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#204379 12/05/11 10:15 PM
Joined: Feb 2008
Posts: 3
M
New Member
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.

Joined: Mar 2004
Posts: 947
T
twh Offline
Member
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.

Joined: Jul 2004
Posts: 9,788
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G
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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.


Greg Fretwell
Joined: Jun 2004
Posts: 1,273
T
Member
Check for corrosion on the Aluminum bus...



Tesla
Joined: Jan 2005
Posts: 5,369
Likes: 1
Cat Servant
Member
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.

Joined: Feb 2008
Posts: 3
M
New Member
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.

Last edited by mikes733; 12/06/11 10:13 AM.
Joined: May 2005
Posts: 984
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G
Member
15kW strip heaters drawing 60 Amps per phase??
What voltage are you running at?


Ghost307
Joined: Jan 2005
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Cat Servant
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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.

Joined: Apr 2002
Posts: 7,333
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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.



John
Joined: Jun 2006
Posts: 613
M
Member
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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