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Hacking Portable Air Conditioners (pmarks.net)
344 points by p1mrx 6 days ago | hide | past | favorite | 240 comments

Very interesting video from Technology Connections <https://www.youtube.com/watch?v=_-mBeYC2KGc> "Portable Air Conditioners - Why you shouldn't like them".

I watched that immediately after buying a portable air conditioner. Thankfully, too, because I think he oversells the inefficiency and effectiveness of portable air conditioners. It's very easy to leave that video thinking you shouldn't bother with one, but the reality is that they're actually pretty damned good machines. Window-mounted units are marginally better, sure, but if that's not an option or you live a place that doesn't stay hot for very long, then they're fine, your electric bill is just a little higher. Which is fine for me because there's two months out of the year I need A/C and the alternative is a fan.

I think you’re talking about a different device. Portable swamp coolers provide zero value in high humidity areas.

The linked video isn't the swamp cooler video (which is something TC also talked about recently).

> but the reality is that they're actually pretty damned good machines

... if you ignore the energy consumption, which is the whole point of the video.

Marginal energy consumption is ignorable

We could probably use some numbers here.

It varies by device and local conditions, but for single tube units a 50% loss in efficiency is not uncommon. In the worst case the air your sucking into the room is extremely humid and you waste a lot of energy constantly condensing water only to then heat that same air and blow it out the room.

Living in a hoa that is loaded with some weird rules... I'm stuck with a portable as traditionals are not allowed. As per noise this was a happy find overtime. A dog of mine developed thunder and fireworks issues. The noise of the ac running helped filter out the thunder/fireworks. Eventually I gravitated towards something more powerful and a bit more expensive and did some self adjusting to the machine bypassing the temperature min so to have the a/c just run continously when I needed it to. This means a room that is typically 51-52ish.

I knew someone that had an HOA rule against window air conditioners. His solution was to keep the window-mount unit inside his bedroom, with the back end (that normally sticks outside the house) enclosed in a box. That box had an intake and exhaust fan, with flexible duct work that routed to a piece of plywood stuck up in the window. From the outside, you just see the screen with the plywood on the other side. But it worked about as effectively as if the whole unit was mounted in the window.

What kind of toxic VOCs do these units give off?

Celsius? My perfect temp is ~70 farenheit

51-52 Celsius would be heat-stroke territory.

51 Farenheit is pretty darn cold and would be insanely expensive to keep up in the South. I always forget the conversion (never use Celsius) so assumed it was warmer, but not insanely high. My apologies lol.

yea. its pricey. i make up for the cost in the winter cause i dont run heat that much which. basically the min for preventing pipes to freeze. which is fine cause i like it cold over hot. ideal weather is mid november fall day. though seems like thats been fluctuating more towards december.

Not sure where you're from, but 41-42°C would be heat stroke territory to me. (I hide in cooled buildings if it's >30°C outside.)

They're pointing out that 50C is not really a liveable temperature so by definition "a room that is typically 51-52ish" can not be celsius, especially not as this is with AC given the context.

That much was clear, but 50C is well beyond where heat strokes start to be a thing, so it sounded weird. Perhaps they're from a place like saudi arabia where there are populated places and it can actually ever get close to 50°C? Hence my remark.

The A/C in an apartment I was living in in Texas failed one summer, and the management firm put one like that in my bedroom temporarily.

Noisy and inefficient is a good description. Granted, it had to run off a regular 15A outlet so it was never going to be as powerful as the one in the attic. But it made sleeping possible by getting the temperature below 85F (30C).

It's a fantastic video, and the guy explaining it all has a natural talent for teaching and dissecting things. Thanks for sharing it!

After watching that video, I decided to relocate my portable air conditioner. The exhaust tube is now super short, directly mounted to a hole in the wall, and insulated to compensate for the inefficiency of these type of devices. It made all the difference.

>Very interesting video

The content might be interesting, but it's way too long. The guy goes on way too many tangents and adds way too much filler. You probably can boil the whole video down to a few bullet points, yet it's 16 minutes long.

On the other hand, I like his long-form video entertainment. I'll eat lunch while watching one maybe. Not everything needs to be optimized into bulletpoints.

I had a deja-vu, I thought I had read this exact comment before in HN. Have you used the same words before?

His long format is very much the point. There’s countless quick format high quality channels out there for this stuff too!

Watching his videos reminds me of university and being in a really high quality lecture or lab session.

These TC videos are meant as a kind of entertainment. I enjoy them a lot but they're definitely not meant as a quick reference.

That's kind of the point though. It's a style and delivery method that makes the content enjoyable. A few bullet points could be broadcast via text+image alone, but that isn't the same thing.

They're intended as entertainment and not condensed informational videos. They're meant to be an exploration into the topic.

Have you considered the possibility of not watching it?

I know I'm old because I immediately thought back to how in my day, my parents complained that kids got bored after 45 minutes or so. If you don't have the patience to watch a short YouTube video, then that's really a personality problem that lies with you, not the video.

Youtube prefers long videos and it returns higher monetization rates because it's "user engagement."

Look at the hugest YouTubers. They aren’t putting out 30m videos once a month like TC is. This isn’t an attempt to game things.

Also, even his older content also has a long format. Usually between 20 and 30 mins. This was way before the changes that ranked longer videos higher.

Ugh, clickbait title. TL;DW get a dual hose model. Mine was $260 from Craigslist. In the video he even says he uses two portable AC's. He backpedals further in his description:

> Seriously, either we need to get more awareness of how dumb single-hose portable A/C units are, or we need to just use window units whenever possible. While I know that there are times a portable unit is the only option (remember, I’m in that boat), it seems that only very high capacity, premium machines have the facility to use two hoses. Which is frankly stupid but then again that’s what I’m trying to tell you now.

Yes, you "shouldn't like them," unless it's you're only option, like in his case.

TL;DW: get a window mount unit. The two hose models are still extremely inefficient.

Portable AC's exist because window units don't fit in sliding windows and you can't move them from room to room. That's the point of being portable! Believe me I'd love to be able to buy a $50 used window AC like I did in college if it fit my window.

In the video, the guy says he owns two portable AC's. So there's that.

> because window units don't fit in sliding windows

Also, don't forget the ever-popular "apartment building doesn't allow anything protruding from the windows" rule.

Someone ought to make a reverse window unit. It would be like a regular one but hanging inward instead so it doesn't protrude. Supporting the weight might be a challenge but solvable with some legs or maybe angle brackets.

Of course it would take up more space and be louder than a regular window unit, but at least it wouldn't require hoses. Plus it could drip condensation out the window through a short tube.

The whole point of a window unit is that the very hot compressor is outside the room you're heating. Without that, you may as well get a portable unit.

That's not a insurmountable problem using a bit of insulation and careful design.

Still just inventing a portable unit at that point.

But one without hoses, with less heat dump into the room, and alternative mounting.

the compressor makes heat in addition to being loud. Thats the other strike against portable AC units. The compressor is heating up in the room you want to cool

Midea has a u-shaped unit that won some awards.

The compressor and radiator are outside. A section a couple inches tall contains the pipes, wiring, and braces. The fan, blower, filter and thermostat are in the front bit. Your window panes (hopefully double glazed or better?) and a couple inches of foam provide the sound dampening. The lowest displacement model claims 47dB with the fan and compressor at full bore.

These exist, usually an off the shelf through-wall AC unit with custom built sleeve and legs. You can see them (or not see them) in some of the landmark pre-war buildings with strict facade rules.

Thanks. Today I learned that window ACs and wall ACs are different things even though they look extremely similar.

For anyone reading this, presumably because windows are thin and walls are thick, window ACs are expected to stick out and thus have vents on the sides, whereas wall ACs have vents only on the back surface.

So as long as you figure out drainage (so condensation doesn't just land on the windowsill), you can install a wall AC in a window and have it not protrude.

This is a thing? I've lived in many apartments (moved yearly for a decade) and never heard of it.

Yes. My apartment building in SF was part of a landmark legal case because many units stay over 80 degrees for large portions of the year due to poor consideration of solar factors. Usually only builders are sued for defective construction, in this case the architect was sued due to poor design.

We received funds but the funds were not enough to retrofit a 600-unit building with central A/C. However, the city of SF will not permit wall-mounted mini-split units nor window units in the building, since that’s a change to the facade. So we’re stuck with portable units...



They'll be really annoyed when everywhere is flooded because they were wasting power, that'll change a lot of facades

Same here. My apartment windows only tilt upwards, so there was no way to use a window mount. A portable unit was the only way to go.

But I created a wedge-shaped mount for the hose ports that fits in the triangular window gap exactly, so the room is still relatively sealed. When summer is over, the mount is disassembled and stored flat.

I've never seen anyone else do this. I've always hated the look of hoses dangling out of open apartment windows and of course that's terribly inefficient. Every time I see our windows from the outside I'm rather jazzed at how great-looking the solution is.

I wish it was just code to have mini splits installed in every apartment. They're straight better than other options at both heating and cooling, and very affordable these days.

Can't say enough good things about my Mitsubishi split unit, installed a couple weeks aho during kitchen reno. It's quiet, efficient, powerful, and highly configurable / programmable.

I recently scored major points with the in-laws by convincing them to get a mini split for $800 instead of a window a/c-heater combo. Their place stays much cooler, and their electric bill went down by $125 last month.

Mini splits are fantastic. My experience from them has been from every home / small store I've ever lived in or visited while in south east asia. Window units can be annoying because of the wind they produce while I've never had issues with former.

Can you please take a picture of your setup? I’ve considered this before myself, but I’d say the barrier is people’s “imagination” around the design.

Send me an email (see profile)

You can fit it in a sliding window. Go to the hardware store and buy a sheet of 1-inch thick foil backed insulating styrofoam. Cut it to fit perfectly above the AC unit.

I don’t understand why we don’t have a vertical AC unit. I think they are just too used to making them square. Might have something to do with constructing the radiator. Or habit.

If I go and look up some numbers, I see things like EER of 12 for window units, 9 for a single hose, and 11 for dual hose. Close enough.

Anecdotally having used both a window unit and a dual hose unit with technically the same BTU (using the new adjusted measurements), the window unit is still night and day better. Not having massive heat radiating tubes and a large electric heater in the same room as you is still a big win.

Widely reported and occasionally video recorded anecdote.

If you live somewhere temperate the single hose will cool from low 70s to 62 in a bedroom for less money/eyesore.

I have central air and I keep my place at 77-80. I would have to wear a sweater if the temp was below 70.

Perception of temperature depends on more than just the temperature - there are other factors. For me, in winter 74 is hot. In summer, 74 is just right - sometimes a bit cool. The level of clothing is the same in both cases. Even within summer I've found quite a bit of variation in perception for the same temperature. A sunny day and a cloudy day feel very different at the same temperature.

I once went hiking. I checked the forecast and the maximum was 72. Great! I almost had a heat stroke - very bad day. I confirmed later that the temperature was not higher. And I've hiked at warmer temperatures just fine.

This is why when I buy a car, I want to make sure it's trivial for me to adjust both the flow of air and the level of cool/heat independent of each other, and not rely on the temperature setting. Almost all cars let you do that these days, but there was a period where some cars did not let you do that. Having a thermostat and letting you maintain a temperature is really not much of a feature if the variance in the "right" temperature is too large.

BMWs have long had a feature that takes these temperature concerns one step further–a knob that controls the vents blowing towards your face, which works independently of the main climate control. So you can set the overall temperature you want for the car, but fine tune the air that you feel most directly. It’s a small detail but something I really appreciate.

It's 75 °F at 67% humidity in the house right now and I can't imagine running an air conditioner to sleep. It will continue to cool off and I'm sure I'll run a fan.

Typically we get just a few days where it stays over 80 °F with high humidity, so I guess it isn't particularly adaptation.

I'm impressed as hell that the customer service guy and engineers at the company were so willing to answer technical questions!

It looks like Edgestar is a company that makes a pretty wide variety of HVAC equipment and prioritizes support. That makes a lot of sense for larger orders, especially for a design/build company. I love finding these kinds of companies, that focus on customer service. It's what made Amazon so special, at least back in the day.

Anyone else know of other companies in this vein?

A few that I go out of my way to recommend: Logitech, Fellows, Dyson and Breville.

Each has just straight up sent me a new unit or full replacement part when the previous one failed with no rma or warranty check - none of that nonsense just great service. Dyson support even sent me full factory service manual for the unit 5 years after it was discontinued (and 7+ out of warranty) since I wanted to troubleshoot a power supply issue which ended up working fine after resoldering the main power cord to the power board.

These companies are increasingly rare.

I had the opposite experience with Dyson. A $350 Dyson vacuum I bought stopped working a month after I bought it. I determined that a faulty battery was to blame. When I called customer support, they tried to sell me a new battery (I forget the price they quoted me, I think it was at least $50). It was only after I protested that they agree to send me a new battery for free. I got the strong impression that their company policy was to first try to sell a replacement part to take advantage of rubes; only if the customer refused to pay would they offer a new battery for free. Really disappointing quality and service from such an intensively marketed brand. It was especially annoying since the vacuum came with this pompous little booklet about "the Dyson story", how Dyson represents British engineering at it's finest, etc.

That's really too bad - my own experience was with a dyson DC21 canister that I bought in 2008 - after 6 years the power head started intermittently turning off while cleaning. They sent an entirely new power head no questions asked. It kept working for another 6 years without any other issues, then it just refused to turn on one day. I called and asked if they could service it and they said sadly the unit was discontinued several years ago but that they could send me the factory service manual and that the issue was likely with the connection between the reeling cord assembly and the main board. Sure enough, I guess reefing on that cord for 12 years caused it to come loose - 30 minutes later it was back up and running and I still use it to this day. Worth noting that this thing still cleans as strong today as it did back then. Perhaps Dyson Canada is different than US - I've seen a LOT of refurbished dysons on various marketplaces so I'm guessing they are not flawless - the fact there are so many refurbs however leads me to believe they are exchanging them without asking questions and that they are quite serviceable.

> These companies are increasingly rare.

Even more so as the existing one are moving away from it, the logitech of today seem significantly worse than the logitech of 10-15 years ago for instance.

Had an issue with my headset after 3 years and they shipped a new one out at no cost to me without any return required.

> Dyson

Interesting! My AM11 fan started screeching and making a strange noise so I called in and my warranty had expired just a month ago and all they could do is replace my unit with a refurbished one.

Sounded fine to me, especially because it was out of warranty, officially, but the unit that came was a different color and cosmetically in horrible condition, much worse than the one I sent in.

At least it didn't squeak or screech and I suppose the fact they even helped out outside of the warranty period is nice.

The trouble with Dyson is low quality parts and build quality in some of their devices. They sell because of amazing marketing.

I had a similar experience with a SunSaver solar charge controller. I was out in the field trying to fix a problem with a solar power supply and I called into their support line to ask about the error lights we were seeing. Within a few minutes, I was talking to an engineer and he spent 15-20 minutes helping us diagnose the problem. It turned out to be something dumb we had done triggering a fault mode in the controller. The controller itself cost less than $100, so we were definitely not worth his time.

> The controller itself cost less than $100, so we were definitely not worth his time.

That's not really true from a design perspective. You really want to know what sort of problems your customers are having in the field. And you don't know really unless you talk to them.

Or connect your product to the internet

Unless you have VC's breathing down your neck to spy on your users so you can sell their data. Or you have VC's trying to force your users into a reoccurring revenue model. You don't want to deal with that for hardware.

You want people to install the stuff and have it just work. 'connected to the internet' is something that fails all the time.

You need to check your tinfoil hat, because no one cares about your air conditioner use data or fault codes.

Connect to the internet is another point of fail that's likely to increase your support calls.

One you leave software as an exploitative service or the customer is the product, which most of the stuff people here work on. And enter the world of hardware that solves peoples real problems you want the customer to install the stuff, have it do what they expected and thus NEVER CALL YOU.

I was going to say the same thing. The idea that the customer service rep actually has the ability to talk to product engineering is pretty incredible.

In 2005, our customer care center was taken offline by a severe hurricane. Software developers, product people, and marketing staffed a temporary call center until the center could re-open. It was eye-opening for me to take customer calls and try to solve them with just the care tools. You can learn an incredible amount by letting/making engineers and product leads talk to customers.

What company is this?

Vistaprint. Looking up the details, I think it may have been Hurricane Dean in 2007, not 2005.

I wish there was a site that allowed you to reviews products on things like this

This is interesting. We collectively spend _so much_ of our energy on heating and cooling buildings, and there's very little change happening.

The problems identified in the article are such low hanging fruit. Everywhere you look in residential housing there's huge efficieny gains to be made, but very little effort is going in to making them.

I'd love to find ways we can use technology to make housing more efficient. We need to - it's such a crucial pillar in dealing with climate change, and the vast majority of housing is so comically inefficient. The single tube air conditioners mentioned in the article are just the icing on the cake of all these massive energy wastes we accept because they're marginally more convenient. Does anyone know how to fix this?

>and there's very little change happening.

There's honestly a lot happening and changing. Obviously you won't see it by buying "HVAC" junk from a box store. What this person should have done is paid an actual HVAC tech to install a ductless mini-split [0]. It would have been a heck of a lot more efficient. He states his one unit is drawing 10 amps (110 volt I assume). Whereas my american standard 4 ton (48,000 btu) unit draws 10 amps as well (240 volt) and cools a 2200 square ft house in 100+ degree texas weather with an electric bill usually not higher than $120 per month (1200 - 1400 kwh or so).

By comparison, at my old house (which was half the size, 1100 sq ft) with a much older 12 Seer unit, my electric bill was regularly over $200. I measured that unit at drawing 18 amps (at 240 volt) and it was only a 3 ton 36,000 btu out door unit. The latest and greatest 21/22 seer units are even more efficient than my current one mentioned above (which is probably only 17 seer).

[0]: https://www.americanstandardair.com/products/heating-and-coo...

One of the biggest reasons portable air conditioners exist is for apartments. It's something anyone can buy without having to get permission from their landlord to make modifications to the property. So I would not compare them directly to anything that cannot be installed by a tenant without additional permission.

And landlords have no incentives to install one for you. That's where regulation steps in (in normal countries)...

Installing a mini-split would be a year-long project, including HOA negotiations, architectural design, electrical load calculations, city permits, and invasive construction. It's not the sort of thing you'd want to attempt at the beginning of a pandemic (or ever, for most people.)

Given the orders of magnitude less work required to find a product and click "Buy", it'd greatly benefit society for portable A/C manufacturers to compete on efficiency.

> a year-long project, including HOA negotiations, architectural design, electrical load calculations, city permits, and invasive construction

Obviously only you know your situation, but just in case any other readers are considering a mini-split: it doesn't have to be this way and it typically isn't.

From firsthand experience installing Mitsubishi mini-splits in multi-unit buildings in very regulated cities, a typical condo installation takes 2 days, including running power from an electrical panel that's not in the unit. A reasonable HOA can often answer in a week or two unless you're the first person to install a mini-split in the building. Larger buildings often recommend specific HVAC contractors. Your contractor will apply for HVAC and/or electrical permits online with very basic drawings; they're often issued immediately ("over-the-counter"), subject to field inspection. There's generally one inspection after it's installed. A good contractor will handle almost all of this.

Basically, it can be complicated but it doesn't need to take a ton of calendar time. Other than cost and needing outdoor space for the condenser, the hardest challenges you & your contractor will encounter are running new electrical circuits from the panel and draining condensate from the indoor head.

> are running new electrical circuits

Why is this needed? Is it because the electricity in the US is at 120V? Over here (Europe) you can just plug the cable from the indoor unit into the electrical outlet.

I learned recently that US housing generally gets 240V, but most circuits use neutral and a single hot to get 120V which is the standard mains in the country, and you'd run dedicated 240V for large appliances e.g. furnaces, dryers, electric oven, induction cooktop.

The AC would not have been planned for when designing the original circuits, so you would need to add a 240V circuit for it unless you put it in a room which already had one.

As the others have noted, since it's a high-power unit anyway you'd really want to have it on its own circuit to avoid adding too much load on the circuit. So even in europe you probably want a circuit exclusive to the AC, meaning you may have to run a new one unless an AC circuit had originally been run "just in case" (and even then it might not have been run to the room you wanted it in e.g. maybe the original builders put the circuit for an eventual AC in the living room but you want it in the bedroom you converted to a study).

Depends, the lower btu units can plug in to any outlet, but even in Europe you can only get so much power.

Regardless, ac draws enough power that you want it on a dedicated circuit no matter where you are. Sharing that outlets with anything else is likely to result in annoying breaker trips when you overload the circuit.

bluGill answered this well. To add a little: the total load of all but the smallest systems (9/12k BTUs/hour) is too large for a typical 15A @ 120V circuit, so most outdoor units need 220V. That means a new circuit. Also, building code in the US typically requires a shut-off box right next to the outdoor unit.

At least in the US, many systems power the indoor unit(s) from the outdoor unit. My guess is that since a control wire is required anyway (for central control of fan speed and direction), the manufacturers think it’s easier to power everything from one run.

This is ridiculous nonsense. A mini split is basically the evaporation coils mounted on the wall and a hole cut to the outside for the refrigerant tubes to run. It would be nice to have it on its own circuit, though a 20 amp circuit might be able to just have it added on. That's pretty much it.

Mount it like a TV, cut a hole in the wall, hook up electricity. No architectural designs needed. I'm not sure who told you that, but there are dozens of DIY youtubers who must have gotten free split units, because there is a flood of videos of people installing a precharged version with only themselves and a helper.

The actual work of installing is a day labor. The pre work to get the paperwork in place so you are allowed to install it can be over a year.

I don't approve of the above, but that is how it is.

I don't think cutting a small hole in between studs requires "architectural design" and "electric load calculations" really means "it uses this many watts". There is nothing typical about someone needing a year to do something relatively simple. Most restrictions probably just say that the condenser coils can't be on the side that faces a street and maybe that it has to be on a dedicated circuit.

You would think, but California is a weird world where often it does take that long.

Both of your comments are basically saying 'this is true' and saying 'this is true' again. Do you have any sources or even reasons why installing a split unit air conditioner in all of california 'often' takes a year?

A year long project to install a mini split? Wow.

Split systems are the norm on my continent, and most can be installed in well under a day. Many installers can do multiple per day into existing dwellings, code compliant, filled, sealed, and on a proper circuit. Units/Apartments are likely to take longer.

All depends on the locality, etc.

Many people don't understand the world of stupid they've joined when they buy an HOA property. Although I have to deal with the psychic trauma of a neighbor who doesn't mow often, living in a reasonable city on a normal block means that permitting nightmares and other bullshit don't really exist. :)

Lawns are really bad for the environment in many ways. A front yard that's all native plants both looks better and produces a healthier local ecosystem.

Hoa claims “we maximize the property value” which I don’t see how they say with a straight face.

At best they achieve a local maximum nowhere near the potential, while costing a mint in fees and preventing one from doing anything crazy like planting native plants in the front instead of grass or not painting your house the right shade of beige.

Working with refrigerants is not that hard. A lot of sailors fix their own fridges in middle of nowhere.

Building code for electrics is probably your largest problem. But then some places you can't even change a damn light bulb.

It'd also greatly benefit society to make the more efficient solutions more accessible (e.g. by reducing permitting requirements, preventing HOAs from regulating them, ...)

> including HOA negotiations

Yah done goofed.

HOAs are rather necessary for condos. When multiple people own a building, some entity needs to manage the common infrastructure.

Surely the US style HOA insanity is not necessary for condos, as demonstrated by the rest of the world.

If an HOA is being an obstacle to ordinary and customary improvements to the property you in theory own, you goofed.

In general if you bought a condo, you goofed.

The go by different names, strata, coop, HOA, condo, but they exist all over the world to manage the shared property.

> What this person should have done is

You can't say what somebody "should have done" without knowing a lot more details about their life.

Mini-split looks like a good design, but our landlord would not be happy about our leaving behind a 3" hole in an exterior wall.

If you have a good relationship with your landlord (and intend of staying some time), might be worth discussing collaboration and leaving the AC when you move? A unit with AC would command a higher rent for the next tentant.

Through wall designs, like you see in cheap motels, require an opening in the wall.

Mini-spits have an outdoor unit and an indoor unit connected by two hoses. The indoor unit basically screws to the wall. You do need a hole through the wall for the hoses but that's it. As a result they are cheap to and quick to install. They are also very efficient.

> You do need a hole through the wall for the hoses but that's it.

That's what they're pointing out. It's not a huge hole but it's still a hole going through the wall, and if they rent and buy the unit with their own money they'd be leaving with it, leaving that hole in the exterior wall. 3" is probably on the upper bound of what you need but it's not wrong. And it's not like the landlord would be much happier with a 2" hole.

Yeah, he should have just spend a few grand on a mini split system to stay cool for one summer at home. Makes sense.

Why do they cost so much in the US? I can buy a decent split unit for $400-$500 + around $150 for installation.

Installation will no doubt be more expensive in the US, but there is no reason for AC itself to be (if anything, most kinds of hardware seem to generally be cheaper in US than in Europe).

Largely because we have an HVAC cartel that charges insane hourly rates for even the simplest jobs. To be fair, a Mitsubishi mini split is going to run closer to $1200-$2000 for the unit itself, but you can expect to pay $2000+ to install on top of that, depending on how hard the job is.

I suppose it's hard to complain too much. HVAC installers need to have some decent technical background, troubleshooting skills, and their bodies tend to get injured/broken by the time they're in their late 40s like most manual labor trades. A HVAC installer/tech can make $80K or more a year, which makes it one of the few jobs still out there where you can make a decent middle class income without tons of schooling.

> you can expect to pay $2000+ to install on top of that, depending on how hard the job is.

Installing a mini split is nowhere the difficulty of an HVAC though, assuming your have the electrical circuit (which I'd guess would be an electrician's job not HVAC) it's a few hours' work, at least for a simple case and if the installer knows what they're doing: pierce the wall, mount the external unit, mount the internal unit, connect the two, charge[0], done.

By "simple" I mean a 1:1 setup with both units mounted on the same wall (and a wall-mounted indoor unit). Obviously a more complicated setup (multi-zone, slim duct, more distance between the two units) would take more time and be more expensive.

I can see $2000 for a non-trivial multi-zone setup.

[0] if you're handy there are mini-splits sold specifically for DIY installations which come pre-charged, though that means the pipes won't exactly fit the distance I guess

It's essentially the same (unless you use one of the DIY kits with pre-charged lines) as a full sized split system (traditional AC unit.) You (should) pressure test your lines and vacuum them out before releasing the charge. You also have to get a create a really good flare connection.

In addition, running the electrical is usually done by the HVAC company and setting up the mounting pad for the outdoor unit.

I completely agree that it isn't rocket science, and it's well within the realm of a skilled DIYer with about $250 in specialized tools. However, I can see why an HVAC company charges as much as they do. For an average install (not dead simple), it's probably 5-6 hours of labor, they have to pay for the company equipment, vehicles, health insurance, permits (my township requires one for a mini), taxes, etc.

That's interesting, I see some lower-end Mitsubishi models for $600 here.

Where? The prices for AC that I've seen in Germany were >1500 EUR, plus >1k for installation.


Fwiw I was told I needed to get a permit and have a 220 line ran to install a mini-split in my house. That hassle put it out of contention for me and my not be an option for people renting.

You'll need to run some kind of line for any kind of mini-split. Seems kinda moot point if it's 220 vs 110. Anything that isn't removed and evidence of install hidden within less than a day is probably not going to be doable with a rental.

> The single tube air conditioners mentioned in the article are just the icing on the cake of all these massive energy wastes we accept because they're marginally more convenient. Does anyone know how to fix this?

I'm using one of those portable units because I live in a rented apartment. There is nothing convenient about it compared to a much more efficient real (split) AC, but I have no other options.

Even if the landlord was OK with allowing it, "green" laws intentionally make it incredibly tedious and expensive to get the permits to install an AC, so people swarm to the option they can get without paperwork.


Builders spend money on things that make them profit and home buyers don't particularly evaluate efficiency.

After that you figure out how to spend public money on lower efficiency structures. Fraught, but spend money where it's likely to pay off and it probably works out okay.

The minimum standards for a portable AC should be a dual-hose one. Single hose ACs make no sense; it is like throwing a lot of efficiency away, just to look a bit sleeker and a very slight increase in installability and mobility.

Also who in their right minds in Europe decided to rate single hose AC at A+, or A efficiency levels; the same as a good split AC? Single hose portables should all start with an F to educate a potential customer as to how dumb this device design is.


I want to buy dual hose, but no luck so far. They are just not sold...

I'm pretty sure the ones listed in the article are on Amazon. I bought my Whynter ARC-14S from Amazon. It's very loud, but it gets things cold. They're not cheap.

edit: loud like air-whooshing loud, not like vibrating compressor loud.

Not in germany :)

Perhaps they are giving the same ratings because, actually, the efficiency difference is not that significant? Or do you think they are handicapping the ratings in some way?

I keep it that I can find no difference between operating in with one or two hoses myself https://news.ycombinator.com/item?id=24025482 .

Split units and hose-based portables are rated on different scales afaik.

100% agree. In summary, in my stupidity and ignorance I got one of those units for the office with my boss' money, whereas I could have had a passively cooled working place. If all of those units were labeled F for Friggin-retarded-noise-and-cooling-levels, it would have made me look into alternatives, because I did totally look at the energy label and noise level and the vast majority was very similar. I figured this was as good as it gets.

Non-summary version:

In the office, the sun bakes the roof to make our rooms a good bit hotter than outside, open windows or no. I was there for my interview on one of the hotter days that year and decided right then and there that either the company was going to buy an AC or I was. It ended up being the company, but I was fairly insistent about needing one so the money was kind of spent for me. If it had been my money, I'd have considered it a sunk cost and good lesson.

It took about one day of using the device for me to start to wonder about its working principles. I mean, I roughly knew: I own a fridge after all. One side gets hot and you cool it with air that is then blown outside; the other side is cold and you use it to cool air that is then blown into the room. But I hadn't really thought about it until after we owned one:

How can this thing have only one hose? What is the air that it blows out replaced by?

I asked that question out loud in the office and, yeah, given that it only blows hot air out, it must be creating negative pressure in the room and basically sucking that hot outside air back into the room. It's nonsensical. I even sketched out for a friend how it should work instead because they didn't get my issue. Turns out I reinvented the dual host system (which I never heard of until today).

To make matters worse, the ground floor apartment I moved into at the same time as starting to work there is amazing: it remains 22-24°C during the summer, also after 2 weeks of 35+°C outside (thick walls and shaded from the sun; no air conditioning involved at all). I didn't know that was possible.

If I had known that it would be fine to work from home for a few weeks per year and that my apartment would be super cool (literally and figuratively), I would never have insisted on some kind of air conditioning to try and counteract 20kW of sunlight[1] hitting the office windows and roof. I could have saved a ton of power/CO2 and quite a bit of money. To make matters worse, we didn't use to be under the roof, we used to have only morning sun through the windows. It was only slightly cooler than the new place, but this unit could actually manage to cool the room down.

But now we've chosen this course and I feel too guilty to say that we should just consider it a sunk cost, I'm not going to use it, it's so loud I can hardly concentrate, and I'll just work elsewhere during the hottest weeks. Can't do it. Recently, one of our smaller windows was replaced with some insulated plates with a hole cut out exactly for the AC hose in an attempt to make it work better. I think it does work better because it's less leaky than the flexible thing we had before to put in the window crack, but it's still a huge waste and we keep sinking money into this shitty "solution".

I don't even get it. Like, how hard is it to put a horizontal piece of foam in the hose and have the dual hose system in one hose? Make sure the hot side is on top and put fins at the end of the top half to make the hot air be blown upwards. May not be as efficient as having them be in separate hoses, but wouldn't that be a lot better? It's also not as if you'd be putting cold air next to hot air: it's about the already-hot outside air that would be running alongside the slightly hotter waste-heat air.

[1] https://hypertextbook.com/facts/1998/ManicaPiputbundit.shtml 1.4kW/m² multiplied by an estimate of window and roof surface area of the single room that the AC is in.

Hell, even if it's a larger expense, for an office which regularly gets very warm for extended periods of time you bite the bullet and get a proper reversible heat pump. That way you have proper AC in the summer, and lower heating costs in winter (or if winters are so harsh the heat pump won't work you at least save some during spring and autumn when the heat pump suffices to keep the office warm).

I have spent a LOT of time researching using a small window AC unit converted to work in a camper van without cutting a giant hole in a wall. There's a fellow on Youtube[1] that did this successfully, and he's the only known example of it that I've seen, and he was only able to because was he a professional HVAC technician and had several unique tools you'd never own if you weren't an HVAC tech.

Essentially what I'm aiming for is this: https://www.cruisencomfortusa.com/hd-series

which is a perfect product, except that it costs $4000 and still uses 20% more power than some of the smallest window units. It's ridiculous that the major difference between this $4000 unit and a $150 window AC is that the $4k version has a rubber hose connecting the compressor to the condenser coils instead of the typical thin copper pipe. I am sure there are other differences - it uses better components that are more suited to a moving vehicle with shocks and vibrations, has a strong compressor to deal with the longer hose length, and is already adapted to run off of 12V. But a $3850 price difference is ridiculous.

As the fellow on Youtube has shown (it's been in his camper van for years without a problem) there's really no reason the components from a $150 window unit won't work.

Whenever I finally do a camper van build I'm going to find an HVAC tech who can help me with a couple steps (mostly removing and then re-adding refrigerant) and convert the copper pipes to PTFE lined stainless braided hoses attached to SAE fittings. It may not work, and I've heard finding an HVAC tech to work on weird projects is very difficult, but I want to give it a try.

[1] https://www.youtube.com/watch?v=AXgHIrFqm9o

As a former HVAC tech assistant, I can say that you'll easily find a tech to help you out if you pay them enough.

That said, refrigerant removal and reinsertion is regulated now and it's somewhat of a pain to do properly even with the right equipment.

Good to hear, and I'm glad to leave the refrigerant stuff to the professionals.

could use a junk-yard AC system as it's likely already been drained, would be pretty standard to refill with automotive product too.

What about the mayor bloomberg route? https://m.youtube.com/watch?v=P5vJWHMlHHg

A lot of camper vans do this - it just looks awful, destroys any stealth value, has to be moved in and out of the opening any time you start driving, and takes up a ton of internal room when not deployed.

Wow, talk about having an axe to grind. That story simultaneously complains about it as a waste of money and says that he's rich so he can/should afford something sleeker.

This might be a stupid question: couldn't you just modify the AC unit already in your van to run off whatever power source you wanted to run your window unit off of?

Not stupid. The problem with most full sized vans is the ac compressor is run off a belt. Not totally insane would be add a second compressor and a three way valve. I've never heard of someone doing that. It's more common to use a RV rooftop AC unit.

Some newer passengers cars and maybe some vans use electric motors to drive the compressor. And EV's tend do that as well. In the EV case no mods are probably needed. Electric vans though are just becoming a thing and have low range and high price tag.

Yes but the issue is power consumption. The idea is to run the AC off solar and batteries which is why the rooftop option doesn't work either - they use a buttload of energy. The AC systems in vehicles consume a ton of power to operate which is typically why they're belt driven by the engine directly. The all electric version in a Tesla uses around 3000 watts if I remember correctly, while a window unit use about 450.

> The all electric version in a Tesla uses around 3000 watts if I remember correctly, while a window unit use about 450.

Surely the 3000W unit will use 3000W when running full tilt and will cool significantly more and faster than a 450W window unit, and would achieve the same cooling as the 450W unit by only running about 15% of the time? (or at 15% power if it's an inverter AC).

I know someone with a Home Depot residential style mini-split mounted on the back of their cargo trailer RV conversion. Probably too much for a van, but no huge hole in the wall.

These unfortunately have absolutely awful reviews everywhere. It's impressive it's lasted as long as it had for him. I believe the manufacturer stopped making these because they suck so bad. They also aren't designed to be serviced and would still require a lot of hacking in the same way a window unit would be

The magic product the writer is looking for does exist — somewhat. It's those Euro style mini-split heat pumps, that pump coolant through an external unit.

Up front cost is higher, but the efficiency gains are huge, and they can cool/heat much faster.

> Euro style

The only place in this wide world I’ve seen anything other than split units is North America, so “Euro style” seems an odd description.

That's accurate: they're the standard in much of the rest of the world due to their lower operating costs.

I was using "Euro" only to help people picture the things, it's a common way I've heard them described.

These are standard in Southeast Asia too.

More than standard, they're basically universal. I'm surprised and shocked it's apparently a rarity in the US.

Is it because HVAC is so common it usually makes sense to plug the AC in the HVAC, and the rest of the market is basically leftovers which get to have window units or crappy portable air conditioners?

Pretty much. Central AC is the default in regions of the US where you really need AC (which is most of the south and west, places that people didn’t really settle in large numbers until post WWII - among other reasons, because AC hadn’t been invented and the climate there is oppressive without it).

In the northeast where buildings are generally the oldest in the country, window units are common - especially in rental units, because the tenant typically provides the AC themselves. One less thing for the landlord to maintain.

The northwest, for the most part, doesn’t use AC much with their climate. Many homes don’t have AC at all.

Mini-splits are becoming more and more common in big cities here now, but only if you’re lucky enough to own a place and you don’t have landmarked facade problems. I’d love to use one instead of my window units, but I rent a street-facing apartment in a landmarked building. Even if I could get my landlord to approve me paying for a mini-split to be installed, I couldn’t put anything outside. The commercial tenants in my building have mini-splits, but they have access to a side of the building which doesn’t front onto the public street, so no landmark concerns.

(The fact that many landmarked facades have a random collection of window ACs hanging off the front seems much uglier to me than a bunch of professionally-installed identical mini-splits compressors would be, but, c'est la vie...)

Anybody got an example of these?

Of a mini-split? https://www.fujitsugeneral.com/us/residential/what-is-a-mini...

It's the the large horizontal vents protruding from the wall you see in pretty much every low-rise (2-3 floors) residential buildings ("apaato"), or if you go to the back of the building you can see each flat's external unit, generally wall-mounted next to or below a window.

They're almost all reversible heat pumps, though their heating capacity tends to be lower than their cooling capacity.

Note that mini splits can also use a more discrete slim duct (as the link notes), but in my experience the wall mount is by far the most common, as that's way simpler and more convenient for multi-unit buildings.

These are called ductless air conditioners in the U.S.

Years ago I bought a used (portable) evaporative cooler for $25. When the temperature is not higher than, say, 85F, it is very effective in the day. I do not live in a dry climate. During the day it's 20-50% humidity, and gets high at night. It's clearly a lot less effective at night, but it's usually cool anyway at night.

Window air conditioners work great, but if you can't have that, consider an evaporative cooler if you can get one at a decent price. Do make sure you get one with a decent air flow as well as a decent sized tank (e.g. one where you can run it all night without the water running out in the middle).

Probably won't work well in humid Midwest or South/East.

Yeah, swamp coolers are great in theory, but they do nothing at all in areas that most desperately need cooling.

They work brilliantly in places with low humidity by high temps - i.e. Arizona, California and my personal experience - towards the middle of Australia.

Yeah they will work nicely in any "dry" desert. They do require access to significant amounts of water, though with the nice side-effect (for the context) that they also act as humidifiers,.

> Yeah, swamp coolers are great in theory

For me, they're great in practice. And I don't live in a dry climate.

I'll do anything to avoid living in a humid place, though. I can take very hot temperatures, but not hot and humid. At least when it's hot and dry I can still enjoy the outdoors.

The places most in need of cooling are those with high wet bulb temps, which are typically high humidity places. I've lived in the south east USA my whole life, and I cannot even imagine adding more humidity to my air.

I bought one for my space in Seattle and it's a game changer. I couldn't get A/C for several reasons, and was really nervous a swamp cooler would do nothing in this climate, but it works great!


- You can (and are supposed to) keep the windows open for air flow. No worrying about closing everything off.

- They're rated for way more square footage than window or portable A/C units (although they are pretty directional). For example, mine is spec'd for 1600 sqft.

- Cost.


- Requires cleaning. Not as much work as maintaining a fish tank, but it reminds me of that :)

> I bought one for my space in Seattle and it's a game changer.

It's funny how when you search the Internet, everyone says "It's useless in Seattle because it rains so much and is never dry."

And yet...

I'm not sure I agree with all your pros, though. I think good brand new ones are quite pricey, and you can easily find used window A/Cs for much cheaper. In my experience, window A/C units work better at cooling, and handle more square footage, but perhaps you simply got a bigger/more powerful evaporative cooler than I have. No way would mine handle 1600 sqft. I assume yours is not portable...?

I grew up on window A/Cs[1] and I think they're the best, to be frank. They cool a room down much better than a central A/C. If you have a decent size house, a central A/C is probably more economical from an utility bill standpoint if you want to cool the whole house. But if I want it as cool as I'd like it, and only want to do 1-2 rooms, nothing beats a window A/C.

But if you want a portable unit, I think an evaporative cooler is much better than a portable A/C. The latter are crap.

[1] They were "window" A/Cs, but were installed in the walls. Unfortunately, few houses are designed with this in mind, and US society has a weird aversion to window A/C's (many HOAs ban them)

I have a model similar to this one: https://www.homedepot.com/p/Hessaire-5-300-CFM-3-Speed-Porta...

It is portable, if a bit large.

The thing about price is: what are you paying to cover a certain square footage? To cover 1600 sqft with a window A/C, you need a 25,000+ BTU unit for $900+. The A/C units in the price range of that evaporative cooler only cover 450–550 sqft.

(Speaking to my situation, I live in a loft that's one big room, and only skylights instead of windows. Thank goodness for the swamp cooler, because even if I made a custom adapter to run a duct up to the skylights, no portable A/C would be able to handle the footage!)

> The thing about price is: what are you paying to cover a certain square footage? To cover 1600 sqft with a window A/C, you need a 25,000+ BTU unit for $900+. The A/C units in the price range of that evaporative cooler only cover 450–550 sqft.

In societies that rely heavily on window A/Cs, people usually have one per room, and the goal is to cool only that room, so a high BTU unit is not needed. They also couple it with a ceiling fan to get an even temperature.

Used window A/Cs are cheap. I'm trying to sell mine for $75 and no one is buying.

It seems like the design of your living space won't allow for it, though.

The temp vs run duration doesn't seem that meaningful. It shows the first 3 minutes of runtime, and doesn't show if all configurations reach equilibrium performance after that. It looks like they might. These things are usually run for hours, is there a chance they'd have similar cooling performance at that length?

The insulated hose is something I'm exploring myself. There's insulated ducting like this: https://www.homedepot.com/p/Speedi-Products-6-in-x-12-ft-Ins... but it looks terrible. I'm kind of worried about having fiberglass being in my living space like that, the PPE is significant https://homeguides.sfgate.com/safe-ways-handle-fiberglass-in... and I'm pretty sure my cats would shred it up. I'm leaning toward adding reflectix sleeves with gaps so that the hose is flexible.

It seems to not be considering "can it reach a temperature", but "how much heat can it remove in 3 minutes", which, IMO, considering constant power usage, is more valuable for "how efficient is this"

For that short a period, it seems like the mass of the condenser would be relevant and disturb any extrapolation to efficiency from a run time which is not largely steady-state.

It's not really a hack is it? More like a fix or an optimization. I was excited for a second cause I have a single hose portable AC and I've been thinking about "hacking" it with an intake hose.

However, the more I use the thing the more I realize that there's nothing wrong with it. Since the rest of the house isn't air conditioned there are open windows and fans throughout. Air is more likely to be drawn in from the rest of the house than through the cracks to the outdoors. Might be an issue in a sealed studio apt, but in our leaky shoebox of a ranch style home, it's hardly the biggest inefficiency.

Anyone else "back in the day" would buy portable air conditioners from the hardware store and sling them into your server broom cupboard in an attempt to keep things from overheating.

It got so boring when we rebuilt with proper falso floors ceilings and real racks.

There's still a number of small ISP and telecom infrastructure sites cooled by setups like a pair of Haier consumer grade, ductless split 18000 to 24000btu/h units. Not an uncommon setup for places like small shelters at hilltop and mountaintop radio sites.

Hooking it up to the Nest was really clever. I've dabbled a bit with IR control of similar units, but that really takes it to the next level

There's really nothing Nest-specific in the design. It just takes two components (AC input optocoupler and resistor) to sense the 24VAC output from any standard thermostat.

Connecting to the Nest was probably easier than turning an ESP32 into a proper thermostat.

The hardest part of the whole project was figuring out how to read a clean signal from a photodiode.

Just read your post and just wanted to say I'm in absolute awe!

This is really cool. Maybe there is a market opening for an open, hackable aircon unit?

One thing I've long wanted to try with mine is use 'heating mode' as a quieter version of cooling mode. They work the same - the unit just runs backwards, with the cold air coming out of the tube instead of the vents - so in theory you can cool your bedroom without having the noisy aircon in the same room. But the thermostat doesn't work properly in this case, because it thinks it's trying to raise the temperature of whatever room you put it in, not cool the other end of the tube, so for this to work properly you need to hack the control board.

Maybe there is a market opening for an open, hackable aircon unit?

In the US, I think the EPA would not let you...

...not that it stops people all that much, as a YouTube search for "DIY AC" will show.

> In the US, I think the EPA would not let you

In Canada, you need to be a licensed something-or-other to purchase or own compressed CO2 canisters. This put SodaStream in an awkward position when entering the Canadian market, since their whole business model is built on selling people CO2. But they figured out a workaround: in Canada, you don't buy their CO2 canisters; instead, you "join a club" that allows you to borrow CO2 canisters (and/or refills the ones you have), and then charges servicing fees for "their" canister equipment. (Sort of like how a catering company would rent a helium tank.)

I wonder if something similar could be done for refrigerant-supply licensing in the US.

Wait, what? I am in Canada and I have a couple of 5pound CO2 canister for home brewing and a modded sodastream to accept any CO2 canister. Where did you find this information?

I even get it filled up at the corner store lol.

I don't know if it's true today, but back when I had a SodaStream (~5 years ago), a "purchased" SodaStream CO2 canister came with a printed copy of this: https://www.sodastream.ca/en/assets/ulc.jpg

Yeah I don’t think that has anything to do with the government. That’s just them trying to prevent you/scare you away from refilling the containers yourself.

Paintball guns run on CO2. You don’t need a special permit to own a paintball gun. You can pick up a paintball tank on eBay and run down to Canadian Tire or any paintball field and they’ll happily fill it up for you. Or at least they used to — it’s been a while for me.

That happens worldwide, they are just trying to contractually drm the canister business.

You can already buy some refrigerants legally without any license, and somewhat amusingly (or sadly), even contribute to global warming by releasing as much of it into the atmosphere as you want! It's not marketed as a refrigerant, because that would make the EPA regulate it, but of course the chemical itself doesn't care about such trivialities and will cool the same when it evaporates. If you want to go down a rabbithole, search for "duster spray AC recharge".

R290 is just propane, and it has a low Global Warming Potential. I see a lot of the new portable A/Cs use it. Apparently it's also more energy efficient. Obvious downside is that it's flammable.

Tangentially related, but how do you find portable ACs that work reasonably and reliably? I always found it so hard to search for them because it always seems like the reviews on these are difficult to trust. I've had at least one bad experience with one of them (single-hose) where it would just blow warm humid air sometimes, which was strictly worse than not running it at all. (At least something that might cool the air nearby consistently would be something useful, even if it can't cool the whole room.) I realize single-hose is probably a bad idea but somehow I don't have much faith in dual-hose either.

Wirecutter has never let me down: https://www.nytimes.com/wirecutter/reviews/the-best-portable...

Interestingly, in their tests, they didn't find dual-hose models to work much better than single-hose, unless it's extremely hot.

Thanks! I did look at Wirecutter actually, but for example the Amazon reviews for LG LP1419IVSM appear a little scary -- average 3.5/5, with 20% of them being 1/5. Have you actually had good experience with portable ACs from Wirecutter recommendations, or did you just recommend them in general?

I hate wasting window space with AC units and did a ton of research this spring while looking at portable ACs. I had the same concerns about the reviews for that LG model, but my conclusion was that most of the negative ones were for issues people ran into right away. Some serious issues, certainly, but maybe more of a quality control problem than a reflection of the performance of a typical unit.

I chanced it and figured I could return it if I got a lemon. On specs alone it’s clearly the most compelling portable on the market right now, and it has turned out to be a really great machine. The past few weeks have been brutally hot in NYC and it has kept our entire apartment very comfortable. With the variable compressor it can run super quietly, and it uses about as much electricity as the two window units it replaced. Freeing up two windows also means we can leave it off more often, which I prefer anyway.

I bought it and it broke within days, wasn’t motivated to go through all the support hoops. It wasn’t very cool even when working. Ended up getting a Fujitsu and it works well. Feels like a product segment ripe for better products to be fair, every model has mixed reviews and none seem well designed.

I don't know about portable, but FWIW the Wirecutter window AC reviews don't match my experience at all. They say that Friedrich is louder than LG, which I know to be false because I have one of each running in adjacent rooms.

Wirecutter reviewed the same models that you have?

It seems to me that portable units are all kind of equally meh. Seem to be about 50% as good as a window unit (which is about 50% as good as a mini-split or whole-home AC in my opinion). The dual-hose units don't seem to be a whole lot better than the single-hose units, honestly. Considering getting someone to professionally install a mini-split in my apartment to replace two portable units (1hose and 2hose).

I have a dual-hose version that looks very similar to OP's. I use it on-and-off when it gets hots. It can keep a poorly insulated bedroom cool, or two rooms bearable. It's loud to the point that I worry slightly about hearing damage if I sleep with it running, but as an AC, it's worked for several years.

> The point of connecting portable A/Cs to a Nest is:

> The usual "smart" stuff that Nest provides

Reminder: https://michaelblume.tumblr.com/post/169525456166/tech-enthu...

> Tech Enthusiasts: Everything in my house is wired to the Internet of Things! I control it all from my smartphone! My smart-house is bluetooth enabled and I can give it voice commands via alexa! I love the future!

> Programmers / Engineers: The most recent piece of technology I own is a printer from 2004 and I keep a loaded gun ready to shoot it if it ever makes an unexpected noise.

> Security technicians: takes a deep swig of whiskey I wish I had been born in the neolithic.

One thing with dual hose ACs that I would also like to see improved is an extension of the exhaust hose. For me often the hot air will heat up the window which then radiates heat back into the room. We do have 1980s aluminum framed windows, which really makes that problem worse.

I did find a big improvement in getting duct insulation and wrapping the exhaust hose in that. For the window portion, I cut out an insulating foam board to mount the hoses, and taped the outside edge with reflecting tape. It's keeping my large bedroom around 76, unless it gets above 95 and will start creeping to low 80s.

There's some pretty basic form factor changes that can go a long way to just eliminating portable units, i.e. these new U shaped designs.


Wonder why there's no "n" designs for obstructive light. Regardless, there's no reason for portable AC, even duo hose ones due to length limitations on hose before inefficiencies. More effort into easy to install window / split units please.

With WFH widely accepted, I wonder if transhumance will regain popularity?

(In my area, the herds would move between valley floor, mid-mountain, and alps. Most people would move between valley floor and mid-mountain. Peasant banking started here when everyone sent their cows up to the same alp, and the resulting cheese had to be divvied up between the owners and the alp crew.)


Dual hose units are increasingly hard to find. Hardly anybody makes them anymore. I've read in a couple places that they don't work great, despite that window units do.

The thing is, dual-hose units could work great. The concept is theoretically sound, but nobody's trying to engineer them properly.

I really doubt that. Most likely the vacuum efect is overrated as hell compared to the other various inefficiencies (e.g. not all the compressor's heat being vented outside)

I paid extra for a dual hose unit and find myself almost never using the second hose at all. The effect is negligible and not worth the small effort of picking up the second duct from the closet.

And on my unit (trotec) you _can_ close the intake vents with a simple switch if you install the 2nd hose, so its not like all manufacturers are idiots.

> The [vacuum] effect is negligible

How did you determine that the effect is negligible? A single-hose A/C should actually blow colder air locally, because it's using cool interior air to cool its condenser. The problem is, it's also throwing cool interior air out the window, which is thermodynamically insane. Every unit of air it expels must be replaced by hot air somewhere else in the building.

> e.g. not all the compressor's heat being vented outside

This is an engineering problem; the compressor should be well-insulated from the room (thermally and acoustically), and cooled using outdoor air.

(I can no longer edit at this point)

> How did you determine that the effect is negligible?

The power bill measures overall how much time the compressor spent running for the same preset, and there's little difference between two hose and one hose mode. I'd presume this is the most effective efficiency measurement I have.

> A single-hose A/C should actually blow colder air locally, because it's using cool interior air to cool its condenser.

Usually it feels as if the air _around_ the ducts/behind the compressor is warmest, rather than around the room's ventilation grills which is where I suspect you would notice warmness if there was a significant negative pressure issue (yes, this is modern France building so I'm forced to keep an aperture to the outside for air renewal, even though otherwise the isolation is topnotch).

> the compressor should be well-insulated from the room (thermally and acoustically),

This obviously makes sense, but it is much easier said that done. People still want to carry the thing between rooms (and/or carry it themselves to their homes) which is why it is a mobile air conditioner in the first place.

By the power bill.

I attempted something similar, at least on the nest side of things. I quickly realized the nest wouldn’t recognize any attached equipment unless connected to a 24vac line. I always wondered how the nest derived DC power to charge its internal battery when a common line was not used. Maybe I’ll research this some more and try again.

The Nest can sort of trickle charge itself through its relay outputs, but for reliability you really want to provide 24VAC between R<->C.

To attach equipment, you can connect a 24VAC-friendly load between (e.g.) Y<->C or W<->C.

Didn’t know about the trickle charging, neat!

Problem with attaching a load is that if you want to build a standalone unit with the nest, you’ll need some type of inverter when powered off DC, or perhaps a simple sine wave generator? I’m more of a digital, DC power guy.

Yeah, you need a sine inverter, either 24VAC, or 120VAC with a 24VAC transformer.

There might be a way to trick the Nest into running on something closer to DC, but I could only guess.

Just get a mini split and save yourself a few hundred man hours - this being the engineering equivalent of polishing a turd.

Even a poor mini split will outperform these in terms of efficiency and silence - and they can be wired directly to a nest or simple thermostat.

Just installed a Carrier (40MAQB12B1 / 38MAQB12R1) mini-split in the shed, which I had spray-foam insulated (and then I installed drywall) beforehand. This for the work-at-home thing which we're doing for at least another 6 months...

The difference between the loud portable unit and the blessed silence and efficiency of the mini-split is chalk and cheese. There really is no comparison.

The mini-split cools the shed down to 72, where I have to increase the temperature to stay comfortable, in about 4 minutes. It's even silent outside, and these units will provide 12k BTU of heating or cooling, so it'll be useful in winter too.

Yep. Had a Fujitsu halcyon 18,000btu and you could not tell it was on. Prior to that I had a delonghi "penguino" 13,000btu portable AC (it cascades water over the hot side of the condenser and ejects it out of the exhaust line) which is light-years ahead of these models in terms of efficiency and quality and it struggled to cool 500sqft while the mini split can easily sustain temperatures in 1200sqft. This particular model can also heat with exterior temperatures as low as -26C (~ -15f) which cuts a ton of heating costs - heat pumps provide ~3x more heat per watt than baseboard heaters. Add to this the fact it's nearly inaudible inside or out and I can't imagine why someone would choose portable ACs over this - even high end ones. The installation is quite straightforward despite requiring a technician to do the refrigerant part and confirm the electrical setup.

Air conditioner's compressor without PWM inverter is less controllable so makes it inefficient. Here in Japan only mini-split type air conditioner features PWM inverter and it's dominant.

What I always wondered is why these units don't come with heat recovery ventilation system inside. Seems obvious.

If you have been getting Whole Foods deliveries, you may have quite a few insulated bags that could be repurposed, with some gaffer tape, to insulating cabinets and ducts.

Could you use one of these units to many a diy fridge? Freezer? Or are they somewhat tied to reducing the air temperature to only room temperature?

This particular model will not cool below 60F/16C. Even if it could, the point of a portable A/C is to avoid cutting holes in the wall, which is not relevant if you're building a custom enclosure.

In theory, you could build an insulated box with a mini-split or window/wall unit, but they're probably all optimized for cooling a large space, not freezing a small space.

Tech Ingredients made a DIY fridge (and a freezer in later videos) using peltier coolers: https://www.youtube.com/watch?v=YWUhwmmZa7A

That's just the thermostat, though. If you powered and ran the compressor directly, it would pump heat until the heat exchanger goes well into negative temperature.

People used to turn portable A/Cs into PC coolers, which was pretty... cool.

The one we have in the office blows out 5-8°C air but indeed refuses to cool below a certain temperature. The unit isn't incapable of fridge temperatures, its software just doesn't want it to.

That was a super interesting video, thanks!

https://www.youtube.com/watch?v=7w4rg3UcsgI also worth a watch, trying to devise a different type of AC system

Get a deep freeze. It costs very little energy to cool an insulated box that only opens at the top. Mechanically, they are simple as hell so not very expensive either.

Yes, we have one, it's great.

Still curious about the diy potential here though...

Edit: It occurs to me you might be suggesting that it would be better to rip out the guts of a freezer than to use an air-conditioner... which does make a certain amount of sense.

Adam Savage did a video where he worked with a guy to build a cooling unit for a cosplay suit. They were using custom compressors that were actually pretty efficient, which makes a lot of sense if you're going to be battery powered.

I think some manufacturer names were mentioned? There are units now with with variable compressors, so you run them constantly at low current instead of full blast. If you want to build your own fridge, just to build one, I'd maybe look at those.

The efficiency of a heat pump is relative to the delta-T you're trying to push. If you are trying to hit 40° sitting in a 72° room? You could probably repurpose a portable unit for that, sure. If you're trying to bring ambient down to 40° for a cabin? I think you're right to be concerned if it's up for it.

There's also the defrost functionality which you won't have.

Re: the cosplay suit — were they essentially trying to recreate the cooling system on EVA suits?

Well, not exactly. Costumes can just be suffocatingly hot. Bulky, poorly ventilated, possibly used in an environment that isn't air conditioned. If the SFX crew for your movie is on their game, you have a cooling system built in and it's not that miserable. But I've heard stories of some people properly suffering in particular roles because it was just so goddamned hot.

If you go to a convention, like Adam is fond of doing, you're gonna be suited up for hours, without support crew. So it's gonna be tricky, and he makes money doing videos about tricky things...

That said, he did start with a surplus EVA (or was it fighter pilot?) base layer with the cooling tubes built in.

Youd have to build the whole enclosure yourself, but otherwise yeah you could do that. It's just a phase change heat pump, after all.

Author mentions Climax-Air as having decent units but out of stock. I think the Toyotomis are also pretty good in this class of A/C.

There are inexpensive minisplits available, they're often a much better choice than two-hose portable ACs.

That would be a great aftermarket product to hook up Nest to portable air conditioners.

I tried to look for something equivalent for those in-wall space heater units. They run on a different voltage, because of course they do.

I think the boxes were like $40, but they looked like electrical junction boxes. Clearly meant to be buried in a wall cavity.

Junction boxes are not meant to be buried in a wall. In fact, any junction box containing wire (not just connections/splices) is required to be accessible without removing any part of the building per the National Electrical Code.

Whoa is this Paul Marks from Purdue? Haha, long time, I miss the Dtella days!

Love the "plant growing forum" reference

What kind of toxic VOCs do these indoor units leak out?

These things should be banned in my opinion. They're so inefficient and never get the room down to a decent temperature.

Unfortunately I guess they're the only solution when it comes to portable AC units. Not everyone is living in a house they own: otherwise I agree

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