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Posted: 6/17/2009 8:10:16 AM EST
Out of curiosity and concern, I am asking the hive mind for some input/answers/opinions. The apt that the SO and I live in is a 2br/2 bath and is about 900sqft. The temperature has been at about 75 at night and anywhere from 90-95 in the daytime. Our AC unit is blowing out what feels like cool air to me but cold air to my SO. We have a programmable thermostat, this one. We have it set to 78 for daytime and set to 65 at about 4pm so the apt will start to cool off before we get home. The problem we have run into is that the apt will be at about 80 or so until nighttime and finally get into the low 70's just before we get up the next morning. My biggest problem is that the AC unit is running full speed ahead and we are having to deal with warmer temperatures. The coil that is inside the apt isn't frosted over and our filter isn't dirty. Is the problem that our AC unit just isn't strong enough to handle the heat? Or is there some other problem we might be dealing with.


**A little background on why maintenance hasn't been called yet. One of their maintenance guys helped burn up our last apt we had with them. He was in the process of replacing a AC unit and wired something wrong and it caught fire. We are not in any rush to have maintenance do anything yet. And yes, that maintenance guy was let go.
Link Posted: 6/17/2009 8:36:21 AM EST
Not an AC expert (that was my dad), but from what I remember is that expect a 20 deg difference from the outside being all that the unit will be able to handle & maintain, so what you are describing sounds perfectly normal.

That is if the outside air temp is 95 deg f, inside temp for the AC unit will need to be set around 75 deg f.

Unless it is over sized it will not be able to keep up with the way you are setting your thermostat.
Link Posted: 6/17/2009 8:42:45 AM EST
Thanks for the input. I am going to try altering the temperature on it.
Link Posted: 6/17/2009 7:42:17 PM EST
Originally Posted By PARover:
Not an AC expert (that was my dad), but from what I remember is that expect a 20 deg difference from the outside being all that the unit will be able to handle & maintain, so what you are describing sounds perfectly normal.

That is if the outside air temp is 95 deg f, inside temp for the AC unit will need to be set around 75 deg f.

Unless it is over sized it will not be able to keep up with the way you are setting your thermostat.


You have it wrong. The 20 degree difference is between the air going into the return(filter area) and the air temp coming out of the supply(vents throughout house).

For the OP, With 90 plus degree temps and your programmable thermostat it will not reach your set temp to sometime in the middle of the night. Programmables suck in the summer time if you live in a hotter climate. You don't save any money and you are uncomfortable. It also sounds like the unit may have a dirty coil or possible low on freon because it should be able to reach the temp you have it set at after it cools off outside sometime in the middle of the night.
Link Posted: 6/18/2009 2:31:49 AM EST
Originally Posted By JoeyP:
Originally Posted By PARover:
Not an AC expert (that was my dad), but from what I remember is that expect a 20 deg difference from the outside being all that the unit will be able to handle & maintain, so what you are describing sounds perfectly normal.

That is if the outside air temp is 95 deg f, inside temp for the AC unit will need to be set around 75 deg f.

Unless it is over sized it will not be able to keep up with the way you are setting your thermostat.


You have it wrong. The 20 degree difference is between the air going into the return(filter area) and the air temp coming out of the supply(vents throughout house).

For the OP, With 90 plus degree temps and your programmable thermostat it will not reach your set temp to sometime in the middle of the night. Programmables suck in the summer time if you live in a hotter climate. You don't save any money and you are uncomfortable. It also sounds like the unit may have a dirty coil or possible low on freon because it should be able to reach the temp you have it set at after it cools off outside sometime in the middle of the night.


Like I said, no expert here. Just enough to be dangerous.

Thanks for the correction... knew it was a 20 degree difference at least.
Link Posted: 6/18/2009 4:48:37 AM EST
Most A/C units are typically undersized and it shows primarily in the hotter worst days. The programmable thermostat isn't helping either. It actually takes more energy to try and recover from the higher setpoint in the heat of the day as opposed to setting it on your desired temp and just leaving it there. It's similar to the the condition of the lower fuel consumption of your car cruising on the freeway at a fixed speed versus the higher consumption of stop anad go traffic. It's not just the "air" you are conditioning but the walls, carpets, furniture, basically everything in your house is holding the heat that has to be removed. Like was earlier mentioned you can get an idea of how well your unit is working by checking the return air temp versus the discharge air temp and you should see a 20 degree drop. If it is doing that, it is doing all it can do. If you go to the outdoor unit and feel the suction (fatter insulated line) it should be cold and wet like a beer can, and the other pipe the thiner liquid line should be about body temp at 90 to 100 degrees. If the liquid line is too hot to touch the condensor coil is probably clocked and needs cleaned. If the suction line is frosty it's low on refrigerant and has a leak that needs repaired. Hpe that helps.
Link Posted: 6/18/2009 5:37:01 AM EST
78 down to 65 is asking a lot for a ac unit in the heat of the day, that's a big drop.

It will take until the sun goes down to get it to want you want at a setting like that.

Try bringing the temp down a different, gradual way.

78 when you leave for work, 72 at 1, 65 at 4.

It's not just the air that is 78 degrees, everything in your house it that temperature (couch,desk,bed)

AC systems have to remove all that heat and that's a pretty big job to bring it down 13 degrees in a couple of hours.
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