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portable air conditioner advice
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=48066		 Page 1 of 1
Author:  wbergman [ Tue Jul 26, 2016 7:33 am ]
Post subject:  portable air conditioner advice
I need a new AC. My windows will not accommodate an AC. The existing one through the wall is too expensive to replace. I plan to use a portable and run the exhaust hose out the wall. I want one that does not need to empty a drain tank or pan. Probably 8000 BTU is enough. Any advice?
Author:  RustySP [ Tue Jul 26, 2016 8:15 am ]
Post subject:  Re: portable air conditioner advice
I bought a portable AC. I think it was a Soleus and probably in the teens btu's.
I had a mason friend knock a round hole in my brick veneer two car garage and I made a nice sheet metal collar/adapter with bug screen to tie it all together and it looked very nice.
Sadly, I actually had to stand close to and directly in front of the louvers to get any comfortable temp air on me.
It was a colossal waste of $500.
Next, i had another friend knock out a lot of bricks and install a proper size window in which I put in a 24K btu unit.(or a little less)
When my house got too warm I would retreat to my garage for cooling, it worked so well.
I my opinion, portable units only work in small bed rooms unless you get the big commercial units that cost more than an arm and a leg.


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Author:  WaddyThomson [ Tue Jul 26, 2016 9:56 am ]
Post subject:  Re: portable air conditioner advice
I, also, had a pretty poor experience with a portable air conditioner. The one I have (will sell for cheap!) was designed to "evaporate" the excess water. That part worked, but it could never keep up with the dehumidifier that was producing heat to beat the band. I moved the temperature on hot days in my shop from 95* to somewhere in the upper 80's. Better, but not a good working temp. It did extend the open time of HHG quite a lot though!

My final solution was a mini split system that also functions as a heat pump in the winter. Keeping the shop cool is a breeze now, and I even have to watch out not to keep it too cool. They aren't cheap though compared to window units, which was not an option for me. Unapproved by the boss of me!
Author:  WilliamS [ Tue Jul 26, 2016 12:00 pm ]
Post subject:  Re: portable air conditioner advice
The problem with the portable a/c's is that they are working against themselves and never properly cool a room.

Basically, since they don't exchange heat out of the room they have to exhaust heated air...that means that the unit is constantly drawing new, un-cooled air into the room-extremely inefficient for both cooling and humidity control. AND, if you have any sort of conduit run for the exhaust, it's radiating heat into the room unless you have it well insulated.
True, if you stand in front of them they do blow cool/cold air. But, the eat up a ton of energy and my experiences with them (in my shop, part of my home, and at work) is that the net drop in temperature for a room is, at max, just a few degrees...and I've actually seen them cause a net INCREASE in temperature when not thoughtfully installed (the one they put in at work).

Also, the one I had in my shop for a short time a couple of years ago was supposedly the type that never needs to be emptied. All I can say is don't count on that feature.
Being familiar with how these things work, I had situated the unit such that the exhaust run would be as short as possible (only about 6-8"). To do this without making any big new holes that would have required approval from the landlord I built a shelf for the unit near an existing, unused hole, about 7' off the ground.
This just so happened to overhang some of my wood storage ever-so-slightly. I knew it was a dumb arrangement and had planned to reorganize the shop in the coming weeks but the unit was supposed to never leak and never need emptying so, if it worked as advertised I would have been fine...

At the time I had some instruments fairly far along and didn't want the shop to get too crazy hot so I would leave the a/c set to 85 even when I wasn't there. At one point I didn't have time to make it back out to the shop for 4-5 days (I live in NYC and rent a space in Brooklyn). When I returned there was water running from beneath the door of my shop.
As it happened, I ended up with several thousands of dollars in tonewood soaked through. I dried and stickered everything immediately and didn't end up loosing much-a few sets do have some water stains that probably won't come out but most seem to be ok.
The a/c unit immediately made it's way to the trash bin. It was incapable of dropping the temperature in the shop by more than about 8-9F net (standing in the path of the air it did seem cool, though), it used a ton of electricity, and since it was drawing in so much outside air, I had to empty my dehumidifier about 3x as often...and this was an 9,000 btu unit in a 150sqft shop (with 12' ceilings),
Author:  Clay S. [ Tue Jul 26, 2016 3:27 pm ]
Post subject:  Re: portable air conditioner advice
Please cure my ignorance. Most AC units dehumidify as they cool. Do you find they aren't dropping the humidity enough and so you still have to run a dehumidifier? Would a bigger AC unit cool and dehumidify better and eliminate the need for the dehumidifier .

"The existing one through the wall is too expensive to replace"

"Next, i had another friend knock out a lot of bricks and install a proper size window in which I put in a 24K btu unit."

One possibility would be to enlarge the existing hole (if necessary) and frame it up to fit a window AC without installing a window.It would be a little cheaper and wouldn't take up window space.
Author:  RustySP [ Tue Jul 26, 2016 6:43 pm ]
Post subject:  Re: portable air conditioner advice
It would have been cheaper to go with a thru-the -wall unit butI had a window put in because I wanted the extra daylight on that side of the garage. Also, I enjoy looking out the window a lot.
I don't know much about the science of AC and my unit does all I ask of it but one thing I do know: I dare not open my garage door on humid days because it will be days if not longer until my unit sucks out all the extra moisture in the air.


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Author:  Barry Daniels [ Tue Jul 26, 2016 8:05 pm ]
Post subject:  Re: portable air conditioner advice
Clay S. wrote:
Please cure my ignorance. Most AC units dehumidify as they cool. Do you find they aren't dropping the humidity enough and so you still have to run a dehumidifier? Would a bigger AC unit cool and dehumidify better and eliminate the need for the dehumidifier.


No, it would do exactly the opposite. A bigger unit will run a shorter time in cooling the room which take out less humidity. If the AC is properly sized then the possible need for a dehumidifier is based solely on your local conditions and the construction of your shop.

I have a 10,000 BTU window unit and a dehumidifier in my two-car garage/shop which is adequate for the Houston subtropical climate.
Author:  dzsmith [ Tue Jul 26, 2016 8:45 pm ]
Post subject:  Re: portable air conditioner advice
Texas summers can be brutal.
My fan gave up.
My wife wanted to install a window unit in the garage, but I figured it would not last long sucking in sawdust. I made a swamp cooler, but it only delivered cool air for 30 minutes.
Dan
Author:  WilliamS [ Tue Jul 26, 2016 9:53 pm ]
Post subject:  Re: portable air conditioner advice
Clay S. wrote:
Please cure my ignorance. Most AC units dehumidify as they cool. Do you find they aren't dropping the humidity enough and so you still have to run a dehumidifier?


These portable units actually constantly draw outside, moist (if you live in a humid area) air into the room so they make controlling humidity much more difficult.
Author:  Hesh [ Tue Jul 26, 2016 11:06 pm ]
Post subject:  Re: portable air conditioner advice
Our commercial shop is around 1,000 square feet and on the third floor, gabled roof lines of a 1890'sish historic house located right smack in the epicenter of the retail/commercial district of the People's Republic of Ann Arbor. We have black roof shingles on our historic roof too on the other side of the walls/gables from us. There likely is not much insulation in the roof either, if any.....

If you are getting the picture it's potentially hot up there especially this time of year.

We run two air conditioners but the one the does the heavy lifting for us is a portable, about three to four years old that we bought for our use. IIRC it's 11,000 - 13,000 BTU and the brand escapes me at the moment but I do recall that it's not a brand that I had ever heard of prior.

Our unit has been installed in a central location in our shop and is vented through an insulated.... duct into another gable that is exposed to the outside air.

We are very comfortable and can reduce the temp from the 90's to the 70's when ever we need to which in our business is round the clock so glues and finish cure reliably.

I was skeptical of portables too when we bought this one but it works great and I have no complaints. It also dehumidifies as AC does. Our unit does drain accumulated moisture as well and we have it plumbed to a laundry type sink.

I'm back in the shop Thursday and if interested can get you the brand and size if you want. What I wanted to add here was a positive, reliable, comfortable experience over at least several years so far with a portable. Go figure. dunno
Author:  WilliamS [ Wed Jul 27, 2016 11:15 am ]
Post subject:  Re: portable air conditioner advice
Hesh, I notice that you say it dehumidifies. Now, obviously it is pulling moisture from the air but just curious if you mean that you are seeing a net dehumidifying effect in the space directly attributable to this unit. That would seem strange to me since it has to draw in an equal amount of fresh air as it is exhausting hot.


Also, I'll add that I think the temperature of the fresh air being pulled in makes a big difference. The three situations where I've had experiences are interior rooms where the air being pulled in is every bit as hot as the ambient room temperature would be without the a/c.

If, however, you are in a space that would be pulling in either a) air from another part of the building that is already cooler than the ambient temp in the space or b) air from outdoors which could be significantly cooler than ambient temp in the space if the space is the top floor of a building, etc. then you might see better cooling than I mentioned. In both of these instances, though, the larger net drop in temperature is as much caused by simply drawing in fresh air as it is by the cooling of the unit.

The portable unit in my home that was next to worthless was an LG @8k btu in a 120sqft space. The one at my shop was, admittedly, an off brand and 9k btu in 150 sqft (12ft ceiling). These were both in use around the same time a couple of years ago.

The one that was installed (against my recommendations) at work last year was a commercial unit in a 2,500 sqft space. It was about 6.5' tall, 3-4' wide and 6' deep (don't recall btu's but suffice to say a LOT). It cost my company $4k per month to rent plus more for the installation. At the 30 min mark it would provide a net drop in room temp by about 5-6F in the space...but, if left running, it would actually increase the temperature by about 3-5F by the 2hr mark (this was due to the way they routed the exhaust into conduit that ran through the ceiling across the room). That experiment lasted all of two months.
Author:  Hesh [ Wed Jul 27, 2016 11:55 am ]
Post subject:  Re: portable air conditioner advice
Hi William. Yep sure enough we see a net reduction in RH directly and quickly attributable to our portable AC unit. We have calibrated via wet bulb method hygrometers in our shop that you can watch seriously reduce the readings within minutes of turning the unit on and the reduction in RH can be 15% or more over outside after its been on an hour or so.

Our "loop" is partially closed, not entirely since our unit takes in some air from our shop and of course vents the air outside the shop but the cooled air is distributed in the shop. To my way of thinking this is a partially closed loop system since some of the cooled air also counts as exhausted back into our shop air. The exhausted outside of our shop air is obviously replaced by air migrating back into the building through every crack and void and there are plenty of those....

Anyway to avoid being pedantic - the sucker works pretty well and we are happy with ours...:)

BTW a goodly amount of OLFers have been saved from sweating their arses off during our classes by our AC too and I suspect that they would also attest that our shop is pretty comfortable even with six bodies at 98.6F or more.
Author:  Alan Carruth [ Wed Jul 27, 2016 12:27 pm ]
Post subject:  Re: portable air conditioner advice
I ran into the problem with a portable unit myself a few years ago. I noticed that when it was running I was smelling creosote, and realized that it was drawing make-up air down the chimney and through my wood stove. I was able to box off the intake for the heat exchanger and run a piece of 4" aluminum dryer flex hose parallel to the hot air hose that went out the window. Both of them attach to a piece of plywood that goes in the window, and I put in a divider that goes some way toward directing the hot air away from the inlet pipe. This allowed me to run the unit through a small window, and gives reasonable efficiency. I generally dislike jury-rigs (even though I' surrounded by them), but this one does work pretty well.
Author:  Mike OMelia [ Wed Jul 27, 2016 8:04 pm ]
Post subject:  Re: portable air conditioner advice
Whatever u do,do not rely on evaporative systems or a hose hanging out the door (water). Lowes, et al, sell a mini pump that collects the water (like a sump) and pumps it out a hose through the window seal. Works great!!!
Author:  SteveSmith [ Thu Jul 28, 2016 8:45 am ]
Post subject:  Re: portable air conditioner advice
Mike O'Melia wrote:
Whatever u do,do not rely on evaporative systems or a hose hanging out the door (water). Lowes, et al, sell a mini pump that collects the water (like a sump) and pumps it out a hose through the window seal. Works great!!!


A good idea. Small sump pumps are used for AC condensers that are mounted indoors. If you use this method provide a drain pan with a water-sensitive shut off switch so the system will be shut down if the pump fails. These switches are also a typical AC component.
Author:  David Collins [ Thu Jul 28, 2016 10:47 am ]
Post subject:  Re: portable air conditioner advice
I can't speak for results others have found, but our setup has proven to work surprisingly well, much better than I expected it would.

We have one window unit in the tool room, probably 15-20 years old with the fins smashed up and clogged with dirt. Then we have the portable unit we installed as Hesh described, more centrally located with an insulated duct to vent the heat exhaustion through a very loose attic. I checked and it's a 12,000 BTU unit from Lowes.

Yes, it does induce some air exchange by having to draw some in as it exhausts heat, but the net result is still significant net cooling. It does also pull out a good amount of moisture - can't say exactly how much, as we set it up to drain direct, but it does effectively act as a dehumidifier as well.

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We basically built a closet around it and our humidifiers, with a big filter on the intake to add air filtration as a bonus. Then for redirecting cool air toward our benches, we used an "air guitar".

Now our shop is on the third floor of an old building, vaulted ceilings with sun beating down on them like a greenhouse, and in the past few weeks of 90-95° sunny days, we've had no problem at all keeping our 1000 square foot high ceiling shop in the 72-74° range.

I know others haven't had as good of luck with this style of unit, and couldn't say what variables may have added up to some working better than others. For us though, it was a very cheap and easy solution that has worked far better than I initially expected it to.
Author:  hugh.evans [ Thu Jul 28, 2016 12:32 pm ]
Post subject:  Re: portable air conditioner advice
Square footage, the presence of any insulation, and capacity of the existing unit are the bare minimum to do even a rough calculation of the required cooling capacity. Thermodynamics are not on your side unless heat from the compressor/condenser is vented by some means or you will just have a very expensive dehumidifier. There is generally a rather forgiving range when it comes to cooling capacity in HVAC design, but there are some basic universal truths. Insufficient units will take a very long time to reach the desired temperature and tend to create lower humidity. Excessive capacity will reach the desired temperature range but run the risk of making the air feel clammy, this is a direct consequence of not allowing it to run long enough for moisture to collect on the evaporator (because the ambient temperature is brought closer to the dew point).

Getting away with 12k BTU for 1000 sq ft suggests you have some insulation, and that one or both of the lower floors is climate controlled. For a typical standalone structure such as a garage 16k-20k BTU would be about right.
Author:  David Collins [ Thu Jul 28, 2016 1:01 pm ]
Post subject:  Re: portable air conditioner advice
Good points Hugh, with some usable numbers!

I would guess our old window unit to be about 8,000 BTU. It's probably operating at 70% today, but it's also old enough that the initial ratings weren't as conflated as most today. ;)

The lower two floors are both climate controlled, so we do get a bump there. I'd say the biggest improvement however, is probably that over the last three years we have been gradually pecking away at sealing up leaks and cracks around windows, attic doors, etc. We've finally made it to where out humidifiers in the winter and air conditioners in summer are not having to run at 100% to keep up with air exchange.
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