding rod. Disconnect the megohmmeter.
11 Repeat this test between braid and pipe.
12 Reconnect bus wires to terminal block.
13 Reconnect the thermostat.
Important: System checkout and regular
maintenance procedures require that insulation
resistance testing be performed from the distribution
panel unless a control and monitoring system is in use.
If no control system is being used, remove both power
feed wires from the breaker and proceed as if testing
heating cable bus wires. If a control and monitoring
system is being used, remove the control equipment
from the circuit and conduct the test directly from the
heating cable.
WARNING:
Fire hazard in hazardous locations.
The insulation resistance test can produce sparks.
Be sure there are no flammable vapors in the area
before performing this test.