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5
Appendix B:
Heating Cable Testing
5.3
Continuity (Resistance) Test –
Test 2
Continuity testing is conducted using a standard Digital
Multimeter (DMM) and measures the resistance between
the cold lead tails or between conductors.
Test Criteria
Measure the resistance of the MI heating cable with the
DMM. Most MI heating cable resistances are less than 100
ohms. If the heating cable length has not been altered, the
approximate resistance can be calculated using the formu-
la: Resistance (ohms) = Volts
age can be found on the heating cable identification tag.
ambient air temperature; the calculated value is the resis-
tance at the operating temperature and may be higher
than the measured value.
Test Procedures
Insulation Resistance and Continuity Test
1. De-energize the circuit.
2. Disconnect the temperature controller or thermostat if
3. Disconnect the heating cable from supply wires or ter-
4. Set Megohmmeter test voltage at 0 Vdc or off.
5. Connect the positive (+) lead to the heating cable
6. Connect the negative (–) lead to one of the heating
7. Turn on the Megohmmeter and set the voltage to
8. Turn off the Megohmmeter.
9. Repeat Steps 6 through 8 for other tail/conductor (for
10. Check insulation resistance between the conductors
11. If the Megohmmeter does not self-discharge, discharge
Note: This measured value is the resistance at the
installed.
minal block, if installed.
sheath.
cable tails (or bare conductor).
500 Vdc; apply the voltage for 1 minute. Meter needle
should stop moving. Rapid deflection indicates a
short. Note the insulation resistance value. It should be
greater than 20 MΩ.
2-conductor cable only).
(for 2-conductor cable only). It should be greater than
20 MΩ.
phase connection to ground with a suitable grounding
rod. Disconnect the Megohmmeter.
2
/ Watts. Voltage and watt-
nVent.com | 49
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