ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Underground phone and coax depth?
by libellis - 02/08/23 08:38 PM
Al Hildenbrand - Minneapolis - obituary
by Bill Addiss - 02/03/23 07:38 PM
Violation?
by renosteinke - 01/27/23 09:52 PM
Does NEC 551.71 (F) apply to dwellings?
by BigB - 01/20/23 10:46 AM
New in the Gallery:
Burger King crown sillyness
Burger King crown sillyness
by wa2ise, December 11
240/208 to a house
240/208 to a house
by wa2ise, October 9
Who's Online Now
0 members (), 22 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Joined: Oct 2002
Posts: 830
S
Member
I have a feeder feeding several Refrigerant motors. The total amperage after applying the 125% for the largest motor comes out to 93.42 amps counting 1 small cooler evaporator that is 120 volts that only pulls 4.73 amps. Is there any reduction of the neutral in a case like this or is it just applied over 200 amps? The rest of the load has no neutral. Thanks..

Stay up to Code with the Latest NEC:


2020 NEC & Related Reference & Study Guides
2020 NEC & Related Reference & Study Guides
Pass Your Exam the FIRST TIME with these Exam Prep Combos:
 

>> Master Electrician Exam Prep     >> JourneyMan Electrician Exam Prep
 

Joined: Oct 2002
Posts: 830
S
Member
Also I have a 3 phase feeder. It's been a long time since I've figured up a 3 phase feeder. Do I divide the total amps by 3?? 93.42 (94 amps)/3= 31.33 ??

Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
Originally Posted by sparkync
Also I have a 3 phase feeder. It's been a long time since I've figured up a 3 phase feeder. Do I divide the total amps by 3?? 93.42 (94 amps)/3= 31.33 ??


Are they single phase motors spread equally across the phases, or are they 3-phase motors?

Joined: Oct 2002
Posts: 830
S
Member
No, there are (3) 3 phase motors, (4) 208/240 volt single phase motors, and (1) 120 volt single phase motor

Joined: Jul 2004
Posts: 9,791
Likes: 14
G
Member
I read 220.61 as saying you could use a #14 for a neutral if your max neutral load is 4 or 5 amps.



Greg Fretwell
Joined: Oct 2002
Posts: 830
S
Member
Greg, if you don't mind me asking, how do you come up with this? thanks. I'm reading from 2011 Code.

Joined: Jul 2004
Posts: 9,791
Likes: 14
G
Member
Quote
220.61 Feeder or Service Neutral Load.
(A) Basic Calculation. The feeder or service neutral load
shall be the maximum unbalance of the load determined by
this article. The maximum unbalanced load shall be the
maximum net calculated load between the neutral conductor
and any one ungrounded conductor.
Exception: For 3-wire, 2-phase or 5-wire, 2-phase systems,
the maximum unbalanced load shall be the maximum
net calculated load between the neutral conductor and any
one ungrounded conductor multiplied by 140 percent


I do not see anything that would make you use more than a #14 if the only unbalanced load is a 4 amp single phase motor.

In the computer room biz we never even brought a neutral beyond the service disconnect because there was never any unbalanced load. (everything was line to line)


Greg Fretwell
Joined: Oct 2002
Posts: 830
S
Member
Thanks Greg. I just wanted to make sure there was not another rule I was missing in the code. I'll figure a bigger neutral just in case in the future they want to add something else that is 120 volts. In fact there is an old outlet attached to one of the units, that the owner said they wouldn't need, but now that I think about it, an outlet is required for "service means" on a roof top. Thanks again

Joined: Jul 2004
Posts: 9,791
Likes: 14
G
Member
If you serve that outlet from another phase, you are still OK with a #14 if it is a 15a circuit. (the way I read it)

I agree as a design issue, running a bigger neutral is probably a good idea.


Greg Fretwell
Joined: Mar 2003
Posts: 849
Y
Member
Article 215
215.2 (A) 2
Grounded Conductor.

Page 1 of 2 1 2

Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
 
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
richard
richard
L.I. New York
Posts: 99
Joined: August 2003
Top Posters(30 Days)
triple 2
Popular Topics(Views)
303,310 Are you busy
232,267 Re: Forum
217,023 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5