Can mini splits work in large space?

[bilede]

I have a odd shaped garage/space to cool. large bay area is 40x80x18 and off of it is another area with a downstairs and upstairs connected to it so that means another 20x40 space.

its a stick built structure, well insulated. R26 walls, r50 is ceiling, 2 garage doors with polyurethane insulation of r21, and 2 small 3x3 dual pane windows. Currently it stays very even inside the building even on hot days over 100 degrees.

I was thinking two 3-ton mini splits (6 tons) on the long wall to maintain reasonable temperatures inside this area when I am working. expectations are not to have 68 in there nor 10 minute recovery when I turn it on or the space is evacuated by opening all doors.

reading online articles I found says large spaces need traditional ducting systems as ductless mini's can't keep it cool. What say you guys?

I am attaching space so you see layout.

 

[Chapter21]

Has nothing to do with ducts. It just needs to be the correct size for the space. I don't know what BTU you would need, but yes, the more units you can spread it across the better it would be. You need some kind of air circulation or a room like that will stratify very quickly, but that looks like a good application for a ceiling fan or two.

 

[karoc]

IMOP- Mini splits have their places and may be good for few yrs but they have to work their tail off, more so where your at. Package unit or split system with duct work will out last mini splits but cost is more and not really a DIY project

 

[theoldwizard1]

Yes, they can work, but in an area that large I think you will need more than 2 air handlers !

I am not an expert, but you might need 4 air handlers AND some ceiling fan to get good distribution in an 80x40 space. For certain the other area needs it own air handler.

Keep in mind that as you add air handler to the compressor efficientcy drops !

 

[yeldogt]

What is the upper area used for? Does it need to be conditioned to the levels of the others?

Placing two units on the long wall blowing towards the cut out would work -- but you have a problem getting the upper area conditioned to what the lowest level would be.

With a big space and high ceilings --- you don't want to use fans to move the air around. All you do is take the hot air and mix it ... this is not how you cool a space. The units would be placed at around 8' and they stratify the air. You cool where people are and let the heat rise.

Cool air sent to the upper part of the bump out is going to flow down --- so placement is going to depend on that upper are and how you want to use or not use it

 

[ericm]

Nice space!

You can calculate how much cooling and heating you'll need here: https://www.loadcalc.net

 

[Chapter21]

The units would be placed at around 8' and they stratify the air. You cool where people are and let the heat rise.

And now the upstairs part is uninhabitable. You have to make a choice, do you want to pay to make the entire thing comfortable? Or are you OK with just half?

Also if you are working in a room with a very light air flow (ceiling fans) generally you can stand warmer temperatures and still be comfortable.

It still really has nothing to do with mini split vs other air conditioners. Same guts. It's just a matter of correct sizing and air distribution. A mini split is not going to work any harder than any other system of the same BTU rating.

 

[yeldogt]

And now the upstairs part is uninhabitable. You have to make a choice, do you want to pay to make the entire thing comfortable? Or are you OK with just half?

Also if you are working in a room with a very light air flow (ceiling fans) generally you can stand warmer temperatures and still be comfortable.

It still really has nothing to do with mini split vs other air conditioners. Same guts. It's just a matter of correct sizing and air distribution. A mini split is not going to work any harder than any other system of the same BTU rating.

That's why I asked him how he was going to use it -- if the up stairs is going to be some type of people space ... then do do it correctly he would need a unit up there ..... but, the air is going to flow down and be usable to the lower area.

High ceilings with fans and AC -- it just makes the AC work harder. There is no benefit to mixing the air .... you cool where the people are.

Go look at any large space -- church ..auditorium w/o balcony etc. They don't mix the air if it's done professional ..

 

[Chapter21]

Go look at any large space -- church ..auditorium w/o balcony etc. They don't mix the air if it's done professional ..

That wouldn't make any sense in the winter time. The OP is in AZ so probably not a concern, but for most other people they get two seasons...

Any commercial building also has a 4 digit+ electric bill, so it's really an entirely different beast. Usually the AC is mounted on the roof, but that's to save outdoor space.

Ceiling fans are fantastic in shops. And very cheap. And they come with a switch, so you can turn them on or off!

 

[bilede]

Thanks for all replies. The upstairs has my desk area but otherwise is storage to keep floors clutter free. At least as much as possible. Currently in summer with 110 out I am staying around 88 inside lower area and upstairs does get warmer. I am hoping to keep downstairs around 80 when I am working and 85 when not so my vehicles don’t cook. I am not upstairs much but could blow cooler air in my desk direction or put a single addition mini split in that specific area.


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[Chapter21]

If you just want some cold air while you're at your desk, you could just use a cheap-o window unit, and just let the hot air into the rest of the shop. Obviously only run it while you sit there...

I used to have a stack of 4 window units mounted on wheels for my shop, I would just move them to blow on me like a fan.

 

[yeldogt]

That wouldn't make any sense in the winter time. The OP is in AZ so probably not a concern, but for most other people they get two seasons...

Any commercial building also has a 4 digit+ electric bill, so it's really an entirely different beast. Usually the AC is mounted on the roof, but that's to save outdoor space.

Ceiling fans are fantastic in shops. And very cheap. And they come with a switch, so you can turn them on or off!

Heat is different .... getting the heat off the ceiling will add to the overall heat down low in a forced air heated building ... not a radiant. That's why you see fans in larger spaces in the winter.

The placement of AC units -- in a commercial space ..like a big box store is all about ease .... they do blow down w/ force to get the cool air at the floor.

You don't want fans in an high ceiling space when cooling ... it's that simple. Look it up ...

 

[yeldogt]

Thanks for all replies. The upstairs has my desk area but otherwise is storage to keep floors clutter free. At least as much as possible. Currently in summer with 110 out I am staying around 88 inside lower area and upstairs does get warmer. I am hoping to keep downstairs around 80 when I am working and 85 when not so my vehicles don’t cook. I am not upstairs much but could blow cooler air in my desk direction or put a single addition mini split in that specific area.


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Find a good calculator -- with those numbers my guess is 6t is too much.

Also --- it may be wise to start out with one up and the other down. Most people don't need perfect coverage in a shop ... they want it cooler or hotter where they typically work. Mini splits have a good throw.

There are DIY air-handlers -- so you could do a ducted system. It comes down cost. A ducted system with some zoning would work

 

[bored350]

Do you really need 6 tons of cooling for a space that well insulated (am I correct in assuming most of 1 long wall is shared with the house)? Given the information you have provided about size and insulation I have to ask why you are considering 2 minis over a conventional system? If you are a DIY person, I could easily see a duct running along the upper left corner with several outlets over the bay and a small trunk to feed the bump-out comfortably. JMO of course.

I have talked about it previously but won't be ready to install until next year. The Mr Cool DIY inverter universal heat pump is on my radar for a solution to my needs. I'm 34x46 with a full bath, small mezzanine (that will probably become an office) and I may zone the building in half down the middle 46'. Just some food for thought. The 5 ton system might work for you and solve all of your concerns with a good price point.

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[Chapter21]

You don't want fans in an high ceiling space when cooling ... it's that simple. Look it up ...

Man you are dense! There is a reason I pointed out ceiling fans are cheap and include switches. Depending on the conditions you can turn them on or off! They are FANTASTIC to have in a shop, especially this particular shape and size, that's how Big *** Fans became so popular.

The room I am sitting in is 600sq ft with a 15' ceiling...and the ceiling fan stays on all summer with the A/C...that's why they have a switch to blow up or down.

With ceiling fans, even in AZ, you might find that is all you need in many circumstances, and the A/C can be switched off. Whoever invented this switch thing was a genius!

 

[shade]

Im also in AZ.
I have an attached garage 40' x 25' - 12' ceilings. Fully insulated
I placed 2 24k units along the longest wall around 9ft.
Keeps the space as cool as I want it. Recovery rate when i bring a hot car into the space is extremely fast.

 

[Noltz]

I watch this dude, he's got a machine shop set up with a Mini-split. I asked our HVAC guys about splits at our shop (the roof needs to be done soon so conventional roof mounted won't work right now). I'm told the air makeup of a mini-split will not do if you're opening garage doors like a shop would, and our insulation was insufficient. But if the doors are staying closed 99% of the time and you have good insulation they'll work.

 

[Chapter21]

I watch this dude, he's got a machine shop set up with a Mini-split. I asked our HVAC guys about splits at our shop (the roof needs to be done soon so conventional roof mounted won't work right now). I'm told the air makeup of a mini-split will not do if you're opening garage doors like a shop would, and our insulation was insufficient. But if the doors are staying closed 99% of the time and you have good insulation they'll work.

As before, none of this has anything to do with mini split vs anything else. The guts are the same. If the BTU rating is the same, nothing is working harder than anything else. Opening garage doors is the same no matter what kind of A/C unit you have.

BTU rating and air distribution are literally the only concerns.

 

[TRWham]

...

BTU rating and air distribution are literally the only concerns.

He was talking about outside air, which a mini-split will not provide. Using outside air to pressurize a building is common in commercial HVAC and done to reduce air infiltration during door openings and improve indoor air quality (IAQ) by changing air. In my experience we usually designed for 10-15% fresh air. In this case, I doubt you can achieve much pressurization versus an open garage door short of a 1,000 hp blower, but you can sure get some air changes.

 

[Alin]

Yes, but in larger area. I am not a pro at it, but most probably 4 air handlers and a ceiling fan will be enough.

 

[yeldogt]

Man you are dense! There is a reason I pointed out ceiling fans are cheap and include switches. Depending on the conditions you can turn them on or off! They are FANTASTIC to have in a shop, especially this particular shape and size, that's how Big *** Fans became so popular.

The room I am sitting in is 600sq ft with a 15' ceiling...and the ceiling fan stays on all summer with the A/C...that's why they have a switch to blow up or down.

With ceiling fans, even in AZ, you might find that is all you need in many circumstances, and the A/C can be switched off. Whoever invented this switch thing was a genius!

I can't change thermodynamics ..... when you mix air ... you have to condition it. It's that simple.

I understand what a ceilings fan is.

Dense is correct .... cold air is and falls .... hot goes up. Keep hot up and allow cool to say where you are.

think they learned that a long time ago ....