I have 1200 s.f. serviced by seven 4"x10" supply registers with two 10" return ducts. I've posted before about my concern about a Trane XV95 60K furnace that I'm supposed to have installed in relation to return airflow, but I'm really concerned about supply also. From what I've been told, high stage airflow on the XV95 starts at around 1100 cfm. Is there some rule of thumb about how many supply registers I'd need for 1100 cfm?
I've had nine salesmen out, all from large dealers, most of the companies advertising NATE certified technicians. None have done any type of load calc, none have even mentioned doing one. Only one has checked the number of vents, he thought I was ok, and another one thought I might need another return.
The system is in a basement and serves the floor above. I have those removable celotex ceiling tile in the basement, so there's fairly easy access to the ductwork. The Trane salesman from the company I've decided to go with is advising that I get the system installed and that the technician will be able to adjust the airflow without any problem. When I told him another salesman mentioned I might need another return, he said if it came to that, since the guys would already be out here doing the install it would 'only' be $ to add a return.
I'm thinking of putting the whole process on hold until I understand what I might need as far as ductwork. I'm not comfortable with getting the system installed first and then worrying about airflow capacity later.