Strange Electricity Spikes

That’s normal behavior for motors and especially compressors. It has to do with getting a motor going with single phase service.

it could possibly be the run capacitor is beginning to fail if it has one. how old is the unit? are the fans working properly? could be a lot of different reasons for the spike, sadly these kind of mysteries are difficult to track down and if something is failing unfortunately until it fails you may never find it. if it started recently the spikes are your warning, 50+ years in the HVAC/Refrigeration business has taught me that

You can’t really assume that very short spikes are necessarily represented precisely in the Sense display. The in-rush current spikes are often sub-second (of the order of 4 x 60Hz cycles) so the translation to the display is not really showing you what’s going on.

Reposting link from above regarding measurement of in-rush:

Zoom all the way in to the waveform and establish the duration. You can pretty much ignore any “line” spike.

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I only found it notable because, of my 7 compressor devices (5 of which are identified), this is the only one where sense records the in-rush current with such stark visibility.

It looks like this example has 2-3 seconds of high current draw. Agree that it looks like there’s a problem here. This kind of problem ought to be audible if you’re near the device that’s causing it when it happens.

@senseinaz I shot you a PM with some possible answers from the DS team :slight_smile:

In short, this is likely to be some sort of AC failure.

As usual in these threads I think we got a little tangled @pswired . I was referring not to the OT but this one:

I agree on the OT determination but was drilling down for @dudleynyc

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Got it. that makes perfect sense to me.

I don’t believe you have a problem, looks as it should. Here is my heat pump that is less than a year old and a refrigerator months old.
Notice the spikes.
You may not see the spikes with inverter driven motors as they are setup like three phase.
Those spikes are normal but I don’t know what is causing all the continuous choppiness on your graph.

“Choppiness” at that scale is pretty normal for the mains PM … I think you might be assuming that was a Device waveform?

Mine is never that choppy. I don’t have any devices that cause it.

Compress your timescale to match, 2hrs/screen or more. Of course it will depend upon what you are running but I don’t think your second graph will “smooth out” if you scale that way. Mine is super-choppy at that scale.

Here is 2 hours. You will see the last hour looks somewhat choppy but that’s actually the Kerrigan secondary 245 heater
I can’t replicate that choppiness at any scale


When you said you “just discovered these spikes”, did you mean:

  • They have been happening for a (long) while and the new alert just pointed you to them.
  • They are a new phenomenon ?

All large AC motors spike when their coils energize but your spikes look very large relative to my 4 ton basic AC unit (a 2000W spike associated with the On transition of 2700W steady state. Your spikes also seem to be associated a motor spinning down (power usage dips). Not sure why that would occurs but AC motors also generate power spikes like that if the loading on a motor suddenly increases.

Thank you Ryan, that info was very thorough and helpful. I’ll try to keep this thread updated as I learn more. Hopefully my experience will help others with similar questions.

I have 2, 3 ton AC units that work well but are quite old as far as ACs go. When these ACs power on I get a spike of about 5k per AC, which drops down to around 3600 watts while running. These recent spikes were much much higher and not something I had seen before. I’ll usually check Sense every few days to spot any patterns and see how my electrical load is for the day. On any given day my electricity will generally hit up to around 15k at peak and that’s at night with 2 ACs, 2 pool pumps, TV, and the dryer running. These spikes up to 20k are far from normal and they stuck out like a sore thumb. The strange thing is that they only happened over a period of ~ an hour and a half. These spikes have not returned since. It has also been much cooler here so I keep monitoring. I do appreciate everyone’s assistance and will keep updating as I learn or see more.

So it’s safe to assume that 15,000 watt spikes indicate a problem? :face_with_raised_eyebrow::grimacing:

Do you have Sense Labs activated?

In your case that could well reveal an issue and lead you to a fix.

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Sorry for not updating this thread. The latest updates are here: Motor Stall - 3Ton HVAC

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