78 Publication 2100-IN012C-EN-P - April 2009
Chapter 7 Final Check List Before Energizing
If you have an MCC with arc-resistant design features, if a unit
has been provided with arc resistant baffles over door vents
and fans, these baffles must be fastened securely in place in
order to maintain the arc resistant capabilities of the MCC. Do
not install any type of filter in place of, or in addition to, the
arc resistant baffles.
15. Check all current transformers for proper polarity and ensure
their secondaries are not ‘open’, but are either connected to
their respective devices or ‘shorted.’
16. Recheck that all barriers and parts that may have been
removed during installation have been reinstalled. Refer to
the barrier checklist.
17. Before closing the enclosure and/or individual units, remove all
tools, metal chips, scrap wire and other debris from the MCC
interior.
If there is an accumulation of dust or dirt, clean out the MCC
using a brush, vacuum cleaner or clean, lint-free rag. Do not
use compressed air - it will redistribute contaminates on
other surfaces.
18. Conduct an electrical insulation resistance test to verify the MCC
wiring integrity.
Conduct this test using an insulation resistance tester (megger)
with a potential of 500...1000V. This megger test should be
conducted phase-to-phase, phase-to-ground, and when
applicable, phase-to-neutral on the MCC buswork. The test
should be conducted with all of the switches or circuit breakers
in the open or OFF/O positions. Typical insulation resistance
values are 50 MΩ or greater.
Next, check the field wiring; for example, motor cables and
incoming line cables. Insulation resistance values are affected by
ATTENTION
Current transformer secondaries should not be ‘open’. To
avoid possible injury and electrical shock to personnel,
do not energize a current transformer with its secondary
open.
ATTENTION
When conducting an electrical insulation resistance
test, isolate equipment sensitive to high test voltages,
such as meters, solid state devices, motor winding
heaters, and capacitor units.
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