# Shop AC



## bss1 (Jun 13, 2017)

I have an un-insulated 640 SF garage/shop.  It has open stud walls and rafters.  The walls are currently clad with Peg Board.  

I am considering installing a window or through wall AC with supplemental heat to provide temporary cooling and heat while I am in the shop and working. I don't expect it to feel like my living room out there.  It gets up in the high 90's for about 3 months and even with doors and windows open and fans running, its not a real pleasant place be.  I am just looking for some cool air blowing on me, maybe supplemented with some fans to move the temperature 10 to maybe 20 degrees to create a more comfortable working environment.    The heat would only be used intermittently during a few cold winter days to keep the temp in the shop above freezing, and to knock the cold edge off when working after a cold front.  6 months of the year I won't need anything but open doors.  This wouldn't be for 24/7 climate control, just mostly used during the time I am out there in the evenings or on weekends, during the few months when it is needed.

I know that it would be better to insulate, but I have future plans to renovate and will address that at that time.  I am just looking for an interim solution for cool air.  It is too humid here to use the evaporative type of coolers and I don't like the thought of all that additional moisture in the air. 

I am looking at the window units sold at HD and LOWES.  They both have a similar selection.  I am limited in power for this effort to either 20 amp 115V circuit or a 20 amp 230V circuit.  There looks like Lowes/HD have a 230V 18,000 BTU unit that draws 7.3 amps cooling and 16 amps heating.  This unit is rated for a 1050 sf area.

18000 BTU unit is more than what is needed for this footprint, but given the lack of insulation and open rafters, I am thinking the larger unit may be a better choice.  Otherwise, I think it may size to a 12 to 14 ton unit.

I am wondering if anyone has done anything similar and if this worth pursuing.  I can accept an increase in the electric bill and don't mind the +/- $500 investment in the unit.

Thanks for your help 

Edited to change tons to BTU's! 

Brad


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## Dave Paine (Jun 13, 2017)

Something is not right with some numbers.  18 tons is a HUGE amount of refrigeration.  

1 Ton of refrigeration = 12,000 BTU/hr

My central heat pump is a 4 ton capacity.

Consider a portable A/C unit.  This style has a flexible duct to vent the warm exhaust air to an outside window.  With this style you can move the unit closer to where you are working.  You may feel cooler even if the overall room is warmer.


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## Tony Wells (Jun 13, 2017)

It wont be 18 tons. There are 12,000 BTU per ton of refrigeration. You may be looking at a 18,000 BTU unit. Always go 220/240 when you can. Down there, your main objective it to remove the humidity, so expect it to run quite a bit and make lots of water, which is a good thing. And if any way possible, get some sort of insulation in the ceiling. Even if it's temporary.


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## bss1 (Jun 13, 2017)

I'm sorry I meant BTU's!


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## Groundhog (Jun 13, 2017)

I have a 20x24 (480 sq.ft.) shop. It has open rafters but is insulated all around. I have a small 110V window (thru the wall) AC and a small ("garage" size) 220V electric heater with a fan. Both work nicely and will keep the shop more than comfortable on 0 degree to 100+ degree days if I give them an hour or so to get started catching up.
I can go out and look at the exact size ratings if anyone wants to know. If not it's nap time!


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## Eddyde (Jun 13, 2017)

As stated above, I don't think your really looking at 18 tons, not with that low power draw. Sounds more like 1.8 tons. Anyway, for what little fiberglass insulation costs, I would at least insulate the roof. Won't take long  if it's all open as you describe. 


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## Bob Korves (Jun 13, 2017)

Look into "mini split" type air conditioner/heat pumps.  They are like a small version of a central air conditioning/heat pump system.  The compressor unit installs outside, only the two hoses need to go through the wall, and then there is a small evaporator unit inside, up on a wall.  It is quiet, unobtrusive, and good ones are even more efficient than a whole house heat pump/air conditioner combo per BTU delivered or removed.  They are not all that expensive, and not that hard to install (pre-charged system and hoses.)
Here is just one vendor, there are lots more...  https://www.ecomfort.com/cooling/mini-split-heat-pump-systems.html?utm_source=bing&utm_medium=cpc&utm_campaign=Style - Mini Split&utm_term=mini split heat pump&utm_content=Mini Split Heat Pumps

Edit:  Insulation and other energy saving changes always come before just wasting electricity or other energy.  You cannot heat or cool the outdoors very well or very cheaply.


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## Steve M (Jun 13, 2017)

Mine is 30x40 with high vented ceilings, insulated all around, two windows per wall, and insulated garage doors on both ends and one side.  Got fans, a portable AC unit, and a rollaround swamp cooler.  The shop is about 20x30.   I sometimes use the AC with assist from a floor fan, but the PortaCool swamp cooler does a pretty good job, too.  Only problem is that it goes through a lot of water.


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## Stonebriar (Jun 13, 2017)

BSS1
I have a 30x30 insulated metal building machine shop area here in east Texas. I have a 3 ton central air system I use (free) when needed and it is wonderful.  But I also have a stand alone dehumidifier I run all of the time set to 45% humidity. That is what really makes the difference in comfort and saves the machines and tooling from surface rust.


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## kvt (Jun 13, 2017)

I have been looking at one of those portable units that you run the hose out a hole or a window. I do not have much Electric to spare,   so looking at that.    One thing I know from being in SA,  is Humidity is the killer,   I'm from the Tx Panhandle and 100 with low humidity is a lot more bearable than the hi 80s down here.   and the few times I have been in the Houston area it was worse there.  So I see where the Swamp cooler is out to start with, but need something that will pull humidity if possible.   If possible even just plastic sheeting on ceiling to help seal it up would help when you put AC in there.    Just my 2 cents.   Hope it helps.


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## scwhite (Jun 13, 2017)

bss1 said:


> I have an un-insulated 640 SF garage/shop.  It has open stud walls and rafters.  The walls are currently clad with Peg Board.
> 
> I am considering installing a window or through wall AC with supplemental heat to provide temporary cooling and heat while I am in the shop and working. I don't expect it to feel like my living room out there.  It gets up in the high 90's for about 3 months and even with doors and windows open and fans running, its not a real pleasant place be.  I am just looking for some cool air blowing on me, maybe supplemented with some fans to move the temperature 10 to maybe 20 degrees to create a more comfortable working environment.    The heat would only be used intermittently during a few cold winter days to keep the temp in the shop above freezing, and to knock the cold edge off when working after a cold front.  6 months of the year I won't need anything but open doors.  This wouldn't be for 24/7 climate control, just mostly used during the time I am out there in the evenings or on weekends, during the few months when it is needed.
> 
> ...


I put a Kenmore 24,000 BTU in my shop
My shop is  9720 cubic feet
It is well insulated and I put a wall right through the middle of it for the machine shop 16'x 26' , the other half is the bigger half is 2o' x 26'
     You can hang meat in that machine shop
     If I was you I would get the biggest one I had power to run .


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## JayMcClellan (Jun 13, 2017)

I have a mini-split in my shop and love it. It has heating, cooling and drying modes so it works as a dehumidifier too. I use heat in winter but don't keep it all that warm, and can warm it up in an hour or so when I plan to work out there (extra capacity and its "powerful heating mode" is nice for that). In summer I use drying mode to keep the shop at 45% humidity for making guitars and the tools love the dry air too. Drying mode also keeps it cool but it's regulated by humidity not temperature. It runs on a 20A 240V circuit.


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## randyjaco (Jun 14, 2017)

I am not too far from you in Friendswood. My shop is @900 sqft. Only the attic is insulated. Several years ago I put in an 18000 btu unit. It does a pretty good job. When it comes time to replace this unit, I will probably go with a 24000 unit. On days like today, it has a hard time keeping up. But it sure does make life in the shop more tolerable in the summer

Randy


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## JayMcClellan (Jun 14, 2017)

Counter-intuitively, I think larger capacity can be much more economical. It costs a little more up front but if you have enough capacity to bring the shop to a comfortable temp in an hour or so, then you're more likely to set the thermostat cooler in winter and warmer in summer, and just give it a boost when you'll be out there. If the unit can barely keep up then you have to leave it set at desired temp all the time. I just took the manufacturer's recommendation and then went up a size.


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## coffmajt (Jun 14, 2017)

I had a mini split system installed in my 900 sq ft shop (garage) that had no insulation in the walls or the ceiling.  While it did work, a few weeks later I decided to see if I could get insulation blown into the sheetrock covered walls without removing the sheetrock, and it not only turned out to be possible but was easier and less expensive than I had expected.  While they were here I also had insulation blown into the ceiling, and the results have been great.  On a 95 degree day I can start the A/C and within 30 min the shop is much drier and quickly becomes comfortable to work in -- Mine is on a 230 volt 20 amp circuit  Good luck with yours -- Jack


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## jocat54 (Jun 14, 2017)

Brad, If you can swing it, insulation will make it much more comfortable and economically easier.
I have a 30x40 metal shop--t was almost unbearable to work in in the summer(and winter). I hung the vinyl faced insulation in the ceiling and walls and it made such a difference!! I then got used to having comfort and wanted more so I built a room inside 11x40 with 8" ceiling (insulated) and installed a 24,000 btu AC in one of the windows. It's really nice to work in 75* when it's 95* outside with 70-80% humidity or 30-40* in the winter.

Getting old does have some perks! And I can't take it with me so might as well enjoy it now.


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## Tony Wells (Jun 14, 2017)

Jay, there is a drawback to oversizing your AC. If it cools the air too quickly and shuts down, less humidity is drawn from the air, so yes you have colder, but wetter air than usually desired. The ideal sizing runs long enough (but not too long) to cool the air and dehumidify it to a comfortable level.


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## Bob Korves (Jun 15, 2017)

Good insulation is always required before heating or air conditioning a space, unless you are the type who likes to light paper money on fire...  Insulation pays for itself quickly with both comfort and cost savings.


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## JayMcClellan (Jun 15, 2017)

Tony Wells said:


> Jay, there is a drawback to oversizing your AC. If it cools the air too quickly and shuts down, less humidity is drawn from the air, so yes you have colder, but wetter air than usually desired. The ideal sizing runs long enough (but not too long) to cool the air and dehumidify it to a comfortable level.


That's true for a constant-speed system, as many are, but my mini-split has a variable-speed compressor so it adjusts it own power level and I presume its software tries to optimize energy efficiency. I've never heard it run at full speed except when I use its temporary "powerful" mode to warm things up quickly in the winter. In summer I use only drying mode, which also cools enough to stay comfortable in my Michigan climate, but presumably is optimized for efficient moisture removal.


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## scwhite (Jun 15, 2017)

JayMcClellan said:


> Counter-intuitively, I think larger capacity can be much more economical. It costs a little more up front but if you have enough capacity to bring the shop to a comfortable temp in an hour or so, then you're more likely to set the thermostat cooler in winter and warmer in summer, and just give it a boost when you'll be out there. If the unit can barely keep up then you have to leave it set at desired temp all the time. I just took the manufacturer's recommendation and then went up a size.


When I bought my AC unit I sent my son and his 
Friend to Sears with my credit card . They was setting up a pool table in the split side of my shop.
   Which is now my Machine shop Toolroom .
     He said it is to hot in the game room for them to 
Enjoy hanging out . I told him to go get a Kenmore 
AC At Sears . About 45 mins. Later he called me 
And said they have a 18,000 BTU 240 volts , 
I said what else do they have - he said a 20,000 BTU
And they have a 24,000 BTU  all run on 240 Volts 
    The 24,000 was the largest one that they have 
I told him to get that one get the biggest one .
     And I never have  regretted it ether .


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## bss1 (Jun 15, 2017)

Thanks for all the input guys.  I know my situation isn't optimal without insulation, but at least the area is fairly well sealed.  All of the exterior siding is older 1" thick wood from the 60's and every joint and lap is caulked, plus a layer of tar paper.  I have plans to renovate and expand in the next few years which would involve stripping this building to the frame or completely rebuilding it.  I am just looking for some help in the few months with extreme temps in the interim.  Its pretty unbearable out there from now through late September.  In the winter during the very few days that the temps get down into the high 20's or low 30's, I am able to push the temps up into the 50's with a small electric heater.  This really takes the edge off and makes being out there much more enjoyable.  I was hoping that installing a small AC unit would do the same for the dog days of summer.  Again, only when I am planning on spending some time out there in the evenings or on weekends, not to run continuously.  Additionally, by keeping the garage door closed, it would hopefully eliminate the pesky mosquitos that seem to fill the place as soon as I open up all the doors and windows.

If I do try it I will report back with the results.  At this time of year, I should know pretty quickly if it will work or not.

Brad


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## Bob Korves (Jun 15, 2017)

I am in Sacramento, and the next week or so is forecast to be 100-105F every day.  My shop is not insulated, and is not heated or cooled.  If I want to do some work in hot weather I get out there very early in the morning when it is relatively cool and quit when it gets too warm.  It usually cools down well overnight here, and the humidity is usually very low, essentially a desert with irrigation and a sea breeze most evenings (but not expected this coming week.)  Of course, I am retired and can play in the shop when I want to.  I set the schedule...


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## scwhite (Jun 15, 2017)

bss1 said:


> Thanks for all the input guys.  I know my situation isn't optimal without insulation, but at least the area is fairly well sealed.  All of the exterior siding is older 1" thick wood from the 60's and every joint and lap is caulked, plus a layer of tar paper.  I have plans to renovate and expand in the next few years which would involve stripping this building to the frame or completely rebuilding it.  I am just looking for some help in the few months with extreme temps in the interim.  Its pretty unbearable out there from now through late September.  In the winter during the very few days that the temps get down into the high 20's or low 30's, I am able to push the temps up into the 50's with a small electric heater.  This really takes the edge off and makes being out there much more enjoyable.  I was hoping that installing a small AC unit would do the same for the dog days of summer.  Again, only when I am planning on spending some time out there in the evenings or on weekends, not to run continuously.  Additionally, by keeping the garage door closed, it would hopefully eliminate the pesky mosquitos that seem to fill the place as soon as I open up all the doors and windows.
> 
> If I do try it I will report back with the results.  At this time of year, I should know pretty quickly if it will work or not.
> Brad



Buy the biggest one you can and use it in your rentavation afterwards


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## gregc (Jun 16, 2017)

Dave Paine said:


> Something is not right with some numbers.  18 tons is a HUGE amount of refrigeration.
> 
> 1 Ton of refrigeration = 12,000 BTU/hr
> 
> ...





Actually it is the cooling capacity of 1 ton of ice rounded with a few assumptions.   Goes back over 100 yrs or so.   So one can also deduce it takes 6 x the energy to melt ice than to raise water 1 deg


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## bss1 (Jul 20, 2017)

As an update, I did purchase and install a 18,000 BTU Cooling/ 16,000BTU heating unit.  So far it seems to be serving the intended purpose.  Its not an optimal set up without a fully insulated envelope, but it works ok.  I framed an opening and utilized a through the wall installation.  Subsequently I added insulation in the east and west facing walls and have also insulated the north facing double garage door.  The south wall is not yet insulated and the ceiling is open to the rafters.  Adding insulation to the walls hasn't seemed to make much difference.  However, insulating the metal garage door did seem to provide a noticeable improvement.  I will probably finish insulating the last (south) wall, but I will have to temporarily move and then re-level my lathe to do so .  However, I really don't see it making much difference unless I enclose  and/or insulate the ceiling. 

I have not really tested the set up to full capacity and not yet left the unit running for more than a few hours.  I have it installed such that I can focus the airflow in the area which I am working.  I have come home from work early a few times and fired it up in the full heat of the afternoon when the inside temperature was around 97 degrees.  Within a half hour it creates a workable less humid environment with a cool dry breeze.  Its kind of like being in your car in the middle of the summer with the AC on high.  It definitely beats a 97 degree furnace with high humidity and mosquitos eating me alive.  In the evenings, I can turn it on and get it into the high 70's pretty quickly.  I have not tried to push it more than that. 

The next size larger unit would have been a better choice, but this was the largest I could use given my electrical imitations.  That is unless I skipped the heating feature as the AC only units require less amperage.  Overall, I think it works better than the portable AC unit I was previously considering.

Thanks for everyone's input and suggestions.

Brad


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## randyjaco (Jul 20, 2017)

Your first effort at insulation should be the ceiling. Eighty percent of your heat loss in the winter goes through your roof. An equivalent amount of heat is radiated through that roof in the summer. Walls, windows and doors only account for @ 10 percent. 

Randy


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## jdedmon91 (Jul 27, 2018)

bss1 said:


> As an update, I did purchase and install a 18,000 BTU Cooling/ 16,000BTU heating unit. So far it seems to be serving the intended purpose. Its not an optimal set up without a fully insulated envelope, but it works ok. I framed an opening and utilized a through the wall installation. Subsequently I added insulation in the east and west facing walls and have also insulated the north facing double garage door. The south wall is not yet insulated and the ceiling is open to the rafters. Adding insulation to the walls hasn't seemed to make much difference. However, insulating the metal garage door did seem to provide a noticeable improvement. I will probably finish insulating the last (south) wall, but I will have to temporarily move and then re-level my lathe to do so . However, I really don't see it making much difference unless I enclose and/or insulate the ceiling.
> 
> I have not really tested the set up to full capacity and not yet left the unit running for more than a few hours. I have it installed such that I can focus the airflow in the area which I am working. I have come home from work early a few times and fired it up in the full heat of the afternoon when the inside temperature was around 97 degrees. Within a half hour it creates a workable less humid environment with a cool dry breeze. Its kind of like being in your car in the middle of the summer with the AC on high. It definitely beats a 97 degree furnace with high humidity and mosquitos eating me alive. In the evenings, I can turn it on and get it into the high 70's pretty quickly. I have not tried to push it more than that.
> 
> ...



I had the same situation in my shop. It’s smaller 14 x 20. Put in the window unit and discovered it just didn’t work well. Insulated walls. Put in foam board for the ceiling with insulation hung over the rafters in the center. Not the best set up. But easiest to do in the shop around machines. 

This works well. This February when I needed heat I started the ceramic heater hit the propane space heater to warm it up. The temperature got up to a comfortable quickly. Then as it got warmer the summer the window AC works well. 

Moral is to insulate especially the ceiling. It doesn’t have to be fancy 


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