Nest Learning Thermostat Gen 3 2-Pipe FCU Wiring

[sketchup22]

I am trying to wire up a Nest Learning Thermostat Gen 3 to my condo unit Vertical Fan Coil Unit.

I have attached an image of the FCU wiring schematic, the original wiring to the original thermostat, and my new proposed wiring on the Nest.

My concern at the moment is that when switching from Cool to Heat, the actuator valve closes. When switched from Heat to Cool, the valve opens. Currently it is summer so this is working as it should but I’m worried when it’s winter and hot water is flowing in the pipes, the valve will be closed when called for heat. I’m also worried that when calling for heat, the electric heater turns on as this would be very expensive.

The actuator is a 3-position valve. Part number is VT3343 if that helps at all. 
I would appreciate any support or guidance to make sure it works. https://imgur.com/a/csT4stM 

[EduardoN]

Hi @sketchup22,

Thanks so much for reaching out to the community! I totally understand that you're trying to connect your Nest Learning Thermostat (3rd gen) to your system, and that you've attached some helpful photos for this process. Your concern about the problem is that in winter, with the hot water circulating through the pipes, it might close, making it very expensive to turn on the electric heater when you turn on the heating. Don't worry, I'm here to help.

Regarding your multi-speed fan system, if your system has more than one fan wire, it's crucial that these are installed by a professional. You should contact a Nest Pro to have your thermostat installed, as incorrect installation settings can damage your system. A professional can also provide you with the correct information about when the valve will close when you call for heat.

Visit our Help Center to learn more about Fan compatibility with Nest thermostats.

Please feel free to share any additional details you think might be relevant.

Best regards,
Eduardo