Originally Posted by
Dominic Caronna
Is it OK to share the return air compartment of 2 FAG furnaces? Both units have seperate returns, filters, thermostats, and supplies. They are set up to run independently and cool the East and West side of the home. They are next to one another on a raised platform--should there be a panel inthe return compartment inside the platform isolating the return so air can not be pulled from the supply of one unit when it is not in use and vise versa? Could the cage of the off unit turn backwards when the other unit is running? Seems like an issue.
DAC
I have never seen this done, and it sounds from a logical point of view as if it might be a problem. When one unit is off and the other is on, unfiltered air will be drawn through the supply registers. This over time will clog the coils on the unit(s). I would also think that if both units are on that one unit will be drawing more air than the other, simply by design or that one unit might have a little more fan speed.
I would call it out for the above reasons.
You might want to call the HVAC manufacturer to see if they could give their blessing on a system like this.