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Old 10-15-2017, 11:02 PM   #1
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critique my swamp cooler idea

I have looked into swamp coolers and they are what I am going with for dry hot climates. I'm making my own. There are the ultimate in simplicity versions, take the 5 gallon bucket design. Search for it on youtube. Some are improved versions, so look for those. If you don't know, swamp cooler uses a fan to pull air from a humid container and it blows it out. Perfect for small, low wattage air cooling vs ac unit. I would expect a temp drop of 10-20 degrees, but that is not from personal experience, it's internet couch-potato knowledge. Mileage may vary. I don't want the bucket because my goal is to get stuff out of the way and off the floor or clear counter space. MY plan is below, tell me if it sucks, I will get over it.

The idea is to use a bucket in the basement. The bucket will have a drip hose and fish tank pump to circulate water onto a duracool mesh. From that, a lid with 3" pvc and 100-120 ish cfm marine bilge type fan. Below deck, I figure it's going to stay cooler. Oh and the fan is strong but loud so I suspect it will be almost unheard below deck esp if I insulate around it. Run it to living quarters ceiling from a corner of room and aim it toward center of room using a flange fitting to spread the air. Maybe take a 3" elbow fitting and heat it to make it flat and spread the cool air.

So far, it's not expensive. Cheap to run, the 120 cfm fan is like 25-35 watts, can't recall atm. I would be cutting a hole in the floor. Haven't put a floor in yet, so not biggie. Would placing the fan so far below be enough or would a second helper fan be needed to get air flow going? Maybe it's all too elaborate or unworkable? I can install the duracool pad in the pipe itself and have the water trickle down through the much of the pipe, thus giving the air more duracool pad to air contact on its way out. Hopefully this made sense.

I could just experiment and report back unless I'm just missing out on a concept here, which is why I'm bouncing the idea off y'all. Skoolie low watt central air!?
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Old 10-15-2017, 11:25 PM   #2
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Quote:
Originally Posted by yello View Post
I have looked into swamp coolers and they are what I am going with for dry hot climates.
I had a swamp cooler when I lived in Az. They used to work well way back, until the new residents decided they wanted lawns, gold courses and swimming pools. They didn't cool so well after that.

You might be ok in rural desert setting. Let us know your findings-good, bad or indifferent.
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Old 10-16-2017, 12:21 AM   #3
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I'll test this out. With November coming I might have to actually work at finding enough heat to test my system out properly. Actually I was so caught up with working on the bus in the 90 deg heat past few days that I forgot it's about to taper off.
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Old 10-16-2017, 08:23 AM   #4
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swamp coolers work god but the indoor climate will tend to get clammy feeling.. . they work as you know by evaporative cooling.. in the desert early summer you can make a nice indoor climate as there is so litle humidity in the air so you make it somewhat comfortable moisture wise wile also getting needed cooling. they use a LOT of water for a larger space. . not sure about a bus.. but the issue comes to be that if your busis sealed decently airtight but gains alot of radiant heat through windows, walls, etc you'll need more cool and end up with too much moisture.. exchanging air is a help, but of course you dont want to add too much 120 degree air to the mix to keep cool.

once you get near the rainier late summer seasons your swamp cooler becomes near useless...

-Christopher
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Old 10-16-2017, 08:00 PM   #5
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It's not a bad idea if you will be spending a lot of time in very dry warm places. We have a house sized swamp cooler on our house in Phoenix, and can make it into mid/late June before having to switch to AC. That's 110 outside, usually 80 or under inside. This requires single digit humidity. Toward the end of June when the monsoon season starts and humidity gets into the teens and 20s it's all over. Inside will be 80s to 90 and Florida sticky. The easiest way to tell is watch the dew point. Dew point above 50 degrees is where it falls apart. You're probably already aware, but to work an evaporative cooler must draw in warm dry air from outside. Cool Damp air must vent out through open windows or vents. You can't recirculate cooled air. You can (and we do) try to "super cool" down as low as you can overnight and then seal everything up tight, and do everything you can to keep insolation down and "coast" as long as you can. Otherwise the cooler has to run continuously, and while less than an AC is still not an insignificant amount of energy consumption.

In terms of the specific design I think you are significantly underestimating how much airflow, water, and evaporation area you need. A bus is not a huge amount of square feet, but like a car suffers significant heat load from window area and insolation. Despite the small volume, many cars/trucks/vans/SUVs require several tons of AC cooling power. What would normally be enough to cool a house. The bus might be a bit better if insulated and you remove or block out windows, and will be better if parked out of the sun and at night. I'd still not be surprised if you need 2-3x the cooling power of the equivalent residential space. Also moving air through the evaporating medium is much more difficult than just moving air round in the open. A little 120cfm vent fan probably isn't going to do much of anything. My house unit uses a 1HP dual speed motor on a giant squirrel cage fan to pull air in through the pad. My portable in the garage is small but still has a substantial squirrel cage blower.

I would look at available portable/window units to get some thoughts on sizing. Here's one example of a smallish window unit, $354 from Home Depot:

Champion Cooler 2800 CFM 2-Speed Window Evaporative Cooler for 600 sq. ft. (with Motor)-WCM28 - The Home Depot

Stated to cool 400-600 sqft, so probably about right for a bus.
- 2800 cfm squirrel cage fan
- Not a standard size motor, but rated 4A @115V =460W
- Intake / Pad Area: 2x21"x13"+1x21x20 = 966 sqin = 6.7 sqft
- No spec on water flow or usage, but a universal cooler pump rated for up to 5500 cfm is spec'd at 245gph.

Both my house and portable unit use a constant water supply, so I don't really know how much they use. But reading around a little I wouldn't be surprised if the unit above was approaching a gallon per hour. Remember it's only the water that evaporates that gives you cooling, and it takes a little over 8000 BTUs of heat to evaporate a gallon. So that gives you some idea of "cooling power" vs. water usage.

Also in the manual for my home unit it states that you need roughly 2sqft of exhaust area (open window, vents, etc) per 1000 cfm.

Rob
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Old 10-16-2017, 10:12 PM   #6
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.03 gallons per minute per ton (12000 btu's) so 1.8 gallons an hour for 1 ton of cooling
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Old 10-17-2017, 12:24 AM   #7
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My windows are tinted, soon too all be foam insulated and I'm about to gut it for as much foam board that I can fit. The roof had Henry's cooling silicone w/e it's called. The water tank holds 150 gallons. I'm going to be in West and lots of Southwest. Interesting considerations, like lack of fan power. Maybe they work best without long pipes. I don't know why dry air would suffer from having moisture in it as long as I don't go over 50 perc. I will consider a small a/c if it comes to that. Seems sensible but I am hoping to try as many passive cooling or lower watt ideas first. I have a 10000 watt generator that I only have for emergencies atm...which there seems to be plenty of these days. Ty


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Old 10-17-2017, 07:24 AM   #8
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the reason for the big fan motors is it takes quite a bit of evaporation to truly feel cool.. miscrms has it exactly right. watch the dewpoint.. thus my comments about rainy season.. ..

ive messed around with various versions of evaporative cooling over the years.. even heat-exchanged versions and always come out in the end that mechanical cooling takes energy. and as noted evaporative cooling adds humidity..

that said, you may be able to reduce the energy that a mechanical cooling system uses such as a minisplit by applying filtered water to the condensor.. again in dry times you can take a Very fine mist of filtered water into the air stream of the condensing unit of a mini split which will allow its compressor to run and fan to run at lower speeds. . into the prime efficiency of the machine.. a micro-controller could help control how much water you put on the coils... by doing this its very possible you could get a minisplit running purely on your solar or a mixture of solar and battery... or much smaller efficient generator..

minisplits have an accumulator so risk of compressor slugging is nearly non existent (unlike misting the coils of a window unit).
this also would give you full mechanical cooling capabilities for rainy or humid days...

you could still install a very small swamp cooler on a fan inside your bus to add a bit of humidity on those single-digit dewpoint days for health reasons.. you want to recirculate your inside air if its cooler than outside.. having a dewpoint in the 30s inside is much healthier than single digits.. and will be high enough your air conditioner wont try to condense any water out (counter productive).

one of the reasons that home swamp coolers like continuous water supply is to keep from gumming up the components.. too little water flow evaporating quickly ends up in a minerally mess on the pads.. (my northern home humidifer pad lasts one season on city water).. filtering your water helps.. and is amust for longevity of a swamp cooler or coil misting device..

a coil misting device should use enough water to place the unit in its efficiency curve but not enough to leave water on the ground.

-Christopher
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Old 10-17-2017, 12:32 PM   #9
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Then there is always https://www.osha.gov/dts/osta/otm/legionnaires/faq.html
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