Boiler blows circuit

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Old 05-19-11, 07:18 PM
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Boiler blows circuit

Hi -

The circuit for my boiler's electronic components keeps tripping (its a Burnham boiler that's like 35 years old). Anyway, I re-energized the circuit and have concluded that the breaker trips out in two scenarios - immediately when the boiler goes to start, or after the boiler has been running for like 3-5 minutes. On close inspection, I noticed a pretty large flash from the butt-end of my BG-100 circulator pump at the moment the breaker tripped. Am I correct to conclude that simply swapping out the circ pump motor will likely solve my tripping breaker issue? Anyone heard of such a thing before? Strangely, in removing the motor, and wiring to another outlet, I don't seem to have any issues - perhaps because without the impeller, there is no load on the motor? I'm puzzled...
 
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Old 05-19-11, 08:00 PM
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You might not have a problem with motor but with the impeller as you may have already found out. The impeller might be be getting stuck causing to stall the motor which you would get the LRA of the motor (which might be listed on the motor) which could as much as 3 times the running current, which could easily trip a breaker if held too long.
 
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Old 05-19-11, 08:58 PM
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I thought that as well but I've removed the motor assembly and can spin the impeller shaft by hand. It's not stuck but I am curious, how freely should the shaft spin? Very freely, like on ball bearings, or should it have some light resistance? I can't spin it like a whirligig and make it spin freely. I just don't know how freely it should spin...
 
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Old 05-20-11, 06:20 AM
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Since you said it will sometimes run a few minutes before tripping the breaker it might be a bearing or bushing that is causing the motor to lock up. Another thing you can do is you get a clamp on meter to measure the current draw of the motor with a load on it and without.
 
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Old 05-20-11, 04:08 PM
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If you are able to get a clamp on meter, check to see if the meter has a 'peak hold' button on it and see what the peak current is when the motor starts.

Don't overlook the fact that you may simply have a defective circuit breaker in the panel! It's happened many times... ppl have troubleshot the heck out of a system only to find the breaker is bad.
 
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