ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Trumpy 5
Recent Posts
What do you do?
by gfretwell. 09/24/17 12:05 PM
75 kva tranformer
by sparkync. 09/23/17 06:41 PM
Another generator question
by gfretwell. 09/23/17 04:15 PM
Supporting conduit bodies
by ghost307. 09/18/17 12:12 PM
Thermal Imaging Camera upgrade
by Potseal. 09/18/17 11:57 AM
New in the Gallery:
Gallery Test
Popular Topics(Views)
240,944 Are you busy
176,740 Re: Forum
168,593 Need opinion
Who's Online Now
0 registered members (), 51 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#189171 - 09/22/09 10:06 PM Secondary of transformers  
SJT  Offline
Member
Joined: Jul 2002
Posts: 241
PATCHOGUE, N.Y.
I was looking at a job that had a 225KVA transformer suspended from the ceiling in a large utility room of Building. Below the transformer there are 2 - 400amp disconnects. The secondary conductors go to these two switches. Is this allowed, or do you need one single disconnect? I believe the transformer is 3 phase 480V to 208V. There is a breaker on the Primary side also. Is there a section in the code about the number of disconnects allowed on the secondary side?
Thanks


2017 / 2014 NEC & Related Books and Study Guides

#189173 - 09/22/09 10:26 PM Re: Secondary of transformers [Re: SJT]  
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 826
Michigan
240.21 (C) Each set of conductors feeding seperate loads Shall be permitted to connected to a transformer secondary. (Notice EACH)Devices must be grouped to meet 450.3 (B) note 2
NEC 2005 Handbook Details this clearly on page 170.
Yoopersup


#189174 - 09/22/09 10:27 PM Re: Secondary of transformers [Re: SJT]  
JBD  Offline
Member
Joined: Jul 2001
Posts: 599
WI, USA
The transformer is protected under article 450.3. If the primary disconnect is sized at not more than 125% of the primary FLA, a single disconnect is not required on the secondary.

The secondary conductors are protected by the tap rules in 240.21(C). There are situations where a set of tap conductors can feed multiple devices.

Last edited by JBD; 09/22/09 10:29 PM.

#189183 - 09/22/09 11:00 PM Re: Secondary of transformers [Re: JBD]  
SJT  Offline
Member
Joined: Jul 2002
Posts: 241
PATCHOGUE, N.Y.
I checked that 240.21 (C) and you were right on with that. We may leave the 2 Disconnects alone and change a distribution panel downstream from those.
Stay Safe




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: 0.015s Queries: 15 (0.003s) Memory: 0.7595 MB (Peak: 0.8929 MB) Zlib enabled. Server Time: 2017-09-26 00:09:54 UTC