While Sense so far has done a pretty poor job of identifying any power consuming devices correctly, I’m wondering if it may have helped me discover a problem with my heat pump. I’ve looked around on the web, and I can’t find anything indicating if this is expected behavior or not, but it certainly surprised me.
Our heat pump seems to use about 9-10kW when it’s running… but for 1-5 minutes before shutting off, the power consumption jumps WAY up to 19-20kW (these figures are absolute, so in reality, about 0.5-1kW less than that is really attributable to the heat pump).
These spikes are consistent, though their duration is not. The screen shot below shows a spike that’s less than 2 minutes long, but as I scroll back in my timeline, I see plenty of other times where it’s 2-5 minutes, and at least one recent instance where it was in the 6-7 minute range. It makes me suspect that, for some reason, the home’s heating system is switching into aux (resistive heating) mode. I live in Virginia, and temperatures have ranged from 35°F on cold nights to 75°F on the warmest recent days, so it’s never been so cold that the heat pump should ever need to fall back to aux/resistive mode in order to keep the house warm.
I’ve never monitored my power usage with this fine a temporal resolution before, so while I suspect this isn’t normal, I don’t know for sure. If this is not normal, does it indicate a problem with my thermostat (a Honeywell 7-day programmable unit), my furnace, or my heat pump?
Here’s a screen shot of the most recent instance: