C wire

[Amitkumarpatel]

I have emerson thermostat which Rh, Rc, w,y,g cable running with AA batteries and 1 extra cable(orange color) which not connected any side(furnace and thermostat). How can I convert that extra wire to as c wire?  I attached here my furnace and thermostat pictures which you can see orange cable not connected any side.

 

 

[dhx227]

Wow, that is a mess.   I was confused and had to look up that thermostat.   Here is the wiring for that:

The non-custom things in the furnace are the Blue wire is connected to the furnace's R terminal and then connected to the thermostat's Rc (typically used for power from the cooling system).   Rh is supposed to be power from the heating system, but your Red wire is connected to something out of sight and then connected to the W terminal.   Black is then connected to Y on the thermostat, but I'm not sure what that terminal is in your furnace.  Also I see a couple more wires that are not connected at your furnace, but they are not even seen in the thermostat - perhaps they are in the wall behind the thermostat?     Also, that red/white wire splice at the furnace really should have a wire nut on it - having unprotected wire's like that is really unsafe!

You should definitely have an HVAC tech come inspect this - it is not right and it's way to hard to simply guess at all the parts that are wired in and whether they are wired in correctly.

[Amitkumarpatel]

I have gas furnace and installed in 1977, I know technician don't follow the right color combination but I will explain briefly now. I have heater and AC. Blue wired work as Rc and it's connected  R in furnace.  Red wire (RH) connected to white cable which goes my gas furnace power for heating. Actually 2 white color wire connected to heating and other side 1 was connected to red color, another  white connected in W terminal and another white cable also connected in W terminal which goes directly to thermostat. There was 2 Black cable connected in Y terminal and one of the Black cable goes  Y. I hope you understand and give me some nice suggestions. Thanks 

[dhx227]

Well, you can certainly try connecting the orange (unused) wire to the (C) on the thermostat and then the post that says "COM" on the furnace.

The better (and clearer to a future tech) would be to look behind the thermostat and see if there are some other unconnected wires.  At the furnace, your thermostat wire has 8 conductors.   I see, orange, yellow, and brown all just hanging there.  So, I wonder if those other two wires (yellow and brown) are just lurking behind the thermostat on the wall.   If that is the case, it would be better to switch what the black wire is being used for over to the yellow wire (that is the more standard wire to use for calling for cooling).   Then use the now available black wire for common (C).    Doing that would be you closer what a standard thermostat wiring would look like.

And just for future reference, the orange and brown wires are usually used for either switching the direction (heating/cooling) of a heat pump system; or activating a secondary stage of a an more complicated heating/cooling system.

[Amitkumarpatel]

 Thanks for your great suggestion,  everything working fine but I shows error N72  wiring report "power wire Rh detected, no connection to equipment. " in setting/equipment. Diagram shows that Rh power in Grey color.  Heating working fine some times and stop sometimes.  Please look pictures I attached here. Thank you