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Discussion Starter · #1 ·
Hello all,

I live in north MS and the heat in my shop is getting pretty severe. My "shop" is my 2 car garage, roughly 20'x20' with no windows. The exterior walls are brick and I'm sure the walls aren't insulated. Above the garage is a bonus room which may or may not be insulated between the garage ceiling and floor space. I have tried using multiple fans and even making one of the homemade AC units seen on youtube with no relief.

I am considering purchasing a portable AC unit. My thoughts are to go with a slightly oversized (14k BTU) unit to account for the uninsulated walls and garage door. I was wondering if anyone had any experience with one of these units, especially in a wood working environment. Seems to me the dust levels could be a major factor in how well these units work.

Thanks for the input.
 

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I have a11K BTU split system AC in my garage. We insulated the outside wall when the siding was replaced. 11 inches of blown insulation in the ceiling (R38). Energy efficient garage door (single car garage).

94 outside, 74 inside. :thumbsup:
Works for me, regardless of cost.
 

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I use a 14k BTU through wall unit in my 15' x 30' garage. I ran it for a couple months before insulating and it had no problems with taking it down 20 degrees in probably 20-30 minutes. With insulated walls and ceiling and an insulated 14' overhead door, I can run it at 64' when it's 85'+ outside and it still cycles on the t-stat (IOW, it would take it even cooler if I told it to).
 

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I have a11K BTU split system AC in my garage. We insulated the outside wall when the siding was replaced. 11 inches of blown insulation in the ceiling (R38). Energy efficient garage door (single car garage).

94 outside, 74 inside. :thumbsup:
Works for me, regardless of cost.
I've used both the portable and mini split systems and the splits are infinitely better units. 3 major reasons come to mind:

1) Footprint - the wall units take up very little space on the wall, no space on the floor and can be placed high enough for good cooling efficiency. A portable will need floor space + clearance around it.

2) Condensate - With a portable unit, you'll either buck up for a self evaporating model or have to deal with dumping, draining or pumping condensate. Mini splits usually are installed with a condensate hose coming through the wall with the refrigerant lines.

3) Installation - A mini split requires a hole about 2-3" punched through for the condensate lines & drain tube. A portable needs 1 or 2 holes at 5". Since you're working in brick, that could be a big pain...

That said, if you're looking for the cheapest, temporary solution, the portables do work. I'd recommend at least shopping for a 2 hose system so that you're not venting you're cooled air outside. In your situation, I'd probably recommend the mini split over a through wall system.
 

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tBaker, I don't know what you go though up there as far as storms and power outages. I live an North of Baton Rouge and get power outages from some hurricanes that come through, have not had any direct hits yet but Katrina came awful close. But anyway I do have windows in my shop with 2 cheap 5,000 BTU window units from Walmart. My shop is not insulated, just cinder block walls and concrete floor but the ceiling is insulated. my shop is about 20x32 and it keeps the temperature down but still to hot to work in the day time. I go out early morning around 1 or 2am and work for 5 or 6 hours before the heat comes in.

The point I wanted to make about the 2 window units is that if I have a storm and power goes out I can move the 2 window units to my house and easily run them off of my generator. I know its probably more of an expense then what you were planning on, but it maybe worth while to install 2 windows for A/C and move them to the house if need be

Something to think about
 

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Do not use a portable AC! I had one and returned it. The problem is that all of the conditioned air is exhausted to the outside, which creates negative air pressure, which in turn, forces warm air to infiltrate the conditioned space. A window unit doesn't exhaust the conditioned air. It either recirculates it all, or there may be an option to bring in fresh air, but in either case, unlike a portable, it doesn't create negative pressure in the room.

I have a small window unit mounted through the wall of my 2 car garage. It keeps my shop comfortable on 100 degree days.
 

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With a portable A/c unit, you need two ducts for outside inlet air and exhust to the outside for the condenser section. Done right, no air conditioned air should be leaving the room.
 

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I put AC into my shop 2 years ago. Best thing ever. I come home smelling fresh and it's a pleasure to work in the shop now. I keep the thermostat at 73-75F depending on how hard the task at hand is.

My shop is a tough cool. A metal building with 24' ceilings, R13 insulation and a lot of solar gain. I put a 4 ton Rheem unit in the shop. During the hottest days it'll keep it at 75. That's if it's sunny. If it's cloudy and hot it'll keep it cooler. The solar gain from the roof is high. All radiant based. If I could get the roof insulated well the 4 ton could be replaced with a two ton.



 

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My garage shop is about your size and I have a window AC unit and a dehumidifer. I run them both 24 hours a day and have to empty the dehumidifer at least twice a day. I water the flowers with the water from the dehumidifer. With all the rain we have had this summer it's been really humid. I look at the money I spent on keeping the shop cool as just another tool. If I didn't have a table saw I couldn't do wood working and if I didn't have my shop cool I wouldn't go out there and work.

Don
 

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David - Machinist in wood
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About two years ago we had our two car garage insulated (two walls & ceiling) for $500. I planned to do it myself but just the materials were going to cost more than that and these guys were here and gone in 4 hours. I had already insulated the door with R11. It's a bit heavy but it doesn't get opened often.

I borrowed a 9,000 BTU portable AC unit to get a feel for how that might work. It didn't. I know it's a bit small but it was inadequate and there was the issue with condensate drain and opening a window to port the exhaust hose.

So, we had a 12,000 BTU, 22 SEER Gree mini-split installed - $2,500. This thing is awesome! It uses less current than my wife's hair dryer, is ultra quiet (not that it matters in my shop), and it does the job. It's been on 24/7 since October 2013 and our electricity bill hasn't increased. We do level payments and our bill was $155 before we installed it and it's still $155.

The garage/shop is on the west wall and has two windows. We put solar blocking film on the windows inside and 90% solar blocking screens on the outside across the entire west side of the house. Now that the shop is cooled/heated and the door into the house stays open most of the time I think that helps with the efficiency of the main unit so that probably contributes to the electric bill stability.

I keep the mini-split on 80 when I'm not in there and about 76-77 when I plan to work for a while. The big thing is the humidity stays where I need it for building acoustic guitars - somewhere in the mid 40's RH. In the winter I keep it on 64 but when I work out there for a while I bump it to about 67-68.

Here's the insulated door -
Furniture Room Wood Floor Flooring


Gree inside unit -
Wall Room Floor Furniture Building


Outside unit is so quite you have to walk up to it and see the fan running to know it working -
Property Home House Lawn Grass
 

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I insulated my garage door with 2" rigid foam panels (I don't want to replace the wood door because having a garage door opener is less of an obstruction than those darn rails on each side of a roll up door). the weight of the rigid foam is inconsequential and does the job. The biggest heat gain is from a section of the roof that isn't insulated. When I'm not making a lot of dust I can also leave the door to the house open to even out the temp a little--that's if my dog doesn't decide to keep walking into the shop which can be a hazard for both of us. :) On the hottest days, the shop temp is around 77 if the AC was turned well prior to the hottest part of the day. My leather apron makes me quite warm so I'd prefer the shop to be colder , but for the less than $180 I spent on the AC, I can live with 77.
 

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Tbaker1350,
Looks like most missed part of your question, dust from the shop getting into the unit and causing issues. I will address that. I would suggest you place additional filter material in front of the inlet of the evaporator coil (on window units this is where the filter is anyway). Saw dust, especially small particals of it, will plug up the factory filter on these pretty quick. Do you have dust collection? Does it work well? Needless to say, if you reduce airflow across evap coil, or condensor coil for that matter, you are lowering the efficiency of the unit. If airflow drops enough, the evap coil will freeze over. Neither if these are good. LOL I use the cheap rolls of blue filter media you can buy at big box stores, just cutting myself and holding it on cover with some self adhesive velcro strips. Does the job...
 

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David - Machinist in wood
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Tbaker1350,
Looks like most missed part of your question, dust from the shop getting into the unit and causing issues.
Yep, I sure did. Look on the top of my unit and you'll see a blue filter. It catches a fair amount of dust before it hits the built in filters on the mini-split unit. I clean the internal filters about once a month but I don't typically have a lot of airborne dust. Plus, I built a shop air cleaner and it does a pretty good job to keep dust to a minimum.
 

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I have a simple, very small window shaker in my shop that keeps things cool enough to work out there even in the heat and humidity of the summer. (I am in eastern Iowa, so we see more humidity probably than extreme heat, relative to other areas of the country.)

My shop is 20' x 28', with 9' ceilings...but the key for me is that I have it very well insulated. No matter your cooling choice, I would really recommend making sure you have your shop well insulated.
 

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If I could get the roof insulated well the 4 ton could be replaced with a two ton.
Spray foam insulation directly to the underside of a roof is called 'hot roof'. Not permitted on all structures, like our house we are building, but after I got the attic a sprayfoam vapor barrier (R-21) the walkout basement provides enough ac to keep the upstairs living area 10 to 15 deg cooler than outside.

Getting spray foam quote and keeping your 4-ton unit (it would save you money by not running for nearly as long to cool) would be two thing I recommend.

Regards,
Steve
 

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David - Machinist in wood
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Getting spray foam quote and keeping your 4-ton unit (it would save you money by not running for nearly as long to cool) would be two thing I recommend.

Regards,
Steve
If the unit is indeed too large for the allotted space it will, as Steve said, run less to keep the desired temperature. The downside is that it won't run long enough to dehumidify the space and that's the greater need for air conditioning is to remove humidity. 77 degrees in my shop at 45% RH is going to feel a lot cooler than 77 degrees in another shop at 65% humidity.

This is especially important if you're building items that are more subject to wood movement. Build it in a 'wet' environment and take it inside a house with 'dry' environment and the piece will change dimensions more than you might think or for which you've allowed.
 

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Discussion Starter · #20 ·
Thanks guys

Thanks for all the feedback. I would like to go the fairly simple route and make a hole for a window unit, but I know the HOA would flip their lid over that. I was hoping against hope that someone had some success with a portable AC unit. As I suspected, that's not the case. I will most likely be going with the split unit, but that will have to wait until funding allows. Besides, I'm a new woodworker and not sure I want to make that much of an investment in my new found hobby. Worse case scenario, I'll just wait a few months till the weather cools off.
 
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