Nest Thermostat E won't function when HVAC system is flipped from Summer to Winter

[Danngo]

Hi,

I replaced my Honeywell T87N1018 with a Nest Thermostat E.  The Nest E works fine in the summer when the cooling system is on, but as soon as they flip over to heating, Nest gives me an error about not having power.  Some perspective...my GTA condo is 35+ years old, and I've been told that this is a Fan Coil System.  I can also choose from (3) fan speeds, but this is a separate turn-button on the wall and not connected to thermostat.  I've contacted Nest and they've confirmed that my wiring is correct, but that's as much information as I can get from there.  I'm thinking that Nest E is not the correct thermostat for my system, but any help/advice would be appreciated.  Would also like to post some photos to show old and new wiring, but not sure how to add them here, lol!

Thanks,

Danngo

[CoolingWizard]

@Danngo , is your Condo heating and cooling supplied by hydronics? That is water system that the condo management company switches from hot water to cold water and vice versa each season change? Or does each condo owner have its own outdoor unit and indoor forced air unit?

The AC Cooling Wizard

[Danngo]

Thank you for responding.  Yes…they pump cold water in summer and hot in winter.  In summer we can control the a/c, but can’t turn on the heater.  No separate units outside.

[CoolingWizard · Accepted solution]

@Danngo , The systems that are like yours actually control a water valve that opens to allow the cool water or the hot water to enter the exchange coil.  What the building was built there was a cheaper decision to use a single water system so every tenant is dependent on the facility manager to switch from cooling to heating and vice versa.  The better systems supply both hot and cold water simultaneously and the thermostat open the hot water valve or cold water valve depending on what is desired.  

AC Cooling Wizard

[Danngo]

So is this what’s preventing Nest E from working when they switch over to heat?