My HVAC system is a 3 ton, and properly sized for my house. It is just over 1.5 years old and hasn't been right from the beginning.
I live in NW Florida so it is very hot right now, but my system can't maintain 76-77 degrees during the day. The AC runs nonstop from 10-9 almost every day.
The first summer I had the system, I couldn't maintain 80 degrees. So the installing contractor came out and "fixed the problem". They claimed I had a block in the filter dryer, so they swapped it out and it appeared to work. 6 months later the refrigerant line coming off the indoor air handler would vibrate violently and would keep my wife and I up at night. Once again installing contractor came out, claimed the system was overcharged, bled off refrigerant and it appeared to work.
Now its summer again and the system runs all day long just to maintain (and sometimes it can't maintain 77 degrees). I live in a new development and an identical model house, with same layout orientation, HVAC system, insulation, etc. has no problem at all. In fact the lady living there complains that her boyfriend keeps it too cold.
I am getting a delta T of 11.5-12.5 (as meas. directly off the plenum and return). The installing contractor came out three weeks ago and replaced the evaporator. He claimed it was a bad TXV. The system worked great for a week and half and now its back to its old tricks.
The installing contractor has been out three consecutive days this week and if anything the system is worse than when he began. The first day he found that poor drainage caused condensate to back up into the chase pipe. THAT'S THE PROBLEM HE SAID!... Wrong, drained the line ensured its dry and still the same thing. The next two days he kept adjusting the charge, but its still not right.
Bottom line, am I right to assume the system isn't performing right because I have a very low Delta T? Secondly, what the heck could be wrong? Gremlins maybe???