I have an 8 year old house with 2 Units (one on the main level and one upstairs). Each level has about 1750 sq. feet. The builder installed a 3 ton unit downstairs and a 2 1/2 ton unit upstairs (where the heat is, go figure).
After "fighting" with the upstairs unit pretty much since we bought the house (it leaked freon, never cooled properly, etc), we decided to have everything ripped out and replaced (new compressor, new coil, new line set). The original system was a 2.5 ton Lennox AC / Furnace system.
I had a new Trane 3 ton XR14 unit and 3 ton XTV Coil installed upstairs (retained the original Lennox furnace as we never had issues heating, just cooling). The contractor also identified issues with our plenum and ducts, so they replaced all of that as well (one of the reasons we chose the contractor we are working with is they asked if we had air flow issues which we did. They were the only ones to identify this issue out of 3 bids we had).
Unfortunately, the unit still is not able to achieve our desired temperature. As it gets very hot in Atlanta, I'm ok with (would like better, but can live with) the unit's performance during the daylight hours (recently, the outside temp hit 94 / 95 degrees, and the unit maintained 76 degrees indoors).
My issue: even 2 1/2 hours after the sun goes down and the outside temperature is in the low 80's, the inside temperature is still sitting at 76 degrees( basically, hasn't moved even though the heat load should've significantly decreased over 2 1/2 hours). Also, on a recent electricity bill, I've registered a 30% increase in the amount of electricity used by the new unit over the older less efficient Lennox unit (the old unit was 10SEER, but it leaked freon so I doubt that it ever got 10 SEER).
The contractor has "double sealed" and insulated all of the supplies and returns, yet, the air temp coming out of the supplies (as measured with a Raytek Infrared Thermometer is between 61 - 65 degrees during the day and the same 2 1/2 hours after the sun has gone down). The contractor says they've meased the temp at the coil at 53 degrees, yet, I'm losing 12 to 15 degrees in the supply lines.
The one exception is one of my children's bedrooms. The air temp coming out of the supply in this room is around 57 / 58 during the day, and this room is 2 - 3 degrees cooler than the rest of the upstairs (reads 74 when the other rooms read 76 / 77). There is a bathroom and another bedroom on the same side of the house (facing West) and they are both reading 76 degrees.
In the morning when I get up (around 5:00), the house is at 72 degrees (where the programmable thermostat is set), and the supplies are putting out air that reads anywhere from 53 - 57 degrees.
The unit is located in my attic with one attic forced exhaust fan set at 90 degrees. I measured the temp in the attic last night at 90 degrees when the sun had been down for 2 1/2 hours with the Raytek.
The contractor has been very pleasant to work with. They have added a supply in the upstairs hallway and added a return in one of the bedrooms that didn't have one. They have been out at least 6 times trying to get the system to perform as we all believe it should. They have looked at the system and claim it is functioning to manufacturer's specification, but even they agree that it should work better.
So, any ideas as to how to get my upstairs temperature down? Is it ?normal? to lose 12 to 15 degrees in air temperature between the coil and the supply vents? Am I asking too much to have the room temperature drop ( even a little!?!) 2 1/2 hours after the sun has gone down?
Any suggestions on things for the contractor or I to look at or advice would be greatly appreciated. I really don't mind investing in getting the home to be comfortable, I just want what I paid for to work.