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Portable AC recommendation needed for garage shop

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Forum topic by Big_T posted 08-08-2016 02:25 AM 1326 views 2 times favorited 32 replies Add to Favorites Watch
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Big_T

119 posts in 818 days


08-08-2016 02:25 AM

Not sure if this is the right forum, moderator please move if necessary.

Now that I am setting up my tools in the garage it is obnoxiously hot in there, 100+ with the laser gauge. I tried my bedroom’s 9,000 btu unit and it does not do much more than remove some of the the heat but does not cool – maybe it broke, who knows. I ran the PVC exhaust pipe down to the garage vents since i wanted the extra floor space but not sure if forcing hot air in the opposite direction is causing problems?!? So I need advice for a portable AC in my 19×20 garage with 9 foot ceiling. The ceiling had R30 batts installed last year and I plan on getting foam insulation for the aluminum garage door, but the walls are CBS with wood paneling. See Pic.

I’m thinking to stay with a portable and get 14,000 btu.

What do you LJs think and brands you recommend?


32 replies so far

View ColonelTravis's profile

ColonelTravis

1189 posts in 1354 days


#1 posted 08-08-2016 02:44 AM

I’m in your situation, typing this at 9:40 p.m. and the temp in my garage right now is 99. I’ve looked into this but passed on portables because they would be a waste of money in a garage in Texas. A window AC would be best, I don’t know if you have a window, I don’t. Guy next door to me put a window AC in his window-less garage, cut a hole in the bricks, did a poor job, the bricks are falling apart.

Not sure what I’m going to do. I’ve got a giant fan going 2-3 feet behind me when I’m in there, not ideal but it’s manageable.

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BulldogLouisiana

215 posts in 600 days


#2 posted 08-08-2016 02:49 AM

Portable AC’s don’t do a very good job of cooling. A 10k window unit would do a much better job. If at all possible get the biggest window AC in that you can. If a window unit isn’t feasible, I’d save up for a ductless mini split. I am afraid you would just be wasting money on a 14k portable unit.

-- There are 10 types of people in the world. Those who understand binary and those who don't.

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gtbuzz

427 posts in 1902 days


#3 posted 08-08-2016 02:53 AM

I think you’ve made the first important step with insulating the ceilings. You really need to be doing the garage doors too though. I’m in a similar situation. 20×20x10 attached garage, walls were all insulated but metal garage door. The ceiling is only insulated where there’s a living space above.

I live in Atlanta, and during our summers, it would hit around 95 in the garage on the hottest days. I went through the effort of adding in foam insulation to the back of the garage doors as well as R10 rigid foam insulation to the portion of the ceiling that wasn’t insulated. That made a huge difference in and of itself, and lowered temps to about 85 on the hottest days.

Recently, I added a 14k BTU (Delonghi heating / cooling unit from Costco) and that does an okay job in the garage. I know going in that it’s a losing battle because of all the air gaps around the garage door but it really does help. On the hottest of days, I can get it down to about 80F. Still not cool, but it’s made a HUGE difference in my desire to work in there. The biggest difference is that it’s significantly less humid when I do that. On cooler days, I don’t seem to have a problem hitting 75.

One thing to keep in mind is that a space like this is going to take a while to cool down. On weekdays, I turn the thing on as soon as I get home if I know I’m going to be working in there. On the weekends, I’ll start it up around 9AM and just leave it running all day. Using a Vornado to circulate the air also helped.

Last thing I could add, based on my trial and error, is definitely go for the largest unit possible. Portable units all run off of a 15A circuit, so they top out at 14k BTU. Don’t even waste your time with anything smaller, as it really won’t be very effective. If it’s possible, go for a window unit. Those things are more efficient and come in 220 flavors that would do a better job cooling down the space.

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newwoodbutcher

552 posts in 2310 days


#4 posted 08-08-2016 04:16 AM

I live in southern California, inland, away from the cooling ocean breeze. It gets really hot. A few weeks ago i installed a 1500 btu window ac unit in my two car oversized garage. It works better than I ever expected. My shop has no insulation in the walls although I did blow in about 6” of attic insulation. There are cracks you can see through around the double garage door. A few weeks ago it was 103 degrees. I got home around noon and turned on the ac. The shop was totally cooled down in 15-20 minutes. I couldn’t be happier.

-- Ken

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dhazelton

2322 posts in 1757 days


#5 posted 08-08-2016 12:04 PM

If that fridge is running then you are wasting a ton of energy trying to cool the heat coming off the back of it.

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Big_T

119 posts in 818 days


#6 posted 08-08-2016 03:19 PM



If that fridge is running then you are wasting a ton of energy trying to cool the heat coming off the back of it.

- dhazelton

Yep both are running, a necessary evil since I buy in bulk at BJs/Costco. The white one is a freezer and the black one (under the wheels) is a fridge.

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Big_T

119 posts in 818 days


#7 posted 08-08-2016 04:32 PM


I m in your situation, typing this at 9:40 p.m. and the temp in my garage right now is 99. I ve looked into this but passed on portables because they would be a waste of money in a garage in Texas. A window AC would be best, I don t know if you have a window, I don t. Guy next door to me put a window AC in his window-less garage, cut a hole in the bricks, did a poor job, the bricks are falling apart.

Not sure what I m going to do. I ve got a giant fan going 2-3 feet behind me when I m in there, not ideal but it s manageable.

- ColonelTravis

Sadly there are NO windows… That would have made this choice easier and cheaper.

So option 1 is pay a handyman to install a wall unit in the concrete wall. I have both 230 and 115v.
-18,000 btu wall ac $500-$600 with EER of 11
-Sleeve $70
-Exterior support bar $30
-Extended warranty $60
-should I get a lintel bar installed?
-what would a “qualified” handyman charge for something like this? The handyman I use said $250 but he specializes in tile work so I’ll get another estimate.
Option 1 Net investmet = $900-$1000

Option 2 is get a DIY Mr. Cool 18,000 btu mini split from HD for $1,300 with SEER of 16, includes 5 year warranty.

Option 3 is a 14000 btu portable with EER of 9 for $500-$600 with extended warranty

Option 4 is two smaller 8000 btu portables for $600-$700 with extended warranties

Any thoughts?

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WhyMe

611 posts in 1021 days


#8 posted 08-08-2016 06:36 PM

One thing to remember is not to oversize the AC for the footage to be cooled. Too large a unit will short cycle on and off too much. The unit needs to be on for long periods to remove humidity. I have a 12000 btu window unit in a 20X20 garage/shop that is insulated R13 walls and R19 ceiling and it cools very well and the temps here have been in the mid to upper 90’s. I say to use anything but a portable AC unit, they are worthless.

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Fred Hargis

3928 posts in 1954 days


#9 posted 08-08-2016 07:59 PM

Here’s another voice that says the portable AC’s are worthless. I used an 8000 BTU window unit in my 24×32x8 shop and it worked well until it crapped out. Thinking I wanted to upgrade, I replaced it with a Honeywell 12000 BTU portable unit. It didn’t cool the shop at all. My thinking is that while running this thing is exhausting a huge amount of air form the shop, and the make up air is at outside temperature. The window unit didn’t do that, it recirculated the interior air after cooling it, at least I think that was a big part of the difference. I gave the portable to the Habitat restore after using it one summer, and replaced it with another window unit. So put me on the list that says the portable units are worthless.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Big_T

119 posts in 818 days


#10 posted 08-12-2016 04:18 AM



One thing to remember is not to oversize the AC for the footage to be cooled. Too large a unit will short cycle on and off too much. The unit needs to be on for long periods to remove humidity. I have a 12000 btu window unit in a 20X20 garage/shop that is insulated R13 walls and R19 ceiling and it cools very well and the temps here have been in the mid to upper 90 s. I say to use anything but a portable AC unit, they are worthless.

- WhyMe

Mine is close to yours in size so I should get the 12000 btu unit. The Mr.Cool ductless unit in that size is $1039 + tax. Does anyone know if these things go on sale?

It’s about the same price as the Jet DXPro BS I’ve been looking at… I guess it will have to wait until next year after I pay off the AC. Thanks WHY ME

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woodbutcherbynight

2414 posts in 1869 days


#11 posted 08-12-2016 01:54 PM

I have been using a 220vt 12,000BTU window unit in my shop since 1997. Has run great for both heat and a/c all this time. They do take some time to heat up and cool down the shop so I have used a hot water heater timer to cycle it on an hour before I come home. When I put this in I did not have any windows so I made a hole in the back wall and installed unit. I added on in 2003 and finally got windows in the shop but left the unit where it was. Even adding on a 10×10 section to one side it still does well to keep the temp down around a workable 80F.

-- Live to tell the stories, they sound better that way.

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WhyMe

611 posts in 1021 days


#12 posted 08-12-2016 02:51 PM


One thing to remember is not to oversize the AC for the footage to be cooled. Too large a unit will short cycle on and off too much. The unit needs to be on for long periods to remove humidity. I have a 12000 btu window unit in a 20X20 garage/shop that is insulated R13 walls and R19 ceiling and it cools very well and the temps here have been in the mid to upper 90 s. I say to use anything but a portable AC unit, they are worthless.

- WhyMe

Mine is close to yours in size so I should get the 12000 btu unit. The Mr.Cool ductless unit in that size is $1039 + tax. Does anyone know if these things go on sale?

It s about the same price as the Jet DXPro BS I ve been looking at… I guess it will have to wait until next year after I pay off the AC. Thanks WHY ME

- Big_T

Your shop has more ceiling insulation than mine plus the Mr Cool is probably better on cooling than a window unit. So you may be fine with a 10K BTU ductless. Check the cooling specs on the 10K ductless.

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Big_T

119 posts in 818 days


#13 posted 08-13-2016 08:25 PM


Your shop has more ceiling insulation than mine plus the Mr Cool is probably better on cooling than a window unit. So you may be fine with a 10K BTU ductless. Check the cooling specs on the 10K ductless.

- WhyMe

They only offer 9k and 12k units. The 9k is at a big disadvantage since it does NOT have a DIY kit and the warranty is only 2 years instead of 7 years. Though the 9k is $330 cheaper, you can see why the price difference. I’m putting the order today for the 12k, thanks for steering me away from the 18k for the reasons you mentioned and I’ll save $300. :)

View clin's profile

clin

510 posts in 456 days


#14 posted 08-13-2016 10:36 PM

The amount of AC you need is not easily determined. It depends on a LOT of variables, where you live, insulation, widows, doors, exterior wall area, roof area, air leakage, slab insulation, wall construction, orientation of house to north, internal sources of heat, etc.

A very conservative estimate is 1-ton of AC (12,000 BTU/hr) per 600 sq-ft. This estimate almost always is an overestimate and result in too much AC. 1000 sq-ft per BTU/hr is not uncommon.

A 12,000 BTU/hr (1 ton) unit in your 380 sq-ft shop is, of course 380 sq-ft per ton and is almost certainly much too much AC. Even with the 9,000 BTU/hr unit that works out to be 506 sq-ft per ton. So even that is too much. But I’m not sure you can buy a mini-splt any smaller.

Of course there’s a big difference if you live in some place extremely hot like Yuma, AZ versus someplace very mild like coastal southern California.

Now, what is meant by too much?

Most mini-splits have variable speed compressors and can throttle themselves. So ideally they just slow down, rather than simple on at full blast, then off. It’s like a car driving on the highway versus in town. This is one reason the mini-splits are so efficient. But, they only throttle to a point, and will shut off when even the slowest they run is too much.

Ideally you want the unit sized so it runs constantly at full power on your hottest days. That will get you the most efficiency. For living spaces, this is also the most comfortable. It removes the most humidity and the air temp doesn’t cycling from getting a bit too cold before it turns off, to a bit too warm before it turns on.

Of course, you’re talking about a shop, and you aren’t looking for the same comfort level you want in your living spaces. So I understand that comfort, beyond just getting cooled, is not likely an issue for you.

Keep in mind that mini-splits are most efficient when running all the time. You typically do not set back the thermostat. Studies have shown that setting back a thermostat daily, results in a very small energy savings.

What I mean by this is the common thing people do is turn their AC off or to a higher temperature while they are at work. But what happens is the house simple absorbs more heat that must be removed later. You get a little more efficiency doing this with common AC units, but come home to a house that is warm and perhaps humid for awhile.

However, with a mini-split there is no advantage to setting your thermostat back for relatively short periods of time. So if you are going to be in your shop daily, just leave the mini-split on all the time. Of course if this also your garage and cars are being pulled in and out, that’s a whole other issue.

If you’re a weekend warrior, then it makes sense to turn it off during the week and turn it back on for the weekend.

I use my shop almost daily so I just let my unit run all the time.

I think you’ll find that a mini-split is so much more efficient than anything you are used to, that you may find it’s just easier to leave it on.

The only reason I would consider the 12,000 BTU/hr unit over the 9,000, is if you expect to allow the space to warm up when not in use and want the extra capacity to cool it faster. Else, I think 9,000 is probably more than enough. But as stated first, there are a lot of variables. Unless you run a Manual J calculation (what the pros do to calculate actual needs), you’re just guessing.

Also, if you haven’t already, insulate EVERYTHING and seal the garage door.

FYI, a $1,300 mini-split sounds very inexpensive, make sure you compare it to the big boys like Mitsubishi and Fujitsu for quality and features. I’m not saying it won’t be fine. But don’t assume all mini-splits are the same.

-- Clin

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MT_Stringer

2851 posts in 2691 days


#15 posted 08-13-2016 11:12 PM

I didn’t read all the replies so I guess I missed the part about insulation. The more the better. My one car garage is insulated and has a mini split AC mounted on the wall. The HOA frowns on through the wall or window AC’s so this was a good solution for me.

I had R-38 insulation blown into the ceiling. Two walls were already insulated. When we replaced the siding on our house, I had the contractor insulate the exterior wall that had been previously uninsulated. Then I replaced the metal garage door with an energy efficient insulated garage door. Even though there are still a few leaks, It is a heaven sent relief to work out there in this Houston heat. 100 outside – 77 in the garage!!!

-- Handcrafted by Mike Henderson - Channelview, Texas

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