Single or dual zone mini split?

[OzarkMan]

I want to cool my 1100 sq foot garage and have it all insulated when we built it.
The question is do I go with dual zone ceiling cassettes or single zone ceiling cassette put in the middle of the space? The sizing says to be 24k btu and living in the greater Phoenix area, I will need it all! Not sure if one ceiling cassette will move the air around enough.









incidentally, the garage does not look this nice anymore!!

 

[ishiboo]

That's a big space. I would think dual zones would be the way to go which would give better air circulation/flow without having to resort to fans.

That seems like a lot of space for only 24k BTU in Phoenix.

Beautiful garage though! Would love to see more pics

 

[ishiboo]

Good god, Photobucket has a lot of annoying ads.

 

[yeldogt]

The cassettes do have 4 outlets and a powerful fan .... the wall units have better controls for humidity ... that may not be a concern.

 

[Jackfre]

My problem with the cassettes is they are much more difficult to clean and in a shop environment and in a dusty area you need to clean the coils and the fans regularly. You will have much better and quicker temp recovery with the high wall units as you get a better circulation pattern set up. Put them on opposing walls if possible about a 1/4-1/3 of the way from the corner.

 

[miketyler]

I had the same concerns as you going in when I was looking at heating and cooling the lower floor of my shop. Mine is 30x40 rectangular with the long walls running parallel to east and west. My tool box and working areas are all located at the west end, which is as you might guess, the warmer end of the space.

I located my 24kbtu Mr Slim heat pump at the east end for two reasons. The first is that power comes in on the east end so it was a shorter power run to the breaker box. The second is that the east end is shaded after 2:00pm so my units wouldn't get the blistering hot Texas sun in the afternoon. This helps keep operating pressures lower and may prolong the life span of the unit. My shop is all open, fully finished out and well insulated. I will tell you I don't have any problem with air distribution. I located the optional wireless thermostat at the wast end and it keeps my shop and toys nice and cool no matter where I am at in the space.

I do have three ceiling fans equally spaced along the south wall (opposite the doors) but they don't seem to make a lot of difference in moving the air. You probably already know this but you will pay a premium for multi-zone units. For me it was going to more than double my costs in parts and installation. (I DIY install everything)

I would go with a good quality, appropriately-sized single wall unit. I think you will be pleasantly surprised at how well it does.

 

[justinjoyal]

What kind of insulation do you have ?

 

[OzarkMan]

R19 in walls and R38 in ceiling. Also the garage is wrapped in 1" insulfoam and stuccoed over that.

 

[LS6 Tommy]

Avoid the cassettes. They have terrible air distribution, they tend to drip off the louvers, and are almost impossible to service when (not IF) the fan run capacitor dies.

Tommy

 

[yeldogt]

Avoid the cassettes. They have terrible air distribution, they tend to drip off the louvers, and are almost impossible to service when (not IF) the fan run capacitor dies.

Tommy

We have 4 of them running in my office for 5 years now with no issues .. I have them in the second floor of one house for two years .. no issues.

I'm not saying its not a possibility ... as, stuff breaks.

We also find the quad outlet moves the air everywhere?

Ours .. mitsubishi ... don't have the same controls as the wall units -- I understand this will finally change and would be a positive move.

 

[LS6 Tommy]

Been involved with at least 40 cassettes from multiple manufacturers. They all had enough that exhibited the same issues I noted that I will never intentionally install one again.

Tommy

 

[OzarkMan]

So I contacted the seller on eBay who deals with the Senville A/C units. I have one that has been running beautifully while the outside unit is exposed to full summer 100º+ heat. I gave the dimensions of my garage to the seller and he comes back with a suggestion that a 18,000 but unit is enough for my 32x34 garage. I have 9' ceilings. I am thinking that is too little of a unit with one ceiling cassette.

 

[yeldogt]

People build energy efficient houses doing 1000sf per ton -- you are at 1088sf. I have done foam houses at around <700sf per ton with no problems .. so .... a foamed house at your SF would be fine with 1.5 ton (18k BTU) and continuous operation.

But, you are in AZ -- I'm in the mid Atlantic ......and it looks like it's got a lot of roof and two doors? Anybody else around with same space and AC ?

 

[dsimatt]

So I contacted the seller on eBay who deals with the Senville A/C units. I have one that has been running beautifully while the outside unit is exposed to full summer 100º+ heat. I gave the dimensions of my garage to the seller and he comes back with a suggestion that a 18,000 but unit is enough for my 32x34 garage. I have 9' ceilings. I am thinking that is too little of a unit with one ceiling cassette.

I'm cooling a similar sized house with 1 18k wall unit and it has done OK so far but and this is a big difference is that it's only hit 86* here and my house is shaded by trees which really helps.

You have done a great job on your garage so you owe it to yourself to have a professional come out and do a calculator on what you need, IMO 18k will be maxed out really easy and not meet your expectations

 

[rebelranger]

Get online and do a manual j. I bet with r10 exterior foam, r19 batts, and r38 attic 18k would work. I would go 18k if you plan to keep the ac on when you are not in the garage, meaning temperature controlled year round. If you plan to turn off the ac when out of shop and want faster cool down times I would go slightly oversized especially if you are getting an invertor unit.

 

[G8rDuc]

So I contacted the seller on eBay who deals with the Senville A/C units. I have one that has been running beautifully while the outside unit is exposed to full summer 100º+ heat. I gave the dimensions of my garage to the seller and he comes back with a suggestion that a 18,000 but unit is enough for my 32x34 garage. I have 9' ceilings. I am thinking that is too little of a unit with one ceiling cassette.

I had an A/C company come out and look at my 30x30. He recommended a 24k mini split. But he said a package A/C would actually be more efficient. Why? Because I could run a duct through the middle of the garage, hanging from the ceiling (15 ft peak) and have vents coming out every 5 feet and it will disperse cool air throughout and be more efficient. Going to look into that. If not, a dual zone 24k will be sought.

 

[ticklechicken]

I had an A/C company come out and look at my 30x30. He recommended a 24k mini split. But he said a package A/C would actually be more efficient. Why? Because I could run a duct through the middle of the garage, hanging from the ceiling (15 ft peak) and have vents coming out every 5 feet and it will disperse cool air throughout and be more efficient. Going to look into that. If not, a dual zone 24k will be sought.

I'm in a similar situation here in central Florida. Did the a/c guy consider all the details about your shop? Ceiling height? Insulation? Shade? Windows/doors? If so, could you share those details?

 

[G8rDuc]

I'm in a similar situation here in central Florida. Did the a/c guy consider all the details about your shop? Ceiling height? Insulation? Shade? Windows/doors? If so, could you share those details?

Yup..first, I'm in North Central Florida (Gainesville area) so we have the humidity and the heat to deal with. Shop Details:

30x30 (900 sq ft) with 12' walls and a 15' peak.
OSB interior walls, metal garage (not the big girder type steel posts)
1 window on each wall, 2 10x10 rollup doors, 1 side door.
No shade (unfortunately).
Used the roll-up solar insulation behind the OSB (I know, not the most efficient but so far, it's made a 15 degree difference), not sure on a roof insulation yet.
Honestly, it's not too bad in there, even on the hottest days, but most of my time would be in there after work, so it's cooler. Either way, need air.

With all of this in consideration, he said a dual-zone mini-split would work and around 24k would be sufficient, but he stressed that a package setup would be more efficient because it would allow me to run a single duct line through the middle of the garage and have air blow throughout on both sides. He also said that, in his experience, the package systems have a longer life then the mini-splits, though he did admit the Mitsubishi mini's are super reliable.

 

[ticklechicken]

I remember the weather in Gainesville, especially when I had to scrape ice off my seat before riding to class. Overall, it's just a little colder than here, but pretty similar.

I have a 24x45x10 metal building with closed cell foam, no windows, one insulated roll-up door. I'm thinking of a 18k + 12k dual mini split system. I'm dividing the shop 60/40 with a wall, so that's why I'm considering different sizes.

Is that Jennings in your avatar?

 

[G8rDuc]

I remember the weather in Gainesville, especially when I had to scrape ice off my seat before riding to class. Overall, it's just a little colder than here, but pretty similar.



I have a 24x45x10 metal building with closed cell foam, no windows, one insulated roll-up door. I'm thinking of a 18k + 12k dual mini split system. I'm dividing the shop 60/40 with a wall, so that's why I'm considering different sizes.



Is that Jennings in your avatar?

Insulated roll-up..I wish I had done that.

Yes it is Jennings! I'm a control rider there


Sent from my iPad using Tapatalk

 

[soob]

It depends how often you use the space. Standard sizing of a/c assumes you're going to condition it 24/7. If you just want your garage to cool down when you need it, you should oversize. Bigtime. Otherwise it could take all day and then some to bring the temperature to where you want it.

If you want to condition it a little 24/7 you'd be better off with two entirely separate units. One can maintain the space and the other can be around for when you want to bring the temp down fast.