Heating & Cooling System Size

tony k

I have a 2,000 sq. ft. house and I would like to know how you determine the size of the heating & cooling system I need. I was told that I should have a 90,000 BTU furnace and a 4 ton A/C system. Is that accurate information???

DanHolohan

Click on

Heat Loss Calcs on the navigation bar and get a free CD-ROM from our friends at Slant/Fin. It's easy to use.

Arthur Binder

options

There are several software programs out for determining heat/cool loads for your house. You will need to know some information about the insulation value in your walls, attic space, types of windows you have, doors, etc. Also your location comes into play (city, state). However, if you are a homeowner it might be easier to find a reputable HVAC rep in the area and sit with him/her (preferably with a blueprint on your house if you have one)and let them figure it out for you. They should be willing to print you a copy of the results for you.

Constantin

Hi Tony

Fellow homeowner here.

I recommend that you perform a proper heat loss or heat gain calculation to see what the house needs to stay comfortable. The numbers you throw out are somewhat meaningless without a context, such as where the house is situated, the design conditions, insulation schedule, etc.

On first glance, it sounds like someone is using a rule of thumb to size your heatign system. 45BTU/h/ft² sounds like a lot, but your place could be leaky as a sieve somewhere in upstate new york, for example, in which case the number makes sense again.

The only way to know is to either measure your present heat loss on as cold a day as possible (i.e. clock your present heating plant) or by resorting to a heat loss calculation estimate. The latter may be more time intensive but it has the added bonus of giving you an estimate for the heat gain as well as the heat loss with the right program. The Slant Fin Heat Explorer is a great value for the money (it's free) but I don't think it calculates heat gain.

If you want to get it all done at once (i.e. calculate heat gain and heat loss at the same time), you might consider trying out HVAC-Calc, which had/has a homeowner special license that is valid for two months ($50 when I tried it).

Dingo_2

I can tell you for sure...

that it needs to be done right to get the right results. I help contractors with processes like this very often and the only common thread that seems to run through is that comventional "rule-of-thumb" wisdom wants to oversize everything.... but with the best intentions of course.

Plug in the right numbers and have faith....

Mad Dog