Quote Originally Posted by beenthere View Post
A. It puts the area served by system B into a negative pressure.
B. It puts the area served by system A into a positive pressure.

So B's area draws unconditioned air from outside through door seals, wall cracks, recepts, and switches.

And A's area blows the air you just paid to condition outside.

In order for a return to work. It has to be able to get the air from the supplies of the area its to serve.

Its kind of like having 2 pick ups. And putting 2 gas tanks on the one for long trips.
But then driving the truck with the single tank instead. Plenty of gas in the duel tank truck, but not enough in the one your driving. And no way for teh gas to get there.

thank you for sharing your knowledge. i understand what your saying now. then i have no choice but to either pull the air handler out and coil, to be able to redo the plenum shorter so i can raise the frame of the air handler up. i can also just leave it alone as is and deal with the noisy return for a while. i would rather redo the plenum,and raise the air handlers base. thanks beenthere .

tinmarine thank you i understand now.

dash this is the best i could do right now to kind of give a view of what im talking about.

the x is the closet unit with returns at bottom of air handler. the number 2 is system A's second return in question.