I’m planning on replacing my 11 yr. old heat pump split system and having problems deciding on the right system size. First, the house is a 1400 SF double wide, but unlike most mobile homes, I spec’d it for efficiency, 2x6 R19 walls, R30 ceiling insulation and R22 floor insulation. Double pane vinyl frame windows and foam core doors. Exterior is cement board. Roof is now metal over the original shingles with a ridge vent, full soffit vent and 3/4 inch venting between the shingles and metal. No Southern exposure due to attached garage but major East and West exposure.
Existing heat pump is 3.5T and definitely too big, the installer just used what they normally use w/o considering the specifics of the house. Like most mobile homes, attic ducting is marginal with limited air flow to the master BR, but there is no practical way to solve this problem. Even now with outside temp at 105 F, the old unit will only run about 20 min. with inside temp set on 77 F and a discharge temp of about 64 F. So, it isn’t running very efficient.
While I haven’t run the industry std. analysis for the house, two other pretty detailed models have given me heat gain numbers of 21,556 BTu’s and 19,822 BTu’s. Downsizing to 3T seems like a no brainer, but going all the way to 2T makes me a little nervous. So, 2.5T might be the right size. It is EZ to find a 3T, 18 SEER dual stage heat pump with a variable speed air handler, but I’m not having any luck identifying a similar 2.5T unit. Does anyone know which brand(s) definitely have 2.5T, 18+ SEER units?
My other question is which would be a better choice, the 3T, 18 SEER system or a 2.5T, 15 or 16 SEER single stage heat pump and maybe w/o the variable speed handler? Something just good enough to get the Tax Credit. Up front cost diff is obvious, but which will cost more to operate and is it significant? What about comfort level, will the benefits of dual stage and variable air flow with short cycles be better or worse than a longer running single stage, fixed speed system? One final point, regardless of which system I install, I might add a 7000-9000 BTu window AC in the master BR for more independent temp control. I’m experimenting now with a portable AC unit in the BR. At 10 pm with outside temp of 95 F, I can shut off the main unit and temp inside the rest of the house will rise to 82 F by 6 am while outside temp drops to 78 F, then it takes less than 1 hr. for the main system to cool the house back to 77 F.
Existing heat pump is 3.5T and definitely too big, the installer just used what they normally use w/o considering the specifics of the house. Like most mobile homes, attic ducting is marginal with limited air flow to the master BR, but there is no practical way to solve this problem. Even now with outside temp at 105 F, the old unit will only run about 20 min. with inside temp set on 77 F and a discharge temp of about 64 F. So, it isn’t running very efficient.
While I haven’t run the industry std. analysis for the house, two other pretty detailed models have given me heat gain numbers of 21,556 BTu’s and 19,822 BTu’s. Downsizing to 3T seems like a no brainer, but going all the way to 2T makes me a little nervous. So, 2.5T might be the right size. It is EZ to find a 3T, 18 SEER dual stage heat pump with a variable speed air handler, but I’m not having any luck identifying a similar 2.5T unit. Does anyone know which brand(s) definitely have 2.5T, 18+ SEER units?
My other question is which would be a better choice, the 3T, 18 SEER system or a 2.5T, 15 or 16 SEER single stage heat pump and maybe w/o the variable speed handler? Something just good enough to get the Tax Credit. Up front cost diff is obvious, but which will cost more to operate and is it significant? What about comfort level, will the benefits of dual stage and variable air flow with short cycles be better or worse than a longer running single stage, fixed speed system? One final point, regardless of which system I install, I might add a 7000-9000 BTu window AC in the master BR for more independent temp control. I’m experimenting now with a portable AC unit in the BR. At 10 pm with outside temp of 95 F, I can shut off the main unit and temp inside the rest of the house will rise to 82 F by 6 am while outside temp drops to 78 F, then it takes less than 1 hr. for the main system to cool the house back to 77 F.
