ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Pull out fuse panel?
by wa2ise. 12/14/18 05:09 PM
Video door bell causing chime activation of coil
by gfretwell. 12/10/18 12:35 AM
Conduit fill Calculations
by gfretwell. 12/08/18 08:39 PM
Swimming Pool question
by HotLine1. 12/05/18 12:37 PM
Tingle off the water spigot
by rmiell. 11/30/18 01:03 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
0 registered members (), 33 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Tap for Transformer #54597
08/02/05 08:37 PM
08/02/05 08:37 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 05:01 AM
08/03/05 05:01 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 05:51 AM
08/03/05 05:51 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
AllClear
AllClear
Belmond Iowa US
Posts: 44
Joined: August 2005
Show All Member Profiles 
Top Posters(30 Days)
Popular Topics(Views)
252,224 Are you busy
189,195 Re: Forum
178,877 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.015s Queries: 14 (0.003s) Memory: 0.9516 MB (Peak: 1.0745 MB) Zlib enabled. Server Time: 2018-12-15 23:56:21 UTC