We're adding on to our house in Atlanta and have decided to replace our 10-year-old package HVAC with a new system. Putting in a new system in the attic should get us a better fit, capacity-wise, and it'll be sealed up much better than the leaky ductwork in the crawlspace.
We had an independent consultant do load calc.s and a blower air door test. Based on reducing some of the measured infiltration by sealing the leaks, he came up with 31.5k Btu's sensible heat gain, 8.3k Btu's latent heat gain, and 54.4k Btu's heat loss.
Now it's time to coordinate with the HVAC sub, and that's where I can use some help. He typically installs Carrier, so although I've lurked and read the Carrier complaints, I've also read that the installer is the key to any mfr.s equipment. So we'll go with Carrier.
Our builder included a 4-ton system in his proposal (heat pump, I believe, though I don't have it handy) based strictly on rule of thumb. We'd like to use a standard AC and gas furnace, with both at higher efficiency (13 SEER minimum, 93% AFUE).
Here's what I haven't figured out from Carrier's site: to put this system together, we basically need a compressor, matched coil, and gas furnace, right? I'm assuming the furnace fan circulates for the AC also. Might be obvious, but this isn't my biz.
Next, it seems that upflow/downflow is prevalent in Carrier's better furnaces. Beyond that, I just get confused in the model numbers. But it appears that the Performance series is the way to go. I'm not clear on whether you can have an Infinity control w/o Infinity equipment. And we might zone sometime in the future, so that flexibility would be useful.
So, to sum up, I could use a check on some of my assumptions, model number choices to go with the load, and correction on anything I'm mistaken about. Also, talking to the HVAC sub this evening briefly, he made some comment about not wanting a higher-efficiency furnace in the attic because of condensation freezing up in the system. Can anyone shed some light on that comment?
thull in ATL