I live alone. I use a window ac unit most of the time. I have had family visit. I turned on the central ac and it has been on for about
8 hours and it is only 77.- posted
16 years ago
I live alone. I use a window ac unit most of the time. I have had family visit. I turned on the central ac and it has been on for about
8 hours and it is only 77.
Come on Terry......give us a little more to work with.
Cooling a house from 90F to 70F means bringing all the contents of the house (interior of the insulation, if there is any) from 90F to 70F
AND cooling & condensing the water vapor in the air as well.
BTW 70F is way too cold 74 to 76F with adequate humidity reduction is a more reasonable temp.
How big is the house? How big is the AC? What's the temp & humidity outside? Are talking Phoenix or Atlanta? What's the sun exposure of the house? Shade trees?
Eight hours to go from 90F to 77F doesn't seem too unreasonable.
Bob
If you've owned this house for any length of time your should already know the AC performance.
Bob
If there is more than two hours from starting the A/C for the temperature to go down to the required level you have either too weak A/C or it requires reparing.
you want to look at leaking ducting and insulation issues..if there has not been any additions to the house and the central system was installed with the correct size for your house and its not leaking freon.. then duct leak and insulation may be the problem
Your unit is undersized, you have too many leaks or not enough insulation.
That's fine if it's 90 out. You want no more than 15 degrees difference and most central air won't deliver much more than 15 unless your a/c contractor gave you an extra ton of capacity.
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.
Huh? The "difference" isn't between inside and outside. It's across the coil.
I disagree. 20 minutes per degree +/- seems reasonable to me. I'm pretty sure our central A/C could accomplish that. Since he's trying to get a 20 degree drop, six or seven hours wouldn't be out of line.
His system is apparently going a bit slower than that, but isn't out of range if it's humid or if he has lots of windows and it's a sunny day.
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.
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.
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.
The coil? Lol you crack me up, who is going to measure that besides you. And yes the difference is between being hot out and cool inside, 10 - 13 degrees should be the max.
So when it's 98 out, it has to 85 or more inside?
Nonsense. When it's 100 degrees out, it's not 90 degrees indoors, or even 87. We can pull it right down to 70 if we're willing to pay for the electricity. Ever been to a shopping mall on a hot day?
That's what he seems to be saying. Ludicrous!
Of your AC was installed in the same state. If you live in phoenix, there is no f****ng 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.
It was 111 degrees here today! I should be satisfied with 96 degrees inside? Fortunately, that 15 degree concept wasn't used to size my system.
SJF
Ok you've argued with everyone about this in this thread. Time for you to f*ck off.
Well around here 15 is fine, wasn't thinking of people who live where it gets that hot.
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