The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by gfretwell
10/24/16 08:46 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 14
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 321 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#129481 - 03/30/05 06:19 PM 3 phase(240/120) delta bank
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Does this configuration have one transformer larger or smaller than the other two (due to the high-leg not being utilized for 120 volt loads)?

#129482 - 03/30/05 07:10 PM Re: 3 phase(240/120) delta bank
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA

The 4 Wire Delta has a center Pot, which is sized according to the expected 120 VAC 1Ø 2 Wire (or combined 120/240 VAC 1Ø 3 Wire loads).

Larger center Transformers where more 1Ø 120 VAC needed, smaller where less is needed.

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#129483 - 04/02/05 06:19 PM Re: 3 phase(240/120) delta bank
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Thanks, Scott.
I thought I'd seen larger ones, then recently, I saw a smaller one. This explains it.

#129484 - 04/04/05 01:05 AM Re: 3 phase(240/120) delta bank
Bjarney Offline

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
(…under construction…)

Truth is, four-wire delta banks can have any size transformers, including one “zero-size” pot—that being only two transformers—a/k/a an “open delta” bank. See IEEE std C57.105-1978 §6/§8 or odds’n’sods from EPE overhead standards linked at (~1MB) for some sizing guidelines (that are not necessarily NEC-based.) A ‘shorthand’ sketch of delta and open-delta secondary interconnection…


[This message has been edited by Bjarney (edited 04-04-2005).]


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals