3
Heating Cable Repair
34 | nVent.com
nVent.com | 35
6 in.
Figure 44: Remove polymer jacket
Check the insulation resistance (IR) of the cable at this
point using a 500 volt Megohmmeter (see Appendix B
for details on testing). This test checks for the presence
of moisture in the magnesium oxide insulation. A
value greater than 20 MΩ should be attained before
proceeding. If the IR is lower, remove the moisture
from the cable by following the
drying out
procedure in
Appendix D. Repeat IR test.
Verify continuity of conductors using a multimeter or
ohmmeter.
Note: If the insulation resistance (IR) for a
polymer jacketed cable is still low after drying out
the cable (see Appendix D), it will be necessary
to remove a a longer length of the polymer jacket
and begin drying out the cable further back from
the end.
Figure 45: Check insulation resistance
Using a vernier caliper (or micrometer), measure
the outside diameter of the heated section (not
including polymer jacket) and select the stainless
steel end cap and plug for Alloy 825 sheath cables
or the brass end cap and plug for copper sheath
cables from Table 7.