I'm a general contractor and have been using the same HVAC sub for the last 5 years, up until last week that is. It's not so much that he is not very good, just not there when i need him and installs seem to take way too long, not to mention poor follow up on any problems. Anyway, that's a different story.
My main problem right now is a new home I built last year. Inside, he installed 16 SEER Carrier Infinity units both up and down. The outside compressors are Carrier Performance Series, a 5 ton down for about 2,300 square feet of living area and a 2 ton on the second floor for about 800 sq. feet of living. 1st floor unit works great...quiet and cools very efficiently.
The problem is with the second floor unit. The home is located in the deep south with typical summer temps of 93 to 98 degrees on a daily basis. The attic usually does not get above 95 degrees. The home is well insulated with R30 in the ceilings and R13 in the wall cavities.
At night the unit cools well, but during the day, when temps rise, with the thermostat set on 70, the temp will not drop below 79 to 75. The system is about one year old and I just had my new HVAC contractor check it. Puron level was about a pound low due to a leaky connection, but he fixed that. It now cools better, but not as good as it should during the day.
The Totaline Digital thermostat is set so that the 1st stage of the compressor never kicks in. I also have it adjusted +10 degrees. The air flow being sucked into the return seems unusually loud. You can hear the sucking noise from downstairs. Could the air return be too small? It's 20"x20" for the 2 ton unit cooling approx. 800 sq. feet, which seems like it should be plenty big enough for the square footage. The owners tried one of those pleated air filters and the unit was so loud they had to go to the cheapie type filter. Also, radiant heat from windows on the second level is not an issue.
We're going to further insulate the attic space with a radiant heat barrier. Not because of the unit in particular, but because it makes such a huge difference in overall comfort of the home in areas where it gets this hot.
Any ideas on what I can do to increase the efficiency of this unit?