temporary service

[tim89s]

I am hooking up a temporary service on a commercial site. I found an already built temporary service at our shop. It consist of a meter with 4/0 AL coming off the line and load side. The load side goes into a gutter and is then tapped with 2 sets of #2 Cu. Each set goes to a 100 amp single phase panel. According to table 310-16 4/0 Al is only good for 180 amps. Wouldn't I need 250kcmil? Or is there something I am missing. Could I change the main breaker in the panels to 80 amp?

 

[tom baker]

Re: temporary service

Yes you'll need 250, 4/0 is good for 200 amps for a single family dwelling per 310.15(B)(6).
The conductor has to be protected at its ampacity. A 180 or 200 amp is a pretty large temp service, most are only 50 amp or so.

 

[iwire]

Re: temporary service

Tom is correct, but for a temp service you might just ask the inspector what they will accept.

In this area most of the inspectors allow that table for temp services.

 

[steve66]

Re: temporary service

Doesn't 230.90(A) exception #2 allow this?
"Fuses and circuit breakers with a rating or seeting that conform with 240.4(B) or (C) and 240.6 shall be permitted.

Or 230.90(A) exception #3?
"Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.

Steve

 

[pierre]

Re: temporary service

The 4/0 Al service conductors feeding the 2-two hundred amp disconnects does not necessarily have to be rated for the two panels. The 4/0 needs to carry the load. If your load calculation does not exceed the rating of the conductor, then you are good to go.

Pierre

 

[iwire]

Re: temporary service

Originally posted by steve66:
Doesn't 230.90(A) exception #2 allow this?
"Fuses and circuit breakers with a rating or seeting that conform with 240.4(B) or (C) and 240.6 shall be permitted.

This exception would allow 4/0 AL with it's rating of 180 amps @ 75 C to be protected with a 200 amp breaker if the load was less than 180 amps as Pierre was saying

Originally posted by steve66:
Or 230.90(A) exception #3?
"Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.

I would say yes again as long as the connected load was less than 180 amps.

Bob