Detached garage grounding again (sorry)

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goldstar

goldstar

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New Jersey
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Electrical Contractor
I'm planning on running a 50 amp 120/240 feeder in PVC ( 3 # 6's and 1 # 8) to a detached garage and installing a main lug panel w/ a max capability of 6 circuits (BTW, garage is literally detached by about 18"). The total run is less than 50' and the main service was upgraded two years ago. Inspector tells me that I need (2) ground rods to re-establish the ground at the sub panel.

A) Do I need 2 ground rods ? The way I read 250.32 I only need one.

B) Do I need a main disconnect in the garage or does the 6 switch rule apply ?

Tnx.
 
You do need two rods and the neutral should be isolated from the equipment grounding conductor and the grounding electrode.

The 6 handle rule applies however most sub panels state that the panel is only suitable as a service equipment when used with a main breaker kit setup. In 2014 this will change. Look at 225.36

Even though it is not a service 225.36 tells us the panel must be so rated.
 
mwm1752 said:
If you have a common foundation the garage would not be detached. 18" remark was the basis for the comment.
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That is not necessarily the case. It is really a call by the EI or the building inspectors. I had a major argument with a local inspector because he was considering the detach garage an attached garage because there was a wooden deck attaching the structures. I had to fight him even with the office of the department of Insurance building and electrical chiefs behind me 100%. I finally got it approved. Some feel if there is a roof between the structures then they are attached---
 
The foundation wall are the footprint of a building. Only one UFUR is required per building. I do not know any building officials that will designate one foundation as two structures. Occupancies yes,
 
Dennis Alwon said:
That is not necessarily the case. It is really a call by the EI or the building inspectors. I had a major argument with a local inspector because he was considering the detach garage an attached garage because there was a wooden deck attaching the structures. I had to fight him even with the office of the department of Insurance building and electrical chiefs behind me 100%. I finally got it approved.
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Taken to the extreme, this would mean that two initially separated buildings, no matter how far apart, would become one building if your built a raised boardwalk between them. Glad you were able to prevail.
 
Aside from what the NEC dictates, I'd like to know what the CMP's logic and thinking was in making this section of the Code. In the scenario I presented the main breaker panel will literally end up being not more than 20' away from the garage breaker panel (as the crow flies, so to speak). Thus, the main service's rods are also located in the same area. Because of the PVC conduit bends and going up and over the rake of the garage the total run will actually end up being about 35-40'. What purpose would 2 more rods serve in such a short distance ? If I increased the ground wire in the conduit to a # 6 wouldn't I be accomplishing the same thing ?
 
mwm1752 said:
If you have a common foundation the garage would not be detached. 18" remark was the basis for the comment.
Click to expand...

Not sure where you get that from as there are many multiple occupancy buildings out there that are in-fact considered completely separate buildings, such as condos, town homes as well as commercial strip malls that are sold as individual structures, and they all have a common foundations, it is the fire wall or fire separation between the buildings that can determine if it is considered a separate building.
Also our IRC does not recognize any fire wall requirements between an attached garage and a dwelling only a gas barrier wall is required to prevent fumes from a vehicles exhaust from being able to enter the home.

Also here an insurance company can refuse a fire claim from a fire caused by someone working on a vehicle in an attached garage or a de-attached garage located closer then 10 feet to the home, I had a few friends as well as a few others who did not know this, that lost everything and the insurance did not pay the claim, the other one they can refuse fire coverage for is if it found that flammable liquids such as gasoline is being stored in the garage the same as above that is not in a vehicles tank, this could be from because Indiana doesn't require a fire wall between the garage and house but I'm not sure on that.
 
Occupancy & fireratings is not the discussion Grounding is.. Rarely do you have more than 1 service supplying a residence in which case the electrode system will connect at the MDP. Afew IBC definitions
BUILDING. Any structure used or intended for supporting or sheltering any use or occupancy.
DWELLING. A building that contains one or two dwelling units used, intended or designed to be used, rented, leased, let or hired out to be occupied for living purposes.
STRUCTURE. That which is built or constructed.
Notice that more than 1 dwelling can be contained in a building. The structural elements within a building can have fire serparation. It does not mean you must run individual services to each fire separated occupancy. Accessable overcurrent devices are rquired but thats not applicable with the OP ? There are many way & circumstances to deal with electrical installs.
 
goldstar said:
Aside from what the NEC dictates, I'd like to know what the CMP's logic and thinking was in making this section of the Code. In the scenario I presented the main breaker panel will literally end up being not more than 20' away from the garage breaker panel (as the crow flies, so to speak). Thus, the main service's rods are also located in the same area. Because of the PVC conduit bends and going up and over the rake of the garage the total run will actually end up being about 35-40'. What purpose would 2 more rods serve in such a short distance ? If I increased the ground wire in the conduit to a # 6 wouldn't I be accomplishing the same thing ?
Click to expand...

I would say yes, but I am not your inspector. It seems silly to add a second ground rod at the garage, if you have two at the main or less than 25 ohms to ground.
 
250.121 covers the use of the EGC installed with the feeders being used as the grounding electrode conductor
225.39 covers the 50 amp feeder being installed

Neither are allowed
 
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