Most efficient and/or lowest startup power air conditioners?

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Most efficient and/or lowest startup power air conditioners?

Postby sparr » Fri Jul 29, 2016 3:50 pm

The people in charge of village power grids that I've dealt with in the past suggest that the startup power draw of an A/C compressor is the biggest problem with air conditioners. Are there any brands or models that are known for minimizing this feature?

Separately, I know that large air conditioners have little difference between their efficiency ratings, but it seems like that holds less for small units. Are there any particularly efficient really small units for a yurt or RV?
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Re: Most efficient and/or lowest startup power air conditioners?

Postby EGAZ » Fri Jul 29, 2016 4:23 pm

Woof. Or a Sanyo Mini Split with DC inverter.

Found on this page.

sparr wrote:....I know that large air conditioners have little difference between their efficiency ratings, but it seems like that holds less for small units.....


They do actually, however, maximum efficiency on the playa for a week is far down the list. It just needs to work. Other than the initial start amps, SEER ratings mean nothing to a burner because we are only there for a week, maybe two. Savings from high SEER units comes from long term operation in years.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby GreyCoyote » Fri Jul 29, 2016 5:21 pm

sparr wrote: The people in charge of village power grids that I've dealt with in the past suggest that the startup power draw of an A/C compressor is the biggest problem with air conditioners. Are there any brands or models that are known for minimizing this feature?


If compressor startup was a "problem", then we engineers would have fixed the "problem" a long time ago. The "problem" is you are using it outside of the basic design parameters, ie, attached to a house where the grid is stiff and the NORMAL startup surge is easily handled. The are no "problems" when these units are used as directed. Your limited understanding of such a simple system is the underlying problem.

But the entertainment really starts about halfway through the first paragraph where you suddenly decide that the very property you earlier called a "problem" is now called a "feature". This tells me you write software for a living because no other profession would ever decide a "problem" was really a "feature" in the same breath.

sparr wrote: Separately, I know that large air conditioners have little difference between their efficiency ratings, but it seems like that holds less for small units. Are there any particularly efficient really small units for a yurt or RV?


You KNOW there is little difference between the efficiency rating of large systems? You KNOW this, how? Take a moment to Google that. In your world does a 4:1 range of efficiency ratings constitute "little difference"? In light of actual fact, the efficiency range between the SMALLER size units is generally narrower than the LARGER units. I wont bore you with why. You love sweating over minutia so Google it.

There would appear to be an underlying assumption on your part that the magnitude of the startup surge is somehow connected to a units efficiency. There is no direct relationship. Again, Google it.

If what you really wanted to ask us is "how can I best cool my yurt/tent/zorb/bus/outhouse without scramming the microgrid I'm attaching myself to", then get back to us with your allowed power/surge budget, a reasonable approximation of the size of the space and its overall R-factor, and we can indeed give you plenty of material to argue endlessly about.

Some search terms for you: EER. COP. SEER. Copeland compressor. Capillary. Thermal Expansion Valve. Hard-start kit. Power-factor correction. Zero-crossing switch. Fluvoxamine
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Popeye » Fri Jul 29, 2016 5:57 pm

^ This :D :D
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Captain Goddammit » Fri Jul 29, 2016 6:26 pm

The exact issue you're asking about - running an A/C on limited generator power - is very well covered by people with lots of real-world experience on RV forums. There is endless discussion about which unit will run on which generator, hard-start capacitor kits, all of that.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby maladroit » Fri Jul 29, 2016 10:50 pm

My inverter generator is in pieces on the floor right now. I have discovered that eco mode is disabled (motor goes to full power) when the eco switch is closed. I'll be wiring this to an externally accessible jack. Next task is to take apart the mini air conditioner and wedge a delayed relay between the controller and the compressor, with another jack to warn the generator it should go out of eco mode for a few seconds before the compressor actually kicks in.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby Admiral Fukkit » Sat Jul 30, 2016 7:03 am

I like it!!
Since you're modding it anyway (and assuming it's a Honda?) you should install a switch in the wire going to the kill switch.
The big on/off switch on the Honda is a mechanical fuel shutoff and an electric kill switch. If you give yourself the option to defeat the electric kill switch when you shut the genny off with the big knob on the side, it'll keep running until it sucks all the fuel out of the carburetor - which is good.
Sure you can pull the side cover and open the carb drain screw but this is easier and gets all the fuel out of the tiny passages inside the carb, particularly the "emulsion tube" which is below the jet and is the main source of trouble with gummed-up Honda carbs.
There's a connector that pulls apart that you can usually manage to reach through the side access panel that you can unplug and manually accomplish this but when you're actively using the generator (like at BM) it's nice to be able to shut it down when you want without waiting a few minutes for it to purge. If you don't do this mod, you should unplug that connector and let the thing suck the carb dry before you put the generator away for storage for any length of time.

With the kill switch mod, you have the option of instant on/off or full carb clean-out just by hitting the button.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby trilobyte » Sat Jul 30, 2016 7:45 am

I'm giving this a nudge to recommendations, since that's a better fit for threads seeking out recommendations on what to buy.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby sparr » Sat Jul 30, 2016 11:07 am

That line of Sanyo products is interesting. I didn't originally specify a budget, but I think I'm limiting my search to maybe double the cost of a typical room A/C, so $300-400 is viable but $1000+ is out.

eldergeekaz wrote:Found on this page.

I think there's one more layer of Google in there than you intended. Also, I didn't know the phrase "room a/c" until now.

sparr wrote:....I know that large air conditioners have little difference between their efficiency ratings, but it seems like that holds less for small units.....

They do actually, however, maximum efficiency on the playa for a week is far down the list. It just needs to work. Other than the initial start amps, SEER ratings mean nothing to a burner because we are only there for a week, maybe two. Savings from high SEER units comes from long term operation in years.[/quote]
I'm not thinking about financial saving, but about more-A/Cs-fit-on-the-village-grid efficiency (which is, not coincidentally, the same thing).

Captain Goddammit wrote:The exact issue you're asking about - running an A/C on limited generator power - is very well covered by people with lots of real-world experience on RV forums. There is endless discussion about which unit will run on which generator, hard-start capacitor kits, all of that.

I expected that there would be some significant conceptual differences between running one A/C from one small generator and running many A/Cs and many other things from one big generator. It sounds like a capacitor kit would be applicable to both situations, so I'll look into that. Thanks.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Admiral Fukkit » Sat Jul 30, 2016 11:13 am

"RV" doesn't always mean "large motorhome" as many burners seem to perceive.
On the RV forums there are threads on everything from tent camping to pop-ups to truck campers to huge bus RVs.
There is a wealth of knowledge and info to be gained there that can apply directly to camping at Burning Man.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby Elderberry » Sat Jul 30, 2016 11:25 am

The AC we have been using for the last 6 or more years we purchased from Home Depot for $99.00. It cools the yurt so well we only have to keep the setting on 2 or 3. Cheap, cheap, cheap. That's all you need to worry about when making the purchase.
Then, the MOST important thing to know is that the higher up you go, the less efficient your generator becomes. The hotter it is, the less efficient your generator becomes. When you add the effects of altitude and heat, it can knock off 20 to 30% of your available watts.

The first year we bought the above AC we also bought the smallest cheapest generator we could find. We tested it before we left and it worked just fine. Got it to the playa and it didn't work at all and we had an AC sitting in the window that had to work as a fan the entire time. Somewhere here I posted the exact calculations for heat and altitude, just do a search.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby maladroit » Mon Aug 01, 2016 10:42 am

Admiral Fukkit wrote:I like it!!
Since you're modding it anyway (and assuming it's a Honda?) you should install a switch in the wire going to the kill switch.
The big on/off switch on the Honda is a mechanical fuel shutoff and an electric kill switch. If you give yourself the option to defeat the electric kill switch when you shut the genny off with the big knob on the side, it'll keep running until it sucks all the fuel out of the carburetor - which is good.
Sure you can pull the side cover and open the carb drain screw but this is easier and gets all the fuel out of the tiny passages inside the carb, particularly the "emulsion tube" which is below the jet and is the main source of trouble with gummed-up Honda carbs.
There's a connector that pulls apart that you can usually manage to reach through the side access panel that you can unplug and manually accomplish this but when you're actively using the generator (like at BM) it's nice to be able to shut it down when you want without waiting a few minutes for it to purge. If you don't do this mod, you should unplug that connector and let the thing suck the carb dry before you put the generator away for storage for any length of time.

With the kill switch mod, you have the option of instant on/off or full carb clean-out just by hitting the button.


This isn't a Honda (it's the Champion inverter). Bless its cheap little heart though, it already has a separate engine cutoff switch and mechanical fuel switch, I've always let it run until the carb is dry.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby Admiral Fukkit » Mon Aug 01, 2016 12:42 pm

So I wrote all that for nothing.
Poop.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby sparr » Mon Aug 01, 2016 1:10 pm

Admiral Fukkit wrote:So I wrote all that for nothing.

Maybe some day someone looking for advice on generator modification will accidentally stumble across this thread and find your post.

The above passive-aggressive response can be reworded in an aggressive-aggressive manner as follows: If you'd made that post in a thread with "generator" in the subject, then it wouldn't have been for nothing because future people in search of info would find it. Keeping discussions on-topic actually does benefit other people, if you care about that sort of thing.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby EspressoDude » Mon Aug 01, 2016 2:29 pm

biggest know a/c problem on the playa:
Black Rock Power Co-op feeding a city block.
3 trailer mounted generators somewhere around 225 kw total.

Hot afternoon in the Orgy Dome with 10 - 12 room/portable a/c units running.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby illy dilly » Mon Aug 01, 2016 5:20 pm

GreyCoyote wrote:Your limited understanding of such a simple system is the underlying problem.
Why don't ya stick your head in that hole and find out? ~piehole
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Admiral Fukkit » Mon Aug 01, 2016 6:56 pm

Admiral Fukkit wrote:So I wrote all that for nothing.
Poop.


That was HUMOR, not passive-aggressive. Who says "poop" when they are actually upset??

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Re: Most efficient and/or lowest startup power air conditioners?

Postby illy dilly » Tue Aug 02, 2016 2:00 pm

Admiral Fukkit wrote:
Admiral Fukkit wrote:So I wrote all that for nothing.
Poop.


That was HUMOR, not passive-aggressive. Who says "poop" when they are actually upset??

Grandma.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby maladroit » Thu Sep 08, 2016 12:55 pm

My generator startup circuit worked well on the playa (it was not tested prior). Required some code tweaks before it was running smoothly. I had to open up the air conditioner controller PCB and scratch off a trace leading to the compressor relay (it was mounted on the same PCB). It was controlled by a ULN2003 darlington sink driver. I tapped off the control signal for that channel into an optoisolator so my microcontroller knew when the AC controller was trying to start the compressor. I used micro latching relays for minimal power draw, the relays reconnected the compressor to the drive circuit and shorted out the generator Eco switch (to force full-RPM operation). A separate wire pair ran alongside my extension cord from the control circuit to the generator.

Operating sequence:
  1. On startup, disable AC compressor and enable generator eco mode
  2. Detect AC compressor enable signal
  3. Close relay to disable eco mode on generator; generator begins to spool up to full RPM
  4. Wait 2-3 seconds (adjustable 0-10 seconds with trimpot)
  5. Close relay to enable AC compressor relay coil
  6. Wait 2-3 seconds after compressor startup
  7. Open relay to enable eco mode on generator (it can stay at full RPMs if needed, but always dropped back to eco with compressor running)
  8. Watch for AC to turn off the compressor and immediately open the compressor relay coil
  9. Sequence is ready to start over when AC needs to run the compressor again.

It was a blast hearing the tiny relay click, the generator ramp up, a little click and RPM dip when the AC compressor kicked in, and then the generator ramping back down to eco RPMs

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Re: Most efficient and/or lowest startup power air conditioners?

Postby Captain Goddammit » Fri Sep 09, 2016 8:00 am

Brilliant!
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Re: Most efficient and/or lowest startup power air conditioners?

Postby maladroit » Fri Sep 09, 2016 1:47 pm

Honestly I think so too, it worked perfectly all week long and I was so proud of that. My campmate had to run their Honda off eco mode the whole time to get the same result. I need to write this up and perhaps make a simple circuit/kit for people to do their own mods.

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Re: Most efficient and/or lowest startup power air conditioners?

Postby Joeln » Sat Sep 10, 2016 5:43 pm

Captain Goddammit wrote:Brilliant!


Couldn't agree more.
Love this kind of hack!
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Re: Most efficient and/or lowest startup power air conditioners?

Postby FlyingMonkey » Sat Sep 10, 2016 9:15 pm

GreyCoyote wrote:
sparr wrote: The people in charge of village power grids that I've dealt with in the past suggest that the startup power draw of an A/C compressor is the biggest problem with air conditioners. Are there any brands or models that are known for minimizing this feature?



If what you really wanted to ask us is "how can I best cool my yurt/tent/zorb/bus/outhouse ......................


I would just like to point out that a Zorb outhouse is a very bad idea!

Sparr, have you considered keeping everything simple & just using a swamp cooler type of set up? They are really simple and the last time I had a spraybar going on the Playa I was shivering. I just had a simple DC pump some tubing & hydroponic sprayers. It worked too good, didn't rely on a noisy/stinky generator, and if I needed to I could have rebuilt it on site with simple tools.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Captain Goddammit » Sat Sep 10, 2016 11:12 pm

But swamp coolers just don't put out as cold air as real A/C
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Canoe » Sun Sep 11, 2016 1:28 am

They don't need to.
They have sufficient CFM that with a correctly placed structure exhaust they simply displace the hot dry dusty air inside the structure with cooled moist dust-free air. This does assume, which some DIY designs have screwed up, that the incoming cooled airflow isn't pointed up at the "ceiling" to mix with the hot air there. A very inefficient way to use cooling.

And one pet peeve with A/C units, is rating them based on the efficiency of their components, NOT the final efficiency in cooling a structure.

"Window" style have two modes:
  • "recirculate" the interior air, chilling it.
    • This is the most efficient of the two types, as it keeps chilling interior air, which becomes more "conditioned" with each pass.
  • "fresh" takes outside air and chills it as it enters the structure through the A/C unit. This sucks, as:
    • it's chilling the hot outside air which is typically much hotter than the air inside, so the chilled air from the A/C isn't as cool, and
    • the incoming air will be trying to replace the interior air. In fact, incoming airflow is limited by what air can leak out through cracks or you need to add an exhaust vent so the incoming air can push out air already in the interior.
    • Issue is, the air it's pushing out to the outside is interior air, which is air you've been running the A/C to chill/condition, so it's throwing out conditioned air...
  • At least that is an easy choice: run window style A/C units in Recirculate mode.
Floor-standing with hose have two types:
  • two-hose type:
    • works like window types in recirculate mode (this is good), so each pass through the A/C unit chills the interior air further
    • the first hose intakes air from outside to flow over the heat exchanger
    • the second hose exhausts that heated air, removing that heat from the interior
    • Issue: exhaust hose gets hot, conducting and radiating heat to the interior air, reducing the efficiency of cooling the air in your structure.
      - Solution: insulate the exhaust hose. Watch it doesn't get so hot it starts melting... Use a heat-rated insulated clothes dryer duct/hose.
      - Further efficiency enhancement: The intake hose is flowing hot playa air, so insulate the intake hose too.
  • one hose type - these suck - and literally too (no, don't try that; just no)
    • the single hose is an exhaust hose
    • The A/C unit sucks the interior conditioned/chilled air into the A/C unit, over the heat exchanger and exhausts it through the single hose routing it to outside the structure
    • like the "fresh" mode of window types, this is throwing away the interior conditioned air
    • Worse: as it sucks interior into the A/C unit, it creates a vacuum pressure inside the structure, so to balance that pressure hot dusty outside air is sucked into the structure through any cracks or vents that are present.
  • IMPORTANT: Efficiency: if you have two A/C floor units, a one-hose unit and a two-hose unit, both with the same power usage and efficiency rating: the two-hose unit will cool down your interior faster and use less energy to maintain your target temperature.
    Additionally, the one-hose unit may not be able to reach your target temperature.
NOTE: Depending on how they're constructed, windows type A/C units in "fresh" mode can suck like one-hose floor units. In "fresh" mode, if the fan is blowing outside air to the inside, then not so bad as that creates a positive interior pressure. If the fan is blowing interior air to the outside, then you have the same issue with vacuum pressure inside the structure as you have with one-hose floor units, sucking hot dry dusty air into the interior.

Floor type vs. Window type.
The choice is not clear.
Generally, a two-hose floor type with insulated hose/ducts will cool better than a window type in recirculate mode. BUT, due to the heat from the floor unit's components being inside the structure, and the window type's components being largely "outside" the structure, and wide variances in the built-quality of the switchable airflow path in window units and the radiative path of its components, there are some window type A/C units that will outperform a two-hose floor unit. Good luck determining which window unit is "built right" (or DIY modifying).
A very good choice are the rarer window type units that have a very distinct housing: an interior section and an exterior section, with a low-height section joining the two. The window descends between the interior and exterior sections, resting on the middle section. This method minimizes the heat from the operation of the A/C from getting into the interior.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Captain Goddammit » Sun Sep 11, 2016 7:03 am

Rooftop A/C is the way to go on a bus like Sparr wishes to cool, not window or floor-standing. However, I own a big floor-standing single hose A/C at home, and despite all the theories that say it shouldn't work, it chills a pretty big space on hot days very nicely on about 400 running watts.

Swamp cooler proponents have all sorts of arguments why A/C shouldn't work, but the fact is it does, and makes colder air than a swamp cooler can.

I run a rooftop A/C in my unshaded camper (which is an oven otherwise) on the playa, and I invite anyone to step inside and see for themselves how much colder it is inside than any swamp-cooled space they have.

Colder is colder, that's the bottom line.

Run a swamp cooler if you haven't got the electricity for A/C, have lots of water to burn away, don't want to be as cool, and don't mind all your stuff being damp.
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Re: Most efficient and/or lowest startup power air conditioners?

Postby Canoe » Sun Sep 11, 2016 8:58 am

Captain Goddammit wrote:Rooftop A/C is the way to go on a bus like Sparr wishes to cool, not window or floor-standing. However, I own a big floor-standing single hose A/C at home, and despite all the theories that say it shouldn't work, it chills a pretty big space on hot days very nicely on about 400 running watts.
Swamp cooler proponents have all sorts of arguments why A/C shouldn't work, but the fact is it does, and makes colder air than a swamp cooler can.
I run a rooftop A/C in my unshaded camper (which is an oven otherwise) on the playa, and I invite anyone to step inside and see for themselves how much colder it is inside than any swamp-cooled space they have.
Colder is colder, that's the bottom line.
Run a swamp cooler if you haven't got the electricity for A/C, have lots of water to burn away, don't want to be as cool, and don't mind all your stuff being damp.
Captain it's not like you to be off technically and promote incorrect information. You're close, but distinctly off. The laws of thermodynamics aren't going to change just to suit your partial understanding. Take the time to read my above post.

Rooftop types can run the two modes that window types do. Run in it recirculate mode for faster and cooler. Unfortunately, it will cause mixing of its chilled air and the interior air, but if sized sufficiently, not an issue if you've got the power to run it.

There's no "theory" that single hose doesn't work. Assuming both types are the same "size": it just doesn't work as well as two hose types, and that either costs you more electricity to do the cooling job as it has to run longer (as it's throwing away some of the air its conditioning), or if you've got a heavy load, it can't do the job. If a single-hose is sized large enough (BTU), then it can do the job, but it will cost more energy to do it.

There are no arguments why "A/C shouldn't work" so please don't go and try to invent any. All you need is a large enough unit (BTUs) that their design efficiency and proper installation allow them to remove enough heat. And the power to run it.

An A/C unit needs to provide cooler air as it's typical mode of use is to mix with the interior air to cool it.
A swamp cooler doesn't need to provide that super chilled air, as it replaces the interior air with its cool air. All a swamp-cooler needs to produce is air at a temperature you find comfortable, and at a high enough flow rate to be removing that air as it gets heated within the space.
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FIGJAM
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Location: apache junction az.

Re: Most efficient and/or lowest startup power air conditioners?

Postby FIGJAM » Sun Sep 11, 2016 9:28 am

Nothing gets "damp", and if you need more than a 30 degree reduction in temperature, AC is the way to go. 8)
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Captain Goddammit
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Location: Seattle, WA

Re: Most efficient and/or lowest startup power air conditioners?

Postby Captain Goddammit » Sun Sep 11, 2016 9:46 am

I don't believe I said anything that wasn't technically correct.

What rooftop A/C unit uses outside air? I've owned several and none of them did anything but recirculate.

I understand how swamp coolers sort of work, and why a single hose freestanding A/C is a bit less efficient.
But the facts remain: my camper is colder than anyone's swamp-cooled space, and those single-hose freestanding units actually work quite well even though they shouldn't.

This is a silly argument. One system makes sort-of cool air, the other makes much colder air.
If you want to sort of cool a tent on a tight budget, a swamp cooler is what you have to make do with.
But this thread is about chilling a bus.
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sparr
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Re: Most efficient and/or lowest startup power air conditioners?

Postby sparr » Sun Sep 11, 2016 10:25 am

Captain Goddammit wrote:What rooftop A/C unit uses outside air? I've owned several and none of them did anything but recirculate.

I've got a 105kBTU rooftop unit from ThermoKing. It can recirculate or pull in outside air, while heating or cooling. It's also a tiny bit overkill for just keeping a couple of people cool :)
If you want to make a reply about my personality instead of about what this thread is about, don't clutter this thread, post over here instead.


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