How was your device detected?
Enabled Sense Labs, and was alerted that a device was stalling immediately upon activation of the feature (by looking at it in the app).
What device has a potential issue?
Outdoor AC Heat Pump (Phoenix, AZ)
- Manufacturer: Goodman
- Model: SSZ140481AG
- Age: ~8 years old, original hardware and original start/run capacitor
- Typical running usage: ~3,400W
Screenshots from Sense Labs: Motor Stall
Stalls detected per day from Labs:
Note: I installed my Sense on 6/6/20, so stalls were almost certainly already occurring (unknown to me!)
Final detected stall from Labs (prior to start/run capacitor replacement):
Peak Value: 21,595 W
Motor Stall from Power Meter (prior to start/run capacitor replacement):
Removed original capacitor
Herm Capacitance: (IS): 17.2 uF (S/B): 45 uF
Fan Capacitance: (IS): 996 nF (S/B): 5 uF
Replaced with new capacitor with Genteq unit from Amazon, on 6/29/20
Values matched stated 45uf/5uf
Power Meter Trace of first startup immediately after replacement:
Notes: The +1203w step was the electric oven which was on at the same time, so 1203w would be the baseline for the Heat Pump startup. The HVAC tag is in the inside air handler starting up ~5 second later.
Power Meter Trace from recent (7/10/20) Heat Pump + Air Handler Startup
Notes: Still showing similar profile.
Definitely appreciate the feature, as it’s likely saved us from additional repairs in the near future! Given that the heat pump has probably been stalling for awhile without my awareness, some damage is probably already done though.
My only complaint is that now Sense has to re-learn to reliably detect my heat pump, but confident it’ll get there! It’s been extremely successful at detecting devices at my house, with 10 devices (primarily major appliances and a few lights) detected since install on 6/6/20.
OH MY, now we’re talking!
Great breakdown of the breakdown.
Thanks for all the details and thanks to Sense. Great to see this progress.
An epic breakdown of a breakdown. So, so extremely helpful.
You’ve set the bar for motor stall reports moving forward, @cbpowell.
Thanks for sharing @cbpowell! Glad you were able to replace it.
Happy to help and provide the details!
I also forgot to mention in my original post - there was a big change and reduction in the running noise from the heat pump unit after replacement. I wish I’d thought to record it before/after as it was very noticeable. It’s been a few days now so I don’t remember the noises as well, but I want to describe it as a large reduction in electrical humming and vibration? I should probably poke through the Inspectapedia page linked by Sense Labs to find a representative “before” audio sample.
The real gotcha (of the good variety) would be if you can quantify the before/after energy use and possibly demonstrate Sense’s core values even more!
Would love to see the hum/vibration waveform/s up against the Sense waveforms! My experience with hum/vibration is that you can pretty-much nail the issues with big multi-phase motors from the sound if you have an ear for it … though I don’t recommend trying too hard because you’ll end up with misophonia like I have.
Well interestingly I don’t think it had much effect on the steady-state power consumption, although that probably makes sense given that it was a capacitor(s) that was replaced.
At a high level on a long timescale, you can certainly tell when the capacitor was replaced though:
Looking at ~3:30am on the days before/after replacement, to get an otherwise electrically-quiet period:
Before @ 3,850 W steady state, ~400W baseline = 3,450W
After @ 3,600 W steady state, ~330W baseline = 3,270W
However I did notice while grabbing these images that there is a definite correlation of steady-state consumption with ambient temperature. So I didn’t control for that between these two images. For example here’s from a little earlier today, with a nice warm 110deg ambient temp:
4740 W, ~420W baseline = 4320W
I don’t have a lot of knowledge on heat pumps though, so maybe that’s well known? I’m happy to donate my data to the Sense team for investigation if needed.
How many CT’s do you have; the original 2? Would an extra CT (or 2 depending on wiring) on this circuit provide any benefit?
Personally I just have the two original CTs installed. I did buy a 2nd set but haven’t installed them yet, though my A/C would be my likely target.
My understanding (and experience) is that Sense is plenty capable of detecting motor stalls with just the two original CTs though. If the 2nd set were installed and motor stalls were detected on them, it would presumably narrow down identifying the source though, if Sense hadn’t done it already…particularly if they were measuring just that one motor!