Is it normal for my home ac not to cool below 83 degrees in 105+ outside temperatures?

Question

I built a new house 3 years ago, so my ac unit is basically new. The outside temp for the past week has been around 104-106 degrees, & I can't get my ac to cool below 83 until around 11 p.m. Not sure the size of the unit but the house is only 1300 sf. although the ceiling in the living room (where the themostats located) has an 18 ft. vault. When the inside temp is at 83-85 the temp coming out the vents is 69-70 and the temp at the return is about 82. I also change the filter monthly and just changed it a week ago. Just wondering if this is normal before I pay for a service call.

Answer 1

22 degree's difference is a normal reading between inside and outside. In fact 22 to 24 is excellent! less than 22 degree's and you need to look at filter's, blocked return air vents, thermostat set too low etc.

Answer 2

If the system cooled down more than that in the past Id say look for lint or dirt in the outdoor coil and wash it out (from the inside to the outside) Don't use enough pressure to bend the fins but enough to wash out the stuff. If it has cooled down in the past then I'm assuming that it is correctly sized. If it never has cooled down when the Temp is 95+ I'm wondering about the Insulation on your home, the size and exposure of your windows and the size of the system. Its possible that you have and air leak in the return air system if everything is sized correctly and insulation is correct for the load calculation. If these steps were not taken at the outset of the installation then its possible your system is doing all it will do. If this is all ok and clean and filters are clean and ductwork is tight. The only item left is the charge of the refrigerant or perhaps a malfunctioning TXV or a stopped up drier. An inefficient compressor could also be the cause. A few years back when scroll compressors came out they had an over temp thermostat that would cut off the out door unit and in some manufacturers it would just stop the compressor not the outdoor fan. So it would look like everything was running but the compressor would be off. Kind of impossible to tell sometimes if the compressor is surrounded by a sound blanket or muffler. Also it is possible to have (although it is really rare) a weak over load inside the compressor and it can cause the compressor motor to cut off with no reason. 1 other thing is the outdoor fan motor. I ahve seen these motors be running and the compressor not. Causing me to believe the compressor is faulty. What happens in this case is that the fan motor cuts off (usually due to bad bearings or missaligned rotor, both of these problems are ware out problems, or internal overload or maybe a bad run capicator) usually stopping and then the compressor continues to run until it over loads and then it cuts off . Usually before I get there the fan motor has cooled off and now is running again but the compressor is off and thus the air temp being felt by the motor is cooler thasn when the compressor is running. A verry hard time diagnosing this problem you almost have to sit on the unit until it hatches the problem again. Make sure or be as sure as you can that the compressor is running all the time you believe it is. And remember just because the fan inside is on dont mean the outdoor unit is running.

Answer 3

That "18 ft. vaulted ceiling" is part of the problem and the size of the AC unit may not be large enough to compensate. That's like a second story and if the vent is that high, you're just not getting enough cold air down to the floor.

In that heat, your vent temp sounds about right. In most cases the inside temp is 20+ degrees less than outside.

A 36" ceiling fan would help.

Filters don't need changed that often.

Answer 4

It depends on the size of your AC unit and the temperature +the relative humididy of the air in your house. It might be fine, but I do think something sounds wrong. If the temp in your house is 83 the air coming out of the vents should be more like 73-75. There should be an 18-20 degree difference. Not 22° like somebody else recommended.

You need to make sure the outside unit is very clean as well as the inside filter and coil. You would be surprised how much difference a good cleaning can make....even if it is fairly new they need to be cleaned a couple times a year. Buy some coil cleaner....follow the directions and spray it clean.

Clean it. Clean it.Clean it. Clean it.Clean it. Clean it.

Answer 5

Sounds a little funny to me. I have a 2608 sq. ft. home with no vaulted ceilings or anything unusual like that and we're experiencing temps. in the 100's here and my house is plenty cool. My A/C is OLD too. I'd get a service guy out to look at your A/C if I were you. You should be cooler than 83.

Answer 6

It could be undersized, but consider this. If the ac handled that kind if temps. with ease, it would be oversized when it's not that hot. An oversized unit will not run long enough to remove humidity. You will have a cool damp house which can be very uncombortable.

Answer 7

before you call a service person, find out if your town is having a brown out (cutting back power). they do this to prevent a black out. make sure the vent isn't pointing at the thermostat. this is a problem we had. you may also want to check to see that the vents are open enough. sometimes service people shut them before closing them down for the winter.

Answer 8

I think under your conditions that is expected unless you go for more tonnage