OK, let me get the model number of the three units so we'll know the tonnage.

In article , TURTLE says...
This is turtle.

We HVAC peoples have air flow charts we have in telling what size we need for
certian tonage units and I'm looking at one. Tell me what it is and I can look
it up.

If a 20'' x 20'' return grill will not let a 20'' X 20'' filter go in it. You
have a big problem there for that is not suppose to happen at all.

TURTLE