ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
by gfretwell. 03/24/18 02:10 AM
Recall Notice Kidde Smoke Alarms
by dougwells. 03/22/18 01:40 PM
Recall notice: Southwire wi-fi wall switches
by sparkyinak. 03/15/18 06:03 PM
Goodman Manufacturing Recalls Modular Blowers
by Admin. 03/13/18 10:40 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 4 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
400 Amp breaker tripping #54199
07/21/05 09:34 PM
07/21/05 09:34 PM
poorboy  Offline OP
Joined: Jun 2005
Posts: 124
Central Maine
One of our accounts has a 3 pole 400 Amp brkr tripping. One of our guys went to get the numbers off the brkr and ordered a new one, looped it at 320 Amps. I am going there Sat to install it, not even sure if breaker is bad, but there seems to be no fault or overload and we need to do something fast, as the plants offices are part of the load served.

Have you seen breakers just go bad so they trip well below their rating?

It's a GE breaker, 208 volt. I always scoffed at people's description of a "weak breaker", but this sounds like the best way to describe this one. It's tripping 3-4 times daily.

Work Gear for Electricians and the Trades
Re: 400 Amp breaker tripping #54200
07/21/05 09:49 PM
07/21/05 09:49 PM
Jps1006  Offline
Joined: Jan 2004
Posts: 615
Northern IL
There is no heat coming off the breaker? I've seen breakers internally go bad with a loose connection and then the overload mechanism takes in heat and eventually trips. But when this happened the breaker itself was HOT to the touch. The load was well within acceptable range. Was an old ITE if I remember correctly. Obsololete and cost $750. Now that I remember.

Re: 400 Amp breaker tripping #54201
07/21/05 11:13 PM
07/21/05 11:13 PM
Ray97502  Offline
Joined: Oct 2004
Posts: 55
Central Point,OR
I don't know what you will pay for the brk you are going to use to replace the one you think might be defective but you might think about renting a Multi Amp Model SR-76 Relay Test Set. It's a bit of over kill but you can determine if the breaker is tripping early and how early. Breakers wear and begin to trip early, usually because they have been burdened an excessive number of times or are used in place of a snap switch to turn the circuit on and off under load.
If the Brk isn't the problem you could install a (Drantz 626) line disturbance analyzer to determine what the voltage and current characteristics are when the brk trips.

Re: 400 Amp breaker tripping #54202
07/22/05 03:21 AM
07/22/05 03:21 AM
poorboy  Offline OP
Joined: Jun 2005
Posts: 124
Central Maine
I'll ask the guy who was there if it was hot...I haven't had the pleasure to go there yet, just am the only one available Sat to install new brkr.

Re: 400 Amp breaker tripping #54203
07/22/05 06:09 AM
07/22/05 06:09 AM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
What is your company going to do if changing the breaker does not help?

Before we went that route we would install a data logger or considering it is tripping 3 - 4 times daily just use an amp clamp with a memory.

If this breaker is running 320 amps continuously a large motor starting may be enough to trip it out.

Hot weather and it may be a AC unit that is starting up or is simply has an internal problem.

I have not found to many larger breakers that have worn out or gotten weak. No one that I know uses a 400 amp breaker as a light switch.

I would make a rough list of the loads on this breaker and look for equipment that starts 3 - 4 times a day. [Linked Image]

Bob Badger
Construction & Maintenance Electrician


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Attic Rat
Attic Rat
Bergen Co.,N.J. USA
Posts: 524
Joined: December 2003
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 5
Admin 5
Popular Topics(Views)
244,891 Are you busy
182,003 Re: Forum
172,033 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.052s Queries: 14 (0.034s) Memory: 0.9681 MB (Peak: 1.1054 MB) Zlib enabled. Server Time: 2018-03-24 13:51:05 UTC