Residential Services

[Dennis Alwon]

Sorry but I disagree with those that say a residential service may be less than 100 amps. Art. 230.79(A)thru (D) does indeed give the rating of the disconnect however article 230.42(B) states the service conductors shall not be less than that req. in 230.79(A) thru (D)

(B) Specific Installations. In addition to the requirements of 230.42(A), the minimum ampacity for ungrounded conductors for specific installations shall not be less than the rating of the service disconnecting means specified in 230.79(A) through (D).

To me that very clearly states 100 amps for a single family residence

 

[pete m.]

Sorry but I disagree with those that say a residential service may be less than 100 amps. Art. 230.79(A)thru (D) does indeed give the rating of the disconnect however article 230.42(B) states the service conductors shall not be less than that req. in 230.79(A) thru (D)



To me that very clearly states 100 amps for a single family residence

The only requirement I see from the two articles is one says the disconnect must have a minimum rating of 100 amps and the other says that the service entrance conductors must have an ampacity of at least the rating of the service disconnect.


If the service disconnect were a fused disconnect I can't find a reason that the fuses in the disconnect could not be sized in accordance with the calculated load. (can't really think of a good reason, design wise, to do this but AFAIK it would be permissible)

Pete

Pete

 

[renosteinke]

"They're called fuses." Sure they are. If I ever see fuses at the pole transformer, I'll be sure to post a pic. (That will probably have to wait for my next visit to Kiwi-land).

Instead, what I see are single transformers powering several homes, without any OCPD until you get to the customer's service equipment. Even the PoCo "cut outs" are on the line side of the transformers.

The idea of putting a 60-amp main breaker / smaller fuse in your service OCPD is certainly allowed, and you would then have a service the 'size' of the OCPD. Point taken. Indeed, if you were 'back feeding' a breaker, chances are that the 100-amp panel is limited by the manufacturer's instructions to individual breakers no larger than 70.

So we need 100-amp wire to a 100-amp disco ... we need a 100-amp meter base ... putting in a smaller OCPD at that point makes me think of the old 'it looks like butter, but it's not' commercials. It looks like 100 amps, but it's not .... it's been re-fused!