ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Switched Receptacles -Top or Bottom?
by gfretwell - 07/28/21 10:06 PM
Lowes Selling this fan
by timmp - 07/25/21 10:58 PM
How's all our Non-US folks doing?
by djk - 07/23/21 09:13 PM
Do You Travel?
by Bill Addiss - 07/20/21 04:26 PM
Backup Generator Done Right
by timmp - 07/18/21 12:20 PM
New in the Gallery:
February, North East Indiana
February, North East Indiana
by timmp, July 25
Red Green would be proud
Red Green would be proud
by timmp, July 25
Who's Online Now
0 members (), 15 guests, and 47 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#54597 08/02/05 09:37 PM
Joined: Apr 2002
Posts: 257
M
Member
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)

#54598 08/03/05 06:01 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
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
#54599 08/03/05 06:51 AM
Joined: Dec 2004
Posts: 1,064
D
Member
How and where does the GEC terminate?


Dnk......


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Samurai
Samurai
Fl.
Posts: 46
Joined: May 2007
Top Posters(30 Days)
timmp 8
Rachel 4
djk 2
Popular Topics(Views)
281,588 Are you busy
215,225 Re: Forum
202,069 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5