I'm getting bids on replacing my old 2.5 ton central a/c with 80K (about this number, don't remember exactly) BTU propane heat. The old unit is about 15 years old and gave up the ghost last year. The wife (just got married) is not liking the space heater so I've called some local HVAC contractors for bids.
Here is where I'm confused: Two contractors are replacing with a 2.5 ton heat pump with 10 kw resistive heat. A third is quoting a 2.0 ton heat pump with 8 kw resistive heat.
What is causing the confusion is that, while the window units were running this summer and the electric space heater this winter, I researched and did a manual J using HVAC-Calc. Using the design loads for Decatur, Alabama (north AL) of:
Summer: 93 F
Winter: 16 F
Summer grains of moisture: 98
Summer: 72 F
Winter: 70 F
Heat Loss: 25,355 BTU
Heat Gain: 13,381 BTU
Called the local Building Department and got:
Winter Design dry bulb: 16 F
Summer Design dry bulb: 93/74 F
Summer Design wet bulb: 77 F
Degree days heating: 3323
Degree days cooling: 1651
Climate Zone: 8
My home is 15 years old, 1410 sq ft, "normal" air infilteration, windows protected by 5 ft over hang (porches), dbl pane windows and low % of fenestration (84 sq ft total window), duct work in attic.
Rising the winter indoor temperature to 73 F, the heat loss is 36,500 BTU. The T'stat will, more than likely, be set between 70 - 73 F in the winter.
When I bought the house the HVAC system worked so poorly, a Janitrol, that I do not feel conformable using it as a gauge for the new equipment size. The two window units are rated at 5000 and 10,000 BTU. The heater is 4000 watts. The windos ac's do not keep up on the hottest days but dehumdify so much that it feels ok (about 74-76 F). The heater has done wonderful, keeping the house at 73 F at all times.
Anyway, I thought I had done all my homework but one of the 2.5 ton contractor guys is saying that 2.0 tons will not have enough "air flow" for 1400 sq ft. He is sizing his equipment based on sq ft and air flow. This sounds reasonable, but doing search on this board says this is not the wisest thing to do.
What gives? Who to trust/believe with this much $$$ on the line? Is my house big enough to even worry over 0.5 ton? One of the 2.5 ton contractors has been in business for +30 years and I was in high school with one of his sons, so I know the family.