Need help with size of new HVAC in SoCal
I am looking to replace the original floor furnacea with a central heating&cooling system. The home was built in 1953, 1700 sqare ft. located in Southern California (about 5 miles from the coast). I've had 7 estimates, most of them very similar, but one (who performed the heat-load calc.) about 50% higher than the others. The calculated numbers are:
BTU Heating: 31,540
Heating CFM: 1,351
BTU Cooling: 34,618
Sensible Cooling: 28,553
Latent Cooling: 6,364
Cooling CFM: 1,353
To satisfy these, that contractor bid Trane equipment that was 3 ton cooling and a two stage, 63,000 BTU furnace. That bid is too expensive.
I am leaning towards the contractor who is bidding Carrier equimpent. However, he recommends 3.5 ton 38HDR air conditioner and the Infinity96 58MVB080-20 (80K BTU, 2-stage, variable speed) furnace.
I think he is oversizing the equipment. He didn't do a heatload calculation, he's been in the business locally for 24 years and says he knows these homes very well. I want to ask him to bid the 3 ton unit instead and the MVB060-14 (60K BTU).
Is he oversizing the equipment? Would my proposed equimpent be sufficient based on the heatcalc numbers?
Depends on the accuracy of the load calculaton,and at what indoor temperature was used in the calc.
If the carrier guy didn't do a calc.,then I'd be inclined to go with the one you have,If it's accurate.
You could do your own ,on this site,see hvac-calc above,for a small fee.
I know you can do the math, but here it is for you:
Calculated required Heat BTU 31540
Calculated required Heat Tons 2.63
Furnace BTU 63000
Furnace Tons 5.25
Furnace oversize 99.7%
Furnace BTU 80000
Furnace Tons 6.67
Furnace oversize 153.6%
If the calculations are correct and they factored in all losses, I doubt you would ever need stage 2 on either furnace. Did the calculator guy use the correct R Value for the exterior walls? Did he know what the window U (R) value truly was? If you guess poorly on both, you could be off by 50% real fast.
These are just my numerical opinions.