Little Help please Honeywell Wify thermostat upgrade replacing Beutler smart vent system

Help Support House Repair Talk:


Jun 21, 2017
Reaction score
I just bought my home and have been here about a month. I wanted to Replace the existing thermostat with a new Honeywell smart thermostat with WIFI. I don't know very much about the current system except that it was upgraded at some point. It uses a Buetler model ZCV2 smart vent controller that is wired and just laying on the unit in my attic. It is connected to a control unit on the wall. It has 4 wires . red, white , yellow and green. I see the unit is 12v at the control head. My new unit is 24v. Looking at a few schematics online I think I can bypass. I have limited understanding of the system. What I think i know......the difference is that because there is a smart vent controller, it makes it a bit more complicated. Instead of the thermostat controlling the on and off wires to the AC and heater, it has rs 485 wires that talks to the controller in the attic, and it controls the ac and heater. Anyone know if I'm right/wrong. Or how to make this work? I will attach pics of the current setup and the online schematic i found. mine only has 1 zone.

If I remove the red wire at the controller in the attic i could connect it to the other 24v red wire. this would power up my Honeywell unit. But I'm not sure if the remaining wires will still work.