ASK THE EXPERTS: PV Breaker Problem


In July 2017, I had a rooftop grid-tied PV system installed. It consists of 32 SolarWorld 290 W black modules connected to one SolarEdge SE7600A-US inverter. I also had my breaker box updated to a 200 A service box. Since it went live, the backfed 40 A breaker has tripped maybe six times. It seems to trip when the array is at or near its peak daily output. I have not tried anything other than resetting the breaker. What’s happening and how can I fix it?

Steven Hambacher • via email

I’m sorry to hear you are having problems with nuisance tripping of that breaker, which is correctly sized for that inverter—at 240 VAC, it has a maximum output of 32 A at 7,600 W. Including the 125% safety factor required by the National Electrical Code, it’s sufficient (32 A ×1.25 = 40 A).

Is the breaker tripping when ambient temperatures are high? Is your breaker panel installed in a location that’s exposed to heat? Breakers can be affected by the ambient temperature, and high temperatures may cause them to trip at lower current.

Another possibility is that the breaker is faulty and needs replacing. There may also be a poor connection along that circuit or a slightly damaged conductor, which can cause an intermittent short-circuit. Call your system installer about the situation. They should be able to troubleshoot this for you. If you figure it out, let us know!

Justine Sanchez • Home Power senior technical editor

The breaker trips on hot and cool days, and when it trips—during peak production time—the sun is overhead and the breaker panel is located on the north side of the house, so high temperature or heat exposure is not likely the issue.

I replaced the 40 A breaker myself so I could eliminate that as a cause. The black-wire contact from the inverter had a stuck screw and may have been loose. I could back out the red wire screw easily, but I could only get half a turn on the black screw. It may have never been seated tightly. The new breaker is in place and both contact screws are seated, and the problem appears cured.

Steven Hambacher • via email

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