Add a C Wire Adapter

Installing your new WiFi thermostat can be a challenge if you don't have enough wires in your wall and can't run new ones from your system. In such cases, adding a C-Wire Adapter can be the best solution.

[@TrishHolmes-l8w]

This is a great tutorial. I followed it and was able to get my wifi thermostat working without a C wire even after our honeywell tech and electrician could not do so. Thank you!

[@marvellstarks2434]

You should of explained the k wire a little better when you hooked up the adapter. You gonna confuse some people.

[@garymanis6305]

My old Honeywell RTH230B is no longer displaying anything. It has 5 connected wires and no spares. None of those wires are connected to C at the furnace. Two are connected to the furnace ignition box, the others are connected to R, G and Y. Nothing is connected to W. Is this adapter a good solution?

[@ResideoSupport]

Hi Gary! RTH230B works directly with batteries to have a display. If you want to upgrade to a Wi-Fi thermostat, you will need a C wire. For a heat and cool system wiring should be R W Y G, and C for having a display. In this case, it will be best if you can contact us directly through a private message on Facebook or directly at 1-800-633-3991 to check your wiring and see if it's compatible. -Dinorah

[@horacioacosta6232]

Can this adapter be use for non-honeywell thermostats? Nest? My ac unit looks like a rats nest with 4 to 6 wires of each color. I just want to use the thermostat without having to replace the batteries every few days.

[@ResideoSupport]

Hi Horacio, thank you for reaching out to us. This C-Wire adapter has not been tested with other brands. We recommend you reaching out to the manufacturer of your thermostat for recommendations. -Maria

[@pricedout]

Does this prevent the use of the fan alone?

[@Steve_Edberg]

I was kind of hoping it ENABLES, not prevents the use of fan alone mode.

[@jontorr2860]

Great video!

[@ghrohrs2020]

I only have three wires to the old, round dial thermostat. We use an oil furnace here. I don't understand where the split C-wire attached to the new T5 control board. I don't have the adapter version. I just have the 24 volt plug with a split C-wire.

[@ResideoSupport]

Hi, CO_NYG56, thank you for reaching us out. We will be happy to assist you with this. If you are trying to install a WI-FI enable thermostat, you will require a C wire. The C, or common wire, brings 24 VAC power to the thermostat. Heating only systems, usually have 2 wires only. If the system has only 2 wires (R-W) and there is no C terminal at the board, the only way to supply the Common/C wire would be to use an external 24V transformer wires to the RC and C terminals of the thermostat. -Juan

[@Steve_Edberg]

How does the K wire perform both the fan and the cool function?? I can understand how you could get three functions (fan, cool and heat) using two wires (K and W) with Boolean logic, but two functions on one wire like you say is a mystery. Do the thermostat change the voltage or frequency to the C-wire adapter to signal which output wire (Y or G) to turn on?? I'm just trying to wrap my head around how this works. Thank you.

[@ResideoSupport]

Hi Steve, we thank you for reaching out and sharing your concerns with us. The C-Wire adapter handles the internal connection to provide both energy and system control. If further questions arise, feel free to communicate with us via Facebook Honeywell Home or at 1-800-468-1502. -Charlie

[@Steve_Edberg]

@@ResideoSupport so does the one wire support both the fan and cool function independently?? I don't want any trade secrets from you on how the device operates, I'm just looking for assurance that this device can perform the task of two wires using just one wire. As long as I have the ability to control my furnace fan alone without having to turn the A/C on then I don't care how it does it.

[@ResideoSupport]

Hello Steve! Thank you for contacting us. Yes, the K label in the C Wire Adapter can control the Fan and the compressor independently. It will provide you two independent wires that you can connect to fan and compressor separately. -Alex

[@Steve_Edberg]

@@ResideoSupport excellent. Thank you Alex. That is all I needed to know. Hope you have a great afternoon. 😊

[@ResideoSupport]

Glad to help, Steve! Have a great day! -Alex

[@yulitaua]

I have 2 unused wires. What should I do?

[@ResideoSupport]

Hello Julie! If you have unlabeled/unsued wires, you will need to trace the wire back to the HVAC system to check the connection on the motherboard, and check the labels to know the function of the wire. If they are connected but not labeled, the best option will be to seek support from an HVAC technician. -Dinorah

[@SGuitar62]

How do you use the extra wire (in my case blue) as a C wire?

[@ResideoSupport]

Hi Joe, thank you for reaching out to us. If you have an unused wire, please trace it back to your air handler/furnace and make sure that it is connected to the C / Com24 terminal. Then go to the thermostat side and connect the wire to the C terminal. -Maria

[@SGuitar62]

@@ResideoSupport Thanks just what I needed

[@ResideoSupport]

You are very welcome. Is there anything else we can assist you with at this moment? -Maria

[@Mctoasty302]

I just bought one of these online just to realize they are not compatible with heat only systems (according to the packaging). 😢

[@ResideoSupport]

Hi, thank you for reaching out. If the heating system has only 2 wires (R-W) and there is no C terminal at the board the only way to supply the Common/C wire would be to use an external 24V transformer wires to the RC and C terminals of the thermostat. -Cesar

[@hvacworkshop4791]

Only good for some Honeywell

[@mikeinsugarland]

Bad tutorial .. goes two fast w/o explanation of that the Y goes into K and G goes into C.

[@ResideoSupport]

Hi Minh, thank you for your feedback. Minute 2:55 makes reference to Y wire becoming K and G turning into C. If you need assistance with your thermostat and the C wire adapter, please feel free to contact our tech support team at [phone] or send us a Private Message to our Honeywell Home Facebook account. -Maria

[@mikeinsugarland]

@@ResideoSupport Should have shown that earlier at 2:12 when hooking up the adapter so people won't get confuse.

[@ResideoSupport]

Hello Minh. Thank you for contacting us! If you are struggling with the C wire adapter installation, you can contact us by a Direct message in Facebook and we can help you with the process. You can find us as "Resideo Pro". -Alex