What is the size of the AC condenser, how big is your house, and what are the indoor and outdoor temperatures? It sounds like the AC could be over sized and is short cycling.

What thermostat do you have? The cycles per hour should be set to 3 or 4.

Proof of whether it is over-sized or not will come on the hottest and most humid days. On those few days, your system should run continuously and marginally hold your set temp.

It may be a little different if you have a modulating system, but we don't know that.

The unit is 3 ton.....the old unit was 2 1/2 ton. The old unit ran very long. The 'expert' said 3 ton, but I now think it is over sized. The thermostat is a Carrier (not programmable). Right now, the outdoor temp hit a high of 88 today.....the temp is set at 70.....anything higher (than 70) during the day feels uncomfortable. The house is older 2 story w/basement maybe 1600 sq ft.

The pros here will probably want model numbers. It seems like it is too humid given that you are not comfortable above 70. Get an inexpensive hygrometer and tell us the relative humidity inside.

My Carrier a/c model number is 24ABC 636 A300. Like I said it cycles too quickly. I said it runs for 10 minutes and shuts off for 15 minutes......I was checking the times and it was off for only 6 or 7 minutes and then kicked on again. The average run time is only 10 to 15 minutes. I've read about what happens if the unit is over sized......the house cools quickly, but the humidity is not removed properly......the house can feel 'clamy'.......the house cools quickly and the thermostat tells the unit to shut off and the cycle of on/off continues. I guess it's actually better to have an undersized unit.......that way it will run for longer periods and work as designed to work. What should I do.....if my a/c is over sized? The 'expert' put in the 3 ton unit......he took no measurements of the house before installation.

If the house is 1600 sq. ft. then a 3 ton condenser is over sized but not by a lot. But the condition you are describing sounds like it is very over sized. I find it odd you have to set the thermostat to 70 to feel comfortable. I would have to where a coat at that temperature.

Did you get a new thermostat with this installation? Perhaps it is a thermostat issue. Have the contractor come back to investigate as to what is happening. A thermostat which limits the cycle per hour will help. I would try 3 cycles per hour. Ask the contractor to see if he can slow down the blower speed. A slower speed will improve removal of humidity.

Really I would not be too concerned. Depending on location and the climate, it is too early in the cooling season to say you are oversized.

Monitor the system's performance including run times, number of cycles/hr, and home's humidity levels in June. Write back in July.

IMO

Really I would not be too concerned. Depending on location and the climate, it is too early in the cooling season to say you are oversized.

Monitor the system's performance including run times, number of cycles/hr, and home's humidity levels in June. Write back in July.

IMO

House had a 2 1/2 ton. Was that cooling well when it was operating as it should have? Get a hygrometer. Everyone with AC should have one to monitor their system's performance. You should have thermometers in addition to the one on your t-stat as well.

House had a 2 1/2 ton. Installer did no measurements and installed a 20% bigger system. It seems quite likely that it is too big unless additions were made between the time the 2.5 ton equipment was installed and now. The duct system might not be big enough.

PROBLEM SOLVED??? The thermostat is in my living room. Besides a cold air return......there are two vents/registers also in this room. The one that was closest to the thermostat.......I closed/shut this register, this register also had a removable deflector attached to help blow air upwards. Anyways, this appeared to solve the problem......this cold air was affecting the thermostat too quickly.......now, with this one register closed.....the a/c seems to be working properly. Now, the unit is running much longer.....instead of short cycling. Is this a good solution to the problem?

I think you have solved the bulk of your problem. The thermostat was getting a cold blast of air which explains why you had to keep the setting at 70 and the cycles were short. Closing the register will help even out the temperature through out the house.

Monitor the temperature and humidity for a few days. You should notice an improvement.