Fan Coil Thermostat Compatibility

[Taereus]

I moved to a condo that has a fan coil system which I'm unfamiliar with. I'd like to install a Nest Learning Thermostat - any idea if I can make this work?

[Taereus]

[CoolingWizard · Accepted solution]

@Taereus ,

It appears you have the four pipe model, that is you have two water valves. One is for heating and the second one for cooling.  You have both Power wires 24VAC  and 24VAC Common.  You have a single wire in location 2 which is yellow and this calls for heat. You have an orange wire in location 4 and this is for cooling.  The valves themselves must have a spring that closes them since there is no wires in locations 1 and 3.  Locations 5,6, and 7 are the the three blower fan speeds.  Lastly 8 and 9 are the power connections. A Neat Learning Thermostat 3rd Generation will be required in order to support the three fan speeds.  
 I have edited this picture to show you your wire colors and where they are going to be attached.   Now then,  when you attach the fan wires, you will need to use the PRO SETUP function to define the Y2 as a Fan wire and the * as a Fan wire as well. 

AC Cooling Wizard

[Taereus]

Thank you so much! Crystal clear.

[Taereus]

Just an update: I needed to swap Black and Red in your diagram in order for it to work.

G= Fan Low
* = Fan High

[Taereus]

Hey again, now that the weather is getting colder, I tried setting the Nest to heat - but I'm not getting any warm air. Any idea how to troubleshoot? 

[CoolingWizard]

@Taereus , The way your thermostat is set up is it activates water valves. If you declare a problem, you need to verify with the building management that hot water is being supplied to the system. As a simple check you can try, is to swap the W1 wire with the Y1 wire. Then activate cooling and see if the air gets warmer.  If it does, then hot water is available and we need to troubleshoot the wiring in the Nest backplate of the W1 location. 

AC Cooling Wizard

[Taereus]

Turns out it was a building management issue. Got them to turn on the heat manually and it solved the problem. 

[CoolingWizard]

@Taereus , Usually the management company would send out a notice when they would be turning on the hot water boiler for the winter months. I a glad to hear the heat is working now.

AC Cooling Wizard