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post #1 of 12 Old 06-09-2011 Thread Starter
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Buzzing from AC panel

Yesterday night, while using around 20 amp's of AC, my main breaker tripped (It is a 30 amp breaker). I have separate 15 amp port and starboard breakers and each was under capacity. When I checked, the main trip was a little warm to the touch (not excessively though). I turned it on and there was some buzzing which in a few seconds turned to some sparking noise together with some oscillations in the amp meter needle. From the back of the panel, I could see little sparks jumping from a main hot post to the bus metal. I turned everything off and unplugged the shore power. The I cleaned the two main posts on the AC hot bus and tightened them. The sparking noise and the amp oscillation was gone but there is still a little buzzing.

Now, I don't remember if that little buzzing was there before. Is that normal? I am thinking of cleaning (Take off the posts one by one, a little sanding to get the slight corrosion off and screw back tight) the whole AC and DC panels. Is that the likely cause or can you think of another problem? Also, any advice on better cleaning these things?

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post #2 of 12 Old 06-09-2011
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The most common things that buzz with age would be the coils in relays ,valves or transformers

I don't know if you have anything like that in the panel BUT if the main breaker is OLD things can loosen up inside OR the contacts can have high resistance from arcing during trips which can do strange things

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post #3 of 12 Old 06-09-2011 Thread Starter
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Thanks tommays, are you saying that buzzing is not due to the contact problems? I guess I need to change the AC breakers anyway. They all look like original 30+ years old equipment although it was well done at the time.

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post #4 of 12 Old 06-09-2011
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buzzing on 110 AC is a problem. May be loose connections, crimps or breakers...but needs to be addressed as it seldom gets better on it's own....usually includes heat at the junction, which can lead to a fire.

There is little, if anything, in that panel or behind it that "should" buzz or crackle...

An infra-red temp gun can help you locate high heat spots
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What kd3 says, but I'd go one further.

Buzzing can be a sign or arcing or other physical faults which CAN CAUSE A FIRE. I'd suggest erring on the side of paranoia, and disconnect the AC from the boat if you cannot find the source of the buzzing and eliminate it.

Could be a relay coil, could be contacts arcing. Breakers have a limited life. Sometimes crud builds up on contacts and the arcing will "safely" burn away the crud. Other times...Get the marshmallows and weenies, the problem can get worse.

I'd rather err on the side of paranoia when it comes to fire.
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I just ordered an IR temp gun. Thanks for the tip.

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Quote:
Originally Posted by hellosailor View Post
What kd3 says, but I'd go one further.

Buzzing can be a sign or arcing or other physical faults which CAN CAUSE A FIRE. I'd suggest erring on the side of paranoia, and disconnect the AC from the boat if you cannot find the source of the buzzing and eliminate it.

Could be a relay coil, could be contacts arcing. Breakers have a limited life. Sometimes crud builds up on contacts and the arcing will "safely" burn away the crud. Other times...Get the marshmallows and weenies, the problem can get worse.

I'd rather err on the side of paranoia when it comes to fire.
I am concerned about it. I am not leaving the boat unattended with AC connected for now. I will change the main AC trips and the temp gun will tell the rest that needs to be done I hope.

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post #8 of 12 Old 06-09-2011
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While you're at it change to one of these... most insurance companies will give you a discount for it.

SmartPlug Systems - Shore Power Products and Accessories

Ron

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Quote:
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While you're at it change to one of these... most insurance companies will give you a discount for it.

SmartPlug Systems - Shore Power Products and Accessories
Yep, that's on my list of things to get. Near the top. But with a new to us 33 year old 50 foot boat that was mostly unused and ignored, that list is longer than the boat.

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No problem finding ways to spend YOUR money!!

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