Can someone let me know is there a minimum size service required by the NEC for a structure, detached building and a sign? I've been told 100 amp is the minimum but others tell me you can install a 60 amp service for signs. The argument is, since the meter can and panel are both rated for 100 amp thats the minimum you can make a service. Opinions are appreciated.
Minimum size service
- Thread starter rcmoon
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Beaches EE
Senior Member
- Location
- NE Florida
- Occupation
- Electrical Engineer / Facilities Manager
A load calculation (220) will tell you what size service is required. As far as minimums, for residential it is 100 amps. Refer to section 230 for Services.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Roger convince me. I know this has been said many times here but I don't see it. 230.79 A_D does say the disconnect but 230.42(B) states the conductors cannot be less than the size of the disco
If it was intended for service sizes to have a minimum size it would be worded to reflect that. Are they just playing with words?
If you had a set of prints that shows a safety switch and conductors to be rated at 100 amps and fuses to be determined by HVAC equipment you would install it as shown but the circuit may end up being 70 amps.
Showing a minimum rating is not mandating a minimum size
Roger
If you had a set of prints that shows a safety switch and conductors to be rated at 100 amps and fuses to be determined by HVAC equipment you would install it as shown but the circuit may end up being 70 amps.
Showing a minimum rating is not mandating a minimum size
Roger
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Sorry Roger, I can't buy that argument. The words, IMO, are there to disagree with what you said.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
IMO you're both correct, if the service is one of the locations mentioned in 230.79(A) through (D) the the SEC's must be sized no smaller than the service disconnect. For other installations the SEC's can be smaller than the service disconnect but a single service would require an OCPD to be sized according to the conductors.
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
The POCO will tell you the minimum service size they will supply. You can always breaker/fuse it less.....
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes you can build a 60 amp service for a sign
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Roger, I don't think they are deliberately playing with words but I believe they inadvertently made it confusing. This, as you know is pretty common in the NEC
Dennis, they already set a precidence in 210.23 by using the word "rating" for receptacles that can be fed smaller than their rating, if they want to use the word for something different they should look to the TCC to help correct it.
Roger
Roger
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
No, there are 2 other options...but yes, option (C) and (D) are as you stated
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