ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Upgrade the old panel
by sparky. 08/20/18 07:26 AM
IRC M1307.3
by gfretwell. 08/18/18 09:08 AM
Light Pole Grounding
by Mosfet74. 08/18/18 08:42 AM
Calling all Non-US members!! (Non-US only)
by Bill Addiss. 08/13/18 05:52 PM
depth of duckbank
by ghost307. 08/12/18 09:26 PM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 6 guests, and 20 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
400 amp 3 phase 120/240 question. #191899
01/17/10 09:10 PM
01/17/10 09:10 PM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
According to 310.15(B)(6), I can feed a 120/240 single phase service with 400 MCM copper. Am I correct that for a 4 wire, 3 phase, 120/240 service that I have to derated per 310.15(B)(2)(a)? If so, I would need 500 MCM, correct? Thanks, Merlin

2017 / 2014 NEC & Related Books and Study Guides
Re: 400 amp 3 phase 120/240 question. [Re: Merlin] #191900
01/17/10 09:26 PM
01/17/10 09:26 PM
S
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,335
Alaska
310.15(B)(6) is for single phase dwelling units service and feeders. Since that you are bringing in a 3 phase service, you can not derate. If you were to then run single phase feeders to like apartment units, those could be derated. Otherwise no derating is allowed.


"Live Awesome!" - Kevin Carosa
Re: 400 amp 3 phase 120/240 question. [Re: sparkyinak] #191901
01/17/10 09:33 PM
01/17/10 09:33 PM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
Thanks Sparky. So if that is the case, then I have to run 500 MCM conductors then. Correct?

Re: 400 amp 3 phase 120/240 question. [Re: Merlin] #191902
01/17/10 09:51 PM
01/17/10 09:51 PM
S
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,335
Alaska
yep


"Live Awesome!" - Kevin Carosa
Re: 400 amp 3 phase 120/240 question. [Re: sparkyinak] #191903
01/17/10 10:03 PM
01/17/10 10:03 PM
S
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,335
Alaska
I stand corrected, yes as far as your original yes. The service wires by code are only required to be big enough to the load caulated in Article 220. However if you are building something off of an engineer's drawing, you need to use was was spec'ed of do a RFI with the designer of record. There may be also local ordinaces. I typically size my feeders based on my main breaker size. This way if the loads increase on the future, the customer will not have to pay twice.


"Live Awesome!" - Kevin Carosa
Re: 400 amp 3 phase 120/240 question. [Re: sparkyinak] #191904
01/17/10 10:12 PM
01/17/10 10:12 PM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
Am I allowed to size according to breaker size at 80%? Therefore allowing me to use 350 MCM. Or would I have to use 100% rating? Thats how I read the code one minute, but the next I'm second guessing myself!

Re: 400 amp 3 phase 120/240 question. [Re: Merlin] #191906
01/17/10 10:49 PM
01/17/10 10:49 PM
F
frenchelectrican  Offline
Member
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
you can run at 100% however if you going to make single phase feeder network you can not reduce the neutal conductor at all espcally feeded from 3 supply.

Merci,Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
BEAMEUP
BEAMEUP
WA
Posts: 27
Joined: December 2004
Show All Member Profiles 
Top Posters(30 Days)
BigB 3
Popular Topics(Views)
248,650 Are you busy
186,388 Re: Forum
175,876 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.023s Queries: 15 (0.004s) Memory: 0.9846 MB (Peak: 1.1403 MB) Zlib enabled. Server Time: 2018-08-20 18:27:51 UTC