topic Re: Two Wires, White and Blue in Nest Thermostats

Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 03:23:18 GMT

Hello, trying to install a nest thermostat but the only wires I have are white and blue. Is this compatible?

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 05:10:30 GMT

Please upload a picture as well as some basic info on your hvac setup.

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 17:52:56 GMT

Not totally sure how to upload a picture but it’s two copper wires, one has blue cloth/wrap and one has white. The thermostat is hooked up to a old Honeywell mercury thermostat and is connecting to the boiler (baseboard radiator heat). Thermostat is heat only.

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 18:04:26 GMT

When you reply, there is a picture icon in the toolbar, the one to the right of B and I etc

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 18:07:29 GMT

Better with a pic but based on the information you provided your setup should be compatible.

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 18:21:44 GMT

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 18:23:04 GMT

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 18:29:29 GMT

So the white wire would go in the W slot but would the blue then go into the R slot?

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 18:32:10 GMT

Correct, blue would go to Rh or R depending on the type of Nest wire plate.

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 18:34:00 GMT

Great, thanks for the quick help!

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 18:35:34 GMT

Anytime. Any further issues/questions, don’t hesitate.

Re: Two Wires, White and Blue

rockdmoon — Mon, 29 Nov 2021 22:45:05 GMT

Yeah actually one more quick question, will I need the C - wire adapter or as is should suffice?

Re: Two Wires, White and Blue

laurentbourg — Mon, 29 Nov 2021 23:04:36 GMT

Most people don’t, but there are cases where boilers are not compatible with the way the nest “steals” current from the Rh and they require a C wire or a C wire adapter.

Re: Two Wires, White and Blue

SCUBASHAWN — Tue, 30 Nov 2021 02:27:06 GMT

Laurentbourg, I have exact same setup which is Honeywell mercury 2 wire to boiler baseboard heater. I have the Nest Thermostat (NOT LEARNING). I also purchased the 120V plug-in transformer which has 2 wires. I think I have to wire that to C and also with R? This means I have a wire from the boiler control board to R and also the transformer to R. Is this correct?

Re: Two Wires, White and Blue

laurentbourg — Tue, 30 Nov 2021 04:37:19 GMT

That is correct Scubashawn, there will be one wire from the transformer inserted into R along with the R wire from the boiler, and the other wire from the transformer (typically stripped) will insert into C.

Re: Two Wires, White and Blue

Skymom — Fri, 03 Dec 2021 01:43:49 GMT

Hi this is very similar to our current setup we just installed the regular nest thermostat tonight to an old boiler oil heater radiator system that just has two wires a red and a white so we connected them to the r and the w connectors. I was able to set up the app and set a schedule for the heat which is all we have there is no cooling) but within 5 or 10 minutes of starting it said that we needed a c wire or a nest power connector which frankly my husband does not want to deal with. I'm getting confused on how to just have it set to turn the heat down when we go to sleep and turn it back up in the morning 7 days a week. Can I just do that from the thermostat itself? My app says it's connected to the Wi-Fi and so does the thermostat. Sorry I'm so confused at this point any help you can give me will be appreciated

Re: Two Wires, White and Blue

SCUBASHAWN — Fri, 03 Dec 2021 03:22:04 GMT

https://www.amazon.com/dp/B07L4DN5R2?psc=1&ref=ppx_yo2_dt_b_product_details

We used a 25 foot length one because we plugged it in the basement receptacle and went up to first floor to the thermostat. This should fix your problem and depending on which Nest you have the wiring might be a little different.

Re: Two Wires, White and Blue

laurentbourg — Fri, 03 Dec 2021 03:30:26 GMT

Hi Skymom, typically hydronic boilers are multi-zone and use controllers that thermostats feed into, so if you see a big green box with Taco written on it somebody handy should be able to easily add a C wire to your system.

Re: Two Wires, White and Blue

Skymom — Fri, 03 Dec 2021 04:04:10 GMT

Hi Laurent, it is only one zone. An oil fired boiler with one control in the center of an old house. No HVAC. Just heating the water delivered to the old cast iron radiators, to heat the house. It's an old system in an old house but we did check compatibility before we got the nest and it said it would work with the two wire system. However now it seems to want us to install a c wire which is really not compatible with our old system. Does that make more sense? I appreciate your help but your last response did not seem to apply to us. thank you

Re: Two Wires, White and Blue

Skymom — Fri, 03 Dec 2021 04:02:15 GMT

Thanks Scuba Shawn, that looks doable. The wiring diagrams being different in our old house from what is pictured in the best instructions has been frustrating, but with just two wires, we simply connected the red wire to "R" and the white wire to "W/Wh". I'm not sure where the c wire would connect if we got this unit you're recommending because so many of the instructional videos do not deal with a system that is not an HVAC or that only has two wires. Which terminal did you connect to your c wire to? Thanks for the product idea, I wasn't sure if it was only compatible with Google products(and personally feel that Google should give those kits to any consumer since they haven't made it compatible with this kind of heating system, which is very common in my area. I guess I'm still pretty frustrated that what was supposed to be a simple install is turning into a pia). Thanks for your help.