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!

Featured:

2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Safety at heights?
by HotLine1
Yesterday at 08:51 PM
International Wire Colour Codes
by Texas_Ranger
Yesterday at 03:29 PM
Looking for older post
by Texas_Ranger
Yesterday at 03:22 PM
Last time to chat here
by Trumpy
01/20/17 11:41 PM
Unsafe Situations
by Trumpy
01/20/17 09:46 PM
New in the Gallery:
Desk-mounted "power-board"
Shout Box

Top Posters (30 Days)
Admin 35
HotLine1 21
Ruben Rocha 17
gfretwell 16
Trumpy 15
Who's Online
0 registered (), 60 Guests and 11 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#92201 - 03/07/05 05:19 AM Sizing Equipment Ground
sparkync Offline
Member

Registered: 10/17/02
Posts: 811
Loc: NC
When running motor circuits in conduit, where the breaker size is 250% of the FLA, is there an exception to the rule of sizing the equipment grounding conductor, according to the rating of the OCD in the circuit? For example I have a machine with a total amperage of 39.8 amps X 250% = 99.5 amps which would put me at a 100 amp. breaker. Is the ground wire size for the conduit still a # 8 or am I missing an exception somewhere when dealing with motor circuits.. I have other smaller motor circuit conductors in the conduit also, but this is the largest. Thanks, Steve

Top
2017 / 2014 NEC & Related Books and Study Guides
#92202 - 03/07/05 07:37 AM Re: Sizing Equipment Ground
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9066
Loc: Estero,Fl,usa
250.122(A) General. Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table 250.122 but shall not be required to be larger than the circuit conductors supplying the equipment.
_________________________
Greg Fretwell

Top
#92203 - 03/07/05 07:41 AM Re: Sizing Equipment Ground
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
If you are using a motor circuit protector or magnetic only breaker for the short circuit and ground fault protection then 250.122(D) lets you size the EGC based on the overload protection rating. In your case, it appears that you are using a thermal magnetic breaker and you must size based on the breaker rating, however as greg pointed out 250.122(A) says the EGC is not required to be larger than the circuit conductors, but that does not change anything for your example as the circuit conductors will be #8 and Table 250.122 calls for a #8 EGC for a 100A OCPD.
Don
_________________________
Don(resqcapt19)

Top


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