ECN Forum Forums General Topics of the Trade General Discussion Area Parallel Breakers?

If my last post seemed harsh cut me some slack I am taking pain killers. (Prescribed)

Anyway


Would they tell me?

After some thought I think there is a good chance that my GE breaker has an internal common trip bar.

Thanks for letting me have one.

Bob

Bob, I was told by a GE engineer that those 4-section GE main breakers consist of a 2-pole 100a breaker paralleled by a pair of non-current-sensing contacts in the outer cases, solely for the purpose of lower overall contact resistance.

I'll do more than that Bob. I'll offer up my prayers that you're soon healed of whatever's troubling you! I really enjoy your posts, the give and take. This has been a very educational experience and I thank you for your part in it.
Joe

Thanks Joe, it's nothing serious but the meds make me a bit cloudy.

Larry they can justify anyway they want.

IMO it is strictly an issue of 'value engineering' what they did costs less than a 200 amp case breaker.

One advantage to the use of double breakers in a loadcenter is the ampacity of the bus connection. By keeping each stab to 100A max they can plug on a larger breaker without having to make a special bus connection and then there are on bolts to tighten.

We use completely separate (non-yoked) parallel breakers all the time for redundancy. Example: Parallel-Redundant UPS system. Also, N+1 generators: each gen has its own output breaker. This is all allowed under NEC and works well in practice, too. EXTREMELY well, too, as in 99.999-99.9999% reliability well. In the case of the generators, they have integrated governer and droop-adjusting circuitry to maintain proportionate load, but the UPSs maintain even load, even in bypass. In a properly cabled system, minute differences in breaker manufacture and cable installation don't amount to much of a current split difference. And if one breaker should trip while the other somehow miraculously doesn't? Alls the better, as you have time to fix the first UPS!

Care has to be taken with interlocks (both key-type and PLC) when multiple switchboards are used, to prevent the branch circuit from becoming a bus tie, but otherwise, it's pretty straightforward.

[This message has been edited by SteveFehr (edited 07-03-2006).]

Steve, You're describing multiple sources with output breakers feeding some sort of reliable or emergency bus. That is apples & oranges to what we are talking about. Now, if one of your UPSs or Gensets had 2, 200A output breakers, instead of 1, 400A output breaker, we would be on the same page.
Joe

JBD


I agree I bet that has a lot to do with it.

SteveFehr

I am familiar with the systems you describe and I have to agree with Joe, that is different set up entirely.