ethylene-propylene rubber (EPR) type meeting the requirements of NEMA WC 70.
For shielded cables of rated circuit voltages above 2,000 volts, the
following provisions shall also apply:
a.
XLPE, if used, shall be tree-retardant.
b.
Insulation shall be chemically bonded to conductor shielding.
c. The insulation material and its manufacturing, handling, extrusion
and vulcanizing processes, shall all be subject to strict procedures to
prevent the inclusion of voids, contamination, or other irregularities
on or in the insulation. Insulation material shall be inspected for
voids and contaminants. Inspection methods, and maximum allowable void
and contaminant content shall be in accordance with Section B of AEIC C8
or AEIC CS6, as applicable.
d. Cables with repaired insulation defects discovered during factory
testing, or with splices or insulation joints, are not acceptable
[unless specifically approved].
2.1.4.2
Insulation Thickness
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NOTE: The rated circuit voltage of the insulation
should be specified to be 600 volts for all circuits
operating below 601 volts. Higher rated circuit
voltages may be required by some applications within
this range, such as control circuits containing
large dc solenoids used in older circuit breakers.
Specifications should then be revised to require
1,000- or 2,000-volt insulation in such cases for
multiple- or single-conductor cables, respectively.
Below 48 volts, 600-volt insulation can be used, but
these are special applications that are best
considered in light of the particular circumstances.
For example, many proprietary detection systems and
programmable controller applications typically use
24-volt, low-power circuits, for which lower rated
circuit voltages may be appropriate. These
specifications also cover rated circuit voltages for
systems operating above 600 volts.
The following insulation thickness options from
Table 3-1 of NEMA Standards WC 7 and WC 8 for
single-conductor cables rated 2,000 volts and below
have been specified: (1) Column A thickness, which
does not require a jacket, may be used only for XLPE
insulated cable. NEMA WC 70 allows Type II EPR to
be used with Column A thickness without a jacket;
however, this application should not be permitted
because the Type II EPR insulation is significantly
short of meeting jacket physical requirements. (2)
Column B thickness may be used for either XLPE or
EPR Type I or II insulated cable, but only with a
jacket. For multiple-conductor cables, NEMA WC 70
may be followed.
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The insulation thickness for each conductor shall be based on its rated
SECTION 16120A
Page 12
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