I have been a frequent reader of this forum and appreciate the advice you all provide. I suspect my Carrier 58MVP (80K BTU) installed in 2002 is nearing its end. I had the ECM blower motor module replaced 5 years ago, and now the ECM inducer motor is occasionally making grinding noises. I suspect it would not be worth the cost to replace the ECM inducer motor. Every HVAC contractor I’ve encountered in this area uses rules of thumb (or even less info) to size equipment, so I want to be prepared if have to replace the furnace.
I used loadcalc.net to estimate the heat load of my house. However, I am unsure how I should calculate the conditioned area or describe the location of the ducts. The house was built in 1967 with standard wood siding. It has 8 ft ceilings, approx. R-30 insulation in the attic, and I assume R-11 in the walls. There is a nearly full basement with concrete walls and floor that is below grade and has no insulation.
For heat load calculations, I would like to consider the basement as unconditioned space, but it has 4 ceiling registers that are on dedicated branches from one of the two main trunks. I leave these 4 registers open. However, if a basement register is on the same branch as a register that heats the main floor, then I leave it closed.
My biggest uncertainty is how I should describe the location of my ducts for loadcalc. The ducts are original, uninsulated metal and are mostly enclosed between the basement ceiling and the floor of main living area. If I tell loadcalc my ducts are in a crawl space, the heat load is estimated at 74K BTUs. If I say the ducts are in conditioned space, then the head load is estimated at 32K BTUs. Ducts in an attic result in heat loads in between those numbers. Whether I include the area of the basement in the load calculation doesn’t seem to have a big effect on the estimated heat load. Should I use the attic setting in this case?
Thanks for your help.
zip code: 59801
Ceiling height: 8 ft
main floor: 1402 sq ft
basement: 1258 sq ft
Outside walls (sq ft): 436 N, 436 S, 226 E, 226 W
Windows (sq ft): 35 N, 56 S, 36 E, 46 W (vinyl double pane and original with storms)
3 exterior doors (60 sq ft) with 17 sq ft of glass, all are metal
I used loadcalc.net to estimate the heat load of my house. However, I am unsure how I should calculate the conditioned area or describe the location of the ducts. The house was built in 1967 with standard wood siding. It has 8 ft ceilings, approx. R-30 insulation in the attic, and I assume R-11 in the walls. There is a nearly full basement with concrete walls and floor that is below grade and has no insulation.
For heat load calculations, I would like to consider the basement as unconditioned space, but it has 4 ceiling registers that are on dedicated branches from one of the two main trunks. I leave these 4 registers open. However, if a basement register is on the same branch as a register that heats the main floor, then I leave it closed.
My biggest uncertainty is how I should describe the location of my ducts for loadcalc. The ducts are original, uninsulated metal and are mostly enclosed between the basement ceiling and the floor of main living area. If I tell loadcalc my ducts are in a crawl space, the heat load is estimated at 74K BTUs. If I say the ducts are in conditioned space, then the head load is estimated at 32K BTUs. Ducts in an attic result in heat loads in between those numbers. Whether I include the area of the basement in the load calculation doesn’t seem to have a big effect on the estimated heat load. Should I use the attic setting in this case?
Thanks for your help.
zip code: 59801
Ceiling height: 8 ft
main floor: 1402 sq ft
basement: 1258 sq ft
Outside walls (sq ft): 436 N, 436 S, 226 E, 226 W
Windows (sq ft): 35 N, 56 S, 36 E, 46 W (vinyl double pane and original with storms)
3 exterior doors (60 sq ft) with 17 sq ft of glass, all are metal
source https://hvac-talk.com/vbb/showthread.php?2223310-questions-on-heat-load-calculation&goto=newpost
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