ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
twh 3
Recent Posts
Ceiling fan distance from outdoor hot tub
by gfretwell. 11/16/17 02:18 AM
diazed fuses
by Texas_Ranger. 11/13/17 03:02 PM
Theft deterrent alarm
by gfretwell. 11/12/17 01:39 PM
EEPROM errors on XC7Z010-2CLG225I chip
by twh. 11/07/17 05:45 PM
Blackened bare copper in panel ?
by twh. 11/04/17 11:16 AM
New in the Gallery:
Gallery Test
Popular Topics(Views)
242,543 Are you busy
178,715 Re: Forum
169,989 Need opinion
Who's Online Now
0 registered members (), 9 guests, and 9 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#218826 - 10/28/17 10:51 AM 1600 amp 480/277v 4 wire Y service  
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 834
Michigan
Four Four inch from utility Transformer to CT Cabinet then to MCC. (XHHW).

three 600MCM & one 350 MCM each Conduit .

600 at 75C 420 amps x 4 = 1680 amp.

Very low Neutral load mostly 480 volt loads.

Using 310.15 (5) so no derating.

Engineer wants to use six six inch with four 400 mcm in each conduit.

I think conduit way over sized!


2017 / 2014 NEC & Related Books and Study Guides

#218827 - 10/28/17 11:05 AM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
Maybe he got hollered at for spec'ing to small a conduit before.
How long and how many bends?
Sometime what "fits" is not what you want to pull.
Your ampacity looks OK to me


Greg Fretwell

#218828 - 10/28/17 12:17 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 834
Michigan
transformer to ct cabinet 35 ft .
ct cabinet to mcc max 10 ft.
you figure.????


#218829 - 10/28/17 08:05 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
It might be interesting to ask the engineer what his thinking is on this project. He may have just decided nobody ever got in trouble going too big ... as long as it isn't his money. wink


Greg Fretwell

#218830 - 10/28/17 09:28 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
twh  Offline
Member
Joined: Mar 2004
Posts: 922
Regina, Sask.
Maybe he will be paid a percentage of the job.


#218832 - 10/29/17 11:53 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,328
Alaska
Space for future expansion? Cost pennies now versus dollars later


"Live Awesome!" - Kevin Carosa

#218833 - 10/30/17 10:33 AM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 834
Michigan
Transformer 1000 KVA ( 1208 Amps ) Switch Gears 1600 amps .

Utility Co. Never sizes as per our calculations. I called them on it.

There reply no problem.


#218835 - 11/02/17 02:52 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
ghost307  Offline
Member
Joined: May 2005
Posts: 917
Chicago Illinois USA
That happens all the time.
Utilities always go much further into their overload ratings than we do.
I remember seeing (3) 2,500A Switchboards fed from a vault that (when I looked inside) only had a single transformer in it.


Ghost307

#218836 - 11/02/17 10:21 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
That is also pretty common in residential. They put a 50 KVA pole pig on 3 "all electric" homes with 200a panels. I understand most of the time they are still loafing along but there are times I am surprised that they are not smoking.
Take a cool Christmas eve, oven going, 2 or 3 burners going on the cook top every light in the house on plus outdoor lighting, hot water and 15kw heat strips going in the air handlers ... times 3


Greg Fretwell

#218837 - 11/03/17 06:05 PM Re: 1600 amp 480/277v 4 wire Y service [Re: Yoopersup]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,874
Brick, NJ USA
Hi guys
Been AWOL for a bit.
Our POCO does not allow any reduced neutrals; no way; all conductors must be full size.
They also 'may' have an issue with 6x6" conduits; next time I talk with my POCO inspector, I'll run it by.

I can't say I've seen anything larger than 4", except for HV


John


Member Spotlight
Vlado
Vlado
Croatia
Posts: 28
Joined: February 2011
Show All Member Profiles 
Featured:

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

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.017s Queries: 15 (0.002s) Memory: 0.8109 MB (Peak: 0.9920 MB) Zlib enabled. Server Time: 2017-11-18 04:40:04 UTC