I am currently considering installing a mini-split air conditioner in my home. I am trying to calculate the required BTU's for two bedrooms. Each room is 17X17 with 8 foot ceilings. Building is cinderblock and concrete construction. Summer temperatures can be in the high 90's with high humidity. One of the rooms will be used as a media room, so that could add some heat from TV and/or stereo. I am getting numerous evaluations, but none seem to match. One seems too much, other seems not enough. Any input is appreciated.

One of the nice things about mini splits is there is no ductwork, so you don't have to worry about if you oversize the unit. When in doubt, go with the larger unit, better to go big than small with a minisplit. Basically think of it as a window air conditioner(only much much efficient), if you were to put in a window ac, you would go with the biggest one you could fit in the window. I would contact a company that installs mini splits, and have them help you with your sizing, and of course, I suggest having them install it, as you will need to have special tools and knowledge to make it work correctly. Good luck, and please let us know what you decide.

mygirlsdad77,
That is the real issue. Different companies giving different requirements. One thing I have read is that too big is bad when you have high humidity. It runs less frequently and therefore may not deal with humidity well. Is that correct?

I would reinforce that "too big is bad" in a high humidity area. It will also make a difference on what temperature you expect to maintain in the room. You will get a cold damp room if the AC is oversized. Now if you expect to set the tstat in the mid 60's then you will need an oversized system as most calculations figure indoor temps in the neighborhood of 75 degrees for cooling.

I live in an area with a lot of humidity. The house has an old 1 ton mini-split in our large kitchen (installed by a previous owner). The room has a LOT of glass, is on the south side of the house, poorly insulated, and a blacktop driveway outside to boot. When the temps get up much over 90 degrees, the system is too small by most standards. EXCEPT that my wife wants it set at 80 and what we really care about is humidity reduction. The system works OK for us.

Ask your contractors how they are figuring their sizing and if they will give a performance guarantee. Check references. That's the best way to get a good system that I know of.

EPM

Oh yes, remodeling that kitchen is in my plans. :^)