cancel
Showing results for 
Search instead for 
Did you mean: 
Replies are disabled for this topic. Start a new one or visit our Help Center.

will 12v ac work on any nest thermostat?

lockwood66
Community Member

I've got a gas furnace with a mercury style thermostat. 12v ac transformer.  no C wire.

3 REPLIES 3

Anonymous
Not applicable

I've read the manual, and I saw 24v there, if it goes lower than 24v, it will not be enough.

CoolingWizard
Platinum Product Expert
Platinum Product Expert

The only Nest thermostat that works with 12VAC is the one that comes with the Nest Heat Link used in Europe. Now, if you are in North America, and have a gas valve directly wired to a thermostat, that connection is 200 to 300 milliamps of DC Current used to operate the gas valve. The DC current comes to the thermostat on the R, and when heat is needed, it is connected by the thermostat to the W and sent back to the gas valve.  This 300 milliamps will cause the gas valve to open.

Ken, The AC Cooling Wizard 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Dolan93
Community Member

Thank you everyone for your replies. 

I ended up getting a new charger off Amazon that wired directly to the thermostat. 

Once connected the thermostat connected to the heat link no problem. 

Thanks again everyone!