ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Ronald and Nancy Reagan in GE commercials
by Bill Addiss. 03/13/19 08:12 PM
Carflex in an RNC connector?
by gfretwell. 03/12/19 05:21 PM
Reverse-feeding transformer in PV system?
by HotLine1. 03/11/19 08:37 AM
Vintage stage lighting and equipment catalogs
by Albert. 03/09/19 06:21 PM
TJX Recalls Heating Pads
by Admin. 03/08/19 09:33 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
1 registered members (Scott35), 18 guests, and 18 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Tap for Transformer #54597
08/02/05 09:37 PM
08/02/05 09:37 PM
M
master66  Offline OP
Member
Joined: Apr 2002
Posts: 257
Masontown, PA, USA
Is this OK?

In a school, there is a 150 KVA transformer (480V delta Primary / 120/208Y secondary) installed 6" away from a MLO panel.

The MLO panel is fed from the MDP (located in an electrical room on the other side of the building) via a 400A Fused switch.

The transformer is fed from the feed-thru lugs in the MLO panel with 4/0 copper in flex.

The transformer then feeds a 120/208Y panel (6" away) with paralleled 4/0 copper in flex terminating in a 400A main breaker.

Does this meet all requirements of articles 240.21 and 450? (2005 NEC)

Work Gear for Electricians and the Trades
Re: Tap for Transformer #54598
08/03/05 06:01 AM
08/03/05 06:01 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Sure. [Linked Image]

The primary current of the 150 KVA transformer is about 180 amps.

Table 450.3(B) allows the primary overcurrent protection to be 250% of the primary current when secondary protection is provided.


180 x 2.5 = 450 amps.

On the secondary side we are allowed 125% and we can round up to the next standard size OCP.

The secondary current of a 150 KVA transformer is 416 amps.

They could have gone higher than 400 amps on the secondary side. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: Tap for Transformer #54599
08/03/05 06:51 AM
08/03/05 06:51 AM
D
Dnkldorf  Offline
Member
Joined: Dec 2004
Posts: 1,064
nowhere usa
How and where does the GEC terminate?


Dnk......


Featured:

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

 

Member Spotlight
mxslick
mxslick
Atomic City, ID USA
Posts: 803
Joined: October 2004
Show All Member Profiles 
Top Posters(30 Days)
Admin 9
Albert 3
Popular Topics(Views)
254,005 Are you busy
190,401 Re: Forum
180,113 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.016s Queries: 14 (0.003s) Memory: 0.9513 MB (Peak: 1.0742 MB) Zlib enabled. Server Time: 2019-03-26 04:52:39 UTC