Portable Air Conditioner Info
March 14, 2015 11:53 AM   Subscribe

What do I need to know about portable air conditioners to get the most bang for my apartment-cooling buck?

I live in an apartment with no air conditioning. This spring, I would like to purchase a portable A/C unit. The apartment has casement windows (the sort that swing out from the side, rather than sliding up or across), and as such window AC units are not an option. I'm looking at portable units, the kind that are free-standing inside the room and have one or two intake/exhaust hoses running to a port installed in the window. Note that I'm not interested in evaporative coolers -- I'm talking about full-on air conditioners.

My apartment is about 800 sq ft, in two rooms -- a bedroom and a combined livingroom/dining room/kitchen. I have carpet. I'm located on the west side in LA, so there's a bit of humidity, and exterior temperatures are in the mid 90s for a few weeks during the summer, and frequently in the 80s. I'm on the 2nd floor with not-entirely-awesome ventilation so my apartment has been as warm as ~95 when I go to bed. I'd like to maintain my bedroom at ~80 or below while sleeping. It would be nice to cool the living room a bit as well, but I understand that there's no way a single ~10k-~14k btu unit is going to cool both particularly well, and would be okay with relocating the unit for weekend days spent inside.

The "window mount" portion of most of the units I've looked at is still intended to slide in a double-hung window, so I've made my peace with paying for a large sheet of acrylic (the size/thickness of the screen) and machining that to install the intake/exhaust hoses. If there are any commercial products that meet this need, especially with better insulating properties than acrylic sheet, I'd be happy to learn about them.

Are double-hose units, with a separate intake and exhaust hose, worth the extra cost? Intuitively it seems like "well, yea" because they'd avoid mixing hot air getting exhausted and relatively cooler air being pulled in, but I'm unsure if it makes a practical difference.

Do you have a unit you're particularly happy (or unhappy) with? Honeywell, DiLonghi, and Whynter seem to be the major brands on Amazon, but I have no direct experience with any of them.

How big a problem is draining condensation? Some units make a big deal about dumping condensation externally, others don't -- is this marketing speak or do some units have a tank/reservoir that requires frequent emptying?

Anything I'm not considering? I've never had to purchase an A/C unit before so I'm somewhat unclear on potential gotchas.
posted by Alterscape to Home & Garden (11 answers total) 7 users marked this as a favorite
My grandmother lived in a small (750sqft) 2 BR house in Fontana and the DeLonghi 12000btu unit I put in for her worked great for the half of her house not cooled by a window unit. The only drawback was the constant low hum, but they all do that. I bought it at Costco so I could return it if it didn't do the job, but that wasn't necessary. It was a single hose unit and I don't remember any condensation problems.
posted by buggzzee23 at 12:06 PM on March 14, 2015

The problem all portable air conditioners have is the exhaust tubing doesn't vent all the heat outside; much of it gets dumped inside, making it that much harder to cool the room.
posted by dfriedman at 12:29 PM on March 14, 2015

Typically, with the free standing units, there is only one hose, and it is the exhaust. Two hoses outside seem inefficient -- you're cooling hot outside air, when you should be re-cooling colder inside air.

You must ensure a short, straight line with this hose to the outside, as short and straight as possible, for max efficiency. Free standing units will have a small internal reservoir. Depending on humidity, this will need to be emptied frequently, perhaps daily.

IMO, you buy the biggest one you can afford. You'll never regret getting one that is overpowered.
posted by Cool Papa Bell at 12:29 PM on March 14, 2015 [1 favorite]

One more thing; They draw a lot of current so make sure your circuit and breaker or fuse are up to the challenge.
posted by buggzzee23 at 12:37 PM on March 14, 2015

An overpowered AC unit won't dehumidify as well because its cooling cycle time will be too short. Energystar.gov has a sizing chart.
posted by Johnny Wallflower at 12:39 PM on March 14, 2015 [1 favorite]

We had a DeLonghi 12,000 BTU model. We were using it to cool a small house, and it didn't work great for us because we were trying to cool one half of the house (the sleeping rooms) vs. just a single room. I think in a single room with the door shut it would have been good. It seemed sturdy and well made, good electronic controls. Biggest issue is ours would drop/leak condensed water out the bottom. I'm sure there was some reason for it but we never really got the kinks worked out. We felt safer running it in the bathtub so at least the water had a place to go.

Storage was also a pain, it's large and heavy.
posted by handful of rain at 12:52 PM on March 14, 2015

Howdy, neighbor!

My place is a studio, about half the size of yours, and my place has already gotten to 84F (inside) this year thanks to this heat wave. I also have the dreaded casement windows.

I have a Sharp unit that I got from Costco at least five years ago and it's never given me any trouble. I'll have to look up the BTU but it's not more than 10,000. (I didn't have the budget for more or I would have gotten it.) This has been good enough but that's basically cooling one large room, with most of the benefit going to the part that the unit is facing. As far as condensation goes, I drain it whenever it's ready to go back in the closet until next summer and I think i get about a cup of water out of it, max. (Mine doesn't have a draining bucket, you hook up a hose when it needs to drain. This is fine here in L.A.)

Now, about the casement window.... The window mine needs to go in is about 6x8 so a custom piece of acrylic is probably expensive. I have one neighbor who just covered the window in a clear plastic shower curtain. But I want to be able to take advantage of the ocean breeze and turn off the machine any chance I get, and that was just too cumbersome.

Another neighbor had a different approach and that what I went with even though it requires some big compromises: I just cut two slits in the lower corner of the screen opposite the hinge and crank. The unit sits close to window so the length of the exhaust hose going out is short, but it's long enough that it can hang out the window. I then close the window as far as it can go, which means the window is still open about as wide as the hose even when it's running. Yes, it's awful. Yes, I'm awful for doing it. But living in 90F is simply unsustainable, especially since I get hit when the sun sets so the place never, ever gets to cool off. And my total energy bill is never more than $30-$32 dollars, even running 24/7. (YMMV.)

I love mine. I think as long as your expectations are reasonable you will be glad you got it, especially if you mainly use it in the bedroom at night. Storage was an issue until i cleared out some closet space, but before I thought I had closet room I was considering building a cheap three-sided enclosure so during the off-season I could push it against the wall and use it as a side table or something. Cleaning the closet was easier. I think L.A. is the perfect place for a portable A/C unit.

I feel you, I really do. I'm on the top floor and it's freaking brutal. Oh, and when I don't need the unit I just flip the screen so the slit is at the top corner so the cat can't escape.
posted by Room 641-A at 1:17 PM on March 14, 2015

I too feel your pain. I lived in an attic apartment for seven years, and after the first hot summer there, I scraped together the money to buy a window AC and that was quite possibly the best $300 I ever spent. The part of Canada I live is prone to bouts of nasty humid days in the summer, up to 90-100 F plus the humidity.

But we had a lengthy seven-year relationship with one of the units you're talking about after I moved out of the place where I had the window unit. Unfortunately, I can't recall the brand. We used this in the upstairs of our two-level apartment, and it kept the place pleasant.

The model we had used a reservoir tank. On obscenely humid days, this would fill up overnight, then fill up over the course of a day.

When the reservoir was full, the AC compressor would kick out so the unit would just run as a fan. The unit also had an option of running the tubing that ran into the reservoir out somewhere, but it wasn't feasible for us to locate the unit where the dripping condensate line wouldn't be an issue.

So, it was just a daily morning/evening ritual of emptying the reservoir so the compressor could kick back in. Also, when the humidity wasn't terribly high, that ritual would often yield a dump of water that was less than half or even a third of the reservoir's capacity.

Also, alot of units come with a timer/thermometer, so if you're out of the house for periods of time, you can set it to kick in/out based on temperature or a timed cycle.

Depending on your back/physical condition, or the layout of your place, humping the reservoir of water into the shower or bathtub might or might not be an issue. Water be heavy. Ours held something like 8-10 litres.

buggzee23 makes an great point: If you're looking at AC models, let's say the unit you're looking at is an efficient 6,000 BTU model that's rated at 5 amps. A standard residential circuit is usually 15 amps. Obviously, it could handle that 5 amp unit, BUT. When an electric motor kicks in, you need to think about inrush current. Meaning, for a split second, it's sucking maybe twice or more of the current it actually requires to run. So the circuit will need to have the additional current required for that left unused.

Think of kitchen lights flickering momentarily when the fridge compressor kicks in, for example, if you've ever seen that happen.

If you have access to a breaker or fuse box in your unit, you can probably figure out what outlets are on which circuit. OTOH, if they're through a central box that's located in a place you can't access, that might be more difficult.

So if you're running some lamps and your tv, etc off the same circuit, you might want to switch up outets so you don't trip the breaker (or fuse).

FWIW, the floor unit we had used two hoses, but the "intake hose" was only engaged when the unit was on "fan" mode with that AC off, so it would draw outside air. This was useful on cooler days when I couldn't be arsed to unseal the window and pull out the unit, especially when I knew a nasty, humid day was just around the corner and we'd need to fire up the AC again. When the AC was engaged, the unit would draw indoor air from a vent on the back, not from the outside intake hose.

As for jury-rigging the window opening, you could consider sandwiching a layer of polyurethane foam between two identically-cut layers of the acrylic. As for forming a seal, duct tape is your friend. You could also consider a few layers of foamcore posterboard as a lower-cost option. It's easy to cut yourself with an x-acto knife, and you could make this several layers thick, then seal as needed with duct tape.

Also, to get the most out of the cooling horsepower you acquire, don't forget about solar load (or gain). It might be one of the variables you can control. If you have windows that get direct sunlight, covering them up with light colours to keep the direct sun out will help keep the place from getting too nasty and let the AC do the best it can.

Stay cool!
posted by mandolin conspiracy at 3:43 PM on March 14, 2015 [1 favorite]

You don't have to do it the day you buy the machine, but have a roll of that foil tape around because that exhaust hose will start to break eventually. You'll be glad you have it.
posted by Room 641-A at 6:52 PM on March 14, 2015 [2 favorites]

I want to address some misconceptions in this thread about how one-hose and two-hose portable air conditioners work.

In my opinion, one of the very most important things when choosing a portable air conditioner is to *always* choose a two-hose unit, and you need to make sure that the unit uses both hoses in air conditioning mode, unlike the unfortunate model that mandolin conspiracy described above.

The only intended purpose of the hose(s) used by a portable air conditioner in air conditioning mode is to give the air conditioner a place to dump the heat that it is trying to remove from your living space.

A regular window air conditioner has two separate air loops. One loop pulls in outside air, uses that air to cool the hot condenser, then exhausts that (now-hotter) air back outside. The other loop pulls air from your living space, draws it across the cold evaporator, then blows the (now-colder) air into your living space. This is the ideal situation, because no hot air is being blown into your living space and no cold air is being sucked out of your living space.

A proper two-hose portable air conditioner will work the same way; it will use one hose to pull outdoor air in, pass that air over the condenser, and then use the other hose to exhaust that (now quite hot) air back outside.

A one-hose air conditioner, however, has to draw the air it will use to cool the condenser from your already-cooled living space. That air is then blown outside through the one hose, and warm outdoor air will flow into your living space (through cracks/etc) to replace it. This represents a significant loss of energy and efficiency, which will reduce the overall cooling capacity of your air conditioner and require that it run longer/more frequently to keep your living space cool. In other words, it both wastes energy (which is expensive) and makes your air conditioner not work as well.
posted by Juffo-Wup at 1:40 PM on March 16, 2015 [2 favorites]

A proper two-hose portable air conditioner will work the same way; it will use one hose to pull outdoor air in, pass that air over the condenser, and then use the other hose to exhaust that (now quite hot) air back outside.

You're absolutely right. I've since found the manual in our file o' electronics manuals and related receipts and stuff. Turns out it was indeed using both hoses in AC mode.

Obviously, that's why it worked well and kept us cool.

This was what we had, and it worked well. Looks like that one's discontinued.

But the articulated hoses did end up cracking a bit over time, so the foil tape solution Room 641-A suggested is spot-on.
posted by mandolin conspiracy at 2:06 PM on March 16, 2015

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