need mini split sizing recommendation

[aaronlalonde]

400 sq ft garage, r13 in two exterior walls, one wall connects to house, fourth wall 16 foot (soon to be insulated) garage door. I just put in between r40 and r60 fiberglass blown in in attic. I will aslo have a deep freeze, a second freezer converted to kegerator and probably 3 or 4 computers. Quick cooldown will be nice as sometimes we open the door and have driveway parties. we do not park in the garage but will be brewing beer as often as necessary.

Im in pearland tx just south of houston, right now it is 85 in garage and has dropped to 80 outside. Im going back and forth between 12k and 18k units and am also looking at heat options.

im not opposed to cheaper brands of the quality is there. I see ajmadison has a 12k fredrich for about 1k.

what do you all recommend i do to cool this space?

 

[pattenp]

Here's a simple calculator.......

http://www.acdirect.com/mitsubishi_learning_center.php?li=2

 

[JakeKohl]

400 sq ft garage, r13 in two exterior walls, one wall connects to house, fourth wall 16 foot (soon to be insulated) garage door. I just put in between r40 and r60 fiberglass blown in in attic. I will aslo have a deep freeze, a second freezer converted to kegerator and probably 3 or 4 computers. Quick cooldown will be nice as sometimes we open the door and have driveway parties. we do not park in the garage but will be brewing beer as often as necessary.

Im in pearland tx just south of houston, right now it is 85 in garage and has dropped to 80 outside. Im going back and forth between 12k and 18k units and am also looking at heat options.

im not opposed to cheaper brands of the quality is there. I see ajmadison has a 12k fredrich for about 1k.

what do you all recommend i do to cool this space?

You didn't mention your garage doors - if you have a standard uninsulated door(s), it will be a huge source of heat gain and greatly affect the needed size of the unit...if you have insulated doors, you can probably get away with a 9k unit but 12k will take care of that easily. I have an 18k LG unit in my 870 sqft garage (with good insulation and insulated garage doors) and it works very well to both heat and cool.

 

[mobiledynamics]

OT...but it's interesting about the inverter heat. I have it on all of mine BUT......
gas is cheap out here, so during the winter, I generally find myself firing up the boiler and keeping my fancy cast iron baseboards hot. I've yet to do the math and compare/contrast wheter there is a savings with the zoned heat of the minisplits + the higher utility cost.

 

[aaronlalonde]

im curious what it costs to run a 12k unit per month compared to my two 3.5 ton units in the back yard.

 

[Ohmthis]

im curious what it costs to run a 12k unit per month compared to my two 3.5 ton units in the back yard.

12k btu is one ton, so your (2) 3.5 tons are 84k btu. You would need 7 of the 12k split systems to match your existing units. Kinda like comparing apples to oranges.

 

[JakeKohl]

im curious what it costs to run a 12k unit per month compared to my two 3.5 ton units in the back yard.

I'm in South Carolina and built a two story 24x36' garage that is well insulated including insulated garage doors. The second story is heated and cooled 100% of the time and the downstairs heated and cooled about 40% of the available time. I have two separate mini-split 18kbtu units upstairs and downstairs and have been running them for about 8 months now. Using my utility company's bill analysis/comparison tool (which also apparently tries to normalize out the weather differences and other variables), it is costing me about $20 extra per month to run the additional building square footage - most of that is the heating and cooling. In the peak of winter (Jan), after normalizing for different weather and electricity rates between this and last year, it cost me an extra $48.

So...not too bad. I'm impressed.

Your results will obviously vary by location

 

[Falcon67]

12K might do it because of your insulation. I used a 12K in my last shop (480 sq/ft) but there was no additional heat loads like your freezers, fridge, beer cooler and computers. It might still be a big much but you also have a high humidity problem down there too. Your 90F with 75%RH is my 105F with 20%RH.

 

[Jinks]

Central Florida, 450 sf garage/shop. It's "L" shaped with the garage portion being a 12' X 23' garage with a 10" insulated garage door. The remainder is shop space with a refrigerator & laptop in it. I have a ceiling fan in each section. While sizing mine I was told that I needed 18K to 24K btu. None of the online calculators indicated anything near that. More like 12K to 15K. Since I don't use the space for entertaining or living I opted for a Mitsubishi 12K air only (don't have much need for heat in C. F.). It does just what I wanted, cools & dehumidifies my work space. If I wait for the space to reach the high 80's or low 90's it takes a while to cool, but it dehumidifies rather quickly. If I turn it on while it's cool in the morning the space stays cool all day, even if I open & close the garage door long enough to move a car or bike in or out.

If you're looking for something that will cool a hot space quickly I'd suggest 15K or 18K, but for normal working conditions 18K will certainly be over kill.