ECN Forum Forums General Topics of the Trade General Discussion Area Residential Main 200A breaker trips and humms

Sounds to me like the heat pump is too large for the service. This record cold could be making it work more than it ever has in the past.
Just so I am sure have the fact correct let me restate them
100 amp main breaker trips when 115 amps and 130amps are going through both legs. Don't see a problem Breaker is doing its job.

100 amp heat pump breaker does not trip when 100 amps is going through it. Sounds normal that the main would trip first.

Sounds like she needs a service upgrade to 200 amps.