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700A Main Breaker nuisance tripping #41509 08/29/04 02:56 PM
Joined: Aug 2004
Posts: 2
M
mgd001 Offline OP
Junior Member
Hi, this is my first post, happy to be on this forum.

The main breaker for our 3-phase/460v building power tripped on Friday and the Emergency Generator and ATS switched on. I noticed that the Genset out put display showed this: 468 v ,60hz , 715 amps total.

but each seperate phase measured around 235amps. is this enough to trip the breaker due to overloading?

I thought that a breaker marked 700 amps could hold 700 amps per pole?

thanks to all.

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Re: 700A Main Breaker nuisance tripping #41510 08/29/04 03:39 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
I am a little confused with how many amps you are drawing, I have never seen a generator with a "Total Amps" meter.

If you have 235 amps per phase then we would say the breaker has a 235 amp load.

Each pole of a 700 amp breaker is rated 700 amps but we do not call it a 2100 amp breaker.

A typical 700 amp breaker should not be loaded to more than 80% (560 amps per leg) for periods exceeding 3 hours. That is unless you have a 100% rated breaker, most are not.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 700A Main Breaker nuisance tripping #41511 08/29/04 05:10 PM
Joined: Aug 2004
Posts: 2
M
mgd001 Offline OP
Junior Member
The amps draw per leg was around 235 each. a=235amps, b=235amps, c=235amps

Thanks for the clarification.

Our Generator was installed a few weeks ago and it has a slick microprocessor display, with the Total amps reading.

This 700 amp breaker has a little switch assembly Called a "ground-censor" on the panel below the breaker that could be sensing a fault somewhere.

I'll post more details soon.


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