Nest compatability with 2-wire system?

[Bob_WH]

     Hi, I'm trying to see if any Nest thermostat would be compatible with our system, and I'm getting conflicting information. Hoping someone here can help!  I'm replacing a very old American Standard (model CA-412, from around 1960).  It is hooked up to a heat-only oil burning furnace.  There are only two wires, one black & one white.  Other information on the old thermostat's label:  ".3 to 1 amp; 30V AC or DC"
   Will any of the Nest thermostats work?  Thanks for any advice you can offer!

[CJaco]

My unit is a 2 wire 24V milliamp unit taht doesn't supply power to the nest thermostat which drains the AAA batteries and requires the nets power adapter. I have a post waiting on someone to answer 1 question. I don't have any where to hook the Nest Power Adapter C wire to and I am needing to know if it is a 110v, 24v, 12v that the C wire needs to be hooked to. 

[luciaaa]

Hi, @CJaco!

Thank you for contacting the community. I understand you've already purchased a Nest Power Connector and are trying to install it. You'd like to know if the device requires low or high voltage. I'm happy to assist you!

To help me provide the best support, please answer the following questions:

• How many thermostats do you have?
• How many HVAC systems do you have?
• Do you have a conventional or heat pump system?
• What is the make and model of your HVAC equipment?

Please keep in mind that if your system doesn't have a C terminal, you'll need to call a Nest Pro to complete the installation.

Regarding your question about voltage, the C wire for a Nest Thermostat typically requires 24 volts AC (24VAC).

Here are some resources to help you install your Nest Power Connector on your HVAC system:

• Nest Power Connector installation article
• How to install the Nest Power Connector - video link

Feel free to reply if you have any questions.

Best regards, 

Ana

[luciaaa]

Hi, @Bob_WH!

Thank you for reaching out to the community. I understand you'd like to know if your current thermostat is compatible with a Nest thermostat. I'm happy to help!

To determine compatibility with a Nest thermostat, could you please share a picture of your previous thermostat's wiring configuration and, if possible, a picture of your control board? (It's usually located near the furnace.) This will help me check the wiring and provide installation guidance.

Also, please share the model of the Nest thermostat you purchased. This article may help you identify it: How to tell which Nest thermostat you have. With this information, I can provide you with more accurate assistance. 

Please keep me updated.

Best regards,

Ana

[Bob_WH]

Hi again, luciaaa

 To clarify, I have not yet purchased a Nest thermostat. I want to make sure that when I do purchase one, it will be compatible.  I cannot seem to attach my photos of the thermostat and board.  But I uploaded them into a folder on my Google Drive -- hopefully you can access them there. Here's the link:
PHOTOS OF THERMOSTAT & CONTROL BOARD 
The photos show...
1.  The thermostat  (just two wires -- no markings that I can see)
2. The control board.
3. A diagram on the inside of the panel that's covering the control board. It's confusing -- seems like the letter markings on the schematic do not correspond to the letter markings on the actual board.
4.  I drew a little map of the letter markings on the actual board, since it's hard to see them all in the photo.

Once again, I appreciate your help. Let me know if you can figure it out!

Bob

[luciaaa]

Hi, @Bob_WH!

Thank you for your quick response. I appreciate the link with the picture. I'd like to help you further, but the link is requesting permission for me to view it. In this case, please share the link with view access for everyone so I can visualize the photos.

Please keep me updated.

Best regards, 

Ana

[Bob_WH]

Sorry!  Here's the unrestricted (I think) link to the photos:

https://drive.google.com/drive/folders/17UiASnWIYRb8J9JIykpAvsF5jSmEthp8?usp=share_link

[luciaaa]

Hi, @Bob_WH!

Thank you for your response and the link with the pictures. The information is very helpful. To better assist you, could you please tell me if the yellow wire in the second picture (the control board) is connected to a "W" terminal? I would greatly appreciate it if you could share that information.

Please keep me updated.

Best regards, 

Ana

[Bob_WH]

No.  In fact, there don't seem to be any terminals marked "W".

There are two yellow wires I can see (upper right corner of the photo). Each of them is connected to  terminals marked "F" on the green base of the board. Those two terminals are also marked "CELL".  (All the markings are upside down for some reason.)

[luciaaa]

Hi, @Bob_WH!

Thank you for your response. To better assist you, I've attached a picture of the terminal. Could you please tell me what letter is displayed on it?

Thank you in advance for your cooperation. 

Please keep me posted. 

Best regards,

Ana

[Bob_WH]

Hi @luciaaa -- You know, right after I sent my last response, it occurred to me you might have been asking about the letter hidden behind the yellow wire in the photo.  It is "R" -- just like the terminal with the black wire next to it.  You can see it in a new photo I added to the Google Drive folder.

[luciaaa]

Hi, @Bob_WH!

Thank you for your response and the detailed information. I appreciate your effort. Based on the information provided, your system might be compatible with Nest thermostats. However, your system's terminals don't match any of the terminals on the Nest thermostat. To be absolutely sure of compatibility, it's best to contact a Nest Pro technician or a technician of your choice.

Please keep me posted.

Best regards,

Ana