Mini Split Sizing 38' x 44'?

[GearHd6]

I live in Connecticut and plan in mainly cooling with the mini split. I'm currently having a 38 x 44 pole barn built that has 12' ceilings. It'll have R30 blown in insulation in the ceiling and R19 in the walls. It'll have two 9x10 doors and one 10x10. There will also be three 3x3 windows. When I run online calculators I get 36,000 BTU and 48,000 BTU depending on the calculator. I feel like the 36k with two 18k heads would be plenty but I don't want it to struggle either.

 

[ericm]

The best calculator I have seen is loadcalc.net. Some of the ones on mini split vendors sites seem designed to sell larger units.

But if you don't complete every relevant field on the loadcalc manual J you can get results that are off.

What design temps are you using? That makes a difference. As does the direction the windows and doors are facing.

 

[GearHd6]

For cooling I think 75 degrees would be good, for heating I'd say 62 degrees. The 3 garage doors would face west and the windows would face north.

 

[theoldwizard1]

I know it will cost more, but 2 smaller units will be more efficient than 1 larger one, mainly because of shorter lines. You will make your money back.

Actually, for that size of a building , 2 units with 2 air handlers each (4 total) would be even better !

 

[GearHd6]

I know it will cost more, but 2 smaller units will be more efficient than 1 larger one, mainly because of shorter lines. You will make your money back.

Actually, for that size of a building , 2 units with 2 air handlers each (4 total) would be even better !

So what are you thinking, two 24k BTU units with four 12k heads?

 

[theoldwizard1]

So what are you thinking, two 24k BTU units with four 12k heads?

What ever air handlers they recommend for a 24K unit.

Yes, it will be expensive, but you will have a more even temperature and recover faster after one of the bay doors is opened.

 

[pcmeiners]

As a comparison, I have a 12k Fujitsu high efficiency unit heating and cooling my 30x36 garage... 2 garage doors, 2 windows, R-15 wall, R 20 ceiling, slab has foam. This 12k unit has plenty of heating/cooling capacity, as I used it to also heat/cool the attached 1280sft home for a while. Perhaps (3) 12k units, giving extra capacity for quick cool down, good air flow, and some redundancy if one unit fails. Should one unit fail, your are not forced to get an expensive emergency service call. Three separate units as single zone splits are the most efficient. You could get by with (2) 12k units, but air flow might be an issue.

 

[My Old Tools]

My 30x40 shop in Texas has far less insulation and 7 big windows. My 36k MrCool is overkill. One head in the middle of one wall works fine.

 

[Notgrownup]

I have no clue of the sizing or load calculation but I found a twin 24k BTU high SEER . I have a 24x24 shop with only a 10’ ceiling. I have a Blueridge 18k btu unit and it’s way overkill but the damn thing doesn’t struggle and cools or heats my shop for maybe an extra $20 a month. Again, no load calculator but you can call Alpine home air and they might help you. You would still need to get it installed But for $4000 that’s 4 tons of cooling.

 

[mike93lx]

Why only r30 in the ceiling? What are you doing for air control?

Will the minis be doing any heating duty or are you covering that with something else?