Device found, recognizing and then dropping out

My Sense had identified my compressor/condenser/fan several days ago, and I wondered about the furnace blower which hadn’t been detected until the last couple of days. Now the weird thing, when the AC kicks on, the furnace is also identified, but only for a few seconds and then disappears from the list or bubbles, and when I try to merge these two, it then knocks them both out of the running (literally).

My system doesn’t have a separate dedicated dehumidifier, the only dehumidification going on happens via the evaporator.

I know it is the furnace fan/blower because it detected it as soon as I turned on just the fan/blower to circulate some air and to see what the amount was for watt consumption.

So the weird thing is the furnace only shows for a second or two when the AC is firing up, and I can’t merge them because then neither of them show.

I had a similar issue recently. Sense first detected the AC compressor (~3000 watts) but no blower motor. A week or so later it detected a second device running concurrently with the AC which had a fairly high naming percentage of “HVAC” among other users. Once I accepted this device and started watching it, I noticed that both HVAC and AC would be detected on startup, but that AC would drop out quite quickly and then the full 3000 watts would show under the HVAC device.

When I contacted support, they confirmed that Sense had basically detected a duplicate device and once the software sees that two duplicates are “on” it simply eliminates one and continues to display the other. Their recommendation was to delete the duplicate. They recommend NOT to merge them.

I suspect that Sense is smart enough to see that two devices are starting simultaneously, but can’t determine how much power each is using. If one of them had a short delay that would likely help. Short of installing a time delay relay, I’m not sure how this could be easily/ quickly resolved.

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So I’m going to give some advice here based on looking at AC detections for two central HVAC systems in my house over 3 years.

  • Don’t try to name them or merge them intelligently for at least a year (one full heating and cooling season).
  • In my house there are really 3 separate components but it takes a full year for all variants to get exposed - furnace minus blower, furnace blower only, AC compressor only
  • Sense might even see an AC compressor operating under different loading conditions as a new AC detection.
  • Putting a smartplug on your furnace unit might help. I have a gas furnaces with 120V plug-in power (yes that’s to code) and have put a smartplug on each. Helps give visibility into the difference between a furnace cycle and blower cycle.

Lots of details in links below

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It is not recognizing them as duplicate devices, it is naming them correctly (e.g. AC, Furnace blower.)
And when I delete it, it shows up again.

Agree with @kevin1 on this one. Sense found my stage 1 compressor (named AC) a week after installing. It found stage 2 (named AC2) a month or so later. I left the names as is and all has been good. I like them as two separate devices because I can see the usage of both stages independently. Sense has yet to find my air handler.

Pretty much the same thing here. Sense found my AC compressor and my furnace fan on day 1, very fast. But, it only seems to recognize the fan as it’s starting up. So my AC will start and be recognized, then the fan will start and be recognized, but after a few seconds the fan will no longer be recognized (though it’s staying on), and the watts it’s using go to Other. This also happens when the fan runs without the AC; it detects the fan for the first few seconds that it starts, but the watts are categorized as Other after the first few seconds. Super frustrating, but I’m hoping it will figure it out eventually.

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So, I’m not the only one.
Also, I don’t have a 2-stage compressor.

Here we are again.

If you ha e a heat pump then getting two detections for the same unit could easily happen. A heat pump reversed the Freon flow depending which mode it’s in and they use more energy in cooling mode than they do in heating mode. It’s usually not a huge difference, just a couple to a few hundred watts. Just merge the two and you’ll have it covered.
Of course, make sure that it is the same device visually before doing so.

Ah, that depends on your heat pump. My geothermal system uses quite a bit less overall power (with 52 degree well water feeding it, cooling is “down hill” and much easier), but the peak power is identical in both modes.

Yes @andy
Geothermal is a totally different setup than a normal heat pump. Geothermal isn’t exchanging with the ambient outdoor ait

Yes, and that’s why it’s so much more efficient. In the dead of a NH winter, zero air temp outside, but the well is still around 50 degrees…so it’s up-hill, but only by 20 degrees or so. Summer is even better, with the well temp nearly what the air coils need, so it’s downhill. Pulling heat out of a 75 degree house and dumping it into the nearly 50 degree water.

But, why wouldn’t an air to air heat pump have the same peak power too, even though the run times (and total power consumption) would be much much longer? It’s still a refrigeration unit running one way or the other.

The compressor has to work hard in an air system hear pump. Because if the direction it’s moving heat.
Any heat or air conditioning apparatus doesn’t actually cool at all. Your always moving heat, never cool. It’s always the removal of heat and a air to air heat pump removes heat from indoor to out door.
Let’s say it’s 100 degrees outside. Your trying to cool indoors to 70. It’s more difficult to to remove heat from 72 and put it where it’s 100 already.
It’s these extremes that put added load on a compressor.

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Ah, never knew that. I’d assumed it always worked at capacity, just for a shorter time. That’s how my geothermal works…exactly the same effort (and power draw) either way, and same temperature delta…5 degrees. Just works more hours going up hill rather than down. Peak power is identical, power consumed MUCH more in winter than summer.

It seems arguable, with improving solar PV efficiency, whether the total energy cycle of ground-source heat pumps (vs air) will remain advantageous. Especially when the average install may involve the debate: “Do I spend money on geothermal infrastructure or PV?”. If you have PV you can potentially EV on solar as well. The energy long-game gets shorter and it seems like Sense will help with those assessments.

Even better is when you get the year round savings of geothermal PLUS providing much/most of its energy from SOLAR. And here in NH, air to air heat pumps don’t do well during winter (to say the least) and neither does solar. Fortunately, we bank KWH during spring, summer, and into fall. Definitely not net zero (that wasn’t our objective), but pretty efficient home overall.

I’ve carefully monitored my geothermal power usage, since way before Sense, and for heating alone, the only thing cheaper around here would be wood from my own property. For cooling, geothermal can’t be beat…that 50 degree heat sink makes it MUCH cheaper than air to air heat pumps and even better when compared to conventional A/C.

Of course, this is also all about ROI, and when I priced geothermal I was shocked. I got quotes ranging from just under $30,000 to $98,000. Once company even told me that ”geothermal systems are very complex and almost take an engineering degree to install”. Nonsense!

Finally, in frustration, I investigated in detail and found that I could purchase a properly sized water to water heat pump for under $3,000 and install it myself…I did take manufacture training, which cost $300, but it’s not rocket science…it’s basic plumbing and electric skills. The only other item was the added cost of the well, making it deeper and wider. So, for about the cost of a good HVAC, we got the geothermal benefits.

I agree about geothermal not taking an engineering degree. They are very simple really. The cost is what prohibited installation for my home. The drilling alone would have been anywhere from $12,000 to $20,000. I live really close to a cliff and the ground is very rocky here in eastern Kentucky. I don’t have near as harsh winters to contend with as you do either.
With our small 1600 ft home, it would have taken too many years to recoup the cost.
Like you @andy, I could easily get the components and do the work myself. Hopefully my new unit outlives me and the kids can worry about it next time.

We were lucky, in that our drinking water well provides the geothermal flow also…a technique used around here called “standing column”, pioneered (partially) by Carl Orio at Water Energy Resources. I did my training there, and they were the distributor for my Climate Master heat pump.

Carl has done geothermal systems in NYC, drilling down under Manhattan buildings for the standing column. Kinda’ crazy, huh?

Had our well not been able to provide both household and geothermal, the economics would have been somewhat different, but still interesting.

Sounds like the same technique used around here. It’s done with vertical drilling down very deep in order to get the volume need in the piping.

Yes, and because most drinking water wells around in the mountains of NH here are quite deep anyway, the added cost to support the geothermal was fairly small.

BTW, I got quotes from three companies, and none of them even mentioned this technique…one wanted to drill four wells, two supply and two return…no wonder they said the whole thing was going to cost $98,000…or almost as much as the house.