I'm replacing an old battery-powered thermostat with one requiring a C-wire. Unfortunately, the wires I currently have sticking from the wall are only two: White (W) and Red (R and Rc jumpered together).
If, as seems apparent, I must add a separate 24VAC transformer, what are my options? There is a standard 1-gang dual power outlet nearby, which is rarely used. Is there a transformer on the market small enough to fit into the 1-gang box instead of the outlet?
I'd then pull the wire behind sheetrock and be happy...
- The new thermostat I'm trying to install is Honeywell TH8110R1008. Its basic functionality works without C-wire (on 4 AA-batteries), but to talk to remote sensors (the functionality, for which I bought it), 24VAC power is required.
- The thermostats throughout the house are all connected to a TACO ZVC 406 box in the boiler room. The box has a transformer inside it, but the cables running from it to each thermostat have only two wires each: white and red. The installer must've saved a fraction of a penny per foot of the cable, but it is too late now.
- To folks worrying about low/high-voltage separation -- I'm looking for a transformer, that would fit in a 1-gang box instead of the dual power socket currently there. There are external transformers out there, which plug-into the power socket and can be semi-permanently wired (like this one). But I'd like it to hide inside the wall, if at all possible, so that no wires are visible.
- Regarding phase -- if I do add a separate transformer, I'll remove the jumper currently connecting the R and Rc terminals on the thermostat. The red-wire will remain on the R-terminal and the additional transformer will connect to the Rc and C-terminals.
- Finally, the furnace and everything else throughout the house all use the same grounding. Can I "cheat" and simply connect the C-terminal of the thermostat to the nearby socket's ground?