View Full Version : 800a service

10-16-2007, 09:40 AM
Not sure if anyone can help, but here it goes.
I have a customer who is installing an 800a commercial service. He ran (2)500mcm copper wires for each leg of the service out of the ct cabinet and up the mast for the power company's (AEP) connection. Now they are telling him he needs to get 4"x8" x 1/4"thick copper plates and drill holes in them for lugs. The power company with then attach their own lugs to the plate to finish the connection.
Has anyone ever heard of such a thing? I was always told that all you have to do is leave the wire out of the mast and they handle it from there.


Bob NH
10-16-2007, 11:33 AM
We don't have all of the information but the copper plates may be the least of his problem.

500 MCM in a raceway is rated at 380 amps at 75C and most terminals are rated at 75C, not 90C. Two of them come to 760 Amps.

If he has them all in one raceway, they must be derated to 80% of the 90C rating of 430 Amps, or 80% of 860 Amps for the pair, which is 688 Amps.

If they are in free air the ampacity is much higher and would be adequate.

10-16-2007, 01:15 PM
The size of the wire is not in question here. The power company allows 500mcm for 400a and parallel runs of 500mcm for 800a. And, for some ungodly reason, the power company doesn't have to follow code.
My question is, has anyone ever came across this with the power company before? Usually, they make the connections before the mast. This is the first time I have ever heard of them requiring you to "make" something up for the wire connections.

10-16-2007, 07:04 PM
500 MCM in a raceway is rated at 380 amps

240.4(B) Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:

10-16-2007, 08:19 PM
The utilities have their own standards and codes. AS for the 1/4" bus if that is in their Standards for Utility Service (their requirements for service) then you have to doi it. Each utility has their own requirements.

1/4"X4"=1000 amps, standard bus available from the same company that makes custom troughs and pull boxes in most jurisdictions I have worked in.