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Central A/C and Furnace Sizing

Central A/C and Furnace Sizing

Central A/C and Furnace Sizing

Can someone help to size a central A/C unit for 2040 sq. ft. townhouse in South New Jersey.  It is a 2 storey townhouse with 7 rooms.  It has 3 exposed walls i.e., front, back and one side.  It also has a basement which is not airconditioned and is not part of the 2,040 sq. ft.

The builder is putting in a 3.5 ton unit (10 SEER).  I do not remember the furnace size but I know for sure it is a gas fired one.  All the insulations are as per Energy Star specs.

Is the A/C unit of the right size?

Your help and guidance will be highly appreciated.

RE: Central A/C and Furnace Sizing

Should be pretty close on capacity, we have a 2200 sq ft 2-story with 4 ton system.  We live in Southern California, so our high temps are a little higher, but we have less humidity.  I would assume your winter temps are probably colder.

We were told (horrors!) that many salespeople will try to sell you a 5 ton system, but that often, your ductwork cannot handle the airflow.  


RE: Central A/C and Furnace Sizing

HVAC-talk is the place to take this question, but, I'm going to give you a headsup that the answer that you're goiong to receive there is to have a licensed contractor perform a load calculation on your home.

Every building is different, and the design conditions differ GREATLY between South Jersey and Southern California.

The peogram mentioned earlier, HVAC-calc, is a good way to get an idea of the size to satisfy your own curiosity, and to confirm what the contractor is telling you. I strongly recommend it. It is the wisest way to invest 40 bucks when you're starting to hire contractors for replacement or new installation of HVAC equipment.

Good luck.


RE: Central A/C and Furnace Sizing


Yes, they may refer him to a pro for the sizing question, but they will be most helpful when discussing all other questions concerning the equipment and install.

RE: Central A/C and Furnace Sizing

  The average is 400 sq. ft per ton which would put you at a 5 ton unit.  Plus with you having multi-levels you would have been better off with two units too have better control over you temps.  With one unit you will have a temp. difference (warmer up and cooler down)  you can help correct this with the duct layout but it will not be as good as two units.  Also the heater should be 125,000 btu input for 5 tons.  If you have a 3.5 ton unit you may have a 75,000 btu furnance.  This may be enough if you house is well sealed(insulation, double windows, all joints sealed), and as stated about if your house is insulated this much you should have a high seer rated unit installed to save energy.  Min.  12 Seer A/C and 2 stage heater.  It will be alittle higher cost upfront but the savings and comfort will be well worth the investment.  Hope this was helpful.


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