It is difficult to say what is going on with the information you provided. It could be existing duct issues, undersized equipment, or bad installation.

Have you discussed this with the contractor? What was the response?

Thanks for the response. Yes I have spoken with the contractor. They sent a tech out to look at the fan speed in the air handler and make any adjustments needed. That didn't seem to amy any difference so not sure if anything he did. I then called the sales person and told them about what happens with the thermostat and how if the house is at 77 and you call for 74 it runs all day and never gets there, never leaves the 77 degree mark, but that I can bring the temp down by doing one degree increments, although, for example if the house is at 75 degrees and I call for 74, the tstat will often go up on the house temp, saying the room is now 76 degrees while trying to get to 74. Weird stuff. They said they would change out the thermostat, but have not been out here to do so...in the meantime I moved the same thermostat we have in the bedroom (we have 4 zones) and replaced the one above with it and it still does not operate correctly. Here is the equipment we just had installed in April.

1st Floor Living area
4TWX5036 3 TON R-410A 15.5 SEER 9 HSPF Heat Pump Unit
TAM7A0C36 Indoor Variable Speed Fan Coil Unit
Trane 15 KW Electric Heater Package
CONT802 Touch Screen Comfort Control
Aprilaire High Efficiency Media Air Filter
Aprilaire Model 700 Humidifier
TAYWAR0082 Ten years parts and labor warranty

It could be a bad thermosat, but the fact that you are having trouble lowering the temperature leads me to believe there may also be zoning issues. Have you had usually hot weather?

yes, temps here in the east have been very high. Yet this a.m. just trying to get the room temp to 74, from 76 and the unit just runs and runs. As soon as I ask for 75 a few minutes later I have 75...I just now asked for 74 and after less than 10 minutes the room temp has now gone up to 76 while I was awaiting for 74. Something is really screwy.

What is location?

If you live in area with high summertime humidity, then you want the 803 stat or identical HW mdl 8321.

That is a rather large heat strip.

What size living area?

Post back.

IMO

Annapolis, Maryland area.

We have about 3000 sq. ft on this floor...which includes the master bedroom, which has a 2 ton similiar set up. leaving the kitchen, fam room and den to run off of this 3 ton unit. These are the new trane designs and compressor is actually smaller than a 2 1/2 ton we put in about a year ago. The air handlers are plastic and I think run on
'positive pressure"? Personally I don't like them. The utility rooms are freezing where the air handlers are located. And trane puts a sticker on the equipment stating that air leakage is normal.

One of the selling points of the new TAM air handlers is less air handler leakage. This bears further investigation.

That heat strip is too large, should be no more than a 10 KW or even better would be Trane's two stage 7/12 KW heat strip.

The 802 thermostat s a poor choice. At the minimum, should be Trane's 803 model or identical stat and less expensive would be HW mdl #8321.

Stat should be changed out regardless.

IMO

Thanks. Well Trane labels the product that it leaks air. It's right on the front of the air handler. Both new units do this. The 3 ton compressor is now smaller than the units I have had for 23 years and is smaller now than the most recent 2 1/2 ton unit I put in last year. I'll discuss the 803 with them. Why is the 803 better? Also, this is a single stage unit.

I am very familiar with Trane's product line.

All air handlers leak including Trane's. As said, Trane makes a selling point of the TAM series new design leaks less.

The 803 and exact HW mdl #8321 has a dehumidification feature in AC cooling through overcooling that the 802 does not have.

If you are interested in operating costs in heating mode, I would follow up on the heat strip options I suggested. Just for info, a 10 KW heat strip yields about 35 KBTUs, a 15 KW about 51 KBTUs.

IMO

Thanks. well I can tell you the old style air handler, metal boxes we have don't leak...negative pressure. And...the two new desiigned ones do. Like I said trane decided they had better put a label on these units, positive pressure, indicating so. I'll ask about the 803.