# Portable A/C unit



## sawedoff (Oct 10, 2011)

I will be setting a shop up soon and am looking into ways to cool my 2 car garage shop. It is 21×23 with 9 foot ceilings. I live in the Fort Worth area so it's hot in the summertime. I've been researching the port a cooler units, mini split a/c units, and am also looking at portable units.

Has anyone had any luck with the portable units?

Thanks


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## BulldogLouisiana (Apr 12, 2015)

Portable units aren't all that great. I live 3 hours east of you and I have a 12000 u it that struggles to cool my master bedroom when the central air goes on the fritz. Window units are way better. The port a cool units I've heard struggle in really humid locations..of course I think they are a Texas company.

A ductless mini split is what I plan on doing eventually. I have the same problem as you.


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## CharleyL (Mar 10, 2009)

How well insulated is your shop? If not insulated, you won't have a chance of getting it comfortable with any unit. Port A Cool units work in very low humidity areas like Arizona by evaporating water, which raises the humidity, but lowers the temperature. It's a high tech version of a portable swamp cooler and they aren't very good where the humidity is above 10-15%. In a woodworking shop this increase of humidity causes rusting of the tools and increased moisture content in the wood, which results in wood shrinkage in your projects after they are complete and you move them to lower humidity areas. If your shop is well insulated, including the garage doors, a 2 1/2 ton central air conditioner or a similar sized mini split system with two inside units could cool a two car garage sized area to a level that would be comfortable in Fort Worth if run 24/7 all Summer. A 3 ton system would do better on those 100+ days. One ton of cooling is the amount of ice that would need to melt to provide equivalent cooling, or 12,000 BTU, so a 3 ton system would be 36,000 Btu. Yes, many whole house air conditioners are this size, and your shop is about the same size as a small house.

Don't waste your money on a Port A Cool. Buy a 3 ton air conditioner and* lots of insulation*. Vent the space just below the roof too. Provide inlet ports in the soffits and exhaust ports at the ridge of the roof so air can flow freely up along the under side of the roof and out. Your shingles will last longer if you do this too.

Charley


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## gargey (Apr 11, 2016)

CharleyL's recommendation is just half-assing it. Don't just buy and install a lot of insulation, rebuild your roof with more ventillation, and install a 600,000 Btu AC unit, because that won't get you anywhere. You should knock down your house, excatave a 100-200 ft deep cave to protect from ground-level temperatures, and install a nuclear reactor to power a 6 trillion Btu AC unit to keep it dry and cool. Make a few cutting boards to pay for it.


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## CharleyL (Mar 10, 2009)

gargey, I'm trying to help sawedoff avoid making bad decisions with my extensive background in HVAC. I once owned an HVAC company and did this for a living.

Portable AC units are not going to get him a cool place to work unless he lives North of Calgary, BC. In Fort Worth he's facing near and above 100 deg F for many days of the Summer, so a 30 deg drop in temperature is what he needs. It won't happen without good insulation and a 2 1/2 - 3 ton air conditioner. Port A Cool type swamp coolers are not the way to cool a wood shop since they create excess humidity and the problems that it creates.

Charley


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## RandyinFlorida (Sep 27, 2012)

I live in NW Florida and I manage with a portable unit. It's doesn't bring the temp down in my 2-1/2 car garage to a perfect 76. But it does take the edge off, as it were. More importantly it lowers the humidity.

I was very lucky to pick it up for just five dollars. Yep, somebody didn't know they had to vent it outside. Duh!


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## KelleyCrafts (May 17, 2016)

> gargey, I m trying to help sawedoff avoid making bad decisions with my extensive background in HVAC. I once owned an HVAC company and did this for a living.
> 
> Portable AC units are not going to get him a cool place to work unless he lives North of Calgary, BC. In Fort Worth he s facing near and above 100 deg F for many days of the Summer, so a 30 deg drop in temperature is what he needs. It won t happen without good insulation and a 2 1/2 - 3 ton air conditioner. Port A Cool type swamp coolers are not the way to cool a wood shop since they create excess humidity and the problems that it creates.
> 
> ...


Texas is more humid so I can't comment but a swamp cooler in AZ does not rust tools. SMH….. HVAC for X number of years doesn't mean you know every climate. I ventilate through a side door in the garage and crack the garage door because a swamp cooler doesn't work if you don't do that. It needs fresh dry air moving through the unit for it to work. Then air escapes through the garage door opened slightly. Makes it probably in the mid 80's most days when it's 110 out but you need dry air outside for it to work. As for tools rusting??? Ummmm….no. You aren't leaving this on 24/7. When I leave the shop, I turn it off. Minutes later it's dry again just like it was before I started.

If you are looking for an inexpensive solution AND you have LOW HUMIDITY outside air, then a swamp/evap cooler is just fine, it's not like the AC in your house but makes it through the tough months. I personally like the cave idea though.


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## moke (Oct 19, 2010)

I really don't know much about HVAC or R-values….what I do know is I had two portable units totalling 20k btu and they worked aweful…..I sold one and bought a 12 k window unit for my 24×36 gargage and it combined with a 8k portable I keep it in the mid 70's. I have to tell you, I am considering not using the on portable I have and just running the window unit. I have insulation in the walls and ceiling, but I don't know what the R value is.

Bottom line….portable units are basically worthless unless you stand in front of it!!!!
Just my .02
Mike


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## bonesbr549 (Jan 1, 2010)

When I built a house back years ago, I had the builder insulate the walls and I had insulated garage doors. I had a window unit running in my 2 car garage and it kept it quite nice. Not 68 but livable on the hottest of days in VA.

I wanted central out there but code said that was a no no if it was the same unit as the house.


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## AnnAnne (Jun 24, 2019)

Recommended Whynter ARC-14S for 500 square foot rooms. We use it in the living room, not too noisy, and the cooling effect is good. If you want to put this portable A/C unit in your store, it should be appropriate, I think.


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## Knockonit (Nov 5, 2017)

Is a 110 the last few days, i cool my garage with a floor portable unit, exhausting to exterior.block wall one side, no insulation, attic has plenty two other walls are adjacent to house, and garage door insulated, with 8 ft cieling, have two cieling fans and a pedestal fan that moves the air, i turn it on an hour or so before i head to garage, don't have a temp ga. but i don't sweat, doing the small stuff, sanding, layout, finishing ect. 
I do have to pull my uni saw out to edge of open door to use, so i pre cut a whole lot of items and work on the tables. 
I have 1k sq. ft metal building due by end of july, which once wired and structual components are set correctly will spray foam the entire building and will cool with a 3 ton unit. Air movement with cooler air equates coolness, i do like the evap coolers and use them on my patio when entertaining, just can't in the shop with the wood, it does create problems. 
best of luck

Rj in Arizona


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## ibewjon (Oct 2, 2010)

The number one rule of air conditioning is BIGGER IS NOT BETTER!! You are in Texas, not Arizona. They have dry air, you have soup, worse than we have in Illinois. Too large of unit will cool before removing humidity, and the shop will be cold and damp. A mini split is the way to go. The LG model I have in my shop has a 28 seer, and costs less than 50 cents per day to keep my shop cool and dry. I have an hour meter and kwh meter on it to prove it. I am well insulated, 12" in ceilings and 6" in walls. 3 outside walls. There are mini splits with one outside unit feeding two units inside, to spread cooling around your space.


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## clin (Sep 3, 2015)

As mentioned, insulate first. If your area is humid, avoid anything that relies on evaporation. As for portable units, some are better than others. Most are a single port. That means it only has one port that connects to the outside. This is the port it blows the hot air out. But, it has no outside input port. So this means it is actually using the cool air of the the space to cool the condensers. This air has to come from somewhere. So more than likely in a garage it will leak in around the garage door.

A dual port will have a separate intake to use outside air. This results in a closed system, like most normal AC units operate. So they will tend to be more efficient.

Concerning your cooling needs, your choice has a lot to do with how you use the space. The difference being are you going to keep it cool most of the time, or expect to back the car out, close the door and have something blast the space and cool it relatively quickly?

A mini-split is a very high efficiency unit, but these are design to keep a space cool, not take a 100+ degree garage and cool it down in 15 minutes. It's like the difference between an economy car cruising on the highway (great gas mileage) as compared to a dragster that can cover a 1/4 mile in a matter of seconds.

Concerning keeping it cool. A continuous load doesn't necessarily mean you have to keep it cooled 24/7. But, if you're a weekend warrior, you might want to start it Friday night or at least start it many hours before you plan to use the space.

If you are looking at a continuous load, where you might use a mini-split, sizing a unit is based on the cooling load. Someone earlier mentioned using something like 2 1/2 to 3 tons of AC. This is grossly oversized for continuous cooling.

There is a rule of thumb, which itself usually results in very oversized system in most cases, but it gets you in the range +/-100% (yes it's not very accurate). This rule of thumb is 1 Ton of AC for every 600 sq-ft of space. You have 482 sq-ft.

The problem with square-foot rules of thumb is they only very crudely relate to cooling load. While square footage will directly relate to cooling load of the ceiling/roof, wall area is equally important. As are windows, compass orientation of windows, eaves and overhangs. And all of these are affected by the home construction. How well insulated, how well sealed, brick, stucco, wood siding? And let's not forget where you live matters a LOT.

All of the above are what is taken into account when running a "Manual J" calculation. This is the professional HVAC way of determining residential heating and cooling loads. Most HVAC installers do NOT do this and will almost always sell you something much bigger than needed (2X to 3X larger is not uncommon). They won't get a call back for over-sizing, as you simply won't know you paid too much, are paying too much for the electricity, and are not as comfortable as you could be.

Without running a Manual J or similar calculation, everyone is just guessing. But, what I can say with near certainty is that 2 1/2 to 3 tons is WAY too much for continuous cooling for a normally insulated space of this size. However, if you want to cool it fast, then of course the bigger it is, the faster it will cool. And if you only run it for a few hours a week while you're in the space, then efficiency doesn't really matter.

Also, as mentioned, in a humid climate, over sizing is not only inefficient and more expensive to buy and operate, it won't dehumidify well.

P.S. Don't trust the BTU/Hr rating of portable units. Any rating is always at some specific conditions and unless you know exactly where this number came from, it's safe to assume it is very optimized conditions and may not apply your situation. This is probably why many people are disappointed with them. They just don't do what they say they will in real-world applications.

But I do have a buddy that uses one in his very small (100 sq-ft) little workspace and it does very well in 100 F summer heat.


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## WoodenDreams (Aug 23, 2018)

Have you thought about large air mover fans. The shop I worked in Tucson,Az used several 42" air mover fans and kept the garage bay doors openhttps://www.grizzly.com/products/MaxxAir-24-Barrel-Fan/T28604


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## bigJohninvegas (May 25, 2014)

I have a 3 car garage shop. Fully insulated, in Las Vegas, Nv. 
Still with no A/C it would get up around 90 degrees in there. 95 the couple weeks we get up to 115 outside. After trying out swamp coolers, and fans drawing air through my laundry room into the garage, Which was working my house a/c hard, and reading about how poor the portable a/c units perform. I bought and installed a Mr Cool DIY Mini Split hvac unit. It is one year old now, and working incredibly well. This year I have let it run 24/7, and my power bill has gone down a little. (not over working the house system I think). I have it set at 80 over night, and when I want to work in the shop I set it at 76. 
Like others have mentioned, Insulate all you can. I also got bids from professional A/C companies, and they all came in at around 6K for a 24000btu or 2 ton unit. This was well outside of my budget. But I did get the info about what size unit I needed, and optimal location in my shop. Remember bigger is not better. 
I did use the heater a couple times. But it typically just does not get that cold here. and it was a mild winter. 
My only regret with going with a mini split a/c is that I waited so long to do it. 
good luck,


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## Monty151 (Nov 1, 2018)

Here in central FL it's hot and humid. I have been making due with a large shop fan, but on days that it gets up to 105 there is no working in that. I am strongly considering a Mr. Cool mini split. Portables cant keep up with this heat.


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## ibewjon (Oct 2, 2010)

What is the SEER of the Mr cool units?


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## CaptainKlutz (Apr 23, 2014)

+1 portable units are joke. Do not waste your money.

+1 There is big difference between AC requirements in different regions. The humidity levels in your area require proper sizing or you will never be comfortable. As some else said, 'cold and damp' is common issue when AC unit is too large for space.

+1 Proper insulation is required, or your cooling costs are higher. No insulation will roughly double the electricity cost .vs. using proper insulation. Plus you need a more AC BTU.

+1 Mini-split is great option for garage. Easy DIY project, if you know how to run the power wiring your self and met code requirements.

One thing I have not seen mentioned:
Do you have an natural gas devices (furnace, water heater, dryer) in garage?
If yes, then HVAC in garage can be more costly challenge. Gas appliances require venting and this increases you heat losses plus raises your cooling costs. Check your local building code to know more.

Another issue is building codes for vehicle storage. 
In many building codes for vehicle garage; are required to have (2) vents (one high/one low) in wall directly to outside to prevent vehicle fumes from entering house. Have to permanently remove ability for vehicle storage to block the vents and reduce HVAC costs.

There are many existing threads on topic of Garage shop AC. 
Try searching.
https://www.lumberjocks.com/search_results?

Best Luck.


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