How long to cool a house from 90 to 70

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On Tue, 03 Jul 2007 08:19:26 -0700, DerbyDad03 wrote:

Thanks, I'm a former tech/installer. I was merely giving a person who wanted a 20 degree temp drop from 90 advice that 12-15 degrees would be fine. Others jumped in with "what about and if it's 110 out" crap and i bailed the thread. I don't like to argue with people who nitpick when they're bored.
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Meat Plow wrote:
<snip>

Not of A/C, I'll bet. Maybe oil changes.

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wrote:

I've seen this before, but I need more explanation.
I thought that the 15 (or 20?) degree difference was between the air before it gets to the evaporator and the air coming out of the AC duct.
Not: the difference between the outside temp and the air coming out the AC vent.
That if it was 90 degrees in the house when one came home and turned on the AC, the air coming out of the vents would be maybe 75.
But after enough 75 degree air was put into the house, replacing 90 degree air, and after the objects in the house were cooled from 90 to something less, the air going into the AC would be more like 85 and the air coming out would be closer to 70. and then 80 in and about 65 out, and so forth, and that if one turned the thermostat to 60, a normally sized AC could lower the temp inside to 60, even if was 90 out
It's certainly true even in my limited experience that if it is 95 or 100 out (which is the only time I use the AC), I can still get my house down to 72.
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mm wrote:

The air temp split between Return Air & Supply Air depends on a number of factors including indoor blower CFM airflow through the evaporator coil; the amount of latent heat humidity everywhere in the home, and how well the home keeps outdoor humidity outdoors.
The length of time that a specific tonnage AC takes to pull the humidity (latent heat) level down to 50 or 55% & the sensible temperature to 75-F varies inversely to the level of the total latent load within the home. The sensible indoor air split is variable between 15 & 25 depending on the rate of CFM airflow & the latent heatload. Using 20" air moving floor type fans & 104-F Heat Index my little 6,000-BTUH Window AC reduces an 850-Sq.Ft. first floor to 76-F 55% RH. http://www.udarrell.com/air-conditioning-latent-heat.html - udarrell
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Of your AC was installed in the same state. If you live in phoenix, there is no fucking way that you're going to have an AC unit that can only do 15 degrees. Right now it's a 115 outside and 75 inside. 40 degree difference.
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wrote:

It is your money and your comfort level. So ignore the others that tell you your system is fine the way it is.
You need to replace the central unit with one that will give you comfort. If it is a 2 ton unit, then replace it with a 5 ton unit. Then use the window unit to hold whatever temerature you are comfortable with, because using the window unit to maintain will remove all the moisture that the oversized unit doesn't have time to remove.
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Rex wrote:

It's inefficient to use a dramatically oversized unit. A properly sized unit will need to run a while to make a big change in temperature.
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Terry wrote:

When is the last time you cleaned the condenser coils? My air conditioners were not keeping up; they were running all the time and blowing cool air (instead of cold) and the house was hot all the time. Both A/C units are only a couple of years old, and they cooled the house just fine when they were new. I thought the problem might be cottonwood tree fuzz clogging up the heat exchanger fins.
I couldn't get to the back side of the condenser coils even when I took the chassis off, so I used a water hose to back-flush the aluminum fins on the coils. It made a world of difference.
Be careful not to mash the aluminum fins flat with the spray of water. They are soft and bend easily. (it will take you a couple of hours to reopen and shape all the fins again; the tip of dull steak knife works pretty well)
Bob
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wrote:

What is your outside temp?
Tom @ www.Consolidated-Loans.info
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