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#42142 - 09/16/04 01:40 PM Sub Panel question  
Delectric  Offline
Member
Joined: Feb 2004
Posts: 33
Silver Springs, NV
Hi All, I upgraded a 100A main to a 200A main. Then installed a 100A sub-panel in a garage (40 ft. away). The Inspector say I have to add a main breaker in the sub panel even though I put a 100A CB in the Main panel feeding the sub. He also wants me to add a separate ground system and add a bushing on the conduit coming into the sub panel even though the conduit is PVC. I thought if I install another ground at the garage it would have to be bonded to the ufer at the house. Any thoughts? Eric


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#42143 - 09/16/04 02:34 PM Re: Sub Panel question  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
Eric,
Sorry the inspector is correct on all counts.
See 225.31(note six or less breakers are permitted to serve as the required building disconnect), 250.32(A) and 300.4(F) and 352.46.
Don


Don(resqcapt19)

#42144 - 09/16/04 08:04 PM Re: Sub Panel question  
CJS  Offline
Member
Joined: Sep 2004
Posts: 35
Sanford,NC, USA
It depends where you live (I guess). In North Carolina, I would not need a MB in the garage panel but would, of course, need the bushing and the ground rod/wire for the garage service.

Of course the "authority having jurisdiction" interprets the code and so it is a good idea to get to know your inspectors before doing work in a new town.

To me it makes no sense to have redundant mains like you describe. The wiring for the 100A garage panel is already protected; why would you want to protect it twice?

Anyway, around here they would not make me do it.

CJS


#42145 - 09/16/04 08:28 PM Re: Sub Panel question  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Welcome CJS to ECN. [Linked Image]

There is no requirement protect the panel twice, as you said it makes no sense.

There is a NEC requirement to have a disconnecting means in a separate building or structure. Check out 225.31 & 225.32.

The garage Delectric is taking about is "40 ft. away" so you need a disconnecting means at that structure.

The easiest way to meet that requirement is a main breaker panel, but you could use a disconnect switch ahead of a main lug panel.

Bob

[This message has been edited by iwire (edited 09-16-2004).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#42146 - 09/16/04 08:36 PM Re: Sub Panel question  
CJS  Offline
Member
Joined: Sep 2004
Posts: 35
Sanford,NC, USA
Only if you have more than 6 breakers.
I'm telling you, here they do not make you put one. I have run a #2 SER all the way across a crawl space to the other side of the house to then go underground another 60' to the garage and then terminate at a 100A ML panel.

I spliced the SER with mechanical lugs in a "J" box and then ran just 3 - #2 URD alum conductors UG to the garage and then grounded the service there.

This is not a seperately derived system and according to this particular county inspector, a main was not needed. Afterall, it is already protected for short and overload at its MB. So, if you have less than 6 breakers in that garage panel you are good (around these parts anyway).
:~)


#42147 - 09/16/04 08:41 PM Re: Sub Panel question  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Yes I agree you may have up to 6 means of disconnect, that could be 6 breakers regardless of panel size. [Linked Image]

If you have 7 or more circuits we are back to needing a main breaker or a disconnect ahead of a main lug panel. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#42148 - 09/16/04 08:54 PM Re: Sub Panel question  
Jim M  Offline
Member
Joined: Aug 2001
Posts: 457
Chestertown, MD, USA
Don't want to sound stupid, but what is the bushing the inspector is requiring? A plastic bushing, a ground bushing?


#42149 - 09/16/04 09:00 PM Re: Sub Panel question  
Dave55  Offline
Member
Joined: May 2004
Posts: 697
Crystal Lake, Illinois, USA
I prefer installing a sub-panel with a main or disconnect. That way if I'm working in the garage I can see that it's off.

Dave


#42150 - 09/16/04 09:05 PM Re: Sub Panel question  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
300.4(F) & 352.46 both require plastic bushings for this PVC.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#42151 - 09/16/04 10:06 PM Re: Sub Panel question  
CJS  Offline
Member
Joined: Sep 2004
Posts: 35
Sanford,NC, USA
It's been awhile since my exam, but you need a plastic bushing on any pipe where the conductors are larger than a #4 (I think). It would be easy enough to find out by going to the book.
I use PB's on all services. Bonding bushings of course are not required on pvc.
I seldom need to use bonding bushings in my work but I've needed them in the past on bigger jobs on conduits carrying a grounding electrode conductor (both ends must get bonded), or on seperately derived systems like transformers when you go to bond the neutral, or..... I could go on and on I suppose.....

We also used to use IMC sweeps on PVC UG pipe runs so the rope or pull string wouldn't cut into the PVC sweep and then you have to bond that sweep (obviously if you think about it) and a bonding bushing is the easiest method.


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