Wiring photo to check compatibility

[slava1]

The red wire is not connected. What should I do? 

[CoolingWizard]

@slava1 ,

if your current thermostat does not have a wire attached to R, there is not a possibility that it is capable of activating your furnace. 

AC Cooling Wizard

[slava1]

Furnace works fine.

[CoolingWizard]

Your furnace absolutely will not work with the thermostat you posted, without the wire connected to R/Rc. The B wire is for the Power Common and the W wire is the furnace activation wire.  In order for your furnace to work, you must have 24VAC a power incoming on R and the thermostat connects that to W for heating. 

AC Cooling Wizard

[slava1]

I traced the wires to a transformer on the boiler. I found the white wire connected to a terminal labeled G and the white wire to a terminal labeled Y. The red was was not connected. There is no circuit board.

I measured the voltage between the black and white wires and found it to be 26.5 VAC.

[CoolingWizard]

The Black wire connected to B on your thermostat is supposed to be connected to the Common side of your transformer.  And the White Wire attached to your thermostat W, should be attached to your boiler T terminal of the control box.  The red wire should be attached to Line side of the transformer and attached to R in your thermostat.  When you thermostat call for heat, it connects the R power to the W terminal, which travels to the other T of the boiler thus energizing the gas valve and starting the heating cycle. The B terminal on the thermostat is never connected to any other terminal on the thermostat. It I used by smart thermostats to provide power to the thermostat itself by using R and B.  

Can you provide a screen shot of your boiler showing the wire connections from the thermostat and the manufacturer  model number of your furnace? Thank you.

AC Cooling Wizard