ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
220/230/240V 60Hz Systems
by gfretwell. 09/23/18 02:50 PM
Inspection camera help
by petey_c. 09/22/18 07:52 AM
Motion detectors and dimmers
by gfretwell. 09/20/18 04:02 PM
Extension cords
by annemarie1. 09/20/18 08:54 AM
Acronis Backup 2017
by gfretwell. 09/16/18 12:46 AM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
1 registered members (ghost307), 33 guests, and 20 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Large Generator Grounding 480/277 V #219569
08/29/18 12:55 PM
08/29/18 12:55 PM
Y
Yoopersup  Offline OP
Member
Joined: Mar 2003
Posts: 849
Michigan
Grounding requirements & Sections.

SDS & Non SDS .

2017 / 2014 NEC & Related Books and Study Guides
Re: Large Generator Grounding 480/277 V [Re: Yoopersup] #219570
08/29/18 06:14 PM
08/29/18 06:14 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,290
Estero,Fl,usa
The biggest difference between SDS and non SDS is whether you bond the neutral (transfer equipment switches the neutral). Otherwise I think you just create a 250.grounding electrode system based on the largest ungrounded conductor ... but that is just off the top of my head.

Last edited by gfretwell; 08/29/18 06:20 PM. Reason: clarification

Greg Fretwell
Re: Large Generator Grounding 480/277 V [Re: Yoopersup] #219571
08/29/18 08:08 PM
08/29/18 08:08 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,290
Estero,Fl,usa
Looking at the code you get to 250.20 that talks about how you ground a SDS connected generator. If it is a non - SDS (unswitched neutral), there are no grounding requirements beyond the 250-122 EGC from the attached service.

From the handbook
Non SDS

[Linked Image]

SDS

[Linked Image]

If you do have an SDS it takes you to 250.30 that points you to 250.66 for the details of the GEC 250.52 for the electrode etc.


Greg Fretwell
Re: Large Generator Grounding 480/277 V [Re: Yoopersup] #219576
08/30/18 02:55 PM
08/30/18 02:55 PM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 7,024
Brick, NJ USA
Greg:

Nice explanation!!


John
Re: Large Generator Grounding 480/277 V [Re: Yoopersup] #219578
08/31/18 02:00 AM
08/31/18 02:00 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,290
Estero,Fl,usa
Thanks, we do lots of generators around here so it is a common question. I usually tell homeowners looking to have transfer equipment installed that, if this is a manual system, the listed panel interlock is usually the best way to go. The labor will be much less and the part, although ridiculous for what you get, is still pretty cheap.
The only thing they really need is a vacant double slot in the panel and moving some breakers around to get your backfed breaker next to the discionnect. You then have to be sure they lift the bonding jumper in the generator to get circuit current off the EGC. This will not be an SDS.


Greg Fretwell

Featured:

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

 

Member Spotlight
mxslick
mxslick
Atomic City, ID USA
Posts: 803
Joined: October 2004
Show All Member Profiles 
Top Posters(30 Days)
Admin 13
Trumpy 9
Popular Topics(Views)
249,439 Are you busy
187,355 Re: Forum
176,696 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.018s Queries: 15 (0.003s) Memory: 0.9691 MB (Peak: 1.1109 MB) Zlib enabled. Server Time: 2018-09-24 23:19:44 UTC