Feeds for breakers 600 amp

[dennyjoe52]

Ordered a 600 amp breaker with wires to bolt on. They sent me parallel feeds of 250 instead of 350 that I thought I need. They said there is a rule about 80 percent and that is all I need. Is this right. We are put this in for a feed for four machines and for furture use. It will be in a pannel and feed a j box. All disconects will be fed off of the j box.

[ November 29, 2004, 12:57 PM: Message edited by: dennyjoe52 ]

 

[ron]

Re: Feeds for breakers 600 amp

It is not an 80% thing.
Technically, if your calculated load was 510A or less, then you can go to the next standard size breaker, 600A, as there is not standard between 510A (rating of (2) 250kCMIL) and 600A.
I would use 350kCMIL minimum myself.

 

[templdl]

Re: Feeds for breakers 600 amp

You got a typical answer from your supplier as most don't have a clue with regard to actual application. They probably don't know the difference between Al and CU ampacities as well as the derating factors that the contractor must consider when sizing cable.
Maybe the standard terminal supplied with the breaker is what you had received but others are available. You have also done some assuming also which is not all that unusual either. From a users perspective it is a learning experience to either find out what the standard terminal is and either it will or will not work, or what optional terminals are available. The catlog that I'm looking at does have (2) terminal options for a 600af breaker, an Al/Cu(2)250-350kcmil, and a Cu (2)250-350kcmil. The manufacture does show Al/Cu (2)400-500kcmil as standard for a 600af.
What is easier is to specify the breaker and to be supplied with terminals that would accept specific cable when ordering.
If you order a simple stock breaker you will get the terminals the manufacture considers as standard.
What really is a big pile of grief if when 'X' feet of cable is pulled and you fine the there is no terminal available to terminate the cable on.
The best advise I have found is not to ever assume. If you don't assume you will at least know the trouble you will have before you get into it and have time to resolve it.