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#19696 - 01/01/03 09:52 AM Rule of thumb for A/C
wocolt Offline
Registered: 12/06/02
Posts: 117
A family member is having there house sized for air-conditioning, and the HVAC guy is telling them they need a 7-ton unit.
the house is 2800 sq.ft.
This comes out to about 24500 VA just for the A/C.
Does this sound high to anyone else ???????

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#19697 - 01/01/03 10:28 AM Re: Rule of thumb for A/C
spyder Offline
Registered: 10/14/02
Posts: 211
Loc: Massachusetts
I am not an HVAC specialist, but 7 tons sounds like alot, but like anything else there are a lot of variables..such as high ceilings..etc...
#19698 - 01/01/03 10:44 AM Re: Rule of thumb for A/C
Wirenuttt Offline
Registered: 11/10/02
Posts: 267
Loc: Massachusetts
Had an hvac specialist size up my home which was built in 95 for central AC. He said 3 tons would be plenty. It's a colonial with 1450 sq ft. this was not including the basement, stays cool enough down stairs. Duct work is insulated. We have 2 returns one on 1st and 2nd fl., which I understand is ok for heat, but a/c should really have a return in each room. There's thermal pane windows, an a high r value of insulation. They told me I can save $300 on installation if I do the wiring, the price was $2400., that's the condensor, A-coil and AC lines.
They told me a house like mine is basically 1 ton per 500 sq ft of floor space.

[This message has been edited by Wirenuttt (edited 01-01-2003).]
#19699 - 01/01/03 11:00 AM Re: Rule of thumb for A/C
go-go Offline
Registered: 08/08/02
Posts: 42
Loc: Fla.
#19700 - 01/01/03 05:12 PM Re: Rule of thumb for A/C
wolfdog Offline
Registered: 10/24/01
Posts: 135
Loc: Dallas,TX
Rules of thumb are riddled with qualifiers.

Here in Dallas,Texas residential a/c is going to be 400- 500 ft² per ton.

How well insulated,how much glass, the exposures, the outside design temp. all figure in.

The link given above offers a heat/cool load calculation software package for homeowners at a very reasonable price and Don supports it well.

If in doubt, run the numbers and see what comes up. Too much a/c can be worse than too little.

[This message has been edited by wolfdog (edited 01-01-2003).]
#19701 - 01/02/03 06:47 AM Re: Rule of thumb for A/C
wocolt Offline
Registered: 12/06/02
Posts: 117
Thanks to everyone who replied. It is my sisters house and she and her husband are doing some remodelling, and the HVAC guys are installing the A/C 7 tons of it. and that comes out to 24500 VA or 102 amps of load since its A/C it has to be taken at 100 %, and the EC wants to put in a 300 amp service, and ironically enough they do live in Texas.
In light of that it looks correct. I understand that there are variables, and just wanted a ballpark to see if she was getting what she needed or getting ripped off.
So thanks again.
#19702 - 01/02/03 02:23 PM Re: Rule of thumb for A/C
WARREN1 Offline
Registered: 05/09/01
Posts: 184
Loc: Greenville, SC, USA
I wonder if she considered other types of Heat/cooling? Such as geothermal? It has a lot of advantages and saves a lot of money in the long haul of things.

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