Thermostat temp swings

Really bummed with the thermostat. Have had nest, eco bee and Honeywell… all for different reasons. Wyze thermostat has wild swings and as others have said, no explanation as to what the “behavior “ slider actually does.

Couple images, one with the Honeywell and one with the Wyze. Playing with the “behavior” slider to see if I can get it to actually act as a thermostat :slight_smile:

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Id be very interested in seeing graphs for the different behavior settings. I don’t think anyone has done that yet and it might help clear up what it does unless Wyze pops in with details.

Will try… this was at “max comfort” assuming it was the most aggressive. I have swapped it to ‘max savings” … I will see what the graph looks like in the morning

Likewise, very interested in this. Thanks @Ieddy

I have tried the most savings, the most comfort and the balanced settings and noticed no difference between the three of them. The Wyze thermostat will always let the temperature slide one degree below the set temperature, during which the App may indicate that it is heating to that temperature, but the thermostat does not say so, and the heater is also still off. Once the heater is finally on, it will not turn off until it is at least one degree over the set temperature, eventually resulting in a temperature that is at least two to three degrees over that set temperature. Others are reporting the same behavior. I hope Wyze will be able to resolve this with App and/or firmware updates.

Not overly optimistic. Here are the results thus far after switching the slider all the way to max savings. Limited timeframe, but I am adjusting the temp down as I go to bed this evening. FYI the thermostat is set at a permanent hold at 71 during these timeframes.

Running the system less often for longer per run is more efficient… so I’d expect the large swings if you have it in cost saving mode. Maybe right now the slider isn’t actually doing anything, and we’re all in cost saving mode…

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Yeah, it doesn’t seem like it made much difference. I’m thinking the behavior slider is only affecting the temp preferences right now.

The line for the honeywell does have me curious though. Does your system run almost constantly with it to maintain that temp? There’s barely any movement there,

The only difference I see when changing the behavior is what the “temperature preferences” adjust to, for Home, Away, and sleep modes.

My old Honeywell thermostat never showed anything but the set temperature and kept it there. It did not keep track of how long it ran, but Wyze’s long runs make it uncomfortable at night, which the Honeywell never did.

On top of that, the long Wyze runs pump more dry air around the house, which in turn causes the humidifier to run longer and at a higher fan speed, so whatever Wyze tries to save goes out the door on the other end :slight_smile:

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Well here is the data so far from today. Dropped the temp to 67 as I went to bed and the “slider” has been set to “Max Savings” since 9pm last night.

Seems from the vague descriptions of “behavior” and as noted above, this may have influence as to the predictive time to temp scheduling and such however there is no significantly discernable affect on the aggressiveness of maintaining a constant temperature.

6 cycles set at 67 degrees and “Max Savings”
Avg. low temp - 65.77
Avg. High temp - 67.6
Delta - 1.8 degrees
Avg. Heat run time - 24.5 minutes
Avg. “Off” time - 65.4 minutes

temp

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Unless you want short cycling of furnace, which in my book is really bad, on a forced air furnace you will have to adjust temperature swings. The delta between when furnace comes on and turns off (and on again) is called hysteresis. If you have no hysteresis, furnace would go and off all the time.
My furnace runs once in the morning, and once in the afternoon. That’s it. But it does it as I allow temperature swings of several degrees. And I look forward to the Wyze as it does allow adjustment of the hysteresis.

Really the only way get get a truly stable indoor temperature is to skip the forced air (as air has so little mass and hence contains so little energy) and go via another medium. Like water in a hydronic system. There the furnace/boiler is not depending on the indoor air temperature, but on the temperature of the water (much slower to heat and cool), and hence you run the furnace/boiler more effectively for longer times, as well as keeping it off for longer times, and the room temperature is controlled by blending hot supply water with the cooler return water. Not by starting stopping the furnace. Far superior.

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@Ieddy thank you for the graphs! It appears in max savings that it is not overshooting as high which (while i am going to use the phrase “make sense,” I recognize the humor in that) makes sense given cutting off heat earlier than max comfort. But it does leave a lot to be desired in the Behavior setting. If you have it in you, keep the analysis coming! Thx!

I have failed back to my previous thermostat pending more Wyze Updates.

I am a fan of Wyze and know they will get this ironed out over time as it is really fixable via software. However at this point I have switched back to the Honeywell.

Some background:
I have been in this house for 21 years and started with a manual thermostat and a monster single stage furnace, when I updated the furnace 15 ish years ago I went with a dual stage and a programmable thermostat. Since I am a geek, I have had quite a few smart thermostats, started as an early adopter with Nest and then a subsequent version of the nest. Then went to the Ecobee for the remote sensors and the much better telematics. I found it frustrating in that it only engaged second stage heat on a timer basis and didn’t use any other logic as well as finding the remote sensors interesting but not of great value. I subsequently installed a “simple” Honeywell ( RTH6580WF1001/U1) that still had WiFi and I could still integrate with my SmartThings and Alexa ecosystem.

I am not a furnace guru, but in my research as over time and technology has improved with higher and higher efficiency furnaces they actually do run more often to better maintain temperature. This results in 3-10 cycles per hour or one every 10-20 minutes and does a great job at maintaining a constant temperature.

My last two images for the time being, the first the Wyze thermostat night before last and the second the Honeywell last night.
Wyze
Noneywell

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Completely understand. I too have a newer variable 2 stage furnace, and my last thermostat (Proliphix IMT550C) allowed me to set a 1 degree deadband (+/- 0.5 to set point) which ran similar to your 3 10 min intervals per hour. Very comfortable. That thermostat is not supported anymore, so was moving on. Big fan of Wyze so trying to stay the course for now. Thanks for info!

Short cycling like this is terrible for your efficiency and will kill your furnace faster (burn out the HX). Your furnace should run twice an hour at the absolute most. Your furnace is undersized if it is running constantly.

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Again not an expert, but a search on “short cycling” is defined as the furnace stopping short of reaching a desired temperature and then starting again to get the desired temperature.

Doing some searching on Furnace Cycle Times all are relatively consistent with the numbers I quoted above. A quote from the below link " an ideal heating session runs for about 7 minutes. And such a session will take place once every 8-20 minutes until the temp drops again"

How Often Should A Furnace Cycle? - How to Air

At this point, whatever my various thermostats have been doing has been keeping me warm and toasty with no adverse effects on the furnace per my yearly maintenance being done by the folks that originally installed it.

I do hope to move back to the Wyze as I have bought into to their ecosystem pretty heavily.

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You really don’t want more than 3 cycles per hour… well, maybe you do, but I don’t. It’s currently 22 outside and I’ve got my thermostat set to 61. It’s running about once every 45 min, for 7-15 minutes per cycle. The more times your furnace starts and stops, the less efficient it is, because it takes time to heat up the heat exchanger to a point where it actually works. Also, the more start and stop cycles you put on your igniter and motor, the faster they will die. this is a fact.

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My variable speed fan runs 100% of the time…based on Insights tab, my heat is running approx 7hrs per day, mid to high 20s outside, tstat set to 69, averaging 16mins of runtime per hour with Wyze (not sure at what interval), I think I’m good.

I average about 5 hours a day, and my house was built in 1903, so the R factor is terrible. :slight_smile:

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