Nest with a normally open valve

[Re_nard]

Hello, I recently moved in a condo, and it seems like previous owner used a smart thermostat, but was replaced with an regular HONEYWELL T822L1000. When I open the old thermostat it was wired to R and Y terminals. But there was also a C wire in the wall not connected.

So I have decided to go with a NEST. I know that heating terminal for a NEST is a W. However, when I connected like that, and thermostat starts heating as it might think, but it is doing opposite, it shuts a zone valve HONEYWELL V8043D1080. Then I realized that I am dealing with an NORMALLY OPEN valve.

Is it possible to change a logic of a NEST? And yes I can not change a valve.

[Patrick_Caezza]

The only way that I can think of is by installing a relay that has COM terminal connected to 24vac and the the N/C terminal connected to the valve.

This will the valve closed unless heat is called for by the thermostat.

[Re_nard]

Hi @Patrick_Caezza,

Sounds too complicated, does GOOGLE have this kind of relay to purchase?

But, I have invented a temporary solution, by adding to the Nest settings a Y wire,  replacing a W wire to a Y terminal, setting Nest to a COOL ONLY mode, so now when the Nest sends signal to a zone valve, it thinks it cools a condo, but the condo cools by the surrounding atmosphere. This setup works very well and I will not return it, however, Nest thinks I am not ECO friendly at all, by cooling a condo with an AC when the outside temperature is -15 degrees Celsius.

[Patrick_Caezza]

@Re_nard 

It is a little complicated.

If you can live with how you have it, I would leave it