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Hi everyone, it's my first time here. (and let me warn you already that I have no professional knowledge about HVACs)

I got an issue with my HRV. It is interlocked (alternate connection) with my Furnace air handler (NO from HRV connected to R on furnace, Common from HRV connected to G on furnace and NC from HRV connected to G from thermostat)

The issue is, my furnace air handler keeps working even when the HRV is not working and I also double checked my thermostat, my fan is turned off. I figured the HRV might be cycling through recirculation but it kept going for days. I'm kind of stuck now and any help would be appreciated.

HRV: Lifebreath 155 Max
Furnace: lennox cbx27uh-036-230-6-01

Maybe the HRV relay is stuck closed.  Disconnect the HRV C wire off the furnace G terminal and attach the thermostat G wire back there and see if the air handler fan stops.

I just tried that and the Air Handler stops and only works when I turn on the fan on the thermostat. How would I go to fix the HRV relay if it is stuck closed in this case? (I'm sorry for my ignorance, trying to figure out how to do this by myself and learn a thing or two)

Attached image of the HRV board

You can try tapping the black relay below the red NO wire and see if that unsticks it.  Likely you need a new board though.

Another option would be to install a smart thermostat like the Ecobee and use it to control the HRV.  It will automatically start the furnace fan when the HRV starts so you could eliminate the interlock wiring and use the HRV as is.  There would be no need for a working HRV relay with this option.

I ended up taking out the board and testing the "click" sound for each relay (with a 9V battery and some alligator clips)and they all seem to be working but when I reversed the polarity, one of them isn't clicking. Does that mean that one isn't working?

I have a nest thermostat at home that I haven't installed yet. I can look into it and see if it can take HRV's, thanks for the suggestion. If I were to order a new board, any idea where I would get one? Tried looking online and couldn't find anything