Main Breaker Tripping on Residential Panel

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jonny1982

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Has anyone ran into this? The main breaker is tripping on a 200 amp residential panel every once in a while. The home owner says it seems to only happen when they leave the house for a week or so for vacation in the winter and then come back. They have an electric heat pump system with (2) outdoor compressors. They say they leave the temp. at about 65 when they are away and when they come home, they turn it up to 70 or so and when the auxiliary heat kicks in, it trips the main. They did say it even happened once just when they went out to eat and came home and upped the temp a little. I clamped A phase of the main and it was drawing 30 amps and I clamped the B phase and it was drawing 40 amps (under normal conditions with the heat running). I did notice however, that while it was clamped, the A phase went up to 90 amps for a couple of seconds and then went back down to 30. I figured this was some sort of in - rush?

I'm thinking possibly a faulty main breaker (Cutler - Hammer)? Or maybe the main can be replaced with one that has some sort of settings that could be adjusted for in-rush?

Thanks
 
Don't believe you can get adjustable (Inst) CBer for load center.

What is the kW of the electric heat for each of the two system ?
Can HP and electric heat run simultaneously....apartments I work on ME locks out HP when electric heat is required.

Then the question is was the service sized for BOTH the HP's and Elect Heat running together.
 
jonny1982 said:
Has anyone ran into this? The main breaker is tripping on a 200 amp residential panel every once in a while. The home owner says it seems to only happen when they leave the house for a week or so for vacation in the winter and then come back. They have an electric heat pump system with (2) outdoor compressors. They say they leave the temp. at about 65 when they are away and when they come home, they turn it up to 70 or so and when the auxiliary heat kicks in, it trips the main. They did say it even happened once just when they went out to eat and came home and upped the temp a little. I clamped A phase of the main and it was drawing 30 amps and I clamped the B phase and it was drawing 40 amps (under normal conditions with the heat running). I did notice however, that while it was clamped, the A phase went up to 90 amps for a couple of seconds and then went back down to 30. I figured this was some sort of in - rush?

I'm thinking possibly a faulty main breaker (Cutler - Hammer)? Or maybe the main can be replaced with one that has some sort of settings that could be adjusted for in-rush?

Thanks
Click to expand...

Look for loose connections line or load side of the Main Breaker. Use an IR thermometer if you have one, $70 or less at places. Do a FOP across the Main CB line conductor to load buss bar. Should be 100 mv or less IIRC. Most of the time you can feel the heat with your hand. Look for all the signs of overheating including the smell test.
 
MyCleveland said:
...What is the kW of the electric heat for each of the two system ?
Can HP and electric heat run simultaneously....apartments I work on ME locks out HP when electric heat is required.

Then the question is was the service sized for BOTH the HP's and Elect Heat running together.
Click to expand...

All the heat pumps I install and service have the aux electric heating available while the compressor is also running. It's sometimes used specifically when the temp rise is called for more than 3 degrees. And then it is also used as an emergency heating if the compressor fails.
 
Jonny,

If the only running major load is the Heat Pump / Aux Heat, then I think ptonsparky (Tom) is on the right track. Over the years, I've experienced Main Breakers that have been operating from the thermal trigger (normally for low level running overload current tripping) where the heat affecting the internal breaker bi-metal trigger is being largely created by a connection that is poor, and, as a result, that is heating.

Other hints come from visible sign of corrosion, water flow, critter/insect activity not just on the main breaker, but anywhere inside the panel.

Now, you haven't given any hint of the other loads that are supplied through this breaker. . .
 
Had one like this a while back , metered everything multiple times / visits...

Finally found two worn connections on the OH serv drop clacking together in the wind

The intermittent stuff can drive one crazy .......

~RJ~
 
ptonsparky said:
Look for loose connections line or load side of the Main Breaker. Use an IR thermometer if you have one, $70 or less at places. Do a FOP across the Main CB line conductor to load buss bar. Should be 100 mv or less IIRC. Most of the time you can feel the heat with your hand. Look for all the signs of overheating including the smell test.
Click to expand...


That's what I would do and I have found several of them even before I bought an IR thermometer just by feeling of the main breaker and service conductors near the lugs. If it's hot it's normally not good.
 
romex jockey said:
Had one like this a while back , metered everything multiple times / visits...

Finally found two worn connections on the OH serv drop clacking together in the wind

The intermittent stuff can drive one crazy .......

~RJ~
Click to expand...
How does that trip breaker located on load side of the problem? Motor dropping out and restarting frequently maybe is one possibility. Most heat pump will have a delay before restarting a compressor and won't have that sort of scenario though.
 
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