What temperature should my central air conditioner be putting out of my vents?
Question:My central air conditioner is a Trane XE1000. During these hot days the temps sometimes run mid 80's to low 90's outside. My unit is almost running constantly and I have it set at 72 degrees. What should the temperature be coming out of the ducts at the floor level. I took a laser temperature and it was running in the mid to high 50s but yet the unit is running like crazy and in my opinion not cooling the house like it should. Last week when it was in the low 90's the house was a balmy 77 degrees inside only getting to the set 72 later that night. Is this normal or should I have it checked??
Answers:
This sounds about right. What you have is a 20 degree temperature drop that you are pushing your AC to provide. Because of the higher temps and the lower setting on your T-stat, it will continue to run until the temperature is met. With opening doors or exposed windows, this will be hard to do when the sun is out. With cooler temps at night time, the unit "catches up" to your thermostat.
If you haven't had maintenance on it yearly, I would suggest getting it cleaned by a certified tech. Your evaporator coil could be dirty, causing less cool air to be blown into your vents.
If the system is sized properly, the air should keep the house at 75 deg. F when outside temp is 90deg, F or a 15 deg difference. And that would be if the equipment is running at design capacity. The design temperature is 15 deg, difference at 90 outside.
If it runs constantly at that temp and keeps the house at 75 or so, it's doing what it was designed for, plus it is probably removing a great deal of humidity.
If you wait until the inside temp gets hot before turning it on, then it will not cool that well, leave it on 24 hours and it will do the best job.
The split (temperature difference between air entering the furnace and the air leaving the furnace - above the evaporator coil.) is normal in the 17-23 degree range.
If it's not in this range, check the blower squirrel cage louvers. Also return air openings, air filter and (this must be done by an HVAC techie) the evap. coil for obstructions or dirt.
Most often, poor performance is due to insufficient air movement.
Good luck.
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