Thermostat on 2 wire boiler w/ext 24vAC

So… Navien NHB-110 boiler with TT connection only. W / R(H) application only. Speaking to Navien the system only requires voltage across TT [ W/Rh] to provide the board with the command to close the contactor and turn on the boiler. Obviously the Wyze Thermostat [WT from now on] requires a common voltage. Reviewing everything and removing the boiler from the equation:

W + RH to the boiler TT landing point
RC + C coming to and from the AC adapter to power WT

Boiler is the only thing in this system

I’m seeing a constant 13v +/- across W/RH _ Just having the WT on the wall. Is this a wire landing issue using ext 24vAC for power or this a WT internal issue?

TT generally doesn’t need external voltage, just a closed circuit. IIRC, the wyze has some diode leakage between Rh and Rc when in external powered mode, so if you wanted a completely isolated contact between Rh and W, you would need an external relay, but that’s generally only an issue in millivolt systems. otherwise the wyze should work for your application.


That’s what I figured as well, but dio leakage at 13volts???

Did you measure AC or DC on your meter? The control voltage is AC, so you should measure AC for an accurate reading.