My brother in law is installing new hvac in a house that had a wall heater and a wall a/c unit. His contractor brought out the equipment and is planning on starting the first of next week. I looked at the equipment and have a question about the CFM of the heater. The square footage is 1300-1400. The heater is a Goodman GMS80704BX and it seems to be 1600 CFM. I'm a plumbing contractor and know about enough to stay away from trouble with HVAC. But I did a little research for my BIL and it seems 1200 CFM would have been plenty. It's a single story with no long duct runs. He has payed for the equipment and if my thinking is right. He may be stuck with it and end up looking for a new contractor. Question one is what should the CFM be? Question two is if he is stuck with the equipment can the blower motor be changed to 1200CFM if my thinking is right or can the wiring be changed on the motor that is in the unit. Thanks in advance. Dave