When we built the house, our original HVAC contractor undersized the furnace and A/C (they calculated for 2,000 square feet and the house is 4,000 square feet).
The HVAC company blamed the builder, and builder blamed the HVAC company, and, well, you get the idea. It was going to cost more to pursue the claim than to simply live with it for awhile and upgrade at our own expense.
So, I installed inexpensive supplemental heat and then when the fan motor went out on the furnace I simply had an efficient, properly sized unit installed. I also received a tax credit.
The A/C finally went out, and though it was a minor repair, I decided to upgrade to a properly sized unit. I received 3 estimates, and chose the company that had installed the new furnace because their price was in the ballpark and they had done satisfactory work previously. The recommended unit was a 14 seer 3 ton Lennox. The old unit was only a 2.5 ton.
The installers screwed up a few things, but to the HVAC company's credit, they were out the next day and resolved the issues at no extra charge. The new unit cools much better. The whole house feels better even at the same temp reading as when we had the old unit.
The bad news is that I have had a humidity spike. While the basement, which was previously stuffy, now is very cool, the humidity spiked from 43% to 53%.
Before I talk to the installers, I want to determine if this is normal and acceptable.
I understand that a larger ton unit will typically run less, but it has been 100 degrees since the new unit was installed and it has been running much of the time, so the humidity spike shouldn't be because the unit is "oversized".
I have a $$$$ Santa Fe Classic dehumidifier for the basement which runs full time. We also have a slightly musty smell in the basement, which we did not have when the humidity was lower.