We have a new 5-ton dual-fuel heat pump with gas aux. We have been fighting balancing problems, as some rooms are up to 8 degrees cooler than others. Also, the total fuel usage (both electricity and gas) of the system is higher than expected. I am worried that there is something that is keeping the system from operating at (or even near) its peak efficiency.
One thing I am worried about is the returns. There are two 12-inch ducts, one at each end of the house, with 20x25 inch filters. Is this adequate for a 5-ton system?
The first duct comes up through the floor into a huge metal box that takes up a large amount of room in one of the bedroom closets. The installer told me that because of the position of the floor joists he had no other choice. There is a 9 3/4" x 20" hole cut into the floor (see attached pictures). This looks very restrictive to me.
The return is open to the interior wall and floor. I am wondering if the amount of unconditioned air being drawn in from the attic and crawlspace could be a problem. I do not see any evidence of sealing compounds used where the sheet metal and wood join. Does leakage in the return matter? I realize the whole house is leaky...