Hooking up Smart Thermostat to a Fan Center Relay

[pavichokche]

This is pretty much how things are wired currently. I have almost the exact same setup as the person in this thread, except for some slightly different model parts, so I re-purposed his wiring diagram:



The thing I'm worried about is the way my gas valve is wired and the fact that there are two separate 120V-24V transformers. There is one transformer inside the fan center relay, providing 24V AC and a common. There is also a second transformer hooked up to the gas valve to power it. This is how the gas valve terminal is hooked up:


When the thermostat demands heat and shorts W and R, current from the main transformer inside the fan center relay will flow through the thermostat and to the W terminal, telling the relay to turn on the fan. Meanwhile, current from the secondary transformer for the gas valve will also flow from R to W through the thermostat to complete its circuit and open the gas valve.

Currently this works without any issues with my old analog mercury blob thermostat. However, I'm worried that this might not jive well with the new smart thermostat I plan to install. I know internally it probably does more or less the same thing as the old one whenever heating/cooling is demanded, but it has much more complex electronics going on.

Does anyone have any thoughts? Do I have anything to worry about?



Info:
The Fan center relay is a honeywell R8405B1009
The gas valve is a honeywell VR800A-1012
The new thermostat I plan to install is an Ecobee4 using the PEK