Are my A/C load calculations correct?

[rockcrawler]

My shop is 35’ X 48’ (1680 sqft) with 14’ walls and it’s 18’ at the roof peak. It has closed cell spray foam insulation, two insulated 10’ X 12’ garage doors and two insulated man doors. I used an online load calculator and it says I need 48K BTU. So, I’m assuming I’ll need two 24K BTU mini-splits. Does this sound right?

I found these two Pioneer units on HighSeer.com.

Pioneer
24K BTU
20.5 SEER
Energy Star
$1,528.00

Pioneer
24K BTU
18 SEER
$1,188.00

Is the higher SEER really worth the extra cost? I’ve also been looking at the Mr. Cool units. I’m only in the shop maybe once a week or so, so the A/C will not be used all of the time. Any comments, opinions and suggestions are welcome. Thanks in advance for the help. (Photos taken before spray foam)

 

[Jim greengo]

I'd put some fans in the peak to help move some of the air.

 

[rockcrawler]

I'd put some fans in the peak to help move some of the air.

Yup, that’s on my list as well.

 

[yeldogt]

how is it holding up with no ac? .... with spray foam +1 ton per 500sf is a lot. Now you do need a bit more capacity of you want to bring the temp down quickly.

How are you going to run them ..... running all the time at 80 degrees will keep the humidity in check.

Also -- with heat rising you don't want to mix the air with a fan if you walk in and turn the AC down ..... you want the head about 8' up on the wall and allow the air to stratify.

 

[rockcrawler]

It’s definitely warm, but the humidity is horrible. You start sweating almost instantly. As far as setup, I don’t know yet. I’m trying to learn, since I want to do this myself due to labor costs. One side of the shop (48’ long) is in the shade almost all day, so I figure I’ll put down two concrete pads on that side so the equipment doesn’t bake in the sun. The other long side is in the sun all day. And, I guess it would be best to space the units apart maybe 20 feet or so and mount the blowers 8 to 10 feet off the floor. As far as unit size, I’m trying to figure that out as well. Two 18K, two 24K, one 18K and one 24K? It’s all so confusing which is why I’m seeking help.

 

[Yankeefarmer]

Just do 2 24k units. Leave one running in “dry” or “dehumidify” mode when you’re not working out there, and start the second when you want to cool it down. The advantage of two 24k units is they will maximize the heat you can get on those cold Dallas days that can occur.

 

[metlmunchr]

Nice building. If you were working in it daily, then it would be worthwhile to go to the higher SEER units. But, for intermittent use, the payback on energy savings vs additional upfront costs would put the break even point so far into the future as to be not worthwhile.

I'd also lean toward the two 24K units for the heating capacity. The ability of the units to ramp down in a/c mode would give you a capacity ranging from 6K btu with one unit running at minimum capacity to 62K btu with both units running at full load.

I agree that you want to take advantage of air stratification during the cooling season and leave any ceiling fans off. In the heating season, you can run a couple ceiling fans blowing upward to overcome the tendency of warm air to rise. Blowing down creates drafts while blowing upward causes the warmer air to travel outward and down the walls which avoids drafts while still getting the warm air back to floor level where it'll do the most good.

Re the Mr Cool units, IMO you pay a substantial premium for nothing more than a pre-charged tubing package. That's fine if Joe Homeowner wants to DIY a single unit in his house and has no interest in investing in any tools. But, for the typical "shop guy" person, it makes more sense to spend the money on a vacuum pump, set of gauges, and pressure testing apparatus which can also be used down the road for troubleshooting and repair of home and auto units as well as any mini splits installed in the shop.
Anyone who's set up for mig welding can use whatever shielding gas they use for mig (CO2, 75/25, etc) as their source for pressure testing rather than investing in a nitrogen cylinder that would likely be seldom used in the future. The cylinder is the big cost as an adapter and regulator can be bought for $50-$60 and have you set up to use whatever cylinder/gas you already have.

One caveat on the line sets that come with the Pioneer units, and it seems to be an issue on many other brands as well, is that the pre made flares on the tubing are too large. It's a simple matter to cut them off and make new flares of the proper size, but it's better to realize this up front and correct prior to installation rather than having to remake them after installation and finding they leak.

I'm a couple years into owning a pair of Pioneer minis and am well pleased with the build quality and performance of both units. I'd recommend the purchase of their line protector kits. They go together as they should and appear to be durable so far. I own a sheet metal shop with full capability to make line covers, but no way would I spend the time or the money for materials to make my own given the price and convenience of the cover kits.

 

[rockcrawler]

Nice building. If you were working in it daily, then it would be worthwhile to go to the higher SEER units. But, for intermittent use, the payback on energy savings vs additional upfront costs would put the break even point so far into the future as to be not worthwhile.

I'd also lean toward the two 24K units for the heating capacity. The ability of the units to ramp down in a/c mode would give you a capacity ranging from 6K btu with one unit running at minimum capacity to 62K btu with both units running at full load.

I agree that you want to take advantage of air stratification during the cooling season and leave any ceiling fans off. In the heating season, you can run a couple ceiling fans blowing upward to overcome the tendency of warm air to rise. Blowing down creates drafts while blowing upward causes the warmer air to travel outward and down the walls which avoids drafts while still getting the warm air back to floor level where it'll do the most good.

Re the Mr Cool units, IMO you pay a substantial premium for nothing more than a pre-charged tubing package. That's fine if Joe Homeowner wants to DIY a single unit in his house and has no interest in investing in any tools. But, for the typical "shop guy" person, it makes more sense to spend the money on a vacuum pump, set of gauges, and pressure testing apparatus which can also be used down the road for troubleshooting and repair of home and auto units as well as any mini splits installed in the shop.
Anyone who's set up for mig welding can use whatever shielding gas they use for mig (CO2, 75/25, etc) as their source for pressure testing rather than investing in a nitrogen cylinder that would likely be seldom used in the future. The cylinder is the big cost as an adapter and regulator can be bought for $50-$60 and have you set up to use whatever cylinder/gas you already have.

One caveat on the line sets that come with the Pioneer units, and it seems to be an issue on many other brands as well, is that the pre made flares on the tubing are too large. It's a simple matter to cut them off and make new flares of the proper size, but it's better to realize this up front and correct prior to installation rather than having to remake them after installation and finding they leak.

I'm a couple years into owning a pair of Pioneer minis and am well pleased with the build quality and performance of both units. I'd recommend the purchase of their line protector kits. They go together as they should and appear to be durable so far. I own a sheet metal shop with full capability to make line covers, but no way would I spend the time or the money for materials to make my own given the price and convenience of the cover kits.

My biggest problem is that I don’t know much about A/C units. But, I’d prefer to do stuff myself. This is how I learn about things, going hands on. You mentioned a few tools. Is there a full list of tools I will need to do the job? As far as the Mr Cool units, I agree. I’d rather not have to deal with the really long lines that are not required. And, I’d prefer not to spend the extra money on the DIY kit. Using that money for tools is more fun.

I have a Hobart Handler 140 MIG welder, but no tanks. I’ve been learning to weld with flux. I’ve been wanting to weld with gas, so this may be an excuse to finally go get tanks.

Does my layout plan seem be a good one?

As far as power supply, I should be good. I have 100A service to the shop and really not much in the box yet.

 

[Hobby_Man22]

Can you add two systems in the same area? I know they told me the biggest I could go was a 5 ton heat pump system. After that I needed 3 phase which I have at the road but didn't really care to do all that at the time. Now I'm going to build another building that's 3000 square ft so was thinking of doing two 3.5 ton systems then just run one system in milder weather and run them both when it's 100 in the summer time

 

[danski0224]

This is one of those times when it might be advisable to hire someone to do the load calculation.

Or continue checking the "free" calculators online.

Or maybe try a limited use/license software purchase.

There are certainly many tales of woe about HVAC not working right in this forum.

The "rules of thumb" are a bad idea when you get into high volume spaces and spray foam.

I would be hesitant to recommend mini splits to condition that kind of space (volume), even though the capacity might be ok.

There are mini split type systems that can be ducted.

 

[rockcrawler]

Just out of curiosity, I had an AC company come by and look at my shop. They told me that no mini-split system would be capable of cooling my shop and that I would have to have a conventional split system starting at $14K to $16K. If this is true, I will never have AC.

 

[Showkey]

Just out of curiosity, I had an AC company come by and look at my shop. They told me that no mini-split system would be capable of cooling my shop and that I would have to have a conventional split system starting at $14K to $16K. If this is true, I will never have AC.

Just thinking out loud ………if this was a 1700 Sqft home in TEXAS with 18’ cathedral ceiling………would multiple mini splits even be considered vs a “conventional“ split heat and AC ???????

The add a metal building which has its own issues or complexity and huge doors that add to the HVAC equation ???

 

[danski0224]

Just thinking out loud ………if this was a 1700 Sqft home in TEXAS with 18’ cathedral ceiling………would multiple mini splits even be considered vs a “conventional“ heat and AC ???????

The add a metal building which has its own issues or complexity and huge doors that add to the HVAC equation ???

Duhhh....

 

[danski0224]

Just out of curiosity, I had an AC company come by and look at my shop. They told me that no mini-split system would be capable of cooling my shop and that I would have to have a conventional split system starting at $14K to $16K. If this is true, I will never have AC.

And this is why you need to pay someone to do a load calculation and duct design, and specify equipment.

Then you have a scope of work, plus plans and specifications.

With that information, you can decide if you can DIY the project.

That same information also allows you to get apple vs apple proposals from contractors.

But yeah, it's much easier to ask a bunch of internet randos what to do...

 

[rockcrawler]

I guess I’ll have to do that. But, if it comes down to that kind of money, it’ll never happen.

 

[Yankeefarmer]

I guess I’ll have to do that. But, if it comes down to that kind of money, it’ll never happen.

Did they quote you a system? If so, what size? I had a quote for $14k for my shop, and bought and self-installed a 5 ton system for under $5k.

 

[danski0224]

I guess I’ll have to do that. But, if it comes down to that kind of money, it’ll never happen.

This is the worst time to shop AC stuff.

There's all of the Charlie-19'er "shortages".

All of the Charlie-19'er price gouging.

All of the regular cooling season price gouging.

Wholesaler price gouging.

There's new efficiency standards requiring new equipment. Be careful what you buy if it isn't installed right away.

"Shortages" of refrigerant and resulting price hikes.

Inflation.

And on and on.

But, you can educate yourself.

And buying it online doesn't mean that you are getting a deal.

 

[yeldogt]

It’s definitely warm, but the humidity is horrible. You start sweating almost instantly. As far as setup, I don’t know yet. I’m trying to learn, since I want to do this myself due to labor costs. One side of the shop (48’ long) is in the shade almost all day, so I figure I’ll put down two concrete pads on that side so the equipment doesn’t bake in the sun. The other long side is in the sun all day. And, I guess it would be best to space the units apart maybe 20 feet or so and mount the blowers 8 to 10 feet off the floor. As far as unit size, I’m trying to figure that out as well. Two 18K, two 24K, one 18K and one 24K? It’s all so confusing which is why I’m seeking help.

How warm is warm ? Are they tight doors?

The humidity is because the foam is holding every thing in --- you need to get some ac running and get the humidity down.

With proper spray foam you should not be feeing any solar gain inside .... ? what are you going to do for heat ?



fyi -- my studio in pa is 1700sf w/ foam and i can heat it in 20 degree weather with 15k btu and the 24k ac never has a problem cooling it.

i would get a 24k mr. cool on the back wall away from main doors and see how it does ... you are going to have to have the unit set and running to keep the humidity in check.

 

[PoorUB]

36,000 might do it, I would go with two 24,000 BTU units, run one on the "cooler" days and run the second when the first doesn't keep up.

You can just set the temp on one for, say 75 degrees and the other for 77degrees and the one will run first, or most of the time and the second will ran if the first falls behind. Change the temps back and forth once in a while so the other unit runs more.

 

[Showkey]

It’s definitely warm, but the humidity is horrible. You start sweating almost instantly. As far as setup, I don’t know yet. I’m trying to learn, since I want to do this myself due to labor costs. One side of the shop (48’ long) is in the shade almost all day, so I figure I’ll put down two concrete pads on that side so the equipment doesn’t bake in the sun. The other long side is in the sun all day. And, I guess it would be best to space the units apart maybe 20 feet or so and mount the blowers 8 to 10 feet off the floor. As far as unit size, I’m trying to figure that out as well. Two 18K, two 24K, one 18K and one 24K? It’s all so confusing which is why I’m seeking help.

Dehumidifier…….…get the indoor humidity below 50% will improve comfort level.

 

[rockcrawler]

Did they quote you a system? If so, what size? I had a quote for $14k for my shop, and bought and self-installed a 5 ton system for under $5k.

I think it was 6 ton 16 seer for 14K plus tubing and vents. He said run a tube with vents in it pretty much the full length of the shop at the ceiling. Id love to do that all for 5K, but it’s just me and I don’t know enough about AC, or have all the specialty tools required. And that might be a job too big for me. I’d have to rent a scissor lift, buy a lot of parts and a lot of specialty tools. Mini-splits seem like something I could do myself.

 

[rockcrawler]

36,000 might do it, I would go with two 24,000 BTU units, run one on the "cooler" days and run the second when the first doesn't keep up.

You can just set the temp on one for, say 75 degrees and the other for 77degrees and the one will run first, or most of the time and the second will ran if the first falls behind. Change the temps back and forth once in a while so the other unit runs more.

That was my plan. Two 24K units. But, now I’m not sure they will handle cooling my space. Although my square footage is 1680’, my ceiling is 18’.

 

[rockcrawler]

How warm is warm ? Are they tight doors?

The humidity is because the foam is holding every thing in --- you need to get some ac running and get the humidity down.

With proper spray foam you should not be feeing any solar gain inside .... ? what are you going to do for heat ?



fyi -- my studio in pa is 1700sf w/ foam and i can heat it in 20 degree weather with 15k btu and the 24k ac never has a problem cooling it.

i would get a 24k mr. cool on the back wall away from main doors and see how it does ... you are going to have to have the unit set and running to keep the humidity in check.

At least 102 outside and 98 in the shop with everything sealed up. The guy who built my shop was pretty much a scam artist and it appears my closed cell from insulation is 1/2” to 1” thick on the walls and I think they did a couple of inches on the roof. So, probably a waste of money. But, my shop is in full sun all day, there is no shade. I think the temp difference should be much more. As far as heat goes, the mini-splits I’m looking at are heat pumps, so heat and AC. All of the doors seal up pretty well. The garage doors have the flaps attached to the rails that do a pretty good job of sealing.

 

[Yankeefarmer]

I think it was 6 ton 16 seer for 14K plus tubing and vents. He said run a tube with vents in it pretty much the full length of the shop at the ceiling. Id love to do that all for 5K, but it’s just me and I don’t know enough about AC, or have all the specialty tools required. And that might be a job too big for me. I’d have to rent a scissor lift, buy a lot of parts and a lot of specialty tools. Mini-splits seem like something I could do myself.

I understand. I used a MRCOOL split system, that didn’t need evacuation (although I had gauges, vacuum pump, etc, from a previous mini split installation). I bought duct from the big orange store, cuz they had the best price. The only special tools I bought were a duct crimper and a sheet metal punch, well under $100 for both. I planned to struggle hanging the duct from ladders, then realized I could use my 4 post lift as a work platform by putting a sheet of plywood on it and moving it around. Being 66, I did the install over about a 3 month period. I wouldn’t say I have AC knowledge, just general fabricating and wiring experience.

Another thing to consider is that we always size for the worst design condition, yet most of the time our systems are operating under less severe conditions. So, you might size it to maintain 70 degrees on a 100 degree day, but if your sizing is off, you’ll likely be very comfortable on a 90 degree day, and it may still be comfortable at 78 or 80 on a 100 degree day due to greatly reduced humidity.

And a high ceiling is good for cooling, because the hot rises and cold air falls. Not so good for heating.

 

[rockcrawler]

I understand. I used a MRCOOL split system, that didn’t need evacuation (although I had gauges, vacuum pump, etc, from a previous mini split installation). I bought duct from the big orange store, cuz they had the best price. The only special tools I bought were a duct crimper and a sheet metal punch, well under $100 for both. I planned to struggle hanging the duct from ladders, then realized I could use my 4 post lift as a work platform by putting a sheet of plywood on it and moving it around. Being 66, I did the install over about a 3 month period. I wouldn’t say I have AC knowledge, just general fabricating and wiring experience.

Another thing to consider is that we always size for the worst design condition, yet most of the time our systems are operating under less severe conditions. So, you might size it to maintain 70 degrees on a 100 degree day, but if your sizing is off, you’ll likely be very comfortable on a 90 degree day, and it may still be comfortable at 78 or 80 on a 100 degree day due to greatly reduced humidity.

And a high ceiling is good for cooling, because the hot rises and cold air falls. Not so good for heating.

Did you use the Mr. Cool Universal system? I’m seeing that I can get their 5 ton for about the same price as the two 24K 2 ton mini-split systems I was looking at. About the same price and 1 ton more. This looks a lot better than $14K. This might be doable. I’ll have to research more. What size ducting will I need to connect to the air handler?

 

[American Locomotive]

I mean, my parents cooled their ~1600 sq ft home with ~20' cathedral ceilings with two 10,000 BTU window air conditioners without much issue. Sure you're in a metal building and in Texas, but I'm pretty sure 4x that cooling capacity should keep that space pretty cool.

I don't think that space would be too hard to cool, honestly. I think two 24k mini-splits, mounted evenly apart, up high, on a wall should keep that space quite cool. Worst that happens if they don't, is you just get a third unit. I'd get the highest SEER you can find within your budget.

FYI: Separate smaller mini-split units are almost always more efficient than the multi-head units.

Dehumidifier…….…get the indoor humidity below 50% will improve comfort level.

Dehumidifier is a waste of time, money and energy on a building that is already hot inside. Sure it will remove water, but it will consume just as much power as an air conditioning removing the same amount of water, while making the space hotter. Might as well just get an air conditioner at that point.

 

[Showkey]

^^^^^^^^^^^^^^^^^^^^Its Texas, window units comparison it’s going to an issue 4 times the size might not work…………….

Agree the dehumidifier wont help if the inside temps are HOT 98* as stated post #28

Its 8:30 PM its 95*
Tomorrow promises 98* with an index 108*
Post 28 is bringing up the poor insulation

 

[brianpgriset]

I’m near Houston. I have 2” of closed cell foam on walls and 3” ceiling. Filled the rest of each stud bay with R19. Building is 30x60 with 14ft walls. I cool it with a 36k Mr Cool Universal. I was sold on it because I get a conventional air handler with the benefits of a mini split.

It has been able to keep the building at 71F even on these 100+ degree days and can ring down the temp from 78 to 72 in few hours. I’m really pleased with the sizing, it’s perfect.

I will say my building is very very tight, no windows and R18 panel doors with exceptional weather sealing.

 

[rockcrawler]

I’m near Houston. I have 2” of closed cell foam on walls and 3” ceiling. Filled the rest of each stud bay with R19. Building is 30x60 with 14ft walls. I cool it with a 36k Mr Cool Universal. I was sold on it because I get a conventional air handler with the benefits of a mini split.

It has been able to keep the building at 71F even on these 100+ degree days and can ring down the temp from 78 to 72 in few hours. I’m really pleased with the sizing, it’s perfect.

I will say my building is very very tight, no windows and R18 panel doors with exceptional weather sealing.

I’m near Houston. I have 2” of closed cell foam on walls and 3” ceiling. Filled the rest of each stud bay with R19. Building is 30x60 with 14ft walls. I cool it with a 36k Mr Cool Universal. I was sold on it because I get a conventional air handler with the benefits of a mini split.

It has been able to keep the building at 71F even on these 100+ degree days and can ring down the temp from 78 to 72 in few hours. I’m really pleased with the sizing, it’s perfect.

I will say my building is very very tight, no windows and R18 panel doors with exceptional weather sealing.

Did you install it yourself? How did you do the duct work?

 

[Yankeefarmer]

Did you use the Mr. Cool Universal system? I’m seeing that I can get their 5 ton for about the same price as the two 24K 2 ton mini-split systems I was looking at. About the same price and 1 ton more. This looks a lot better than $14K. This might be doable. I’ll have to research more. What size ducting will I need to connect to the air handler?

Yes, that’s what I used. I transitioned from the air handler outlet to 18” round, then built my own two way splitter to go to 14” round ducts by using a short piece of 18” round duct with two 14” takeoffs. Each of the 14” ducts has a single grill.

 

[Yankeefarmer]

I’m near Houston. I have 2” of closed cell foam on walls and 3” ceiling. Filled the rest of each stud bay with R19. Building is 30x60 with 14ft walls. I cool it with a 36k Mr Cool Universal. I was sold on it because I get a conventional air handler with the benefits of a mini split.

It has been able to keep the building at 71F even on these 100+ degree days and can ring down the temp from 78 to 72 in few hours. I’m really pleased with the sizing, it’s perfect.

I will say my building is very very tight, no windows and R18 panel doors with exceptional weather sealing.

I remember a “conversation” here with you when you were planning that install. Glad to hear that you are happy with it!

 

[brianpgriset]

Did you install it yourself? How did you do the duct work?

I did do the installation myself, using the pre-charged line set. I have a friend that offered to help me install a conventional split system, which he has done many times, but with the pre-charged line set Mr Cool gives you a 10 year warranty if you register the unit, which was another consideration in my purchase.

By the time you add in all the tools to self install a conventional system the price difference was close enough to make me jump for the Mr Cool with good warranty and high SEER.

Similar to Yankeefarmer, I did The ducting myself, which is currently only partially completed. Right now I just have an 18” main trunk from the AHU the just dumps out the attic access hole in the ceiling. When I get a few other things taken care of I plan to install a plenum with two large diameter branch lines that will discharge right in the middle of the two ”halves“ of the shop. It honestly works great now just dumping the 18“ trunk. I will say I used flex which I know isn’t ideal but my runs are very short.

 

[brianpgriset]

Couple of pics of the install. I still have a bunch of small things to take care of with it (finish ducting, build an access door for the AHU, etc) but it’s been working great since last August.

 

[brianpgriset]

I remember a “conversation” here with you when you were planning that install. Glad to hear that you are happy with it!

I’m glad you suggested it! To me it’s the ideal option for a self installed shop AC setup.

 

[American Locomotive]

FWIW: Much of the efficiency of minisplits comes from the fact that they're ductless. The entirely self-contained unit allows them tight control over air flow and other parameter, which allows them that high efficiency. For example, the 4-ton Mr. Cool universal system is rated "up to" 17 SEER. That would be 17 SEER which absolutely perfect air flow and duct design. Realistically, your ducting is not going to anywhere close to perfect or ideal.

I'm not saying the Mr. Cool universal system is bad by any means, just that a "conventional" 15-17 SEER heat pump system will likely perform just as well, and cost about the same or less. Really the only advantage would be the pre-filled line-set.

 

[brianpgriset]

FWIW: Much of the efficiency of minisplits comes from the fact that they're ductless. The entirely self-contained unit allows them tight control over air flow and other parameter, which allows them that high efficiency. For example, the 4-ton Mr. Cool universal system is rated "up to" 17 SEER. That would be 17 SEER which absolutely perfect air flow and duct design. Realistically, your ducting is not going to anywhere close to perfect or ideal.

I'm not saying the Mr. Cool universal system is bad by any means, just that a "conventional" 15-17 SEER heat pump system will likely perform just as well, and cost about the same or less. Really the only advantage would be the pre-filled line-set.

Good consideration for sure.

One other thing I think is worth mentioning is that the Mr Cool system itself is marketed as a DIY homeowner unit. This kinda goes back to the warranty. I’d guess if you filed a warranty claim for other conventional split systems and you did the install yourself, it makes it a bit dicey if they claimed would be honored if not installed by a professional.

Generally, from what I’ve seen here, Mr Cool and the authorized distributors have been good about honoring DIY warranty claims.

 

[Yankeefarmer]

FWIW: Much of the efficiency of minisplits comes from the fact that they're ductless. The entirely self-contained unit allows them tight control over air flow and other parameter, which allows them that high efficiency. For example, the 4-ton Mr. Cool universal system is rated "up to" 17 SEER. That would be 17 SEER which absolutely perfect air flow and duct design. Realistically, your ducting is not going to anywhere close to perfect or ideal.

I'm not saying the Mr. Cool universal system is bad by any means, just that a "conventional" 15-17 SEER heat pump system will likely perform just as well, and cost about the same or less. Really the only advantage would be the pre-filled line-set.

Keep in mind, too, that we are installing these in shops, so maybe not running at design indoor temperatures 24/7 where max efficiency will provide best payback. Another advantage I see to split systems in a shop is the ability to use conventional filters and easy access to the coil for deeper cleaning if needed.

 

[rockcrawler]

If I where to mount the air handler horizontal at the ceiling, how does the return work with these systems? Will I need to run a duct down to a lower location for cooler air to be drawn into the system? I really don’t want to loose floor or wall space which is why I’d rather mount it up high. I’m thinking with the air handler horizontal at the ceiling, I can simply run a duct from it all the way across the peak of the ceiling to the opposite side of the shop. Then have vents spaced out along the duct.

 

[Yankeefarmer]

This guy installed one high in a workspace without ductwork and says it’s working well for him:

 

[Yankeefarmer]

Another thought, though, is that a mini split might be better for your situation if you are looking to control humidity 24/7. They generally have a setting where they can dehumidify with lower energy consumption than full on air conditioning. They do this by running the evap cold with very low air flow, and it’s very effective. Ducted split systems don’t see to offer such settings.