Opinions on size

[ATCGA]

I’m finishing my 1500sf building and I’m trying to figure out what to use for cooling. It’s fully insulated with 12 foot eave height and 16 feet high in the center. I’ll install a couple of ceiling fans to keep the air moving.

Occasional use of the building and just need to knock down the inside temperature. What do you think of the idea of a 2 ton mini-split or a 3 ton multi zone mini-split?

I’d appreciate hearing from you guys that have experience or installed these types of units.

Thanks in advance.

 

[toyotadriver]

You need a Manual J. We don't know how much insulation the building has and how many doors.

That said, I'll spitball a number. I'm assuming you aren't cooling it full time. You also have a tall building so have a lot of cubic foot area to cool. I think I'd plan for a 3 ton. If you were cooling it full time, you might be able to get by with 2 tons as long as it's well insulated. If you only plan to drop the temp when you're working out there (and that appears to be your goal from your post) then I'd go slightly larger.

I think I'd likely do a 3 ton with two heads. At least that's what I would plan on till I got the Manual J calculation. You can have it done by a company online if you need a calculation done.

 

[chrispyny]

What TD said is good advice. Definately 3 ton. Definately 2 heads.

I’m gonna go even further.

Highseer has a 16 seer 24k btu unit (2 ton) for $968 including install kit (lineset, electrical, passthru etc). I’d buy TWO of them, one for each side.
Remember, ductless a/c units work most efficiently at a 75-80% load. You have what i read as 16’ ceilings. The price difference between two 18k btu units and two 24k btu units is $360. What a shame it would be to undersize your a/c by trying to have saved $360.

My raised ranch has a 24k btu head unit in the dining/living room. The kitchen is off the side. I placed and designed the 24k btu unit to cool the kitchen, livingroom, dining room, and spill into the hallway leading to the bedrooms. It does VERY well.

When we are cooking with the oven in the summer, the 24k unit is on full blast. Its perfectly sized as thats the only time is goes 100%, but when it does, it holds the house temp, but barely. Once the oven is off and cool, the unit settles back down to almost nothing.

I suggest you size the a/c in the building to a most extreme situation when the summer heat is at its hottest, and you want cool comfort. This is why i lead to a two unit ductless system, at 24k btu a piece.
Definately add fans as you mentioned.

Your in Alabama man. It gets hot and gross down there!! For less than 2 grand, you will be a happy man! Good luck. And please come back and tell us how u did.

 

[ATCGA]

Thank you both for the great info. I like the 3 ton idea. It does get hot and gross for sure and I’m not scrimping on the cooling! I’ve waited too damn long to build my shop and I plan on enjoying it to the fullest. I’ll definitely report back in a couple of weeks when I’m finished.

Thanks again!

 

[LS6 Tommy]

I'd guesstimate a 3 ton mini split, too. I suggest something with an inverter driven compressor. It will never be too big.

Tommy

 

[ATCGA]

I'd guesstimate a 3 ton mini split, too. I suggest something with an inverter driven compressor. It will never be too big.

Tommy

Thanks!

 

[DC73]

I think you're on the right track by considering a 3 ton unit. I did quite a bit of heat gain calculations on my workshop and ended up needing just shy of 1.5 tons of cooling for about 1,000 sq. ft.

Your ceilings are taller than mine and you have much more latent heat gain due to the humidity of your climate (we're dry out here). Because of that, I don't think 2 tons will be near enough for you.

DC

 

[ATCGA]

I think you're on the right track by considering a 3 ton unit. I did quite a bit of heat gain calculations on my workshop and ended up needing just shy of 1.5 tons of cooling for about 1,000 sq. ft.

Your ceilings are taller than mine and you have much more latent heat gain due to the humidity of your climate (we're dry out here). Because of that, I don't think 2 tons will be near enough for you.

DC

Thanks for the info. I’ve got a good friend in Lubbock. It gets pretty hot there too.

 

[Renfrick]

I think your Closer to 3.3 tons. I used 450sqft per ton


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[Falcon67]

Thanks for the info. I’ve got a good friend in Lubbock. It gets pretty hot there too.

Depends on where in AL you sit. Lubbock is a long way from the coast and really dry. Doesn't take as much to knock down 100F when the RH is 20%. vs trying to knock down 95 @ 80%. We're on the dry side of Texas, think you are on the wet side of the Mississippi.

 

[ATCGA]

Depends on where in AL you sit. Lubbock is a long way from the coast and really dry. Doesn't take as much to knock down 100F when the RH is 20%. vs trying to knock down 95 @ 80%. We're on the dry side of Texas, think you are on the wet side of the Mississippi.

Agreed. Wet it is!

 

[toyotadriver]

If you go with two units, you could go with 2 18k BTU units. Use one when you just need a little cooling and both when you need a lot. Or, do 1 24k BTU unit and 1 18k BTU unit.

 

[James-W]

Have you considered a couple window units? If you don't need heat, and being from Alabama you probably don't, then I would think two window units would work out well.

 

[cory58]

Just went through the same thing with my new 1500 sf garage (13' walls, 4/12 pitch). It's a metal building with cheap insulation on the walls and roof.

I know a couple of people here in Charlotte, NC with similar garages who are not happy with 3 ton units, so I am going with a 4 ton package unit heat pump. Should be installed by the end of April.


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[James-W]

I probably shouldn't say this, it sort of makes me look like a dirty old man. But when I first saw the thread title I was thinking of something totally different.