ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
Why cables look like they do
by LongRunner. 04/26/17 09:36 AM
Dimmable LED 2x4 lay in fixtures
by HotLine1. 04/24/17 05:43 PM
Old decora style outlets
by Lostazhell. 04/22/17 07:59 PM
Permit Snafus...AHJs and Contractors Jump in
by gfretwell. 04/22/17 01:11 PM
How do you find a good employee?
by HotLine1. 04/22/17 10:44 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
234,751 Are you busy
169,498 Re: Forum
162,792 Need opinion
Who's Online Now
0 registered members (), 57 guests, and 7 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#23732 - 03/25/03 11:01 PM back up generator  
wolfdog  Offline
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

#23733 - 03/26/03 12:05 AM Re: back up generator  
russ m  Offline
Joined: Feb 2003
Posts: 169
Try these links.;f=18;t=005123;f=18;t=005233#000000

#23734 - 03/26/03 01:26 AM Re: back up generator  
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.

#23735 - 03/26/03 08:44 AM Re: back up generator  
wolfdog  Offline
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.

Member Spotlight
Montreal, Quebec, Canada
Posts: 28
Joined: March 2011
Show All Member Profiles 

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.012s Queries: 14 (0.004s) Memory: 0.7588 MB (Peak: 0.8886 MB) Zlib enabled. Server Time: 2017-04-26 21:38:56 UTC