ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
VDE 0100 to introduce AFCIs
by sparky. 01/19/18 08:03 PM
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 6 guests, and 13 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Rule of thumb for A/C #19696
01/01/03 12:52 PM
01/01/03 12:52 PM
wocolt  Offline OP
Joined: Dec 2002
Posts: 110
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 ???????


Work Gear for Electricians and the Trades
Re: Rule of thumb for A/C #19697
01/01/03 01:28 PM
01/01/03 01:28 PM
spyder  Offline
Joined: Oct 2002
Posts: 210
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...

Re: Rule of thumb for A/C #19698
01/01/03 01:44 PM
01/01/03 01:44 PM
Wirenuttt  Offline
Joined: Nov 2002
Posts: 267
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).]

Re: Rule of thumb for A/C #19699
01/01/03 02:00 PM
01/01/03 02:00 PM
go-go  Offline
Joined: Aug 2002
Posts: 42

Re: Rule of thumb for A/C #19700
01/01/03 08:12 PM
01/01/03 08:12 PM
wolfdog  Offline
Joined: Oct 2001
Posts: 135
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).]

Re: Rule of thumb for A/C #19701
01/02/03 09:47 AM
01/02/03 09:47 AM
wocolt  Offline OP
Joined: Dec 2002
Posts: 110
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.

Re: Rule of thumb for A/C #19702
01/02/03 05:23 PM
01/02/03 05:23 PM
WARREN1  Offline
Joined: May 2001
Posts: 176
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.


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Attic Rat
Attic Rat
Bergen Co.,N.J. USA
Posts: 524
Joined: December 2003
Show All Member Profiles 
Top Posters(30 Days)
Admin 20
sparky 16
Potseal 15
Popular Topics(Views)
243,561 Are you busy
180,362 Re: Forum
170,840 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.014s Queries: 14 (0.003s) Memory: 0.9829 MB (Peak: 1.1338 MB) Zlib enabled. Server Time: 2018-01-20 13:18:12 UTC