310.15 Revisted...But w/Pics

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360Youth

Senior Member
Location
Newport, NC
I know this topic has seen its share of discuusion recently but I was wondering how many feel the installation of an ATS I installed yesterday would pass where ever you are.

The meter base feeds a 400 amp SE rated ATS with parallel 2/0 and the ATS feeds two 200 amp house panels. Each panel is fed with 2/0 runs. To me the new wording of 310.15 allows reduction of feeder cable only if that feeder serves the entire load. In this case, neither of the 2/0 runs feed the "entire load" of the house, so I was all set to run 3/0 from ATS to each house panel. But I had a converstion with a different inspector the previous day and he reads it as still allowable in this scenario so I "took a chance" that it would fly and ran the 2/0. (I always have 2/0 on hand but only get 3/0 as I need, plus it obviously less expensive). Based on the pics below, does this still fall under allowable residential reductions, or should the house feeders been 3/0. The install passed with no questions.



 

sparkyboys

Senior Member
Location
Columbus, ga
i am not an expert on residential, but i do see that you used copper rather than aluminum. wouldnt aluminum have been cheaper @ 4/0?

didnt you do the calculation?
 

macmikeman

Senior Member
Not to change subject but looking at the picture, wouldn't a gr bushing on the nipple between the ats and the meter pan be required? (unless there is one on the other end of the nipple of course)
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
The meter base feeds a 400 amp SE rated ATS with parallel 2/0 and the ATS feeds two 200 amp house panels. Each panel is fed with 2/0 runs. To me the new wording of 310.15 allows reduction of feeder cable only if that feeder serves the entire load. In this case, neither of the 2/0 runs feed the "entire load" of the house, so I was all set to run 3/0 from ATS to each house panel.
Thom I have to disagree with the inspector. There is no way that the wording in 310.15 allows 2/0 in this case. I bet if you call Ron Chilton he will tell you the same. You passed and I would not lose sleep over it but it is not code compliant.
 

360Youth

Senior Member
Location
Newport, NC
Thom I have to disagree with the inspector. There is no way that the wording in 310.15 allows 2/0 in this case. I bet if you call Ron Chilton he will tell you the same. You passed and I would not lose sleep over it but it is not code compliant.
My feelings, too (and I have talked to Ron). I guess you could say I took the easy/lazy way out on this one. The AHJs are pretty thorough in this area, so I wasn't trying to slip anything by someone.
 

360Youth

Senior Member
Location
Newport, NC
My feelings, too (and I have talked to Ron). I guess you could say I took the easy/lazy way out on this one. The AHJs are pretty thorough in this area, so I wasn't trying to slip anything by someone.
I guess I should add that I was trying to be non-compliant, I just took a chance on a less expensive interpretation of the code.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I guess I should add that I was trying to be non-compliant, I just took a chance on a less expensive interpretation of the code.
I have seen 2/0 used in this situation all over the place. I don't even stock 2/0 anymore since 99% of the services I do are 400 amp. 3/0 with a 1/0 neutral is my MO.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Ditto.

Need for bushings of any sort do not change because you are working in a residential area vs commercial or industrial. #4 and larger requires a bushing.

NEC 2002 (because my laptop is in a farmers field):

(F) Insulated Fittings. Where raceways containing ungrounded conductors 4 AWG or larger enter a cabinet, box enclosure, or raceway, the conductors shall be protected by a substantial fitting providing a smoothly rounded insulating surface, unless the conductors are separated from the fitting or raceway by substantial insulating material that is securely fastened in place.
Exception: Where threaded hubs or bosses that are an integral part of a cabinet, box enclosure, or raceway provide a smoothly rounded or flared entry for conductors.
Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway. The insulating fitting or insulating material shall have a temperature rating not less than the insulation temperature rating of the installed conductors.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Need for bushings of any sort do not change because you are working in a residential area vs commercial or industrial. #4 and larger requires a bushing.
Macmillian asked about grounding bushings. I did not notice the pipe to the left without a bushing. I thought that was a pvc slip fitting. Plastic bushing are fine however one is needed to the left.

I believe Bob was talking about low voltage cable in with high voltage going to the genny.
 

iwire

Moderator
Staff member
Location
Massachusetts
Ditto.

Need for bushings of any sort do not change because you are working in a residential area vs commercial or industrial. #4 and larger requires a bushing.
The only one that might require a grounding bushing is the raceway coming from the meter into the bottom left side, that one contains service conductors, the rest are feeders.

The one on the bottom left may be PVC or it may be bonded on the other end. The NEC does not require each raceway to be bonded twice.
 

360Youth

Senior Member
Location
Newport, NC
The nipples from ATS to house panels, actually, all of them, are PVC. The one coming from meter to ATS does not have a bushing because it would not catch with the sealing locknut.
 
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