Nest Learning Thermostat G3 no connection to Rh when A/C connected

[ToryBatt]

I have 2 Nest thermostats. One heat only, one has heat and A/C. The A/C and boiler are totally separate units with their own 24v source. Both worked fine until I replaced boiler. Now the Heat-only thermostat still works and charges the Nest battery, but the Heat + A/C thermostat gives a "no connection to equipment message" on Rh. When I disconnect the wires from the A/C it works fine - Rh is connected and charges the battery. I am obviously wiring something wrong between the A/C and heat. Does anyone have a wiring suggestion? My A/C has three leads: Y1 is white, G is green and Rc is red. I get 28v between Y1 and Rc and between G and Rc. Heat is just Rh and W1 with 28v between them. And Yes, I have a Nest Power connector wired "Heat only" and that does not solve it.

[Jhonleanmel]

Hi ToryBatt,

Thanks for reaching out. I'd love to know more about this. Could you share a photo of your current thermostat's wiring? 

Thanks,
Mel

[Jhonleanmel]

Hey there ToryBatt,

Checking back in should you still have some questions here. Let us know by replying to this thread. 

Best, 
Mel

[ToryBatt]

Hi Mel,

Sorry. I have been away. I am new to this and not sure how to post a photo. Basically before I disconnected the A/C to test it, I had red wire from transformer to the Rh on thermostat. And white W1 to terminal 1 on Taco zone valve. I added common “C” from the other side of the transformer. On the A/C side yellow to Y, green to G and red to Rc. The result was a faded out C and W1 on the diagram you see within the nest. What I learned in a You Tube video, from someone with a similar problem, was that the thermostat wants 24 volts from the A/C side and the C wire from the A/C side. They say there is some internal conflict within the Nest. I have not been able to test this because, to add to my issues, my thermostat came up with w5 error. So I contacted Nest and following some troubleshooting, they have agreed for me to send my thermostat and they would send a replacement. I hope to have the new one in a couple of days.

If you can tell me how to add a photo, I can share with more detail. I appreciate any support I can get to try and sort this out.

thanks,

Tory

[Jenelyn_O]

Hi ToryBatt,

I saw your post and wanted to chime in. I'm sorry for the delay. Please let  me know if you still need assistance as I'll be willing to assist you from here.

I appreciate your help @Jhonleanmel.

Best,

Jenelyn

[Jake]

Hey there,

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Best regards,
Jake

[Jake]

Hey there,

I wanted to check in, and let you know that I will be locking the thread in 24 hours.

Best regards,

Jake

[ToryBatt]

Hi, sorry I have not replied. I have disconnected the A/C wires as a workaround to get through the winter. Clearly adding the A/C is the source of the issue, as it has been working fine with only heat hooked up. I do not know what the correct wiring should be when I add back the A/C. I do not know how to upload the wiring diagram.  If someone can explain that, I can show you better what I am dealing with. From some of my searches, I am clearly not the only person with this problem.

thanks for any support. It is appreciated!
Tory

[Jake]

Hey there,

You can upload a picture of your current wiring by selecting the picture icon above your reply. Please let me know if you have any trouble with that, as I want to ensure you are good to go.

Best regards,

Jake

[Jake]

Hey there,

I wanted to follow up with you. Please let me know once you are able to upload a picture, as I would be happy to take a closer look.

Best regards,

Jake

[ToryBatt]

I'm sorry. I guess I am not going to get this. I click on the camera icon and I get a pop up box asking for "Source"  + "Image Description" + "Dimensions" and then an "X". I tried to copy and paste in the text box but get the message I "Do not have permission to upload images." If you can explain what i have to do, otherwise not sure.

To top it all off, the thermostat they sent to replace the earlier one with the w5 error, just got a w5 error of it's own. I sent a note to customer support, but no response yet.