cooling your tent or van

[andrew0180]

So, it's June and I'm trying to get this nailed down early this time... Does anyone have any updated advice on a higher power fan for a larger swamp cooler design? The Endless Breeze which I've found mentioned in previous years seems to be no longer available. I found something similar called the Boundless Breeze, but no specs are available. Anyone have any experience with this fan, have any idea roughly what the CFM is for this fan?

Also, I'm considering radiator fans available on Amazon. Anyone have experience?

Worth noting: It will be used to cool a 10x14 Kodiak tent which has inward slanted walls that will move a bit in the wind. The tent will be in the shade, aside from a few gaps in shade walls. I'm using a 14 gallon food storage drum rather than a rectangular trash can, so the fan will be mounted on top as in the original design bc I like the ability to run a duct from the top rather than place the swamp cooler against a wall.

The new cooler is technically already built, using 2x Wathai 120mm fans that put out around 230CFM each (since Delta fans seem to be hard to come by also right now), but I’d like just a bit more output, so trying to find a solution that pushes more air but doesn’t use much/any more power - these pull 25W each, and one more would push my power limits. I currently have 1x 100W solar panel and the larger Costco deep cycle battery, and I'll need to charge portable devices also, so trying to keep the total draw under 70W so I don't have to worry about having enough sunlight to recharge every day. I'll buy another panel if necessary, but I'd prefer to avoid this. I considered multiple 5 gal buckets b/c I don’t need to design anything, but it would be a pain to manage 3+ buckets to get the 650+ CFM I’m aiming for (I think my tent is around 900 cubic feet inside?). Plus, it’s fun putting a decade of swamp cooler experience to use, pushing myself a little bit.

Any advice on fans would be appreciated, thanks in advance!


Also, this will be my first build since my original 5 gal bucket back in 2013, which made my 6 ft stretch yurt very comfortable all day long! Thank you Figjam for your designs, and for continuing to help keep this discussion active for so long, along with so many others!

[Token]

…
The new cooler is technically already built, using 2x Wathai 120mm fans that put out around 230CFM each (since Delta fans seem to be hard to come by also right now), but I’d like just a bit more output, so trying to find a solution that pushes more air but doesn’t use much/any more power - these pull 25W each …

Power, energy, work …

If your power budget is set, the thing to do is go for efficiency.

The cheap Chinese fans promise allot but also suck power and are noisy.

The thing about energy, power and work that is done … getting half way to the target RPM doesn’t use much power … getting the second half of the RPM range is where you burn power exponentially.

If you swap the twin 25W 5300RPM fans out for 6 high efficiency 7W 3000RPM fans, you can get 960CFM crammed into that power budget.

Check out Noctua.

https://noctua.at/en/nf-a14-industrialp ... cification

Their 140mm 2000 RPM fan is ~ 100CFM for ~ 2.5W … 6 would get you close to that 600CFM and at a mere 15W.

The 3-phase motors make a big difference in efficiency.

[FIGJAM]

...and the boundless breeze works the same as the endless.

[andrew0180]

…
If you swap the twin 25W 5300RPM fans out for 6 high efficiency 7W 3000RPM fans, you can get 960CFM crammed into that power budget.

Check out Noctua.

https://noctua.at/en/nf-a14-industrialp ... cification

I've been considering a setup using fans like that, but it would involve at least two very large ducts to capture air from all those fans, if I place the swamp cooler outside and run a duct. And I'd have to go with a square design that has a nice flat top tight fitting lid to run ducts like that. The build costs would likely exceed the cost of another solar panel since some of what I bought cannot be returned or used on that design, containers like that appear to be a bit difficult to find, and it would involve completely starting over. So, it's a last resort if I can't find a fan solution that fits on a 15" drum lid.

That said, the fan you recommended (and a similar 120mm option from Noctua) seem to be a bit better than the Wathai options. Mostly just b/c I trust the company more - Wathai seems to exist only on Amazon. Thanks!

[andrew0180]

...and the boundless breeze works the same as the endless.

Thanks. Same CFM? I actually went ahead and bought one, delivered last night. It's hard to tell if it's pushing more air by feel due to the difference in surface area the airflow is spread across - the 120mm 230CFM fans have more force, but it's clearly concentrated in a smaller area.

Regarding power usage: the charging station I have it plugged into says it's pulling 50W at max speed, which seems to be higher than the 2.6A (so 31W?) I believe the Endless Breeze was said to use.

[Popeye]

" I currently have 1x 100W solar panel and the larger Costco deep cycle battery, and I'll need to charge portable devices also, so trying to keep the total draw under 70W so I don't have to worry about having enough sunlight to recharge every day."

A 100 watt solar panel is rated by the manufactured at the best possible amount of sunlight, dust free, cloud free, etc. Most times a 100W panel is assumed to put out 50W.
Don't know what batteries you are using but a lead acid can be discharged to almost 50% of charge before damaging it. A lithium battery can be discharged to 5-10% of charge.

[andrew0180]

A 100 watt solar panel is rated by the manufactured at the best possible amount of sunlight, dust free, cloud free, etc. Most times a 100W panel is assumed to put out 50W.
Don't know what batteries you are using but a lead acid can be discharged to almost 50% of charge before damaging it. A lithium battery can be discharged to 5-10% of charge.

Thanks! I'm not converting to lithium at this point b/c it's very expensive. Deep cycle Costco batteries still offer the best bang for your buck for capacity vs solar generator setups or even standalone lithium batteries even considering the difference in discharge limits, granted with some extra required parts and skills. Might convert in a future year, but not until my deep cycle battery dies. Also trying to decide if I'll ever get an electric bike/scooter, I'm trying to not invest in gear that I'll just need to upgrade in a year or two - this would involve a complete re-thinking of my electricity resources.

I'm aiming for a max of 65W on my swamp cooler to account for the fact that my panel actually pulls around 65W, and I expect my daily needs to be 3-6 hours of swamp cooler run time. Should be enough to ensure a full charge every day, or close to it.

[Popeye]

OK, I assumed that your 70W figure was 70W across the day. Sounds like you have 70W of use for 3-6 hours/day so 210 to 420 watt hours per day. With a 50W charge time of 6+ hours per day you should get at least 300 watt hours per day of charge.

[Sporkster]

Circling back to the FIGJAM cooler. Is there a less moopy pad than the original blue Duracool? Mine is flaking badly, and I'd like to replace it with something a little more durable.

[FIGJAM]

I don't know of anything that works better.

[Packet]

I'm building out the figjam cooler and was considering not getting an inverter and just powering everything off of USB which should be much more efficient as it's DC to DC. I'm buying these USB Step Down Converter: https://a.co/d/2GTcUNv

Anyone already try this? Any gotchas or problems people see with it?

[spolsky]

That sounds like a great idea. These days you can readily get 5v, USB-powered fans. I really like the AC Infinity multi-fans which I use to cool my project enclosures for LED power supplies. There are a lot of cheap USB pumps, too.

[Popeye]

I'm building out the figjam cooler and was considering not getting an inverter and just powering everything off of USB which should be much more efficient as it's DC to DC. I'm buying these USB Step Down Converter: https://a.co/d/2GTcUNv

Anyone already try this? Any gotchas or problems people see with it?

Won't work.
A USB connection is limited to 5 volts at .5 amps so 2.5 watts. Not enough power to supply enough water from the pump or enough wind from the fan. Read the thread and go with the proven methods.
BTW You don't need an inverter, which changes DC to AC, use a 12V fan and pump as described in the thread.

[Packet]

The fan and pump will be direct wired as per the specs as I understand them (which I could be wrong), is the inverter used for anything else? It seems like everything will be powered from the battery and the inverter is just there to provide power to other devices? Or am I confused?

[Packet]

And I re-read your response, I will have a 12v car battery from the list (with solar too) and that will power the pump and fan. The link I provided is for USB hubs with step down designed to be plugged directly into a 12V battery. I got two of them and all the other stuff I want to use is all USB powered like my lights and stuff. I don't have any need for AC so as you said I don't need an inverter.

I did get the "premium package" battery so I'm hopeful with solar I can charge all the stuff and with the solar I can recharge enough. I guess it's time to fess up on the other thing I did differently which is to get a fold up panel (https://a.co/d/6IVLbcV) which seems to work great.

[Halfbreed]

Howdy all

Just built my first swamp cooler, thanks @figjam for the brilliant design!

When I did a test run of my cooler, I noticed that when the water level is low (bottom 1/4 of bucket), the DuraCool pad tends to become top heavy and sags within the bucket- think loose socks that gather around your ankles.

I’m concerned it may totally collapses on the playa, and not hold its shape enough to be a sufficient evap surface. I.e., flaccid DuraCool cylinder.

Questions: Does that affect performance?
Any pro tips to prevent DuraCool cylinder ED?

[Popeye]

And I re-read your response, I will have a 12v car battery from the list (with solar too) and that will power the pump and fan. The link I provided is for USB hubs with step down designed to be plugged directly into a 12V battery. I got two of them and all the other stuff I want to use is all USB powered like my lights and stuff. I don't have any need for AC so as you said I don't need an inverter.

I did get the "premium package" battery so I'm hopeful with solar I can charge all the stuff and with the solar I can recharge enough. I guess it's time to fess up on the other thing I did differently which is to get a fold up panel (https://a.co/d/6IVLbcV) which seems to work great.

The fold up panel is fine. Your battery, for best use should be a Deep Cycle battery, usually labeled Marine. You can discharge this type of battery further without damaging it.

[FIGJAM]

[quote=Halfbreed post_id=1224947 time=1689528634 user_id=140729]
Howdy all

Just built my first swamp cooler, thanks @figjam for the brilliant design!

When I did a test run of my cooler, I noticed that when the water level is low (bottom 1/4 of bucket), the DuraCool pad tends to become top heavy and sags within the bucket- think loose socks that gather around your ankles.

I’m concerned it may totally collapses on the playa, and not hold its shape enough to be a sufficient evap surface. I.e., flaccid DuraCool cylinder.

Questions: Does that affect performance?
Any pro tips to prevent DuraCool cylinder ED?
[/quote]

The pad actually has a grain that helps it stay up.

Don't worry,

Last one I made I did a frame, but you can take strips of stiff plastic and slide them between the pads to help them, stand up.

Six should do it.

[attachment=0]DSC01904.JPG[/attachment]

[Halfbreed]

Thanks Figjam!

I was going to repurpose the metal support out if an old furnace filter and sandwich that as a support frame between the two layers.

[philthy_3]

Did the Unicooler ever become adopted as the go-to or is the original Bucket still the GOAT?

[FIGJAM]

The bucket works fine for a small tent.

The unicooler is for larger spaces that need a lot more air flow.

[attachment=0]409069199.jpg[/attachment]

[philthy_3]

Good deal! Building mine for a 10x14 Kodiak. Sounds like the 5gal will be enough. I also am using the Attwood Bilge fan that people have commented

Sorry if this has been answered before: should the duracool touch the inside of the 5 gal bucket or better to leave some space? I've read up to 1-1.5 inches is best. I'm unclear about the science on this

I'm also going to add a pre-filter to the outside of the bucket to keep playa out as much as possible:

[FIGJAM]

I would consider that a large tent.

Even if it is under shade, the bucket will only help a little.

The blue pad is all you need as a filter.

Anything more will just block air flow.

Any dust in the bucket settles to the bottom in a thin layer and will be fine.

[philthy_3]

Got it. May build a second one then or go unicooler route! We will point the vents at our heads/under our sheet for best results. Also tent will be covered by a camp shade structure and then I'll prob do another air gapped shade structure of aluminet.

When I asked about it touching the inside of the bucket I meant if the rolled up duracool should be in contact with the inside circumference of the bucket itself or if it's better to leave an air gap between duracool and the inner plastic walls of the bucket? Assuming no air gaps on top or bottom..

Thanks for all your help!!

[FIGJAM]

The bucket is slightly tapered, so the pad "tube" will be about a 1/4 inch from the sides of the bucket where the holes are.

If the pad comes in contact with the holes, the water may find a way out.

[messer]

@FIGJAM you're a rockstar not only for developing this, but keeping up with Qs! Got some more for you, or the many other experts here. Searched this thread a lot for certain terms, but couldn't find the following. I'm building a bucket cooler for our SUV, which will be shaded in an enclosed carport, duct entering through foam board replacing front passenger window, rear window open same square inches for venting. Powering with solar & deep cycle battery on the playa. But afterwards back home in Tucson, I’d like to run this bucket rig off a USB power bank for more portable cooling while working round the ranch.

1) PWM fan options:
Has anybody figured out min static pressure at various cfm reqs? Only need ~100cfm for the suv. I'd like a PWM fan that's compatible with a $15 thermostat I found [had to edit out links bc this post formatted weird, but pic attached] so it automatically turns on when it gets hot in the morning, varies fan speed according to temp, and doesn't waste power at lower speeds like resistor speed controls do (need to conserve battery for 12V cooler-style fridge at BM). PWM appears to rule out the Delta fans. And I want quiet. Interestingly, Google reports big box fans are loud (55–65dB, max speeds ranging 800–1500rpm) but they don’t bother me much, while that same db at higher pitch/rpm really does. Maybe all the fans that fit in a bucket will be annoying compared to a much larger box fan, but I'd like to try getting the rpm to as low as a box fan's to find out. I know 200mm fans have low static pressure, but might they be enough for only 100cfm? Anyone know if static pressure scales roughly equally with cfm/rpm? If so, here's a list of fans I've found in ascending static pressures AT 100cfm. LMK which you think will meet the minimum I need for 100cfm, considering I could also dial up the pressure to the max listed if I need to. Or if you know a better fan. I don't care ab cost as long as <$50 and ideally under 15W:

@100cfm (rpm): --- max specs:
1.4mmH2O (680) --- 200mm 1.9mmH2O 132cfm 27db 5.0w 900rpm $20 --- Thermaltake CT200
1.5mmH2O (840) --- 180mm 2.2mmH2O 143cfm 35db 3.7w 1200rpm $40 --- Silverstone AP184
2.3mmH2O (1070) --- 180mm 3.2mmH2O 140cfm 37db 3.6w 1500rpm $46 --- Silverstone AP183
4.2mmH2O (1890) --- 140mm 6.6mmH2O 159cfm 41db 6.6w 3000rpm $33 --- Noctua NFA14iPPC3000
4.5mmH2O (1520) --- 140mm 10.0mmH2 223cfm 40db 13.2 3400rpm $27 --- Silverstone FHS140X
12.9mmH2 (2300) --- 120mm 29.7mmH2 230cfm 60db 22.8 5300rpm $20 --- Wathai 12038

Note: Wathai is over 15W so not usable later with most power banks, nor a manual-dial PWM fan speed controller that I plan to use later with the power bank bc it has a built-in 5V–12V converter.

2) Wicking humidifier filters:
Do wicking filters require considerable more static pressure than the Duracool pad? Anyone test them both in the same rig to find out how much if any difference there is? They look like they would, but no idea to what degree. It would be good to know if one of the fans above would pair nicely with wicking filters, not drying the filters out, while meeting the relatively low ~100 cfm target. With a pwm variable speed control, I'm wondering if I could make them work.

3) Separate reservoir?
Even if wicking filters would work with one of the fans above, I may pump anyway. I was going to put the bucket on a stand outside the suv passenger window. Just realized why not make this stand from other 5gal buckets that can nest with it for compact transport, plus act as larger reservoir so I'm not having to refill so often. What's the best way to do this? I'm thinking pump in the bottom bucket with outlet tube all the way to drip ring, with larger gravity 'daisy-chain' tube mounted in top bucket side wall just a little above top bucket's bottom, which then spirals down to enter bottom bucket side wall near it's very top? I'm thinking a larger tube & gradual descent spiral may be necessary to maintain a vent at the top of the tube to prevent airlock? Anybody got a suggestion on bushings/tubing to use for the daisy-chain? May try to find 3/4" hose thread male bushings, and a short washer hose? I want to be able use the top bucket alone in portable mode, so want to have some sort of threaded bushing I can cap when not using it with the bottom bucket. (Or maybe I just transfer all the guts to the bottom bucket for portable mode...but that might be a bit more work)

4) Intake ratio:
Anybody figure out an ideal ratio of air intake area to fan size, after which there are diminishing returns on cooling performance vs water consumption? Ideal hole size, number, & spacing to max out the bucket intake area, while keeping it just structural enough? If the answer is as much intake as possible, then surely someone has tried big rectangular cut outs, with just three or four ~1" wide vertical pieces remaining to hold the top of the bucket up?

5) Pump:
What flow rate do we want at the drip ring? There's a Playa Labs Swamp Cooler website that recommends a 12V 240L/hr pump with a 3 meter head. That's certainly more head than needed for the 28" height of 2 buckets (even 3 buckets at 42"). But I'm wondering what the flow will be at those heights because I don't see pump curve for that pump. I also went looking for a PWM pump so that the thermostat pictured could turn both it and the fan on at the same time. Amazon had multiple results that said PWM pump...but all had pics displaying a pump with sticker specs identical to the 12V 240L/hr pump, including just the standard red & black leads. Anyone know of any reason why that thermostat couldn't power the pump too, just using the power pins of a PWM harness coming off the thermostat (splitter harness: 1 to fan, 1 to pump)?

6) Multiple fans:
Final Q for the bomb-ass people still reading: for a separate box cooler build I'm considering for my RV, I read that multiple fans do not produce a linear cfm gain. Anybody want to hazard a guess on roughly what % cfm gain a 2nd fan provides? 3rd?

Thanks!

[Popeye]

What sticks out to me is your comment "I’d like to run this bucket rig off a USB power bank for more portable cooling while working round the ranch." USB will not work, low current and 5V is not enough to power a swamp cooler.
Specifications Max. Voltage Max. Current
USB 2.0 5V 500mA
USB 3.0 / USB3.1 5V 900mA

[FIGJAM]

There's a lot to unpack here.

100cfm is not going to do what you want.

We've found that the fan [model afb1212she 1.60 amps 190cfm] is the minimum for an affective bucket cooler.

Since the bucket is outside the space, I'd be surprised if you noticed the noise.

I don't think it will cool enough to trigger a thermostat, so that and a speed controller aren't needed.

The holes in the bucket are double the size of the output vent.

Blue pad is best.

Anything else restricts air flow.

2 gallons of water last 5 hours and you don't need to run it when your not there.

For the box cooler fan, the boundless breeze puts out 250 cfm on low [1.50 amps] 500 cfm on medium [2.50 amps] and 900cfm on high [3 amps].

I kept the design simple because playatime is irreplaceable and you don't need to be fooling around with the cooler when you could be fooling around with somebody else. LOL

[messer]

What sticks out to me is your comment "I’d like to run this bucket rig off a USB power bank for more portable cooling while working round the ranch." USB will not work, low current and 5V is not enough to power a swamp cooler.
Specifications Max. Voltage Max. Current
USB 2.0 5V 500mA
USB 3.0 / USB3.1 5V 900mA

Confused by this. Watts is power, not voltage, and 5V x 3A = 15W. It was originally just USB-C that offered 5V 3A, so any old power bank with a USB-C out should work to power up to 15W fan with appropriate rated cable/adapter. I was a bit surprised to see there are even power banks these days that list 5V 3A on USB-A size ports (which seems risky bc most USB-A cables aren't rated at 3A, but you can buy them). Many power banks offer even higher wattages, but rarely at 12V (there are a few), more typically 15V.

[messer]

There's a lot to unpack here.

100cfm is not going to do what you want.

Not for a much smaller space? I followed the procedure outlined at https://basc.pnnl.gov/resource-guides/e ... escription to calculate 96.5 cfm needed for an air change every 2 minutes, instead of 3. And that after conservatively measuring the size of our suv cabin. So that 100cfm figure actually has a lot of built-in 'safety' margin on top of whatever margin might be in the original formula for comfort.

I can buy multiple fans to test them out (I live in Tucson so should be a great test) and return whatever doesn't work well. I was just posting to ask if anyone has already figured out a minimum static pressure for cooling much smaller spaces that don't need as much cfm, since this thread has clearly led to so much awesome burner experimentation already

We've found that the fan [model afb1212she 1.60 amps 190cfm] is the minimum for an affective bucket cooler.

Since the bucket is outside the space, I'd be surprised if you noticed the noise.

I figured sound will travel through the short duct into the space with the air? With a small space and lots of glass/sound-reflective surfaces, I'm thinking a high pitched fan is going to be a lot more annoying.

I don't think it will cool enough to trigger a thermostat, so that and a speed controller aren't needed.

The first listed review of that t-stat is a great one which describes all the ways it can be programmed. You can program it to gradually ramp up fan speed from min to max with as little as a 5 degree difference (or more if you set it that way), and cycle on and off with as little as 2 degree difference. Since your bucket cooler sounds like it has proven its ability to cool to much greater differences than that, I can't see any reason why it wouldn't work? I actually don't care about it turning off on its own I just want it to turn on in the morning without us having to wake to do it so we can sleep in a bit more, and ideally ramp up as necessary as it gets hotter. We'll unplug it when not in the SUV to cool off.

Also, I did plan on getting a longer temp probe, and putting it at the back end of the car. For all the potential benefits this gets us (less noise, fan speed ramps up only as necessary, auto-on) for <$20, seems like a good idea to me.

The holes in the bucket are double the size of the output vent.

Blue pad is best.

Anything else restricts air flow.

2 gallons of water last 5 hours and you don't need to run it when your not there.

For the box cooler fan, the boundless breeze puts out 250 cfm on low [1.50 amps] 500 cfm on medium [2.50 amps] and 900cfm on high [3 amps].

Thanks for these specs on that fan. It sounds like it uses a bit more power than the old endless breeze, but since that one can't be got anymore, and this one's so much cheaper..

For the future RV box cooler, I plan to mount it on top of our RV with duct turning down through an existing pop-up vent, so I was wondering about using lower-profile fans just so the cooler didn't stick up as high. I'll need 480cfm for an air change every 2 mins in that, so I'll prob go with boundless breeze on medium speed for less noise, since it would otherwise need 2 smaller fans running full blast. But I'm still curious if anyone knows roughly what cfm % an additional fan adds.

I kept the design simple because playatime is irreplaceable and you don't need to be fooling around with the cooler when you could be fooling around with somebody else. LOL

I appreciate your years of real-world experimentation and keeping your advice to what you know works well. But our use cases are different, and I don't need as much cooling capacity. If I didn't care about being able to use this apart from BM (or more noise than I need), I'd just follow the recipe. But I do want to be able to use it more often, and a design that cools up to 600 cubic feet is far more than we'll need in the SUV. I think especially, when it's going to be shaded in an enclosed carport. So shouldn't a slightly less powerful fan work? What stands out on the Delta SHE is its static pressure at 14.5mm. If I went with the SilverStone 140x offering 10mm of static pressure, that's got~70% of the max static pressure of the Delta SHE, when I need far less than either fan's overall cfm capacity. I noticed earlier in this thread people were discussing fans they were using with ~3mm of static pressure.