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#204379 - 12/05/11 07:15 PM breaker meltdown
mikes733 Offline
New Member

Registered: 02/09/08
Posts: 3
Loc: kentucky
I had a customer call with a breaker melted to the bussbar. this was the second or third breaker that has done this according to him.the bussbar was fine but the breaker fell apart I installed a new breaker and it made good tight connection and the amp load was in range. any Ideas? I think it was a g&s panel with challenger breakers.

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#204380 - 12/05/11 08:08 PM Re: breaker meltdown [Re: mikes733]
twh Offline
Member

Registered: 03/11/04
Posts: 898
Loc: Regina, Sask.
Load up the circuits and check the voltage drop from the feed conductor to the load conductor terminations. You'll be looking for voltages around 100 ma on the low end to about a volt, depending on the load and the size of breaker. Compare readings for the various breakers for an idea about what is normal in that panel. If the voltage drop seems high, move the probe from the feed wire to the bussbar by the breaker, then the metal part of the breaker.

It's the equivalent of checking the temperature of the connection points, but it's faster and easier to pinpoint the problem because voltage drop doesn't migrate the way heat does.

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#204381 - 12/05/11 08:17 PM Re: breaker meltdown [Re: mikes733]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
Do you have a non contact thermometer? They are getting cheap enough for the mortal man and will let you further track down this heat thing. TWH is right about starting with your meter to see where the leak is.
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Greg Fretwell

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#204382 - 12/05/11 08:50 PM Re: breaker meltdown [Re: mikes733]
Tesla Offline
Member

Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
Check for corrosion on the Aluminum bus...
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#204384 - 12/06/11 05:57 AM Re: breaker meltdown [Re: mikes733]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Repeat problem and the buss doesn't seem damaged? That doesn't make sense.

However ...

1) Water dripping, condensing on the breaker might;

2) Some load that was not available to you (like a space heater) might; and,

3) the customer's own actions (not shared with you) might.

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#204385 - 12/06/11 07:05 AM Re: breaker meltdown [Re: mikes733]
mikes733 Offline
New Member

Registered: 02/09/08
Posts: 3
Loc: kentucky
thanks for the input. The bussbar was damaged from a previous breaker but the breaker I removed did not appear to have damaged the buss.I did sand the buss and applied corrosion inhibiter with the new breaker. The breaker is feeding 15 kw heat strips and is pulling 60 amps on each leg.


Edited by mikes733 (12/06/11 07:13 AM)

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#204386 - 12/06/11 07:33 AM Re: breaker meltdown [Re: mikes733]
ghost307 Offline
Member

Registered: 05/09/05
Posts: 884
Loc: Chicago Illinois USA
15kW strip heaters drawing 60 Amps per phase??
What voltage are you running at?
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#204387 - 12/06/11 08:27 AM Re: breaker meltdown [Re: mikes733]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
If you can't re-locate that breaker to an undamaged part of the buss - perhaps swapping places with a much smaller one - then you really need to replace the busses.

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#204388 - 12/06/11 08:55 AM Re: breaker meltdown [Re: mikes733]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Is this a bolt-in or push in CB? 'sanding' the buss may not have been a good move. The contact tension on the push in type CB may be compromised, resulting in failure over a period of time.

If you are running 208 volt, 3 phase, with a 60 amp CB and 15KW of heat you also have an issue with the 'continuous load' (80%).

Conductor size?

Like Greg said, see if you can get your hands on an IR unit, you may have a heating issue due to the design.
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John

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#204394 - 12/06/11 02:55 PM Re: breaker meltdown [Re: mikes733]
mikesh Offline
Member

Registered: 06/07/06
Posts: 614
Loc: Victoria, BC, Canada
Since your load is linear my idea that it may be related to non linear loads is not going to explain it.
A 3 phase 15 KW load on a 60 amp breaker should be around 42 amps so the breaker looks correct for 3 phase, Single phase would be a 90 amp breaker and a 72 amp load, Note that the 90 amp breaker is actually 1/8th of an amp too much load for the 90 amp breaker but most inspectors would give that much away.

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