Residential Line Voltage Monitors to Remedy Utility Issues Causing Heat Pump Tripping Circuit Breaker

[marmathsen]

I have a small back yard ADU project that was finished a few months ago. It has a new 200A service that shares an overhead drop from the utility that feeds both the main house (200A) and the ADU (200A).

They have had issues with the heat pump circuit tripping about once per week on Sunday night/Monday morning.

As a first attempt we swapped out the GFCI breaker (HOM230GFI). The install instructions require GFCI protection and no one is willing to OK installing a standard breaker.

We also setup new (temporary) wiring from the panel all the way to the unit including a new fused disconnect.

The equipment rep for Mitzubishi came out and logged the heat pump during operations and stated"

"you have installed a fresh breaker and a new circuit. And it all appears to be more than sufficient to handle this load.

The equipment has been thoroughly tested and has no shorts. I ran the system through an entire test mode while testing inrush, average and maximum amp draw. Inrush was 1.6 amps, dropping to 1.3 amps. Maximum draw at high call from all 3 zones was 7.9 amps"

"Generally when we see all of these symptoms like this, the process of elimination always comes down to an incoming power issue.

I have, in the past used data loggers and an oscilloscope to show these power anomalies, and even with hard evidence the utility providers have denied fault. And then when cornered a bit, they sometimes acquiesce and admit that it is a problem that they cannot do anything about it. So protecting the equipment with an external device becomes the answer."

He gave an example of a church he helped troubleshoot who was replacing 2-3 boards per cooling season. After 2 weeks of logging, he

"recorded about a dozen surges exceeding 150 VAC and more than 60 brownout events where voltage dropped below 105 VAC. The key distinction was in the duration: surges and overvoltage events lasted less than a cycle, while undervoltage events persisted for 2 to 5 seconds or longer."

He is recommending installing a live voltage monitor, which would disconnect the equipment until the anomaly resolves. Either the RectorSeal RSH-50 VRMDC or the ICM ICM493

I guess I'm hoping those in the forum can share any experience they have with similar scenarios.
I've never seen this in Seattle, is it more common in other areas?
Is it common for the utility to shrug and say, "not our problem"?
Have you had good luck with these products or something similar?

edit: And does it seem accurate that these claimed voltage issues would cause just the one circuit to continue to trip?

Rob G
Seattle

 

[Jraef]

One circuit, unlikely.

Heat pump, tripping only at night, GFCI breaker, I immediately think condensation forming when it gets cooler at night under certain circumstances and causing something to get wet and become a ground fault. Then when the heat pump isn’t running, less temperature difference, condensation goes away, no more tripping until the conditions are right again. Mitzi tech can’t duplicate the exact scenario.

Water displacers like WD-40 might help, or a desiccant pack in the electrical compartment. If that lessens the occurrence, it proves the theory.