How big of an air conditioner do I need for central air in 3500 sq/ft house?
In a hot climate like San Diego, I’d figure about 1 ton per 500sf, meaning roughly 7 ton. If you have a two story home with only one system, the upstairs is likely to be warmer than downstairs. Heated air rises, while at the same time the sun’s beating down on the roof directly above. Having the AC run and run isn’t necessarily a bad thing, as long as it does the job. Over sized systems don’t run as much, but can actually cost more on the electric bill, due to higher start and run amp draw. Long cycle times on the smaller system also help dehumidify better. (Probably not an issue in San Diego) I’d suggest having a small, supplemental system installed, dedicated to the second floor. If you have and accessable attic, it can be installed there;….other options may be available, depending on the layout of the house. There’s always a way, though you’ll be looking at a minimum of $8-$10 grand for the install. For the time being, let the blower on the existing system run continuously, this m
