this post was submitted on 20 Sep 2024
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Hello all, I am moving into a new apartment, and was planning on replacing the thermostats with Z-Wave ones. I currently have a Honeywell T6 Pro Z-Wave in my current apartment, and was planning on picking up a couple more.

When I was at the new place today, I took a look inside of one of the thermostats and saw something I was not expecting. They are all 120VAC line voltage thermostats. The heating and cooling is shared between the building, and whether heating or cooling is on is a whole building schedule. The person in the leasing office that was touring us around the new place when we got our keys said that it switches to heat in october or November.

Attached are a couple of photos of the thermostat and a photo of the vent in the wall (although not sure if that is helpful). The thermostat is a Honeywell T651A. I am not sure of what the actual HVAC equipment looks like.

This obviously throws a hamper in my plans, and now I have to look for alternatives. I am not super familiar with 120VAC HVAC, so I wanted to get some advice from others. I believe it is a heated/chilled water system, and the thermostat simply controls the pump/blower in the wall panel (one of the photos). The fact that there is both heating and cooling is what is confusing me, since all of the 120VAC thermostats I have seen are only for heating. Obviously it all boils down to how the temperature is compared to the set point. If the building switches to cooling (which won't be a problem for about 6 months after it switches I am guessing), the comparison will be backwards.

If anyone is able to point me to any resources on how I can learn about this control system, that would be great. I found the Stelpro KI Z-Wave Thermostat which I think will work, but I am not sure what happens when it switches to cooling in the spring. I prefer Z-Wave since I have found it to be far more reliable (especially in a larger building. This is a 7 floor building with ~15 units on each floor. So there is a lot of 2.4GHz traffic I assume), however if anyone knows of a product that will work for this (if the Stelpro one won't) I'm all ears.

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[–] [email protected] 2 points 2 months ago* (last edited 2 months ago) (2 children)

Maybe I'm wrong, but if it's whole building heating, doesn't that mean it's some sort of boiler and radiator system situation? I don't think you have actual control of the heat temperature with a thermostat in that case.

I'm not sure how AC would work in this situation if it was also via water cooling and such if you also flushing cold water through the radiators system. I don't think you'd want any kind of "smart" thermostat on it if so.

[–] white_nrdy 1 points 2 months ago (1 children)

I don't have control of the water temp, but I have pseudo control of the heating cooling by just turning it on or off. Which is pretty much the same premise as "normal" HVAC.

[–] [email protected] 2 points 2 months ago

Well there's plenty of smart radiator controllers out there if you care to go that route. If the unit you've linked to does the right wiring and replaced the existing one, then go for it.