A/C system plan for shop

[rattle_snake]

I have a 34' x 40' (~1300sqft) shop with 12' ceilings. I would like to install a A/C system this winter, so trying to put together a well though out plan.

No heat needed (who would heat their shop?!? that is what the sun is for). Shop is well insulated (R30+) and has no windows. I really only need to take the edge off the 90-100 indoor temps that occur later in the day, and really only on one side of the building where I spend 95% of my time. This is the area I want to cool


So I have shopped mini splits and think I would need to get one with at least 2 heads to cover the area. Original plan was to install both on west wall (shown above), above workbench and machines. Ran this by a friend, he recommended putting them on opposite walls (N and S) like this:

But since then I have seen some ducted regular split installs and I wonder if that is a better route. I have a shelf above the west wall that I can mount the evap and ducting, with duct through shelf and registers on the bottom of the shelf.

Aside from the tonnage, will the ducted system have superior flow, filtration and distribution? or are the mini heads good enough for my application. Again I am not trying to have an even temp distribution in the whole building.

As for size, I was thinking a 2.5 or 3T. I would run on weekends and evenings, so pumping down the temp as opposed to maintaining a set temp. I also park vehicles in this shop at the end of the night after they cool down.

Any and all feedback appreciated.

 

[PoorOwner]

With the mini split low fan mode it tends to create a cool zone in the near by area.
I would just go with one head something like a 24k and let it cool the strip that you want. If the AC isn’t overwhelmed, eventually the whole shop will cool as well.

When you mount it, if you don’t mount it too high it will cool better as well. Something like at least a foot from the ceiling. It can throw about 30 feet in the higher fan speeds if you mount it around 8 foot or so.

Regular split might be cheaper. Get some quotes.

 

[minytrker]

I have a mini split in part of my shop 24x40 is walled off in a 24x66 shop. I have 2 oscillating fans mounted up higher to move air and I can get my shop down in the sixties. I keep the ac set on 78-79 and it stays 77-78 in there all day with zero issues. At 68 I justed wanted to lay down and sleep it felt so good in there, lol.

 

[firebirdparts]

It's all one big room. If you go with duct, you need to send the air to part of the shop away from the air return. If you really just want to cool one spot you can do that with a ducted system and just one outlet, in fact. With all that insulation you have, it won't take much effort to cool it.

The ducted system will move more air in one place if you choose to.

 

[ticklechicken]

I agree with PoorOwner. A single 24k on your south (hottest) wall will do what you want.

Don't worry about monthly electrical costs in your decision. It doesn't add up to much. I put a pair of 22 SEER mini splits in my shop a few months ago here in Florida. My shop is on its own meter, and I haven't had a total bill over $20 yet. I have similar insulation and am never stingy with the thermostat.

 

[rattle_snake]

Thanks for the info guys. Perhaps a single head on south wall would be enough. I don't have person experience with how much air they move, but I would think a 2.5-3T unit would move a fair amount of CFMs to achieve its BTU rating.

I need to determine location of condenser and figure out plan for power.

 

[theoldwizard1]

Don't worry about monthly electrical costs in your decision. It doesn't add up to much. I put a pair of 22 SEER mini splits in my shop a few months ago here in Florida. My shop is on its own meter, and I haven't had a total bill over $20 yet. I have similar insulation and am never stingy with the thermostat.

WOW ! That is awesome !! What brand and what size ?

 

[ticklechicken]

WOW ! That is awesome !! What brand and what size ?

Two Pioneer 18k units.

 

[Jackfre]

I would install the mshp's on the opposite walls diagonally from each other. That will give you the best even air temperature.

 

[justinjoyal]

I would install the mshp's on the opposite walls diagonally from each other. That will give you the best even air temperature.

Agreed.

Don’t mount the handlers too far up the wall. 8 ft is plenty.

 

[peter2772000]

Thanks for the info guys. Perhaps a single head on south wall would be enough. I don't have person experience with how much air they move, but I would think a 2.5-3T unit would move a fair amount of CFMs to achieve its BTU rating.

I need to determine location of condenser and figure out plan for power.

The general rule is 400 CFM per ton. 2.5 - 3 tons sounds like a lot, but you are in AZ, so...

I'd personally go with two heads mounted about 8' up as was already suggested.

 

[yeldogt]

I really don't see you needing more than one head -- mounted high on the wall. The only issue with mini's is the filter -- they don't like dirty dusty environments. I have a similar setup with no issues.

It's important to remember that not too long ago the average split systems was under SEER 8 ... even today the minimum is 13 .. and that's only been about 10 years (it was SEER 10 just before) and the old ones were around and sold for years after. Mini splits are now running way into the 20's with no duct loss of the split systems. If you are comparing running costs with a neighbor who has a 15 year old builder grade split -- a new mini could be 4x cheaper to operate. Refrigeration operating costs are 1/4 of what was around 30 years

 

[rattle_snake]

I would install the mshp's on the opposite walls diagonally from each other. That will give you the best even air temperature.

Are you saying to mount them in the corner, under the shelf in the pic above, at a 45* angle (effectively pointing to center of the space)?
The heads are fairly long (40-50")

The general rule is 400 CFM per ton. 2.5 - 3 tons sounds like a lot, but you are in AZ, so...

I'd personally go with two heads mounted about 8' up as was already suggested.

I'm going a bit big as I would use it to pump down 10-15 degrees not maintain a set temp.
In what orientation? opposite walls like drawing above, or same wall (west), diagonal, or ?

I really don't see you needing more than one head -- mounted high on the wall. The only issue with mini's is the filter -- they don't like dirty dusty environments. I have a similar setup with no issues.

It's important to remember that not too long ago the average split systems was under SEER 8 ... even today the minimum is 13 .. and that's only been about 10 years (it was SEER 10 just before) and the old ones were around and sold for years after. Mini splits are now running way into the 20's with no duct loss of the split systems. If you are comparing running costs with a neighbor who has a 15 year old builder grade split -- a new mini could be 4x cheaper to operate. Refrigeration operating costs are 1/4 of what was around 30 years

Looks like the filters are foam like an RV a/c and won't do much filtration compared to a ducted system with a big *** pleated filter. I'm OK with that, they would need to stay clean to get full cfm.

 

[justinjoyal]

The filters are plastic screens. Easy to clean.

After a few years inspect the blower because stuff tends to build up on them causing poor performance.

 

[peter2772000]

If I was quoting this job, I'd suggest opposite sides for the most uniform cooling and to have the air be thrown within the area needed to be cooled, rather than towards that area and beyond, towards the vehicles.

 

[Uncle Fester]

Loving the feedback, soon to be building a shop also in AZ and was looking at the ductless systems for ease of install. I do not plan on having doors open so would be looking to maintain a temperature and keep any humidity out of the air. Shop will be primarily vehicle storage.

 

[rattle_snake]

Still pondering options on this. Looked for 2 head 2.5-3T units and saw that this is a less common option compared to the others. Found one that had different sized heads (a 9k and a 18k on a 24k oudoor unit) and got me thinking...
Also considering of a pair of units, in various sizes.

A few options:
2T + 1T
1.5T + 1.5T
1.5T + 1T

So a possibility would be to install a single 2T unit on the south wall (one of the recommendations in this thread) and see how it performs this summer. If not enough then another on the north wall.

My friend who has an A/C business recommends/installs the Daiken brand. Experiences, opinions?

 

[yeldogt]

Still pondering options on this. Looked for 2 head 2.5-3T units and saw that this is a less common option compared to the others. Found one that had different sized heads (a 9k and a 18k on a 24k oudoor unit) and got me thinking...
Also considering of a pair of units, in various sizes.

A few options:
2T + 1T
1.5T + 1.5T
1.5T + 1T

So a possibility would be to install a single 2T unit on the south wall (one of the recommendations in this thread) and see how it performs this summer. If not enough then another on the north wall.

My friend who has an A/C business recommends/installs the Daiken brand. Experiences, opinions?

The multi head units can be configured many different ways -- the head outputs don't have to match. For your application Daiken/Fujitsu/ Mitsibushi -- all top brands.

My first space was 36 x36 with a wall unit and it worked great. The size and capacity of your unit will depend on how you plan to use the shop. I found that maintaining a reasonable temp both winter and summer did not cost all that much more vs doing big setbacks. That only made a big difference when I was away for many days. Trying to drop from 90 degrees when it's 100 out takes a lot of capacity

 

[minytrker]

read my previous post...1 will just fine IMO.

 

[peter2772000]

.......
My friend who has an A/C business recommends/installs the Daiken brand. Experiences, opinions?

In my professional opinion, cream of the cream is Daiken, Mitsubishi and Fujitsu. If you can find a Freidrich, it's a carbon-copy of Fujitsu (or at least it was up to a year or two ago) at a cheaper price. When I say carbon-copy, I mean same panels/PC boards etc.

We've sold Daiken and Fujitsu/Freidrich and have relatively few problems. Haier...takes forever to get replacement parts and Gree is ...well, ya gets what you paid outta it.

 

[justinjoyal]

In my professional opinion, cream of the cream is Daiken, Mitsubishi and Fujitsu. If you can find a Freidrich, it's a carbon-copy of Fujitsu (or at least it was up to a year or two ago) at a cheaper price. When I say carbon-copy, I mean same panels/PC boards etc.



We've sold Daiken and Fujitsu/Freidrich and have relatively few problems. Haier...takes forever to get replacement parts and Gree is ...well, ya gets what you paid outta it.

FYI, Friedrichs are no longer rebranded Fujitsus.

I always find it funny when people mention Gree like they’re some sort of inferior products, because I have sold, installed and used Fujitsu/Friedrich products and would go with a Gree in a heartbeat. (Even more so considering they offer a 10yr parts and labor warranty in Quebec!) They are up there with the big names (as if Gree wasnt big right..) like Mitsubishi, Fujitsu, Daikin, etc...

 

[peter2772000]

FYI, Friedrichs are no longer rebranded Fujitsus.

I always find it funny when people mention Gree like they’re some sort of inferior products, because I have sold, installed and used Fujitsu/Friedrich products and would go with a Gree in a heartbeat. (Even more so considering they offer a 10yr parts and labor warranty in Quebec!) They are up there with the big names (as if Gree wasnt big right..) like Mitsubishi, Fujitsu, Daikin, etc...

Thx for posting, I didn't know that Freidrich was no longer a Fujitsu clone. I'm guessing you do a lot more residential work, as the only time we sell mini-splits is in commercial apps. The water ban in Montreal is killer for sales, btw.

As far as quality of a Gree comparing to a Fujitsu; Gree's basic lines only run 5 + 5 yrs, the cheapest models even less. The 10 + 10 is only on their high-end models, according to my salesman at Master. I asked my salesman & techs for their opinions on Gree vs Fujitsu, they all insisted that Fujitsu was superior. But again, we only install 10-20 of these a year.

If you primarily serve the residential market and are selling tons of mini-splits, your opinion has much more merit than mine due to your personal experience. But at the end of the day, I'd still rather pay more & install a Fujitsu in my garage.

 

[justinjoyal]

Thx for posting, I didn't know that Freidrich was no longer a Fujitsu clone. I'm guessing you do a lot more residential work, as the only time we sell mini-splits is in commercial apps. The water ban in Montreal is killer for sales, btw.



As far as quality of a Gree comparing to a Fujitsu; Gree's basic lines only run 5 + 5 yrs, the cheapest models even less. The 10 + 10 is only on their high-end models, according to my salesman at Master. I asked my salesman & techs for their opinions on Gree vs Fujitsu, they all insisted that Fujitsu was superior. But again, we only install 10-20 of these a year.



If you primarily serve the residential market and are selling tons of mini-splits, your opinion has much more merit than mine due to your personal experience. But at the end of the day, I'd still rather pay more & install a Fujitsu in my garage.

You are right about the warranty, 5yrs for the lower models, 10yrs for both higher end models.

I do almost only residential work, mini-splits and central air. Small family business in between MTL and QC. ;-)

I was disappointed by the last Fujitsu I installed. Looked and felt cheap. Performance/efficiency was no different than a comparable Gree unit.

We install mostly Gree mini-splits. Some HEC (Haier) units as well, new line from Master this year and they have sold a whooooole lot!

After 100s of different Gree units installed, I am really confident selling them. We had very very few calls for service.

Their pricing is really attractive for customers because they are significantly cheaper than Fujitsu or Mitsubishi with equal or even better performance and good to great warranty coverage.

When we first started out we were selling Fujitsu/Friedrich and to be totally honest, we were worried/uncertain when our Master rep told us they were switching mainly to Gree. Mea culpa. We had no reason to be worried.

I had a 1yo Friedrich mini-split (2013) in my last house that was replaced with a then new Gree (Crowne) model to try it out whenit came out and I was amazed. Now I have central forced air in my new house but had I gone for wall mount I wouldve put a Gree in, definitely!

 

[Finallygotit]

Justin, another avenue to explore could be a two head mini split system with ceiling cassettes instead of wall mounted units.

Here's something to read from Mitsubishi.

 

[OutlawDrifter]

I would price out a full on ducted system at the same time. The full system ended up being cheaper than the minis I looked at, and I've got a heavy duty filter setup, which I need in my shop. My Trane heat pump is stupid efficient, actually surprisingly so. It keeps my 36x40x14 @ 58* with no noticeable increase in my electric bill. When I go in to work I kick it up to 62-64 and it's there in 10-15 minutes and more than comfortable to work in. I know heat isn't your issue, but the short amount of time I used it to cool this fall, it would drop the humidity and keep it at 75* easy. Food for thought.

 

[justinjoyal]

Justin, another avenue to explore could be a two head mini split system with ceiling cassettes instead of wall mounted units.

Here's something to read from Mitsubishi.

I would definitely stay away from cassettes, reliability being an issue.

I would price out a full on ducted system at the same time. The full system ended up being cheaper than the minis I looked at, and I've got a heavy duty filter setup, which I need in my shop. My Trane heat pump is stupid efficient, actually surprisingly so. It keeps my 36x40x14 @ 58* with no noticeable increase in my electric bill.

Mid and high end mini-splits are much more efficient than central/ducted heatpumps.

 

[OutlawDrifter]

Mid and high end mini-splits are much more efficient than central/ducted heatpumps.

It would have taken 2 minis to cover my shop as I needed and been waaaaaayyyyyy more money up front. It would take years to recoup that in energy savings. Plus, I needed better filtration from my HVAC than a mini can provide. Suited MY shop better, definitely not the solution for everyone.

 

[justinjoyal]

It would have taken 2 minis to cover my shop as I needed and been waaaaaayyyyyy more money up front. It would take years to recoup that in energy savings. Plus, I needed better filtration from my HVAC than a mini can provide. Suited MY shop better, definitely not the solution for everyone.

Yeah i wasnt saying minis were better for you. Just saying minis are much more efficient, so if you think your hp is «*@#$stupid efficient*@#$» you’d be blown away by the best minis. [emoji16]

 

[nsula_country]

Justin,

For your size and insulated shop mini's would probably be the way to go. Without a Manual J, I don't know what your heat load is. Shooting from the hip based on your climate I would say you need 3-4 tons of capacity. Especially if you expect to quickly take 10-15 points down. You have low humidity so short cycling if oversized should not be a concern.

Ducted is what I would do with a 2"-4" filter base. Run a straight duct down center (long wall), have registers throwing towards walls (short walls). Return back at the source and tstat at return.

With splits you need 2 heads. If you don't need heat go straight cool. Heat required, heat pumps. I looked at mini's for our shop and I would need no less than 4 big *** heads $$$$$. And filtration ***** for wood work and welding. For my little 18x20 room we plan to build a mini will shine!

I'd be curious to see what quotes you get for each option.

CT

 

[Finallygotit]

I would definitely stay away from cassettes, reliability being an issue.

I didn't know that. Thanks for the input!

 

[LSVLance]

I am currently researching ways to cool my new shop also. I asked every HVAC guy I could at the recent home show and each of them said the splits are great at keeping constant temps but would not recover well especially in my situation. They all recommended a heat pump system instead. Two of them have been out to do load calcs and both recommended the exact same 5 ton heat pump.

The shop is 51 x 31 x 16, 2x6 walls with wet cellulose, R30 bats in the ceiling, all finished sheetrock, with (2) 14' and (1) 9' non-insulated overhead doors.

I plan to put my office in the shop so would keep it at a constant temp vs raising and lowering the temp. Oh yeah, the building is in Phoenix...so high outside temps are a given.

I was leaning to go with a heat pump hanging the air handler horizontal near the back wall with a turn down with a filter box on the return and the feed blowing straight out toward the front wall. One installer suggested a mushroom head on the feed side to spread the air out as it leaves the air handler.

The comments here have me rethinking the split systems now though.

 

[justinjoyal]

Split system and mini-splits are different.

A split system is a outside unit paired with a air handler/furnace and ducts.

A mini-split is, well.. a mini-split, often wall-mounted.

For large environnements requiring better filtration, split(forced air) systems are better IMO.

 

[Jamie V]

I just installed a ducted unit in my 24’x40’x10’ pole barn. I’m a sheet metal worker so no way an I going ductless....


I do t have a completed photo on my phone but you get the point.

 

[HAP]

rattle snake, you might consider regaining that precious bench top space by mounting you stereo equip up under that shelf your speakers are on. Worth the effort for sure...
R,
HAP

 

[LS6 Tommy]

I would definitely stay away from cassettes, reliability being an issue.

X2. I wouldn't sell a cassette to my worst enemy.

Tommy

 

[bobbyjean]

what size is space you will condition-you can go big with ductless as they are inverter driven and can ramp up/down ...thinking 18k single head or throw two 12's and do the whole shop..as mentioned stick with the quality brand's

 

[LSVLance]

Split system and mini-splits are different.

A split system is a outside unit paired with a air handler/furnace and ducts.

A mini-split is, well.. a mini-split, often wall-mounted.

For large environnements requiring better filtration, split(forced air) systems are better IMO.

Ah, gotcha... That makes a bit more sense now. Thanks.

 

[rattle_snake]

rattle snake, you might consider regaining that precious bench top space by mounting you stereo equip up under that shelf your speakers are on. Worth the effort for sure...
R,
HAP

Interesting you mention that... I'm 2/3 of the way through that very process. Amps, processors and beer fridge went in a custom rack I made and main speakers got painted and hung.
Still need to finish and relocate subs, they are still in the same location now behind doors. They are very heavy, ~75lbs so hanging them will require some stout mounts.
My current plan for A/C puts the subs and an air handler in the same area so trying to make a plan that will work together.

 

[rattle_snake]

I am currently researching ways to cool my new shop also. I asked every HVAC guy I could at the recent home show and each of them said the splits are great at keeping constant temps but would not recover well especially in my situation. They all recommended a heat pump system instead. Two of them have been out to do load calcs and both recommended the exact same 5 ton heat pump.

The shop is 51 x 31 x 16, 2x6 walls with wet cellulose, R30 bats in the ceiling, all finished sheetrock, with (2) 14' and (1) 9' non-insulated overhead doors.

I plan to put my office in the shop so would keep it at a constant temp vs raising and lowering the temp. Oh yeah, the building is in Phoenix...so high outside temps are a given.

I was leaning to go with a heat pump hanging the air handler horizontal near the back wall with a turn down with a filter box on the return and the feed blowing straight out toward the front wall. One installer suggested a mushroom head on the feed side to spread the air out as it leaves the air handler.

The comments here have me rethinking the split systems now though.

Wow, 5 tons...
Those non-insulated door will be a problem... I would put insulating them high on your priority list, A/C or not.
My insulated OH doors get to 180* in the sun on the exterior, and still 100 on the interior (foam) of the door. Easy enough to do yourself.

 

[Finallygotit]

I'm with Justin, insulate the begeezuz out of those overhead doors. What direction do those doors face? I don't suppose you can paint those doors a real light color like BRIGHT white?