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440.22
Short-Circuit and Ground-Fault Protection Devices for A/C and
Refrigeration Equipment
What's Wrong
Here?
Code Q&A
Code Quiz
Deadline Fast
Approaching
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Top 50 NEC Rules
440.22
Short-Circuit and Ground-Fault Protection Devices for A/C and
Refrigeration Equipment
By Mike Holt
Short-circuit and ground-fault protection for
air-conditioning and refrigeration equipment must be sized no larger
than identified on the equipment's nameplate. If the equipment doesn't
have a nameplate specifying the size and type of protection device,
then
the protection device must be sized in accordance with (A) or (B).
(A) One Motor Compressor. The short-circuit and ground-fault
protection device must not be greater than 175% of the motor-compressor
current rating. If the protection device sized at 175% isn't capable of
carrying the starting current of the motor-compressor, the next size
larger protection device can be used, but in no case can it exceed 225%
of the motor-compressor current rating.
(B) Rating for Equipment. Where the equipment incorporates
more than one hermetic refrigerant motor-compressor, or a hermetic
refrigerant motor-compressor and other motors or other loads, the
equipment short-circuit and ground-fault protection must be sized as
follows:
(1) Motor-Compressor Largest Load. The rating of the
branch-circuit short-circuit and ground-fault protective device must
not
be greater than the largest motor-compressor short-circuit ground-fault
protection device, plus the sum of the rated load currents of the other
compressors.
The branch-circuit conductors are sized at 125% of the larger
motor-compressor current, plus the sum of the rated load currents of
the
other compressors [440.33].
Editor's note: This information was extracted from Mike
Holt's
textbook, Understanding
the National Electrical Code
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Code Challenge
What's Wrong Here?
By Joe Tedesco
Think you know how this installation violates the
NEC? Visit EC&M's
Web site to see the answer.
Hint: Damaged equipment in Las Vegas.
Code Q&A
By Mike Holt
Q. A 400A service is made up of two 200A main
breaker panelboards that are nippled together. Can the service
conductors pass through one of the cabinets to supply the other
panelboard?
Visit EC&M's Web
site to see the answer.
Code Quiz
By Steven Owen
Q. What is the allowable ampacity of any one of
the current-carrying 12 AWG THHN insulated conductors installed in a
cellular concrete floor raceway with 29 other current-carrying 12 AWG
THHN conductors and five equipment grounding conductors? Disregard the
terminals in your calculations.
- 30A
- 20A
- 13.5A
- 11.25A
Visit EC&M's
Web site for the answer and explanation.
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Code News Update
Deadline Fast Approaching
The Notice of Intent to Make a Motion closing date for
the next revision of NFPA 70E: Standard for Electrical Safety in the
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