electricalhvacthermostatthermostat-c-wire
Hi guys I'm trying to figure out I'm using a dual heat and cool thermostat so i decided to get myself a smart thermostat and want to connect both thermostats into 1 but I'm having trouble location the c wire to power my thermostat. As you can tell the white thermostat and red thermostat wires aren't attached to anything.
You'll want to focus your attention to the wiring at the bottom of your last photo, that's where all the control wiring is.
Don't touch the wiring on the primary side of the transformer, as it's at line voltage and could cause a nasty shock.
If you clip the zip tie holding the bundle of wires together, you should be able to get a better look at what's going on. I can't tell exactly what's going on from the photo, so I'll explain what would typically be seen.
You should see a cable with a red, blue, green, yellow, white, and possibly brown wires. This is the cable that runs between the air handler and the thermostat. You should see another cable with a red and white wire (it may include other colored wires as well), which runs between the air handler and the condensing unit. According to the schematic, there should be a red and brown wire coming from the secondary side of the transformer.
The red wire from the transformer should be connected to the red wire from the thermostat, this is your Rc wire. The yellow wire (Y) from the thermostat cable, should be connected to a the red wire from the condensing unit cable. The blue wire (C) from the thermostat cable, should be connected to the white wire from the condensing unit, and the brown wire from the transformer. The green wire (G) from the thermostat cable, should be connected to the black and green wire from the air handler.
At the new thermostat you should have two cables, one from the air handler and one from the boiler.
Rh and Rc, if one exists.Rh. W.Rc.Y.G.C.NOTE: This is all based on typical wiring, your wiring may vary.
NOTE: Some thermostats may only use the Rh and C wires for power, so supplying an Rc/C combination may not work.
C terminal.C terminal.C terminal with the new C wire, and the other end of the scrap bit of wire.When finished, the two C wires should be connected together, along with the wire that's connected to the C terminal.
This type of connection is known as a "pigtail".
Best Answer
This wiring could do with a bit of cleaning up
As you pointed out that Cable 3 (the rightmost cable in the photo) at the air handler goes nowhere, we can take it out of the circuit entirely by nutting the red wire from the air handler to the red wire from Cable 1 instead of the red wire from Cable 3. (This means that the blue wire from Cable 3 is no longer nutted to the red wire from Cable 1, too.)
Once that's done, finding C isn't so hard after all
Now that we have that useless cable removed from the picture, we can find C rather readily, given that we know how the outdoor unit is wired; in particular, green and blue in the cable to the outdoor unit are connected to the contactor, with the other wires left unused. Since we know that the blue wire in the cable to the outdoor unit is connected to the blue wire in the cable from the thermostat, we can safely presume that this blue wire is the Y wire, leaving the green wire to connect to C on the air handler.
Since we have a good indication that brown is C as well from the scant documentation available for your make of air handlers, we can safely assume that the junction between the thick brown wire and the thin green wire is where you need to connect the white wire in your thermostat cable to use that white wire as C.