UPDATE: this may be R and V, not R and Y, although I'm still not sure how it was set up.

I am replacing an old thermostat in my house (the house is from the 60s, I'm not sure how old the thermostat is). When I took the faceplate off, there are two wires. One, which is white, is hooked to a connection marked R. The other, which is red, is hooked to a Y connection.

Based on what I've read, Y is for central air. So I should be running connecting R and W wires for a two-wire connection. Is that right? Or should I connect these wires to the R and Y connection in the new thermostat.

Here's a picture-I marked the two connections as they're faded.

enter image description here

  • 1
    What do you have for an HVAC system? – ThreePhaseEel Oct 22 '18 at 11:35
  • Hello, and welcome to Stack Exchange. Where are you located? Is this heat-only, or AC-only (it doesn't seem like it could be both)? Are you changing anything else about the system? – Daniel Griscom Oct 22 '18 at 13:11
  • thanks. I'm in New England, I have a gas boiler with water heat. The system is heat only. I'm not changing anything, just putting in a new thermostat (that has more wire options than the old). – PSR Oct 22 '18 at 23:47

Old-style 2-wire thermostats are, de-facto, switches and switches doesn't have an 'order'. In new stat, if it is battery powered, is the same. In any case just connect R(H) and common (W). Anyway, if you wire the new stat wrong-way, worst case scenario is stat not working (no risk of rupture)

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  • Can anyone clarify why this was downvoted? – PSR Oct 28 '18 at 20:10
  • To expand on the answer, since the old thermostat was just a switch, it didn't matter which wire colors were hooked up to which terminal for heat control You can look at the heat system end, and use the correct wires for your new 'stat. – DaveM Apr 14 at 17:45

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