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
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
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
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.
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
WISDOM PRINCIPLE DIRECTED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and WISDOM BASED PEOPLE EMPOWERMENT
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
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
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
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