Sense for AC diagnostics?

12ft ceiling “loft”, and yes, two separate spaces (rooms) within.

Even a relatively small (theoretical 8000BTU) 12SEER LG window AC can cool the space with air circulation between rooms but the heating is the more problematic factor. I’ve insulated as much as is practical in an all exposed brick 19thC building (my walls are lined with R7.5 Foamular and so on) but I still use around 4kW (for good number of hours) to keep the place warm. I am all electric out of necessity.

I’m “handy” so intend to do most of the install myself but keeping the warranties & codes intact involves a licensed HVAC/electrical installer to do the final hookup (vacuum pumping) … and in striking a deal it was determined I could get 2 for almost the price of one (installed) so I went with a “redundant” system.

My space will be more RAID 1 than RAID 0. :wink:

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My AC unit was popping the circuit breaker just like yours. It turned out the breaker switch was the culprit. Since I replaced it, no problem.

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There is another thing that could have been going on. You said it was a couple of very hot days, that means everyone was likely running their AC. When this happens sometimes Utilities reduce voltage to be able to meet the demand. When this happens you unit will pull more amperage which both heats things up and can trip breakers. It is possible that the low voltage is what actually killed this older unit that was on its last legs.


Good point.

I believe though that @kevin1’s problem was traced to something more systemic than brownout voltage drops.

I was involved in a high-rise building renovation and witnessed a few super-long extension cords run to power tools on scaffolds spontaneously combust due to the same problem.

BTW: There are calls in the Community (mine included) to get alerts when supply voltages drop …

@dave has done some legwork in that regard


Glad you got this sorted out! But I feel I have to offer a word of caution for situations such as these. When a breaker trips, it’s usually for a good reason (excepting of course the “bad breaker” scenario mentioned above). Continually resetting it without understanding the reason for the trips can be very, very dangerous. Breakers are sized for load that the wires can safely carry. More current can result in excessive heating of the wires, which can eventually cause a fire if a breaker is reset while the wire is still heated. I’m not whistling dixie either. I’m a fire officer, and 3 weeks ago we went to a house fire which destroyed much of the house- but specifically the refrigerator (which was the point of origin of the fire). When the homeowners arrived home, they offered that they were continually having problems with the icemaker tripping the breaker- they just kept resetting the breaker…


Thanks for the cautions… I watched my Sense very carefully over those 2 1/2 days for any signs that the power / current were above the usual but did not see any excursions beyond the usual 4500W. But that dis have me questioning what makes a thermo-magnetic breaker pop. I couldn’t find in the Square D specifications - is it pure peak current that uses an electromagnet ? Or is there also a measure of current over time (or accumulated energy) that triggers a breaker on the thermal side ?

Seems like the only thing that could have been popping my breaker was a spike that I couldn’t see at Sense Power Meter half second RMS average resolution.

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I think you are looking at current over time that triggers a residential type breaker. try this site and look for the time overcurrent downloads or tripping curves for the type of breaker you have, This site is Schneider Electric. They are the parent of Square D, or at lease the current owner.
Many people are surprised that a 20 amp breaker may take 15minutes or longer to trip at 20 amp and maybe 100 amp to trip in one second.


I mentioned (above) HACR breakers which are designed for HVAC & motors … they have higher overcurrent spike tolerance.

Correct me if I’m wrong, licensed people, but most/all HVAC should have that type of breaker.
They are code-required by NEC as far as I’m aware.

Post 1995 I think UL started to require that all the bigger breakers would need to be HVAC-capable … so if you have an old breaker there’s a chance it’s not labeled HACR.

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Exactly what I was wondering, but I couldn’t find the other day. At less than 1/2 second, it would take 8x the rated current to trip. I could see that at the peak of an inductive spike.