I have an 8-ton AC and when I turn it on with a setpoint of 77, it takes a long time to get there?

Question

it looks like it's having a hard time going below 81. It does reach 81 quick, but it takes ages to go below 81

Answer 1

Take the other posters advice and make certain that the condensor and evaporator coils are good a clean.  Also check the temp out put of your registers it should be around 55 degrees.  If it more that could be sign of compressor weakness, leaky duct work, or leaky air returns.  If you are allowing the house to set for extended times at high temps this can also affect the cooling ability as every piece of furniture, sheetrock, flooring, drape, etc will retain heat making it difficult to lower the temp. quickly.  A properly sized AC unit should take some time to reach the set temp. as it has a dual duty of also removing moisture from the air.  If the unit is taking a while but your power bill isnt sky rocketing, your register temps look OK, the coils are clean, and the unit isn't freezing up it could be the AC is just working like it is supposed to.

Answer 2

Maybe it's too small for the room or the room is not insulated enough.  Are you sure your thermometer control is working?

Answer 3

This coould be caused by several failures. (1) low on refrigerant, (2) a dirty air filter, (3) dirty evap coil, (4) dirty condenser coil, (5) defective thernmostat. (6) a weak valve in the compressor. You should have a 20 degree differentail in air temperature between supply and return vents.  

Answer 4

wow 8 ton.....how big is ur house?  mine is 5000 sq ft and i only have 7 ton....but i have 2 units....has it always done this?  what is the temp outside when ur trying to pull the temp inside down?... off top of my head......clean the coil, check freon, change all filters...

i would like to know how many returns u have with ur system....there should be no less than 4 with this system.....returns really help!....

lic. gen. contractor

Answer 5

It takes a longtime to bring the temperature down when the whole place is warm. Once it gets down to 77 degrees it just cycles to keep it at that temperature so it doesn't run real long.