AC Air Handler comes on when Radiator Heat is turned on - Nest Gen 3

[KIngKong]

I have a Nest Gen 3 thermostat and the AC air handler comes on when I turn on ny baseboard radiator heat.  I checked equipment type for the heat and it is set correctly to Radiator.  How can I fix this issue without disconnecting the fan wire which is in slot G?  Also, suddenly my Nest app crashed on the iPhone and says trouble communicating.  I have multiple thermostats so resetting each one may be cumbersome.  I am able to connect to the thermostats using Google Home but prefer to use the Nest app.  Help would be greatly appreciated.

Thank you.

[AxelD]

Hi KingKong,

Thanks for reaching out to the Community! I'm sorry to hear that your air handler turns on when you call for heating. Don't worry, we can figure this out together. If you're not comfortable disconnecting the G-wire, you can find information about fan control with a Nest thermostat in this article. It outlines the available configurations so you don't need to make any hardware changes.

Please take a look and let me know how it goes.

Regards,
Axel.

[Roger_A_02635]

I have a Nest Learning Thermostat Model Display-3.7, Back plate -5.26, Software 6.2-27. I have disconnected the G wire and find during the heating season my fan in my AC handler does come on inconsistently. This is a problem since I have a three season room which I air condition in the summer and I minimally heat in the winter. The fan causes air from the three season room to mix with air from the rest of the house. I power my heating system and my AC system with different transformers. The AC system powers the Nest Learning Thermostat.

My solution last year was to disconnect power from my blower inside the AC handler. To me this turning on the AC blower is incorrect operation of the NEST thermostat.

[AxelD]

Hi Roger_A_02635,

Thanks for posting in the Community! I really appreciate the information you shared about the solution you found for this situation with the fan getting on when it isn't supposed to work. This information is valuable to the Community and can help other members that are experiencing the same situation.

Regards,
Axel. 

[Roger_A_02635]

Axel -

Sorry I am not satisfied with your reply to my post.

The NEST Learning Thermostat is not functioning properly. When the heat type set to radiator, the fan (wire G) should not cause the AC handler turn on the blower.

Also, as I told you in the post, I also experience the fan coming on when the G wire is disconnected. 

The previous thermostat I had installed never experienced this problem.

[KIngKong]

I have the same problem. Also, every HVAC person ive spoken to has only bad things to say about Nest. I, umfortunately converted my entire house to Nest and have had instances where the thermostat has malfunctioned and had to be replaced.  This is unacceptable for a $300 thermostat - i cant recall having issues with the cheaoer digital thermostats. Bottom line, stay away from Nest products. They're a royal pain in the neck and their claims of savings are unsubstantiated and not worth the expense and hassle.