34
Insulation Resistance (Megger) Test
The insulation resistance test detects potential damage that
could result in the cable shorting out. A megohmmeter is used
to measure the insulation resistance between the conductive
core and the grounding braid, and the reading is compared
to the allowable minimum resistance reading (See Table 4).
The megohmmeter should be a minimum of 1000 Vdc, but
the use of 2500 Vdc is preferred. If possible, the meter should
be battery-operated, though digital or analog meters can also
be used.
1. De-energize the circuit.
2. Open the cover on the power termination kit.
3. Disconnect the bus wires and braid from the terminals.
4. Set the test voltage to 0 Vdc.
5. Connect the negative lead to the ground braid and the
positive lead to the bus wires.
6. Turn on the megohmmeter and perform insulation resis-
tance test for one minute, until the needle on the meter
stops moving.
7. Check the reading and ensure it is above the allowable
minimum resistance reading.
8. Record the tested value in the log.
9. Turn off the megohmmeter and discharge it with an ap-
propriate grounding rod (if the meter does not self-dis-
charge).
10. Reconnect the wires and close the power termination kit.
For additional information about this test, please watch the
“Heat Trace Megger Testing Procedure” video in the Chro-
malox video library:
https://www.chromalox.com/en/Resources-and-Support/
Technical-Resources/Video-Library/Video-Library
Stabilized Current Test
The stabilized current test determines the cable current at
full voltage. It ensures that the cable power output is correct
for design and that it is stable. To perform this test, a stan-
dard multimeter with an Amp clamp or an all-in-one unit is
required. Ensure the meter has an auto-range up to 100A. If
possible, the meter should be battery-operated, though digi-
tal or analog meters can also be used.
1. De-energize the circuit.
2. Open the cover on the power termination kit.
3. Disconnect the bus wires from the terminals.
4. Clamp the meter onto one bus wire.
5. Energize the circuit.
6. Allow the circuit to run for at least 20 minutes.
7. Take the current reading and record in the log.
8. De-energize the circuit.
9. Disconnect and turn off the meter.
10. Reconnect the bus wires and close the termination kit.
To determine the thermal output, complete the calculation
below:
Thermal output = (Current Reading / Circuit Length) x Voltage
Compare the result to the charted output temperature in the
“Chromalox Design Guide for Heat Tracing Products”.
For additional information about this test, please watch the
“Stabilized Current Test” video in the Chromalox video library:
https://www.chromalox.com/en/Resources-and-Support/
Technical-Resources/Video-Library/Video-Library
End of Current Voltage Test
This test determines the voltage at the end of the line, which
verifies the proper voltage. To perform the test, a standard
multimeter with auto-range up to 600V is required. If pos-
sible, the meter should be battery-operated, though digital or
analog meters can also be used.
1. De-energize the circuit.
2. Remove the end cap.
3. Expose the bus wires.
4. Connect one test lead to each bus wire and energize the
circuit
5. Read the resulting voltage and compare it to the desired
value.
6. Record the reading in the test log.
7. De-energize the circuit.
8. Disconnect and turn off the multimeter.
9. Reconnect the end cap.
For additional information about this test, please watch the
“End of Current Voltage Test” video in the Chromalox video
library:
https://www.chromalox.com/en/Resources-and-Support/
Technical-Resources/Video-Library/Video-Library
Maintenance
Recommended maintenance for Chromalox heat tracing sys-
tems consists of performing the steps involved in the com-
mission testing on a regular basis. For those systems con-
trolled by line sensing thermostats, Chromalox recommends
checking the system at least twice per year. Systems con-
trolled by an ambient-sensing thermostat should be checked
when the season requiring their use is approaching.
Repair or replace all damaged heater cable, connections,
thermal insulation and weatherproofing using only Chromal-
ox connections and methods before testing the system.
Record all repairs made and measurements taken in the in-
stallation and maintenance log.
To Next Page
Loading...
Need help?
General