I have a 2.5 story house with two HVAC units. The unit for the second and "third" floor is a a Carrier 38CKC030330.
The second and third floors always seem hot. If I have the thermostat set at 76 for those floors, the temp will get up to around 80 degrees for most of the day while the air conditioner is running. Typically you can't get the temp to 76 or below until the evening hours (I live in North Carolina so the outside temp gets up there). It will typically run almost constantly from 10-11am until 8-9pm with short breaks throughout the day (15-30 minutes).
I had someone come look at that AC unit a year or so ago and he said that the compressor wasn't keeping a constant pressure. He tried removing all the refrigerant and putting a "negative pressure" on the system for a certain amount of time, then refilled the system with refrigerant. After he did that, the system still wouldn't keep a constant pressure and he said that it looked like the compressor would need to be replaced, but due to the age of the compressor and building code changes I couldn't replace just the compressor and would have to replace the entire system. The estimated replacement cost for just this one system was about $7,500.
Does that sound like it could be true? Is there anyway that I could buy a replacement compressor and just pay someone to install it?
Is there anything else I can try to make my AC unit run more efficiently.