16K or 22K Cooling BTUs

[MarkD]

Hello Everyone,

I'm going to buy a Mr. Slim ductless A/C to cool my 480 sqft garage workshop with 10 foot ceilings. Most of the BTU calculators online recommend a 18K BTU A/C. Mitsubishi offers a 16K and a 22K BTU unit. Which one do I buy?

I don't want to oversize the unit, but I don't want to spend all this money and not have it be as cool as I want.

Is anyone here cooling a garage in a similar way?

Mark

 

[Roospike]

The rule of thumb is BTU per ton is 12,000 at/per 1 ton ( 12,ooo BTU ) cools 600- 1200 sf depending on insulation.

Read this thread here.
http://www.garagejournal.com/forum/showthread.php?t=9526



Oversized air conditioners run in short inefficient cycles. They waste energy since they must run for a few minutes at the beginning of every cycle just to cool down their coils, fins, and ducts. Only then can they cool and de-humidify your home. That original cool-down energy is lost after the air conditioner shuts off.

An air conditioner's ability to remove heat is expressed in Btus per hour, or “tons” of cooling. Each ton equals 12,000 Btus per hour. Your air conditioner should have a ton of cooling capacity for every 600 to 1,200 square feet of floor area, depending on your home's energy efficiency and your local climate.

A poorly shaded home with little insulation and lots of air leaks might need a ton of air conditioning for every 600 square feet of floor area. A well-insulated and well-shaded home with few air leaks might only need one ton per 1200 square feet.

 

[Roospike]

So to answer your question i would go with the smaller unit. The idea is for the A/C unit to run longer to take out the humidity in the air. With the bigger unit it will cost more $$ to run even tho for shorter times , the bigger unit will blast cold air faster but not run like it should and you will end up with humid cool air for the out come.

Get the smaller unit and make sure its a high SEER unit. ( or EER for window )

 

[Charles (in GA)]

Depends on alot of things. How much info do these online calculators ask for so far as insulation, doors, windows, etc.

If your garage/shop is build like your house, fully insulated, sheetrock on the walls and ceiling, and a good tight fitting door and energy efficient windows, then the 16K will probably work just fine.

If the calculators make too many assumptions, and your garage is not up to what the calculators expect for their "standard" building, then you might consider going to the higher rated unit.

Charles

 

[MarkD]

Thanks for the replies.

The garage is sheetrocked and insulated, the door is also insulated. In my last garage I used two portable a/c units, one 12000 BTU and the other 8000 BTU. I was never really satisfied with that set up. It would never really cool the garage down, so that's why I am worried about the size of the unit I'm currently considering.

Mark

 

[Roospike]

for the 12,000 & 8,000 BTU units ( 20,000 BTU ) we dont know any information on your "last garage" so it really dont tell us anything ..........

Are you looking to walk out to your garage in the middle of the day @ say 90° already and turn on the A/C unit and want it to be cold in just a little wile ? if so then there will be a sizing issue with any correct size A/C unit.

A/C units have to run to work correct so you should have to turn on the A/C unit a long wile before going out there.

I had a older house with a 5,600 BTU window A/C unit in the master bedroom and when you let her run and do her thing it always kept the room very cool with very little humidity but forget to turn it on and fire that unit up as your going to bed then forget it , it would take almost 3-4 hours in the warmer weather to get the room temp and humidity to were it needed to be.

How you run the A/C unit has everything to do with how it will work for you.

A 22,000 BTU A/C ( 2 ton ) should cool around 1,200 - 1,800 sf . and your looking to cool 480 sf .......... man , I dont see good thing with an over sized unit.

Call around to 4-5 A/C dealers and see that thay tell you .

Best of luck.

 

[Roospike]

AIR CONDITIONER BTU requirement



Footage @ sf............Btu's Required

250-300 ...................7,000

300-350 ...................8,000

350-450 ..................10,000

450-650 ..................12,000

650-850 ..................13,000

850-1,100 ...............18,000

1,100-1,400 .............24,000

1,400-1,800 .............25,000

1,800-2,500 ............29,000

 

[MarkD]

I've suspected all along that I needed the smaller unit. Just needed some reassurance. I tend to over-build everything. I guess for air conditioners, bigger is not necessarily better.

I'm going to order it next week. I'll post pics.

Thanks again.

Mark