Using the HVAC Calc

[turfgrass]

I spent sometime today trying to figure out this free trial. I want to see how over sized my furnace is and how undersized my dicts may be. Recent posts suggest to start with the Heat gain and lost calculation. I plugged in dimensions for the first and second floors. However, I'm not sure if I have the ceiling type correct for the first floor. I chose under a ventilated attic, but that is what I selected for the second floor. What should I use in that spot?
I also wasn't sure what "over a conditioned space" was for flooring. I selected that for both the 1st and 2nd floors. My 1st floor is over a basement that maintains around 54 degrees. Would a conditioned space apply?
The final results display total for heat gain and loss for ceilings, doors and windows. If I did everything correctly.

total CFM 1,200

heat loss heat gain

ceilings 14,371 36,199
windows 7,058 10,591
glass door 1,305 2,306

[beenthere]

Don't enter a ceiling for the first floor. Since you have a second floor that is conditioned.

Over unconditioned basement for first floor's floor.

In HVAC Calc, you don't enter any surface area that doesn't have a heat loss or gain, with the exception of the floor.

[ACResearcher]

I'd like to do a calc for my house also. But I don't want to spend $400.00 for a one use. Are there any free software options?

Thanks,

AC Researcher

[beenthere]

The home owner version is only 49 dollars.

[turfgrass]

I made the changes to the 1st floor ceiling, but I'm stilll not sure about the floor and basement relationship. The options are either over condition space or over unheated basement. I went with the unheated basement. It does have supply vents and reads 54 degrees.

[beenthere]

Most below grade basements will hold 50 to 55 without heat.

I don't heat my basement, and it holds 50 except for the coldest days. And if I fixed the the hole where my cable and phone come in, along with the water hand pump hole, it would probably hold on the coldest days too.

[tostaos]

I made the changes to the 1st floor ceiling, but I'm stilll not sure about the floor and basement relationship. The options are either over condition space or over unheated basement. I went with the unheated basement. It does have supply vents and reads 54 degrees.

unheated basement is correct

[turfgrass]

I added the new calculations, but don't understand the difference between when reporting the heat loss and gain. You can either select "sort by heat loss" or "sort by heat gain".

sort by heat gain

sensible gain 11,271
Latent gain 690
Total heat gain 11,961
Total heat loss 16,707

sort by heat loss

sensible gain 11,412
Latent gain 0
Total heat gain 11,412
Total heat loss 22,805

I need to calculate the furnace's CFM rating in order to determine the duct cfm calc.. Would this be printed on the furnace?

[beenthere]

I need to calculate the furnace's CFM rating in order to determine the duct cfm calc.. Would this be printed on the furnace?

No.
You determine furnace CFM by the allowable temp rise for the furnace.

[turfgrass]

I found a calculation for furnace CFM but this could be just a general rule of thumb. Take the furnaces btus and divide by 10,000. Then multiply by 100 for CFM

Furnace spec sheet
btuh input 140,000
btuh output 114,000

140,000/10,000x100= 1,400 cfm

so, 1400 would be used to figure the duct sizing?

[beenthere]

I found a calculation for furnace CFM but this could be just a general rule of thumb. Take the furnaces btus and divide by 10,000. Then multiply by 100 for CFM

Furnace spec sheet
btuh input 140,000
btuh output 114,000

140,000/10,000x100= 1,400 cfm

so, 1400 would be used to figure the duct sizing?

That method would make for a bad install since to would cause a temp rise above allowable limit for most gas furnaces.

[turfgrass]

sorry, i have a forced hot air oil furnace. Still a bad install?

[beenthere]

sorry, i have a forced hot air oil furnace. Still a bad install?

Using that rule of thumb, it would/will be.

You really want 145 to 155° supply registers.