Could backup battery have damaged my refrigerator?

[hmulligan]

I have been working with a great company to install a solar system in my house. The system has a 10kWh backup battery system that can provide power to a subset of our circuits in the event of a power outage. The company sent a technician to do the final check of the battery system. I am not certain exactly what the tests involved, but we know it involved turning power to the battery-connected circuits on and off.

While he was working, our kitchen light (integrated LED) stopped working. Then, the next morning, we noticed that our coffeemaker would not turn on and that our refrigerator had not been keeping temperature (the lights were on so we didn't notice it wasn't cooling).

We are now trying to figure out what happened. The technician came back, checked the battery's logs and the voltage in our outlets. The company says that it was a power surge from outside the house that was unrelated to their work and that the battery couldn't produce that much power anyway (or there would be a record). We are convinced that because all of the damaged items are on the battery circuit and because it happened during their work that the damage was caused not by a surge but by cycling the power. I would appreciate any ideas for what might have happened in our house.

 

[Lucien Nunes]

Power cycling these items shouldn't cause damage. About the most severe effect I'd expect would be to temporarily lock out the compressor on the fridge by attempting a restart against residual pressure that trips the thermal protector.

The inverter is also unlikely to be able to produce excessive voltage that would cause damage, although it might produce DC or some other out-of spec power in the event of a serious malfunction.

Does the inverter supply both hot legs of your panel (i.e. 120/240 output) or 120V only? A 240V unit with a disconnected neutral can cause 240V to appear across 120V loads on one leg if a much heavier load is connected to the other. This failure mechanism might have damaged the control circuits in the coffee machine and fridge and the LED driver.

Keep an open mind at this stage; convincing yourself that the installation technician caused the event might make you overlook something, even something that proves that theory correct.

 

[hmulligan]

Power cycling these items shouldn't cause damage. About the most severe effect I'd expect would be to temporarily lock out the compressor on the fridge by attempting a restart against residual pressure that trips the thermal protector.

The inverter is also unlikely to be able to produce excessive voltage that would cause damage, although it might produce DC or some other out-of spec power in the event of a serious malfunction.

Does the inverter supply both hot legs of your panel (i.e. 120/240 output) or 120V only? A 240V unit with a disconnected neutral can cause 240V to appear across 120V loads on one leg if a much heavier load is connected to the other. This failure mechanism might have damaged the control circuits in the coffee machine and fridge and the LED driver.

Keep an open mind at this stage; convincing yourself that the installation technician caused the event might make you overlook something, even something that proves that theory correct.

Thanks for the prompt and thorough reply. The inverter just supplies 110V and passes all tests. I'm stumped as to what happened. It seems like either there is some external event, though the weather was good (no lightning) and nobody in our neighborhood has reported anything unusual, or something unusual that happened during the testing. I've read a few things about refrigerators not fairing well if power flickers, for example "what damages a refrigerator or window A/C is not so much surges but the times when the electrical service "blinks" or goes off for just a very short time and then back on. The compressors are then re-starting under load and this will do expensive damage." That would seem to fit with the battery testing procedure. But, it doesn't explain the light or the coffee maker.

 

[Lucien Nunes]

That comment is somewhat alarmist; refrigeration compressors are designed to withstand power glitches. They stall, the protector trips, three minutes later it resets, if the pressure has bled down enough the compressor starts, otherwise it trips again and retries after another 3 minutes. It's not ideal but it happens and I've never knowingly seen a compressor destroyed by a single power glitch.

To carry out any further useful analysis one would need to know exactly what is damaged in each of the items.