ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Air Compressor feeder conductor sizing
by Potseal. 01/15/18 09:08 PM
VDE 0100 to introduce AFCIs
by LongRunner. 01/15/18 11:38 AM
Under carpet cable?
by HotLine1. 01/15/18 09:57 AM
Any New Years Resolutions?
by Bill Addiss. 01/13/18 10:21 AM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 19 guests, and 11 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
back up generator #23732
03/25/03 10:01 PM
03/25/03 10:01 PM
wolfdog  Offline OP
Joined: Oct 2001
Posts: 135
This question was asked of me at another web site and I don't have a good answer. Would you folks enlighten me so I can pass it on.

Consider a commercial building with a three phase service and 100% generator back up.

If you use a 3 pole transfer switch, you don't break the neutral.

If you use a 4 pole switch, you break the neutral, add some extra grounding, and the system is now "Separately Derived".

When in your opinion do you have to have the 4 pole transfer switch and the separately derived system?

I would like your opinion on tapping service feeders also.

[This message has been edited by wolfdog (edited 03-25-2003).]

Work Gear for Electricians and the Trades
Re: back up generator #23733
03/25/03 11:05 PM
03/25/03 11:05 PM
russ m  Offline
Joined: Feb 2003
Posts: 169
Try these links.;f=18;t=005123;f=18;t=005233#000000

Re: back up generator #23734
03/26/03 12:26 AM
03/26/03 12:26 AM
Nick  Offline
Joined: Aug 2001
Posts: 599
Riverside, CA
Short answer: When ground fault protection is required on either the service entrance or generator or both.

Re: back up generator #23735
03/26/03 07:44 AM
03/26/03 07:44 AM
wolfdog  Offline OP
Joined: Oct 2001
Posts: 135
Thanks for the responses and links.

Obviously, I have not been keeping up very well with the Mike Holt forum.


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


Member Spotlight
Posts: 165
Joined: March 2007
Show All Member Profiles 
Top Posters(30 Days)
sparky 23
Admin 19
Potseal 13
Popular Topics(Views)
243,511 Are you busy
180,298 Re: Forum
170,800 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.019s Queries: 14 (0.004s) Memory: 0.9571 MB (Peak: 1.0860 MB) Zlib enabled. Server Time: 2018-01-16 15:25:14 UTC