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it was 95F outside yesterday but after having the system on (1st floor only of about 1500sqft) for 4 hours, it only managed to cool the 1st floor from 84F to 81F. Even though it's an open floor plan, this does not sound right. There is obviously the stairway to the 2nd floor but all the doors up there were closed. The air return with the filter is only up on the 2nd floor hallway. Could it be that the warm air isn't being sucked back up there efficiently enough? Do you guys have a return on the 1st floor as well? On a warm day, does your CAC cool the house very rapidly (inside an hour) or does it take hours after you turn it on? Please state if you have a return on the 1st floor as well if so since I'm trying to get to the root of the problem.
Do you guys leave it switched on all the time and let the thermostat control on/off? My installer said this is why it took hours yesterday but others have said a CAC system should still cool it over 10 degrees inside of an hour.
Each floor is using a 30,000BTU unit outside with a 36,000BTU air handler in the attic which I heard is sufficient?
Sounds about right. CAC can only max cool 15 degrees of the air it sucks in, this is theortical maximum. YMMV and probably will. When its this hot it takes a while for it to cool down, night time will help and the CAC should be able to get and keep it at the temp you want.
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95 is considered an extreme day unless you installed a heavy duty system which I doubt. Most systems are sized for the average load/conditions that you can expect in your area. That said I don't understand how the "downstairs" only was on, do you have two systems? If running a/c you should run the whole house not part of it. we find when starting it up to do it either early morning or late evening as it takes less time to get to the desired temperature. One of the main effects of a/c is that it dehumidifys the house and that can take a little time. I know it's real common up north but try to avoid turning it on in the morning then off at night because it got cooler, you'll be spending much more money haveing to re-establish the cooled enviroment than what it costs to run all night. Ceiling fans help in that they create a draft making it feel much cooler.
My coworker came in this morning complaining of a similar issue. After discussing it with the HVAC guy here it was determined the attic was too hot and the air running through the ductwork heated up in the attic. The suggestion was to cut in a ridge vent, vented soffits, gable vents and a mushroom exhaust fan.
Wow, that’s crazy that a 30,000 BTU did not cool that area. Maybe it's a TAD too large of a space for one a/c unit. So, the first floor is 1500 sq ft on its own? My a/c more than cools our entire open space (not including the bedrooms). I believe ours is 25,000 BTU. It gets freezing. Sometimes I’d love central a/c, but with the way the a/c cools the house, there really is no need. But our open space is likely only 800-900 sq feet (not including the rooms). We most def. have separate a/c units for the bedrooms.
I keep my first floor at 74-76 depending on how busy I am. We have returns on the first, second and 3rd floor. First floor is one system and second & third are another. I have no trouble keeping the first floor cool, but I have a pretty shaded back of the house. The front gets a decent amount of sun but I keep the drapes pulled closed.
My system is always on, I have programmable thermostats. I have it set for different temps over the course of the day. I keep it at 80 downstairs overnight since no one is down there usually after 8 p.m.
Yesterday I think it was 96 here and it hardly ran but my first floor was set at 76 and the temp downstairs believe it or not stayed at 76 all day. I can tolerate that if I'm not busy, especially cooking. I get a decent amount of cool air spilling down the stairs and that probably keeps the thermostat reading the temp a bit lower since it's near the bottom of the stairs.
Last edited by twingles; 06-22-2012 at 11:10 AM..
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