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Bedroom AFCI breaker randomly tripping when Central A/C unit turns on

Bedroom AFCI breaker randomly tripping when Central A/C unit turns on

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  #1  
Old 02-07-13, 11:12 AM
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Location: Ithaca, NY
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Bedroom AFCI breaker randomly tripping when Central A/C unit turns on

When we first moved in to our house 3 months ago my UPS in my office would randomly trip. It was a cheap UPS so I thought it was having an issue. I stopped using it and have been using plain circuit breakers ever since.
Well, about 3-5 days ago the breaker for the room started tripping frequently, but didn't seem to coincide with any appliance usage.
I pulled the 15A AFCI combo breaker and noticed the contact to the center post was a little black so I replaced it.
I also replaced the outlet in the room that has the computer plugged in to it because it was a little loose. Also I was hoping that they used 12ga wires so I could upgrade the breaker to 20A... no such luck.
One thing I noticed at this outlet is that there are 3 sets of hots and neutrals all spliced together. It might be typical, but I don't remember seeing that in our old home where I replaced all of the outlets.

So after those two replacements the 15A breaker continues to trip at random times. It did trip when the A/C kicked on this morning, but it is central A/C and it is on it's own double pole 30A breaker. I've noted that the 30A breaker is directly across from the 15A breaker in the panel.

I've monitored the voltage in the room when the A/C turns on and there is a slight voltage fluctuation of 3-5 volts... nothing big.

Right now I am at the same computer and the A/C unit is running on and off and no circuit breaking.... I tried running a vacuum cleaner in the room to see if I'm overloading the circuit and no circuit break.

As a further diagnostic I've added up the max wattage on all appliances in the room. It would be about 1200W IF I was running everything and it is more likely 800W when the breaker is tripping since the computer can only pull 700W max and more typically runs at 500W. Also I'm not running most appliances that I include in the 1200W figure. At any rate, 1200W is high, but a 15A breaker should be able to handle it.

I'm now running my computer to a separate outlet in the room via heavy duty extension cord. I'll have to wait until the breaker trips again to see if that is any difference. This may take a long time since the computer can run all day without tripping the breaker, but sometimes it will run less that 10 minutes.

I continuously wonder if it is the AC unit and if it is occurring when the unit hasn't be running for an extended period of time. Is it possible that the AC unit on a different breaker (that is directly across from the 15A breaker with the issue) is causing the problem.

Please help! I don't want to have to wire in a new circuit to the room just for the computer.

Thanks!!
 
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  #2  
Old 02-07-13, 12:10 PM
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I can't think of how the 240 volt A/C has any affect on a 120 volt circuit.

How old is the house?
 
  #3  
Old 02-07-13, 01:08 PM
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1960s, but the panel is all new. Wiring and outlets look new too.
The house had a fire a couple of years ago and was almost completely remodeled.
 
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