Had 4 techs come out and no one can fix the problem. My thermostat honeywell 8000 is set to 76 and the temp stays at 80 when its over 90 outside. At night and during cool days it cools perfectly fine. The coil is in great condition from what all techs have told me, filter is good, one tech did sub cooling on it and he said it was good( at 15 dgr I believe) The TXV is working fine and the ductwork is all in decent shape.
Temparature at the return is at 78 and at the registers its at 59.

I am running out of ideas and of money! What else could be the problem.

The house is 1500 sq ft and the outside unit is a 3.5 ton brand new. Inside air handler is 3.0 ton ruud about 8 yrs old.

Is it possible the thermostat is bad/ But it cools great when temperatures arnt high! :(

Should I replace air handler instead of having another tachnician take m money and tell me the same thing??

Please HELP

Had 4 techs come out and no one can fix the problem. My thermostat honeywell 8000 is set to 76 and the temp stays at 80 when its over 90 outside. At night and during cool days it cools perfectly fine. The coil is in great condition from what all techs have told me, filter is good, one tech did sub cooling on it and he said it was good( at 15 dgr i believe) The TXV is working fine and the ductwork is all in decent shape.
Temparature at the return is at 78 and at the registers its at 59.
I am running out of ideas and of money! what else could be the problem.

The house is 1500 sq ft and the outside unit is a 3.5 ton brand new. Inside air handler is 3.0 ton ruud about 8 yrs old.

Is it possible the thermostat is bad/ But it cools great when temperatures arnt high! :(

Shoudl i replace air handler instead of having another tachnician take m money and tell me the same thing???

please HELP

You really cannot install a 3.5 ton unit on a 3 ton coil for starters.

Is this in a home or mobile home?

1500 sf only needs about a 2 1/2 ton. As hvac said you can not put a 3 1/2 ton on a 3 ton coil. And if it is a 13 seer outdoor unit and a 10 seer indoor unit. No wonder it is not working.

You really cannot install a 3.5 ton unit on a 3 ton coil for starters.

Is this in a home or mobile home?


It's a residential home. Does it really make that big a difference when it comes to SEER rating, I tought that was the electric efficiency?

Lol I have seen all of your post and getting ready to ask you to come fix it... seems like you know HVAC very well. Plane ticket on me.. jk

Thanks for the help. What else could I check for?

its a residential home. does it really make that big a difference when it comes to SEER rating, i tought that was the electric efficiency?

lol i have seen all of your post and getting ready to ask you to come fix it.... seems like you know HVAC very well. Plane ticket on me ..jk

thanks for the help. What else could i check for?

does it really make that big a difference when it comes to SEER rating

Yes and no. For starters you have an old 3 ton 10 SEER or smaller (8 or 6 SEER) older coil that cannot function well with a 3 1/2 ton outside unit. But to make matters worse the new 3 1/2 ton outside unit being a 13 SEER needs an indoor coil designed for a 13 SEER outdoor unit.

The newer 13 SEER units use a much larger indoor coil not only as part of there listing for the higher efficiency but also to offer a larger absorption area to pick up the heat and moisture off the return air that is entering the indoor cooling coil.

So two items are killing the cooling
Coil to small for the outdoor unit
Coil of different efficiency design. IE 10, 8, or 6, SEER

One of the better professionals might be able to get it working by lowering the refrigerant charge and adjusting the refrigerant flow there by shrinking the outside unit to a 3 ton per say but it will never run correctly, will use more utilities (electric) and may not last very long.

You will be better served by replacing the indoor coil with one that matches the outside unit.

Many factors are involved. How well is your house insulated? How many windows do you have? Do you get direct west sun? Do you have curtains on all windows, and are they closed? Do you have any air leakage around doors/windows? Do you have high ceilings? Do you run ceiling fans? Is your thermostat set at the same temp all day, or lowered for cooling down in the evening? All of these factors affect the temp in your home and have nothing to do with efficiency of the a/c unit. A 15-20 degree variance between outside/inside temperature is normal in most homes if there are no other issues (listed above).

Have you checked the temperature in your attic when things are working satisfactorily and when they are not? Do you have any uninsulated ductwork up there?