Any HVAC experts?

[Seriak]

Originally Posted by wingedfish

You won't fix it yourself unless you can understand what everything does. Before you had the AC installed the HRV was interconnected to your furnace/airhandler fan. The a/c guys tied into this same system. When your tstat calls for a/c, an inter connection in the tstat brings the air handler fan on also. What is happening to you is it is back feeding so when you turn on the HRV, the a/c turns on as well. This is very bad. To verify if i'm right, turn on your hrv and if the a/c is on, flip the fan switch on the tstat to "on". The a/c should turn off. At best it will cost a boat load of power. At worst it will ruin the compressor. Let the a/c guys know and they will likely fix it up for you.

Well you must be a HVAC installer as you were right. If the fan is going on the a/c unit after I turn on the Air exchanger and I turn the fan from auto to on, the fan does shut off. I am assuming this is a simple fix and it shouldn't cost me very much?