How much cooling power can I expect from a mini split ac unit?

[4570Man]

So I’ve got a 30x40x11 high woodworking shop. The building is well insulated and doesn’t get terribly hot. The humidity is the real killer. It’s unenjoyable to work in in the summer months so it’s pretty much only used over the winter. So if I had a mini split unit and a smart thermostat that I could turn on an hour before I planned on working would it make a big difference in that timeframe? I’ve tried a dehumidifier but the heat off the unit raises the temperature in the sealed building more than it helps.

 

[RNeumann]

This is crude but should give you an idea.

Air Conditioning Sizing Estimator - Alpine Home Air Products

 

[Lineman North Florida]

I recently installed a 1&1/2 ton Mr Cool in my 20'x 40' hunting camp and it cools it with no problem but it only has 8' ceilings for your situation you are going to want to go bigger, mine was the DIY model and was really pretty easy to do, I believe you will be well pleased with a properly sized mini split.

 

[newbury]

So I’ve got a 30x40x11 high woodworking shop. The building is well insulated and doesn’t get terribly hot. The humidity is the real killer. It’s unenjoyable to work in in the summer months so it’s pretty much only used over the winter. So if I had a mini split unit and a smart thermostat that I could turn on an hour before I planned on working would it make a big difference in that timeframe? I’ve tried a dehumidifier but the heat off the unit raises the temperature in the sealed building more than it helps.

How do you define "doesn’t get terribly hot."??
By "well insulated" is that against just heat or heat and moisture?
Your about 100 miles north of me. My uninsulated sheds routinely get to 95 during the summer.
If you want to control humidity you need to do it 24/7.
Reads like you need a unit with the coils and motor outside. A minisplit would probably be ideal.

 

[Professor Marvel]

that is a long way for 1 evaporator to push air. especially for dehumidification. maybe 1 at each end. either 2 inside units with 1 outside unit or possibly just cheaper to go with 2 complete units. you know 2 smaller units. you only dehumidify the air that crosses the coils.
i agree it needs to be 24/7 for dehumidification.

 

[4570Man]

How do you define "doesn’t get terribly hot."??
By "well insulated" is that against just heat or heat and moisture?
Your about 100 miles north of me. My uninsulated sheds routinely get to 95 during the summer.
If you want to control humidity you need to do it 24/7.
Reads like you need a unit with the coils and motor outside. A minisplit would probably be ideal.

The moisture is coming from the air. It never gets hotter than the ambient temperature usually a little cooler.

 

[LouNY]

You can get mini-splits up to 48,000 btu that I know of, quite likely even higher.
One of those with 2 or 3 heads will make a heck of a difference.
One of my 36,000 btu units has an 18,000 btu interior unit and two 9,000 btu units.

 

[TnAndy]

Cheaper route to go rather than multiple head or mutiple unit mini-splits might be a 'package' unit. Everything (compressor/evaporator) comes in a single unit that sits on a pad outside. You basically plug it into power, connect a thermostat and run it.

GPC1536H41 - 3 Ton 15 Seer Goodman Package Air Conditioner

You would have to run a small amount of duct work, it has to have a supply duct and return duct run to it......but that is fairly easy in a wide open shop situation. Run the supply up a wall about the middle of the shop long wall, and simply let it blow out at ceiling, or run a short T and let it blow toward both ends (you could add the T later as you see how it performs). The return would be a real short duct run from down low on the inside wall to the unit sitting just outside.

The big advantage of mini-splits is not having to run any duct work....and you can get far better SEER ratings. But when you start looking at the price difference, given the amount of time you might use the unit, you may well find one of these is a whole lot cheaper in the long run.

Also, since this a wood shop, you're gonna generate a lot of 'fine' dust....even with a good dust collector. The package unit would have a pretty easy to access air filter in the return down where you'd be more likely to inspect and change it versus the little screen filters on mini-split units on the inside head. That fine dust is gonna play heck on the coils on an evaporator if you don't keep it out. I was envisioning a 'double' return where I'd mount two filters side by side feeding into the return to give me a lot more filtration and return air movement. The wood furnace I have in the shop center has a plenum box built on the back with a filter mounted in it, and that filter I have to change REAL regular in the winter time when I'm working in the shop or it plugs plumb up.

I've considered the same for my shop...it's 35x75, with the main part inside open to 60' length. Has 8' side walls, then the ceiling slopes up at the first angle to a flat ceiling at 13', then back down the other side the same. On the upper side (opposite), the wall is cinder block below grade for 4-5' of the 8' vertical wall. Perfect spot to plug in a package unit sitting just outside, short return duct, and not too much supply duct either....up the 45 degree slope inside, run a T on the flat ceiling blowing toward either end of the open part.

 

[jhasafety1]

I have a 30x40x10 shop with a 24,000 btu mini split and I have no trouble heating and cooling. My building is two years old and well insulated. My unit is a Mr. Cool DIY unit from Home Depot and I installed it myself with no problems.

 

[Milo]

I am just finishing up my 28' x 38' (9' ceiling) very well insulated shop that consists of three rooms, 24' x 28', 14' x 12', and 14' x 16'. All rooms are cooled/heated from a single mini split head in the larger room. So far it's only got into the low 80's but just running it continuously in low "dehumidify" mode (not even "cool") gets it too cold so I have to turn it off or change to cool mode with the temp set at 73 or more. So yes I believe a single head mini split will do a great job for you. Mine is a Carrier (I don't have the models of the outside and head units handy) but professionally installed.

 

[dstig1]

If you are fine with the temps, then why not just get a dehumidifier? I put one in my shop a couple years back. It is very well insulated and I keep the doors closed as much as possible when the humidity is up. This is just a 120 pint frigidaire portable unit, made for a house. It make a HUGE difference in there. Shop is 32x80x13 high. I have to empty tanks as I don't have a drain, but if you had a drain,l you could run it straight into that and never have to do much other than clean the filter from time to time. I have found that I don't even notice how how it gets with the humidity down. It can easily be mid 70s in there and it feels cool even.

 

[4570Man]

The dehumidifier makes too much heat and I ceased operating it. And I don’t like the temperature it would just be a lot better without the humidity.

 

[Milo]

The dehumidifier makes too much heat and I ceased operating it. And I don’t like the temperature it would just be a lot better without the humidity.

The nice thing about a mini split in "dehumidify mode" is it makes adds cool inside, the heat is outside.

 

[dstig1]

The dehumidifier makes too much heat and I ceased operating it. And I don’t like the temperature it would just be a lot better without the humidity.

Yeah I wondered about that as you are in a much warmer spot than I am. It seems to do the trick for me up here at least...

 

[Milo]

If you don't need heat, only dehumidify and cool, what about putting a sleeve in an outside wall (or window) and slide in a window AC? Inexpensive yet surprisingly effective. My previous home had a small shop consisting of a 24 x 24, and a 12 x 24 room. The shop was brick, built in 1990, pretty well insulated, and had it's own small high efficiency gas furnace but no AC. Because it was well insulated it never got terribly hot inside maybe up to 80 on a hot day but that and the humidity made it pretty uncomfortable in Summer. I decided to set an AC in one of only 2 small casement windows in the shop which happened to be in the larger room. The only AC I could find that'd fit was a really small unit I forget how many BTU but not a lot, it was made in China and cheap but what the **** I removed the little casement pane and put it in. After reading about all the settings I put it at 75, Auto, Economy mode, and it made a huge improvement. 75 and low humidity is worlds better than 78 and high humidity.
After temp would drop to 75 it would shut down but even if the temp stayed at 75 about every 30 minutes the fan would start and run for 10 minutes to circulate air then either shut off again or if called for the compressor would come on and it'd cool it back to 75. I just left it set at that all Summer and if there was a bump in the electric bill it wasn't even noticeable.

 

[Tractor Seabee]

Back to the OPs original question! They will produce the amount of cooling indicated by the units tonnage rating, BTU rating, or Horsepower. Basically 1 HP = 1 Ton of heat extraction or 12,000 BTUs. As stated earlier; to determine if a specific unit will do the job, you need a space heat gain calculation, or if calculating for heating, the heat loss at expected ambient temps. If using for both heating and cooling with no other heat input to the space you need to base unit size on the heating load. Your local utility can usually answer some questions short of doing the calculations.

Ron

 

[4570Man]

I don’t need heat because I already have a natural gas heater.

 

[Barnbuilder]

We put one in a man cave I built about 8 years ago. 36x40, I think the ceiling was maybe 20'. It was 3 units. 2 ran off one pump.

 

[3Ts]

The thing I don't like about the mini-splits is access to the filter. It's in the top of the head unit which is mounted about 8' up (10' wall) and I have to climb on the washer and dryer to get to it. Otherwise they are really nice units and relatively easy to install.

As for reducing humidity, an AC can only do so much and a dehumidifier is the real answer (yes they do seem to make it warmer). I would use a ducted dehumidifer with a filter at the intake and the exhaust plumbed to the opposite corner so you get an air flow. Then use the AC to cool the shop.

The mini-split I have is 18,000 BTU and is used in a 24 x 36 x 10' shop with 5.5" spray foam in the walls. It's more than enough, if I ever have to replace it, I'll probably go smaller. Keep in mind that the AC is not dehumidifing if it's not running. I also have a dehumidifier in there that's always on.

 

[Smokeydog]

Mini split is the way to go. I put a filter on top the indoor unit to help with the big dirt and hair.

We have a 26x45 two story old log cabin. Heated with wood and cooled with window acs. Upgraded to a Mitsubishi best minisplit heat pump, heat/cool. One ton unit the biggest I could fit in the stairwell to heat/cool both levels. Was planning to install two. This thing is amazing. Don’t use window acs anymore. Needed one fire last winter. Better at dehumidification. Much quieter. Avg <$100/mo electric on all electric home. Paid for itself many times in eight years. 26seer.
Only con is it is hard to clean inside coils and fan once a year when switching from cooling to heat.
With a lot of company and cooking could use a second unit for cooling.