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I am in a high rise built in the early seventies. The hot water is provided by the building gas furnace, it heats the apartment via baseboard radiators. I have a downright ancient thermostat on the wall which I believe to be a Siemens Powers 192 or similar. It looks like one and it hisses when it switches on :) and a sparkie already looked at it hoping to replace it with a modern one and said it was not electric but pneumatic.

I would like to upgrade. While I know nothing about this, the way I imagine there is a pump which gets switched on by the thermostat using pneumatics. I guess I could get it modernized and get an electric switch setting going on -- I presume I would need to get a licensed/insured professional to do this. Then comes the question of the thermostat. Again, without knowing much about the system, I presume a thermostat is just a glorified switch.

The way I imagine this could work without running new wires is Powerline Ethernet or similar. In my dreams I would have

[pump] -- [Powerline Ethernet converter] -- [existing power cable] -- [Powerline Ethernet Thermostat receiver] -- [Wireless thermostat unit].

(There's just no way for the wireless unit to reach the pump directly.)

Is this actually doable? I do not want to connect my heating to the Internet.

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    Start with your building management, as the folks that should know what the system is, how it works, and how it can be upgraded, if it can.
    – Ecnerwal
    Oct 12 at 23:19
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    Eeeeeeeeeeeeeeeh, first let's see what's available on the market, I would wager no one did serious work in this direction. Sure, some people gutted their suite and rebuilt it but just small scalle? I doubt. As far as I am aware , for example , mine is the only apartment where the phone wire has been replaced with Ethernet cabling. That sort of practical tricks is what I am looking for.
    – chx
    Oct 13 at 0:08
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    Looks like there are companies that have done this, but from what I’ve seen, they are in the business of converting a whole building. You’d have to research more to see if you could buy and use one unit.
    – JPhi1618
    Oct 13 at 2:03
  • Set your wall stat to the highest setting and wrap it in a sealed plastic box with a tiny heater. Control the heater with a smart thermostat. When the smart thermostat wants heat it turns the tiny heater off. A non invasive solution that fools the wall stat into doing what you want
    – jay613
    Oct 13 at 9:46
  • If the thermostat is pneumatic, should be compressor somethere in your apartment. My guess it is electrical with bi- metal spring. You can replace it with digital, it will works on batteries.
    – user263983
    Oct 13 at 10:27
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If the thermostat in your apartment is pneumatic then the whole building including all the control valves is pneumatic. I know of no way to convert your thermostat to an electrical unit. There are many different type of pneumatic systems that control a buildings temperature. I would check with the buildings management people to see if they can have your request completed. There is a compressor that is probably in the machinery room which provides a given pressure of air to the whole buildings temperature control system. Your thermostat controls the heat and/or cooling system in your apartment by changing the air supply pressure to control the appropriate heat or cool valve. They may be able to provide a better degree of sophistication with a newer thermostat.

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While not quite like I imagined some solutions exist. These devices connect to existing pneumatic tubes and provide wireless connection from that point. Range extension is made possible with wireless repeaters.

The Johnson Controls WT-4002-MCM is made for this situation, it was discontinued in 2020 October due to the component shortage. At the time of this writing there are two on eBay, one brand new with two year warranty for 756 USD and one open box for 399 USD. In comparison, a plain old pneumatic thermostat can be had for <100 USD.

Millenialnet introduced the Wi-Stat IIIp-S but there's no trace of it anywhere except the company itself who offers them in single quantities as "samples". These two are using piezo electronics.

Cypress has a Wireless Pneumatic Thermostat but it seems it is made for commercial applications with hundreds of thermostats and requires a central "green box" which is 1500 USD. I will confirm with Cypress it is not possible to use it without.

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