Off Topic: HVAC guys, Furnace C-wire Question

[keh9qd]

Im trying to install a WIFI thermostat and it needs a C-wire.

Currently my old unit is setup with 4 wires and a fifth wite not in use and stuffed
in the wall.

Connections at the thermostat
1. Green wire to G
2. White wire to W
3. Yellow Wire to Y
4. Red wire to Rc/o
-Jumper wire from Rc/o to Rh/B
5. Blue. spare wire in wall not used


Connections at furnace
1. Green wire to G
2. White wire to W
3. Yellow wire to C/3
4. Red wire to R/2
5. Blue spare wire not used

The terminals on furnace are as follows
Y, G, W, R/2, C/3, D1

Furnace: Nordyne KG6RA072C-16

 

[keh9qd]

Picture of wiring at furnace

 

[keh9qd]

New thermostat connections

 

[keh9qd]

More info.

It turns out that the yellow wire from the thermostat actually connects to 2 wires coming in from the Air Conditioner outside. Those become 1 yellow wire that run into the furnace and connected as mentioned above.

 

[Numsee]

Land the blue wire on C at both spots. The yellow in the furnace is the common for the contacter in your outside unit

 

[keh9qd]

Land the blue wire on C at both spots. The yellow in the furnace is the common for the contacter in your outside unit

Thanks for the help. I understood what you said to some degree. Are you saying connect the blue wire to the C/3 and keep the yellow on C3 also? Please explain

 

[Numsee]

Keep everything in the furnace the same as it is now. Land the blue wire on c on the stat and blue in furnace. Should be R red, W white G green Y yellow C blue on stat. Might have Rc, Rh instead of one R. Just jump them together if thats it. Furnace will be R red W white G green C yellow and blue. Do not mess with wires going outside to the AC. And turn off the power to the furnace while doing this so you don't short out your transformer

 

[keh9qd]

Keep everything in the furnace the same as it is now. Land the blue wire on c on the stat and blue in furnace. Should be R red, W white G green Y yellow C blue on stat. Might have Rc, Rh instead of one R. Just jump them together if thats it. Furnace will be R red W white G green C yellow and blue. Do not mess with wires going outside to the AC. And turn off the power to the furnace while doing this so you don't short out your transformer

Ok so here is the current furnace wiring:

1. Green wire to G
2. White wire to W
3. Yellow wire to C/3
4. Red wire to R/2

I understand the thermostat wiring you mentioned. Thats easy.

To be clear, the yellow wire that is coming from the thermostat into the C/3 has the AC wires spliced into it already.

So all I need to do, if I understand you is keep the yellow wire from the thermostat ( with a/c spliced in) and add the blue wire with it on the C/3 in the furnace?

Sorry Im OCD but Ive almost got it

 

[Numsee]

Yep leave everything in furnace as is and add the blue to the common C

 

[keh9qd]

Works like a champ! Thanks!

 

[Alex3344]

I'm glad that you have found the solution and coped with this work by yourself! Good job! Personally I'm not tech savvy, so I'm clueless about thermostats in general. I want to change mine (and I've already found out how much will it cost me to install it on https://servicewhale.com/services/hvac-service-cost), but I haven't chosen a good thermostat. I read about Netatmo learning thermostat that is connected via Wifi, and it seems to be a good choice. Could you give me any advice? Thanks in advance!

 

[keh9qd]

I'm glad that you have found the solution and coped with this work by yourself! Good job! Personally I'm not tech savvy, so I'm clueless about thermostats in general. I want to change mine (and I've already found out how much will it cost me to install it on https://servicewhale.com/services/hvac-service-cost), but I haven't chosen a good thermostat. I read about Netatmo learning thermostat that is connected via Wifi, and it seems to be a good choice. Could you give me any advice? Thanks in advance!

Ive used two different Honeywell wifi units in my last two homes. I like them but both of my homes were built in the 70’s so its not plug and play although it is simple for someone who understands the systems. My first one I wired incorrectly and didnt know it until summer time came and my a/c wouldnt kick on. It wasnt getting proper voltage to run so that cost me to have an hvac professional to visit to let me know that was the issue. I paid $100for the first thermostat and it was the lower model. I personally wouldnt mess with it but I was at home depot and scored this thermostat on clearance from $219 to $55 and couldnt pass it up. A friend of mine has a Nest unit and really likes it. My issue ia with the aquariums and having someone home all day I really cant utilize the power savings like some can.