I live in a condo with hot water baseboards that are connected to a shared boiler system. I currently have a simple bimetallic strip thermostat that I'd like to replace with a digital or a smart thermostat. I'm having trouble figuring out if I can install a smart/digital thermostat and if I can how I would even connect it up.

Current Setup

Naked thermostat

Wiring behind thermostat

As you can see in the pictures above I removed the face plate and the thermostat itself to get a better look at what's going on. I have 4 wires, 2 red and 2 black. The black wires connect to R and Y and the red wires are connected together. The wires are 24VAC, verified using a multi-meter (and I found the transformer that supplies the 24VAC).

My Questions

  • Can I install a smart/digital thermostat? Most of them say I need a C wire, which I don't know if I have in this case
    • In my head it seems like I should be able to run a thermostat off these wires since they carry power
  • What are the proper names for these wires?
    • When I looked up the different names Y seems wrong in this case
  • How does this system work?
    • Not important but I'm curious. My assumption is 1 pair of wires is providing 24V and the second pair is connected to the valves on my baseboards. When the thermostat is trigger it's just completing the circuit and opening the valves.
  • 1
    does that video look helpful? youtube.com/watch?v=V2ElRkI6YF8 Jul 29, 2021 at 23:11
  • Do you want "smart" (wireless connectivity, fancy cloud features) functionality, or would a basic programmable 'stat suffice? Jul 30, 2021 at 1:50
  • I haven't decided yet honestly. I'm guessing it makes a difference otherwise you wouldn't ask lol My ideal solution would be a 'stat that doesn't require external power (batteries or a wall wart) to run, if that eliminates one of the options I'd go with whatever fits my ideal. If my ideal solution eliminates all the options...I'll be sad I guess
    – amura.cxg
    Jul 30, 2021 at 2:28


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