Received a call from a customer. Seems that her heatpump (with electric backup) was acting up. According to her the service man had said something shorted out in the heatpump electric backup and this caused the main 200A breaker to kick off. This kicked off several times and was reset by her within about 3 hours while waiting for the HVAC man to show up. This happened two weeks ago. She called me to come over to look at the main breaker because the guy said it should not have tripped. I hesitated in going because the individual circuit breaker should have tripped not the main but went over. Not much I could do so I told her to see if it does it again. While waiting the time in between when the first guy worked on the heatpump and when the second guy came yesterday to replace a part nothing happened (no tripping). He leaves and then she calls me because it happened again. This time while he was there he noticed that there was a humming coming from the electrical panel so he advised her to call me. After he left the main breaker kicked off again. I went over and noticed that the main breaker was very warm. Then I actually heard it humm a bit. I shut off the breaker (100A 2 pole) feeding the heatpump electric backup and then reset the main breaker. Leaving the 100A breaker off so the heatpump elec won't come on I measured the amps on each line 120v line to neutral on one and 120v line to neutral on the other. I also took a reading of the amps on each line side of the main with the 100a breaker off. One side I got 22a and the other 33a. Then I put the 100a breaker back on to the elec backup and waited for it to come back on. When it did I took a reading of the lines again. One side was 115a the other 130a (total about 245A) while the elec backup was running. About 3 minutes later the main started to humm and kicked off. I shut off the 100A breaker again and reset the main breaker. I noticed the main breaker was very warm but did not humm while the 100a breaker was off. I tugged and wiggled the lines going into the main breaker and they are secure. One line wire wasw very warm and almost hot the other line wire was cool. Let it sit without the electric backup running and the main cooled off. Repeated the process again of turning on the 100A breaker, allowing the elec backu to come back on, measure the lines and ended up with the same 245 amps and the main breaker heated up again. What is strange is that she has had this heatpump for 7 years and has added nothing in the house in the way of large consuming energy devices/appliances. Also her stove was not on when the main tripped. This seems to started only when the elec back up had a problem and needed servicing.
NOTE: During this tripping of the main not once did the 2 pole 100A breaker feeding the heatpump elec backup tripped nor did the 2 60A breakers on the electric backup trip.
Any ideas would be helpful here.Thanks
Last edited by AFJES; 01/23/14 02:44 PM.
