Nest Learning Wiring Question

[baretak]

Hello All,

My first post here.

My old thermostat was wired as follows

Rh = Red wire

Rc = Blue wire

Y = Yellow wire

W = White wire

G = Green wire

I wired the nest to match the old wiring.

The system seems to be working fine. I've run the equipment test and the boiler and AC both turn on and off. There are two issues. One is that the nest shows an error at the Rh terminal (red wire).

The error is N72, power is detected at the Rh terminal (red wire) but no equipment is detected.

The second issue is that on the power page, the Vin and lin are low when the AC is running

but normal voltage when the AC is off.

Does anyone have a clue as to what might be going on? Thank you in advance for your help!

Andrew

[Markjosephp]

Hello Andrew,

Thanks for reaching out to the Google Nest Community Forum. I'd be happy to take a look at your system's wiring configuration.

I appreciate the detailed explanation of the situation when installing your Nest Thermostat. I noticed a wire with a label C, could you confirm if it was connected to a terminal? Also, to be sure, please share with us a photo of your control panel from your HVAC system? This is to see how they are being labeled.

I'll look forward to your response.

Regards,
Mark

[baretak]

Hi Mark,

Thank you for your response. We had a house guest over the weekend so I wasn't able to get back to you as quickly as I would have liked.

The C label is one that I put on myself. I don't recall the circumstances but the wiring of the old thermostat (which is currently connected and working) had the red wire (labeled C) going into the Rh terminal.

I believe that I have a dual system -- separate transformers for heating and cooling. Here's a photo of the inside of the boiler. If there's something else you need let me know. If you need a photo of the control panel of the air handler let me know and I'll arrange that.

Best regards,

Andrew Barrett