Mini Split Considerations

18 years ago

Live in Charlotte, NC...hot, humid summers and relatively mild winters.

We are putting on a 350 sq ft master suite addition with bedroom(~200 sqft), bathroom(~100 sqft) and closet. The space is a 21' x 17' rectangle and there is a partition wall with a pocket door on either side opening off the main room into the bathroom and closet. Bedroom has a vaulted ceiling.

We plan to use a combination of radiant floor heating and a ductless mini-split unit for cooling. We plan to have a Manual J done before determining the final size of the cooling unit (probably 9K of 12K Btu).

My question is will a single unit properly sized and positioned in the bedroom be able to cool/dehumidify the bathroom effectively as well? Right now the plan is to position the mini-split unit high up on the partition wall. Will a higher CFM unit be more likely to cool/dehumidify well?

Any advice and suggestions would be greatly appreciated.

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Comments (2)

ktddog
18 years ago
the units are sized acording to btu, so a higher cfm, means more btu, you didnt say if this was upstairs, over a garage, on a slab, with a crawl space, why would you say your getting a load calc, but not give that info on your question? what R are the windows, Isulation, etc, I would go with the 12,000, depending on manufacter, most units come with a dehumidification mode, that comes on afer setpiont is satisfied, ask your Installer kdog
dan_martyn
18 years ago
Air Conditioning when properly sized, is a natural dehumidifier. You need to first determine your load before you can talk sizing. Selecting an air conditioning unit which "Matches" your load, or is "Slightly" smaller than your load will provide the most "energy efficient" and provide the maximum dehumidification. On a peak cooling day, your A/C should run continuously. Over sizing air conditioning units will lead to short cycling, humidity buildup and premature equipment failure.

"My question is will a single unit properly sized and positioned in the bedroom be able to cool/dehumidify the bathroom effectively as well?"

Your bathroom @ 100 sq. ft. should have an exhaust fan which will pull in cooler air when in use. To determine the fan size;

1) Find the cubic volumne Lenght x Width x Height.
I.E. 10' x 10' x 9' = 900 cu ft

2) Multiply the Cubic feet by the required air changes per hour. 900 Cu Ft x 6 ACH = 5400.

3) Find the CFM, Divide the result by 60 minutes per hour.
5400 / 60 = 90 CFM Exhaust fan.

Six air changes per hour is one air change every 10 minutes.
Four air changes per hour is one air change every 15 mins...

Dan Martyn
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