Conductor Size for A/C and Refrigeration Equipment -- One Motor
Comments Sought on
VISIT THE EC&M
About this Newsletter
e-newsletter is brought to you from the
publisher of EC&M magazine.
Let you know what could be changing in the Code®.
Help you brush up on your ability to apply the
Test your knowledge of the Code® with a Q&A format.
Provide information on upcoming Code® seminars and
Give you an opportunity to sound off on
We want to make sure we're providing you with the content you need to
better manage your business or enhance your technical skills. E-mail us and let us know
what you want to see in future issues of this e-newsletter. We will do
our best to address your request in a future issue of CodeWatch.
To unsubscribe from this newsletter go to: Unsubscribe|
To subscribe to this newsletter, go to: Subscribe
To get this newsletter in a different format (Text or HTML),
or to change your e-mail address, please visit your profile
page to change your delivery preferences.
issue? Visit the
CodeWatch archive on EC&M's Web site.|
Tell a friend about CodeWatch
Do you know
of someone who'd like to receive CodeWatch? Visit the subscriber site, enter
their e-mail address and spread the wealth!|
To find out
how to advertise in this newsletter, e-mail David Miller or call him at
The designations "National Electrical Code? and ?NEC? refer to the
National Electrical Code®, which is a registered
trademark of the
National Fire Protection Association.
Top 50 NEC Rules
Conductor Size for A/C and Refrigeration Equipment -- One Motor
By Mike Holt
The branch-circuit conductors for air-conditioning and
refrigeration equipment must be sized not smaller than identified on
equipment's nameplate. If the equipment doesn't have a nameplate
specifying the branch-circuit conductors, the conductors must be sized
in accordance with 440.32.
If equipment doesn't have a nameplate identifying the minimum
circuit ampacity, the branch-circuit conductors to a single
motor-compressor must have an ampacity not less than 125% of the
motor-compressor rated load current or the branch-circuit selection
current, whichever is greater.
In accordance with 440.22(A), branch-circuit conductors must have
branch-circuit protection sized between 175% and 225% of the rated load
current to provide protection against short circuits and ground faults.
Let's review an example to better explain these requirements.
What size conductor and protection device is required for an 18A
Step 1. Refer to Table 310.16 to determine the proper size
18A x 1.25 = 22.5A
Therefore, you should use a 12AWG conductor, rated 25A at
Step 2. Refer to Sections 240.6(A) and 440.22(A) to determine the
proper size protection device.
18A x 1.75 = 31.5A
Use the next size down device, rated 30A.
If the 30A protection device isn't capable of carrying the starting
current, then the protection device can be sized up to 225% of the
equipment load current rating.
18A x 2.25 = 40.5A
Use the next size down device, rated 40A.
Editor's note: This information was extracted from Mike
Holt's textbook, Understanding
the National Electrical Code
The Fluke 1735 Power Logger is the ideal electrician or technician's
power meter for conducting energy studies and basic power quality
logging. Set the Power Logger up in seconds with the included flexible
current probes and color display. The power quality meter measures most
electrical power parameters, harmonics, and captures voltage events. www.fluke.com/codewatch
What's Wrong Here?
By Joe Tedesco
Think you know how this installation violates the
Web site to see the answer.
Hint: 7th floor problems.
By Mike Holt
Q. Is GFCI protection required for drinking
fountains in office buildings?
Visit EC&M's Web
site to see the answer.
By Steven Owen
Q. Which of the following methods for connecting
grounding and bonding conductors to equipment is the only one not
permitted by the NEC?
- listed pressure connectors
- exothermic welding process
- green-colored "tapcon" self-tapping concrete anchors drilled
directly through a metal box (no threads engaged), and used to connect
the grounding and bonding conductors
- thread-forming machine screws that engage not less than two
threads in the enclosure
Web site for the answer and explanation.
Walk-thru the basics of an Arc Flash study: Free
One-Line, Arc Flash and PDC Demonstration Videos now available to watch
on your own time-frame, plus Free Demo for download! Streamline the
implementation of your Arc Flash and Electrical Safety Program; what
used to take days, now takes mere seconds! EasyPower delivers the
easiest-to-use, most accurate Windows®-based tools for
analyzing, and monitoring electrical power systems. Visit our website today!
Code News Update
Comments Sought on Proposed
As published in the March issue of NFPA News,
following Tentative Interim Amendment (TIA) has been proposed to the
NFPA 79-2007, Electrical Standard for Industrial
TIA Log No. 901
Submitter: Christine Livingston, Ford Motor Co.
1. Revise 188.8.131.52 to read as follows: "The color ORANGE or
YELLOW shall be used to identify ungrounded conductors that remain
energized when the main supply circuit disconnecting means is in the
position. This color identification shall be strictly reserved for this
2. Revise A.184.108.40.206 by removing the first sentence only.
Substantiation: Add the color yellow as an additional color
option for ungrounded conductors that remain energized when the main
disconnect is in the off position. This option was allowed in the 2002
edition, but was removed from the 2007 publication. Traditionally,
U.S.-based manufacturing has used the yellow color option exclusively
excepted circuits so there is a large installation base using this
Emergency Nature: By removing the yellow option from the list
of colors designated for excepted circuits in the standard, we have
opened the door for use of this color in other applications, creating
confusion and dangerous conditions.
This TIA has been published for public review and comment. Comments
should be filed with the Secretary, Standards Council by May 2, 2008.
You should identify the TIA number when submitting your comments. The
Standards Council will review the technical committees’ ballot
results, the public comments, and any other information that has been
submitted when it considers the issuance of the TIA at its July 22-24,
Cool Electronic Cabinets
EXAIR's low cost Cabinet Coolers stop electronic control downtime due
heat, dirt and moisture. UL Listed Cabinet Coolers produce 20 degree
Fahrenheit air from an ordinary supply of compressed air to cool
electrical controls. Thermostat control minimizes air usage. Maintains
the NEMA 4, 4X (stainless steel) and 12 rating of the enclosure. Web
site offers detailed information, downloadable drawings and PDF
Shows and Events
VISIT THE EC&M e-TRADESHOW
Look for these FREE live conferences, scheduled for THIS MONTH:
Monday, March 24, 10 a.m. EST and PST: "Harmonic
Solutions: Side-by-Side Comparisons" presented by Dan Carnovale,
P.E., Eaton Corp.
Learn about side-by-side comparisons of various harmonic mitigation
technologies, based on testing conducted in a test lab specially
constructed to evaluate all of the major categories of harmonic
solutions for industrial and commercial power systems. See the results
of this testing, including considerations for generator applications,
harmonic resonance, and the application of phase shifting. Energy
savings observations will also be discussed. Video recordings of the
testing will be included.
- "Understanding Electrical Safety and PPE Selection"
- "Implementing an Arc Flash Safety Compliance Program"
- "Preparing an Arc Flash Hazard Study"
Visit the many exhibitors in this virtual tradeshow and take a look
at the On-Demand Theater, where you can view past online conferences
Go to www.ecmweb.com
for information on accessing the EC&M e-Tradeshow and visiting
the On-Demand Library.
It takes more than the UL Mark on a product to satisfy code
requirements. Before your next installation, use UL's Code Compliance
Database to identify the correlation between model codes and UL
Certified products, as well as find manufacturers of certified
Click here today to
find up-to-date UL Listed products at the UL Code Correlation Database.
You are subscribed to this newsletter as #email#
For questions concerning delivery of this newsletter, please contact
Customer Service Department at:
Customer Service Department
A Penton Media publication
US Toll Free: 866-505-7173
Penton | 1166 Avenue of the Americas, 10th Floor | New York, NY 10036
Copyright 2014, Penton. All rights reserved. This article is
protected by United States copyright and other intellectual property
laws and may not be reproduced, rewritten, distributed,
displayed, published or broadcast, directly or indirectly, in any
without the prior written permission of Penton Media, Inc.