wiring hvac 24 ac transformer color code wires sec

The smart thermostat also uses a C wire so it can power itself (R to C is 24v). Whats important is that if you have voltage on the R terminal, that voltage is connected to W. The 24v transformer supplies power to the thermostat on the R terminal and the thermostat connects the R wire to W for heat, Y for cool and G for the fan. This is how a thermostat works for a typical HVAC system. To start, read this excellent answer about how a thermostat works Hours of troubleshooting have gone by and I'm not having any luck.Īm I going about this the right way (in that I can plug in the transformer, connect the leads to existing wires which go to the thermostat?) However, my Nest backplate does not have a Rc, only an R.

I read that from here you plug in the blue wire into C and the yellow into Rc. I bought a plug in transformer online and I thought I could plug in the transformer, attach one lead it to the unused blue wire near my furnace (to create C) and attach the other lead to another unused wire, yellow. After learning that my oil control does not have a C terminal I was recommended to buy a transformer to be able to create a C wire for my WiFi thermostat. I have 5 wires going from my furnace to my thermostat (only the two are used). I have an older two wire heating system (R, W). Thanks to all for everyone's help and I hope this post can help someone in the future. I had a initial scare where it did not function but I interchanged the two AC connections and ensured all the wire nut connections were secure and it functioned quickly after. Using the diagrams provided by the Amazon reviewer 'GK' and JPhi1618's diagrams below I was able to successfully install a Nest Thermostat on a two wire heat only system. I bought this ( ) AC Transformer and relay. If you have a 2 wire system you might likely need a relay. Wanted to finally say this is SOLVED with help from (see conversation below).

Continuation from Can I use any of my existing oil control terminals (TTFFAA) for a C wire?

Wiring hvac 24 ac transformer color code wires sec