Prepping: The Texas Swamp Cooler Adventure

Almost the “hot months” here in East Texas.  During June through the end of September, going outside can be a miserable task because it’s usually 80 F by 9:00 AM and the heat doesn’t really break until after sunset.  100-105 is not uncommon to  these parts and it may not break under 85-90 till past midnight.

Obviously, under these conditions, there’s a need for some kind of cooling.  According to experts, the right solution here is an air conditioner.  16 SEER heat pump was not quite free.  Are swamp coolers the answer?  Maybe…But there are lots of caveats and asterisks.  No two people’s results will be the same and your experience will vary.

First a word about the operating principles.  An air conditioner is well-understood.  A compressor liquefies a refrigerant which is then piped to an evaporator” and that moves heat around.  Magic of state-change.

With a swamp cooler, there’s a simple water pump that makes an air penetrable set of pads wet as air is blown through this “pad.”  Evaporation takes care of the rest.

The US is set up into evap cooling zones A through D.  Out west, zone’s A and B are up a ways from the Mexico sieve (used to be a border, lol).  In those areas, like much of New Mexico, Arizona, and desert parts of California – where the humidity is low – you can use a simple swamp cooler and remain very comfortable.  The problem in Zone C (which is where our slice of Texas is) the swamp cooler becomes a marginal proposition.  A few miles south of us, toward the Gulf and Houston you transition into Zone D and a swamp cooler won’t do much good. Just never gets really dry-enough air.

The key thing is to understand is what your local relative humidity is  when you will need cooling.  Here’s a chart that I borrowed from a physics discussion site here (and looks like they borrowed it, too…) but I have made some “bright yellow highlights” to show where our new 2250 CFM evaporative (swamp) cooler is chilling to:

I don’t spend a tremendous amount of time in the shop, but it’s nice to be able to jump out from my office (air conditioned, 73 F and 40% or less humidity) into a shop that might have been 90-95 F previously but is now a much more comfortable 79-81 F at the workbench.

There are several things about the shop that make it suitable for a swamp cooler.  First and foremost is it has a high roof.  The peak is about 20-feet off the ground and since it’s an open truss poll building, heat can rise and go out the ends of the building which are open (but screened).

Second thing is the doors are not tight and lots of air can move around. With a swamp cooler, you want a “loose” building so the static pressure doesn’t build up…because that small pressure will reduce the airflow over your pads in the cooler.  Think catalytic converter back-pressure if you’re a gear-head.  Same idea.

Monday of this week was about typical for this time of year,.  Outside, the Temp was 87 F and the outdoor humidity was 56%.

You can look at the chart above and see that the output temperature ought to be between 77 and 82 F on the cooler output.

As the summer moves along, there will be continued drying.  It’s not uncommon here for the relative humidity where we live to drop to the 45 and even 35% range on hot days. Like a 100 F and higher.

Again, referring to the chart, the 35% humidity and the 100-degree day is what I live in hopes of to justify this expendiment.  The cooler will likely chill to the 82 F range under those conditions.

The nice thing about the swamp cooler is it doesn’t use too much water under these conditions.  Maybe 20-gallons a day.  Where the real savings comes in is from much smaller electrical use.

In the Monday comparison numbers, my office was running 73 F but the air conditioner was running about 60+ percent of the time and during that it was pulled a bit more than 13-Amps from the power center.  Yeah, it’s a big unit and power-hungry, to boot.   Pencils out to an 8 Amp draw.  Remember, that’s running 60 percent of the time at 13 Amps when it’s 86 F outside.

We can run our first simple calculation here.  86 F – 73 F = 13 F of cooling.  At the 8 Amp level, that’s 960 watts worth of power.  Then, we divide the 13 into this 960 watts and we see 73.85 watts of power.

At the same time, the swamp cooler was running on the middle fan setting (200 watts) and the temperature drop was from 86 F to 78 F…and it climbed up later to 79 F…so let’s roll with that.  7-degrees of cooling.  Here’s the thing:  200 watts divided by 7-degrees is a bout 28.6 watts/per degrees.  Yeah, I like 2/3rd’s less energy…you bet!

Still, it’s not all peaches and creme (or is that cream?).  First and foremost, until the temperature hits 80 F, there’s no point  turning on the shop evap cooler.  Evap coolers are standard fare for cooling chicken farms in the Mississippi River region in the summer…read a lot on those.  Don’t bother with ’em until 79-80 F.

The Ag Extension services say pretty much the same as what I’m telling:  Not only do you need a bigger cooler than you thought, but helps to have lots of “tunnel fans” too, to make sure the hot air is being blown out of the building.  (Did you know chickens don’t sweat?  They do, however. pant…thrilling huh?)

One more visit back to the chart.  This time, let’s see what a high of 92 degrees and 15% humidity would chill down to with a swamp cooler:   70 to 72 degrees on the output, maybe?  Can’t beat that with a stick.  Which is why so many homes in Phoenix, Arizona and other dry arid places have both swamp coolers AND conventional a/c systems installed.  The swamp cooler will be cheaper to operate, but if you get monsoon rains come through “the Valley” (PHX) in late summer, well, then there’s nothing like the “no humidity-added” feature of conventional AC.

Which means what to preppers?

Well, if you are cheap, you will still want to avoid those 100 F days if possible.  You can do it a bit with misters, but only outside.  Evap coolers work, but you won’t be reaching for an overcoat until the air is thoroughly dry.  And right out of the box, the first half-hour, or so, an evap cooler will smell like wet cardboard (or gym socks) because the pads look like cardboard that’s specially built for cooling use.

On the plus side, they do offer reasonable bang for the buck and if you have the option to slip into a real “cold room” to take off a light sweat from working in 80-83 F every 15-30 minutes or so (gotta check the market anyway, right?) then one might make sense.

Oh, a light dusting of Lysol Spray on the outside of the unit while running, but not right on the plastic, freshens up the air in the shop to something approaching a pleasant aroma…Bang! fresh smelling shop.

The one we’re using is a Hessaire MC37M portable Evaporative Air Cooler for 750 sq. ft.. As a practical matter, always go larger than you need.  The shop (all in) is about 1,000 feet and we could have used larger.  But, do I need to keep the paint storage rack cold?  Hmm….

As I closed up the expendiment Monday, the outside air was 86 and 50%.  Output of the evap cooler (which is sitting outside an open window that has cardboard air baffles now) was 75F and 76% humidity.

Over at the main workbench the air temp was 81F with  70% humidity.  I use a small (20″) box fan to “help the air along” to the bench.  It’s sitting on the table saw where the temp is about 79 F and 73%…

Thus ends today’s new hybrid learning program:  Science project and prepping all in one omelette.  Figure we can run lots of evap in a pinch in a grid-down condition and still have the energy for the fridge and freezer.

Beer?  Almost warm enough now….

Write when you chill,  (pop!)

16 thoughts on “Prepping: The Texas Swamp Cooler Adventure”

  1. My maternal grandparents had a swamp cooler for their big house from the 50s until my mother inherited it in the 90s. Thinking back I don’t remember them keeping any window open so air would flow so that’d mean the house was being pressurized plus the hallway the cooled air discharged into was always having the wall paper deteriorate faster than other parts of the house. I don’t remember any cases of black mold but we weren’t running around with our hair on fire about that back then. Perhaps the back door was open so the air would make a circle through the house but it’s been too long to remember for sure.

    This year in West Texas has been a very light year in terms of cooling costs, so far. It’s 75F at 7:30 in the morning now, humidity has dropped to the mid-30s and the A/C has just come on for the first time since I’ve been up.

    Last year I finally broke down and tried an experiment with water misters on the A/C condenser coils outside. The misters are wired so that they come on when the outside unit does and I positioned them so that some evaporation was already occurring by the time the mist hit the coils. This meant it was cooler AIR going across them rather than our mineralized water. The water solenoids run on the same voltage as the unit’s control circuit does so that’s handy. 24vac, I think. Either way they match and it didn’t overload the control circuit’s transformer.

    I can’t say it really did anything to help but I’d become desperately tired of listening to the A/C run almost constantly while sweating our tails off inside. I also had a repair guy come out and take the outer body off to get to the coils and clean them. In our dusty environment this helped probably more than the misting did. Water poured out of the coil looking like chocolate milk plus a mat of lint and animal hair had almost sealed the inner side due to the placement of the unit lo these many years. I did put a calcium filter on the misters but that didn’t stop the calcium buildup I observed on the outer body louvers so I’ve abandoned that idea. Cleaning calcium off the coils requires a certain type of mild acid and I don’t know how long the aluminum of the coils would stand up to that. If anyone has had more success with this type of A/C assistance post it as it’s the only idea I know of that actually has a significant chance of working short of getting a new outside unit.

    One idea I’ve had in roof designs is to make a double roof with about a 6 to 8 inch breezeway between the outer heat shield and the actual roof that seals in the attic. It’s not a cheap solution but might be a long lasting one. Not much fun in a tornado but as long as there’s any kind of air movement, natural or forced, it might interdict the heat before it super heats your attic and your house. I’ve always thought solar panels would have this secondary effect, too, but they don’t cover all the roof area. It would have to be sturdy enough to walk around on plus have penetration points for all the vents and such on the roof. Lord only knows how many critters would find it a worthwhile place to nest, though. Guess you could build it as panels that would lift up for cleaning.

    • Interesting trick with double-wides here in E Texas: You buy one of those 40′ long two car wide RV covers and have it installed a foot about the house . Presto. Pays back in 5-years.
      Looks like shitty, but red-necking it sure works on the pocket book. I haven’t done it, since we have huge trees instead, but by golly….

      • Yep, half of our house has the “big tree effect” in place. Just wish it was on the other side to shield from the afternoon sun. Egg fryin’ time on the roof then.

        The RV cover might be an interesting, quick-fix option, though. I just worry about the winds blowing it over to the neighbors’ area and try to figure liability into that. Damn … neighbors. The screwer-overs of all great ideas!

      • Not that this is legal advice, but I believe inTexas a fallen tree belongs to whomever it fell on. I think if you could prove that the tree had been dead for some time, and the original owner was negligent in not having a dead tree removed, that there might be liability. I once used that argument to get a landlord to deal with a giant towering dead pine tree leaning in a neighbors direction. Otherwise, it’s usually between you and your insurance company. G____ is too far out in the sticks for the neighbor issues to be a problem.
        Best to get a real lawyer’s opinion if you have a potential tree / neighbor issue. Note that I only rarely and reluctantly advise talking to shysters.

      • Good idea. I’m thinking of just taking some old trusses that I got from an auction and setting them on a pole frame around a single wide I have elsewhere. Then install a metal roof and trim it right. It should make an old trailer look more like a house and provide both sun protection and save the real roof from the elements. I figure it won’t cost much out of pocket, and maybe a month or so of work to put it in. Then, of course, I’d be tempted to strip the metal from the trailer, insulate with foamboard and side it with stucco or something equally simple. Sadly, the orientation is totally wrong for solar and it’s virtually immovable.

        Unfortunately, it’s way down the list of other projects that need to come first.

      • Anything hanging over your fence can certainly have done to it whatever you wish. I don’t think, however, that anything the wind picks up and transports 10 miles away is subject to liability for the original owner. I’d just be concerned about anything of mine that would be dropped on the people’s house across the backyard fence that might otherwise have been argued to have not been secured sufficiently. However, “red necking” the place has certainly crossed my mind in the past. I’m scared the type of people starting to move in around us are going to push for a HOA before it’s all over. Then it’ll be time to get “creative”. Hmmm. Engine in the tree or skinning rack?

  2. I use a 48″ fan set on its side in a shop built stand/cage on wheels. One downside is you spend a lot of time chasing your hat and any lighter weight tools and equipment around when you get the bad boy up to speed. Pretty well shuts down any painting projects too unless you are looking for that rough non skid finish. Doesn’t help when both of the 16-foot shop doors are wide open either.

    My own version of the swamp cooler is to stop by the well house to hose down then stand next to the “Ozark Clipper” while taking a break.


  3. A properly sized attic vent vent fan will reduce the A/C load. Even with California mandated semi reflective shingles, the attic air space can reach over a 100 degrees with an outside temperature of only 80 degrees. In July of last year the Sacramento daily highs exceeded 100 degrees for the entire month. After looking into it, I installed a ‘smart’ attic fan. It has a multi-speed motor, which turns on the motor at the lowest speed, when the attic temperature reaches 80 degrees, and the speed increases as the attic temperature does. This action pulls the hotter air out of the attic, and replaces it with ‘cooler’ outside air. The unit I picked also has a humidity sensor that turns the fan on it the attic humidity gets above a threshold. I installed the fan last summer, so I don’t have a full years electric cost savings yet, but it has helped. If you are just below it in the house, you can barely hear it running on a hot day, so the noise has not been a factor. As a note, our home has 1200 sq ft., a tile roof and is well insulated with a foot of blown in insulation on the attic floor. The fan is rated for up to 1500 sq ft attic area. It is installed inside the code required attic vent. Since my wife won’t let me climb a ladder into the attic anymore, I hired a local contractor to provide the fan and do the installation to code. (It’s California, after all) The attic has a light and a 120 VAC outlet, so the ould just be plugged in to get it running.

  4. Hi George,

    Great Article! Regarding Evaporative cooling in the shop… What does the swamp cooler bring the RH% up to in the shop? Do you have any issues with tool corrosion or the electronics beginning to hate life from the moisture? Do you take any preventative measures for these things?

    • Only been in a few days now.
      Increase in RH is !11% from outside shop reference level
      Not a big increase since in the morning, the shop is 75F today and 81% RH before chiller went on.
      It’s a high RH day here, so shop is running 82F inside and 79% while outside is 82F and 70%…so there’s very little to play with in cooling today.
      With the evap off for 20 minutes, inside warmed to 83F with 81% (workbench) so there’s some improvement.
      Point is, in front of the evap, I will likely not exceed 85 even on 100F plus day – and that’s a decent win for the team. More data to come…running temps on evap ouput, fan on low, pump on…

      • Thanks George.

        If you can, please keep an eye on your tools. Corrosion loves Humidity.
        I’m interested in your ongoing observations in that arena!

        Tool maintenance and preservation is a big deal to me.

      • rusty tools Here is what I do.. and its cheap… Just drop a camphor block in each of the tool boxes.. and drawers.. just open it up or put it in a humidor.. or tea ball and toss it in.. for your big tools.. I wax them then toss a camphor tablet cover with a tarp or plastic sheet.. your good to go..just make sure the tool box is an enclosed space..

  5. A caveat: In my experience, the increased humidity in a space cooled by a swamp cooler causes tools, hardware and metal shop materials to rust more quickly.

  6. Might want to do a little research on the chemicals in lysol. I did a web seach ‘is lysol toxic’ and was surprised by the results. Just a thought.

  7. Ok.. the old man.. mad scientist lab……….

    and cooling the good old shop… a few years ago I made the mistake of showing the grandkids how to melt stone.. bad mistake..a really bad mistake…. never again …

    so I decided.. well lets show how to cool using the sun.. out comes the solar beer chiller idea…
    which worked great…

    I first took the idea from Albert Einstein and his fridge.. had someone get ahold of me.. they found what they thought was a heater in a junk pile.. then when they didn’t know what it was someone said hey there is this idiot with an ugly hat that would probably know.. I did and he didn’t want it so he sent it to me to play with..
    It was the crosley icey ball.. here is a picture of the unit he sent me.. I gave it to a friend that wanted to play with it.. in florida.. gave the solar beer chiller away last fall so the wife would be able to park her car in the garage..I made it to look like a retro coke machine.. really nice.. the kids I gave it to love to have back yard picnics.. and what is a better conversation piece than a solar cooled pop cooler LOL…

    nice unit worked really good..
    How it works…

    heat up the chamber with the liquid amonia in it.. now I thought it was pure amonia nope.. about forty percent.. ( you can buy that as an industrial cleaner..) the amonia just like the Einstein fridge evaporates and then expands cooling rapidly..

    with that in mind I decided.. heck I can do that.. why not make a solar beer chiller.. instead of sticking the supply side in a fire or have a fire beneath it.. use the sun..
    I made a dap cone..

    easy to make.. I ended up doing a simple trough.. but the original thought was to use a parabol then put the solution container in the center.. the trough was easier.. and I could use a peice of pipe.. heat up the solution.. you get someplace around two or three thousand degrees heat.. depending on the concentration point.. heats up the amonia water the amonia evaporates off.. I wanted to use a bromide.. since the bromides in a vacuum will evaporate quicker.. the hose coming off went up to the condenser.. I had a piece of steel wool in a piece of pvc pipe with a drain back.. this went into the coil in a bucket of water then down into the expansion chamber.. a check valve on the bottom back to the bottom of the solution container.. virtually a closed loop system.. it worked great except.. I had to have ice in the beer chiller so the beer didn’t freeze..

    It is simple easy to make and I had thought about using salt to absorb the solution to then at night when it cooled down.. remove the return line.. you can easily construct something like that and have the expansion chamber inside the building in the form of a pipe radiator.. with a fan behind it..

    Or.. better yet.. if I owned a back hoe or a tractor.. I would do something so much easier altogether..

    years and years ago.. i was asked about a way to cool and heat a building.. I did a set of drawings for them.. the theory was to use the soil.. dig down six foot drop your coil.. then use the building and the sun to cool and heat the building..
    there have been ancient civilizations that used this method.. the romans used it all the time.. cool and heat using a thermal heat tube… it is easy.. you can use PVC pipe to do it.. you can even use a closed loop.. use the heat of the tin roof to move the air.. simple easy and will cool the building down to about fifty five degrees..

    and cost a small amount of money…

    Me I always wanted to build a house get an acreage build the house out of ceb blocks.. and use the earth and sun to heat and cool the building in a closed loop design.. a thermal envelope.. but that is a pipe dream.. if it quits raining long enough I will have a storm shelter that way..

  8. another one I would love to try… and keep thinking about it is an indirect evaporation cooler with the cooling chamber separate but as a vortex tube. recirc house air with that one..
    the vortex tubes are the large side warm room air in cool room air out.. the evaporation outdoor air in cool moist air back out doors.. pretty simple..
    should work good just running it through my mind now.. If the kids clean out the garage I should get the grandkids to start drinking two liter bottles of pop LOL.. step it down to the three quarter inch output by using various cooling chambers.( different sizes of bottles)..make sure it is at least two feet in distance ( four different size bottles) to give the best temperature drop at output chamber..(box fan)..

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