I am wondering if any company offers an evaporative cooler designed to reduce RV A/C condenser inlet air temp to assist in 95+ deg temps? I designed such a system (inspired by some mechanical engineers I worked with) for our residential central A/C back in the late 70's when the condensing units had coils only on one side making the design much simpler. I had the system in place during the torrid 1980 TX heat wave when peak temps reached 113 deg. The system functioned as a nearly constant condenser inlet temperature regulator. As the temperature increased during the day the relative humidity decreased and the evaporative cooling delta t increased so for outside ambient air temp of 113 deg the condenser inlet air temp was 85. This reduced compressor hgh side pressure and consequently lowered current draw. Our unit cycled nicely even in those extreme temps. The main complication for RV A/C applications to me is the condensing air inlet being on both sides of the unit requiring some ducting of the evaporative cooler's output air or maybe an enclosure over the whole unit except for the back for the condenser's air exhaust with a single duct feeding the cooled air to the enclosure. Maybe just block off the side inlets and feed the cooled air into the units cover. Based on Coleman's Evaluating RV A/C performance document, you would expect compressor current draw to increase 1A over LRA for every 5 deg above 95 and also decrease the same amount for every 5 deg below 95 so there would be benefits for reducing power consumption. I would welcome any thoughts/feedback.

What exactly are you considering an evaporative cooler? Is it simply a mister that sprays across the condenser or are you thinking of a separate unit (swamp cooler) that then feeds pre-cooled air to the condenser.Where are you getting the water for the system? The normal water you see dripping off RV air/con units is pure water condensed from the air with no mineral content. Your typical campground water supply is mineral laden well water. If the excess slowly drips down the side of the unit, it would presumably leave heavy mineral deposits. In principal reduced power consumption is good but unless you are on a permanent site, electricity is typically included in the site rental, so no savings for the end user.

I remember installing a few "through the wall" A/C units in a few apartments and these units would use the condenser fan to blow the condensate onto the condenser coils for better cooling. Too bad RV units do not use this old technology to improve efficiency. Otherwise the move to mini-split units will not happen fast enough.

valhalla360 wrote:What exactly are you considering an evaporative cooler? Is it simply a mister that sprays across the condenser or are you thinking of a separate unit (swamp cooler) that then feeds pre-cooled air to the condenser.Where are you getting the water for the system? The normal water you see dripping off RV air/con units is pure water condensed from the air with no mineral content. Your typical campground water supply is mineral laden well water. If the excess slowly drips down the side of the unit, it would presumably leave heavy mineral deposits. In principal reduced power consumption is good but unless you are on a permanent site, electricity is typically included in the site rental, so no savings for the end user.I am talking about a true evaporative cooler to deal with the issue of keeping water off the condenser coils for the reasons you mention. The system I designed years ago used the old style Aspen wood evaporator cooler pad held by a wood frame with chicken wire to contain the pad and heavy rubber foam weather stripping where it mated to the condenser cabinet in front of the condenser coils. A pvc pipe with small holes drilled at one inch intervals fed by clear vinyl slide on hose attached to an evaporator cooler pump kept the pad wet. The pump sat in a plastic dish pan in a hole in the ground so the top of the pan was level with the top of the condenser concrete pad. Water was collected by a tray made of aluminum flashing and was open at one end to drain into the dish pan so the pump could recirculate the water back to the top of the pad. The dish pan had a water float valve fed by a quarter inch copper water line connected to an outdoor faucet. The pump was wired into one side of the contactor and only ran when the condenser unit was operating. I had to make one change to the original design adding a cover to the dishpan when I discovered a frog happily perched on top of the float which caused water to flow continuously and overflow.With respect to power saving I was thinking of those running off generator and at our house when we are prepping our trailer in hot TX Aug. for a trip to the mountains. We run the A/C for several days before leaving to help the RV fridge deal with 98+ deg temp sitting in full sun in our backyard. In addition based on my research years ago, an A/C's BTU capacity is rated at 95 deg. As the ambient temp goes up above that temp the unit loses capacity when you need it the most. The evaporative cooler keeps you from losing capacity.

time2roll wrote: use the condenser fan to blow the condensate onto the condenser coils for better cooling. Slinger ring, work great.

dclark1946 wrote:I am wondering if any company offers an evaporative cooler designed to reduce RV A/C condenser inlet air temp to assist in 95+ deg temps? I designed such a system (inspired by some mechanical engineers I worked with) for our residential central A/C back in the late 70's when the condensing units had coils only on one side making the design much simpler. I had the system in place during the torrid 1980 TX heat wave when peak temps reached 113 deg. The system functioned as a nearly constant condenser inlet temperature regulator. As the temperature increased during the day the relative humidity decreased and the evaporative cooling delta t increased so for outside ambient air temp of 113 deg the condenser inlet air temp was 85. This reduced compressor hgh side pressure and consequently lowered current draw. Our unit cycled nicely even in those extreme temps. The main complication for RV A/C applications to me is the condensing air inlet being on both sides of the unit requiring some ducting of the evaporative cooler's output air or maybe an enclosure over the whole unit except for the back for the condenser's air exhaust with a single duct feeding the cooled air to the enclosure. Maybe just block off the side inlets and feed the cooled air into the units cover. Based on Coleman's Evaluating RV A/C performance document, you would expect compressor current draw to increase 1A over LRA for every 5 deg above 95 and also decrease the same amount for every 5 deg below 95 so there would be benefits for reducing power consumption. I would welcome any thoughts/feedback.3 years ago at a Jayco Factory training session, the RVP rep brought up that 5 degree figure. Well for the previous 41 years as a TRAINED RV Technician from both Dometic and RVP and the correct figure is 10 degrees. While the rep and I argued the 5 degree in class, I had my smart phone under the table and connected to RVP Technical. THEY confirmed the 10 degree is the correct figure, which made the RVP rep extremely angry. I would bet RVP has not changed to the correct figure for their on line troubleshooting. So, use the 10 degree figure. As I pointed out to that rep, IF I use the 5 degree temp differential when doing a check out under warranty, I could condemn every RVP AC and get RVP to send a new one. BTW, I use the 10 degree figure as of today and the amp draws ARE CORRECT for temp compensated Amp draw. Doug

A/C Condenser Evaporative Cooling Assist | Good Sam Community

dclark1946
Explorer
Aug 21, 2020
red31 wrote:
dclark1946 wrote:

I decided to not pursue the misting approach partially due to the issues you mentioned as well as mineral buildup on the condenser coils. I would however be interested in any test data you can share with/without misters vs temp.

I used 1/2" PVC coupler with brass mister, 24v irrigation valve powered via outside compressor unit, wall mounted thermostat to come on over 90F, inline calcium filter. Final config (Mr. Mister) was PVC on the ground ~12" from unit with 2 misters per 3 sides. Measured rotation of electric meter with mist was 10% longer for one revolution. Misters clogged often, 20+y/o freon unit, replaced that winter. IIRC, 10F drop in exit air temp.

Nice piece of engineering. The devil is in the details. I used the watt hour meter revolutions over 10 minutes to compare power consumed with/without cooling before committing to designing and building my home system. Your calcium filter work pretty good for you? Which one did you use?
red31
Explorer
Aug 21, 2020
dclark1946 wrote:
Your calcium filter work pretty good for you. Which one did you use?

Not sure it did much as the misters clogged regularly, cleaned with striped bread twist tie wire or replace w/ new or vinegar soaked, inline calcuim inhibitor for outside misting

Calcium inhibitor
Chum_lee
Explorer
Aug 21, 2020
dclark1946 wrote:
Chum lee wrote:
dclark1946 wrote:
Chum lee wrote:
Yep, it works, but only in hot dry climates when you have a relatively pure inexhaustible water source. Try that in the desert in any MH. Come on guys, you have ask yourself WHY ALL the major HVAC manufacturers DO NOT do this for their factory installations. It's all you 100 mpg carburetor, fuel additive, free energy, Banks chip tuning, tweaky guys who want to talk endlessly about these things. (with NO long term substantiated evidence)

Chum lee

The quality of the water is not an issue since you are not spraying water on the condenser coils. You are pulling hot ambient air over a wet pad and part of the pad moisture evaporates which cools the air before it passes over the condenser coils. The water that does not evaporate returns to the reservoir and is pumped back up to the top of the pad. You only have to replace the water that evaporates from the pad. In the example I gave in Dallas we had 113 deg air temp one summer and the air leaving the Aspen pad was 85 deg. That dropped the compressor high side pressure and reduces the power consumption. For a 95 deg day the electrical consumption was reduced about 14%. Even better I was not losing BTU capacity as the temp went above 95.

Well, we'll have to disagree on that. Eventually the dissolved solid content of the water precipitates out on the pads, (or someplace else) unless you flush the system regularly. That's why you have to replace the pads. Lived in the deserts SW for years. This is no news. I suggest you take/pass a college level general chemistry class. Not a sales/marketing class.

Chum lee

Theoretically you are correct however we have a significant amount of minerals in our Dallas water supply and from a practical standpoint it was not an issue. I operated our evaporative cooling home central A/C assist for about 6 years each full cooling season and replaced the pad at the beginning of each season and the cooling remained effective over the season.

If you recall, the earlier residential central A/C systems condensers were water cooled. The heated water was pumped to a redwood cooling tower which sprayed the water downward at the top of the tower and the water dripped down the wood tower slats partially evaporating and cooling the water which was then collecting at the bottom of the reservoir and then pumped back to the condensor. These systems were more efficient compared to the air cooled systems introduced later. The major issue with the cooling towers was algae buildup requiring periodic draining and flushing and addition of chemicals to minimize algae growth.

With regard to taking a college level chemistry class, I have a MS in electrical engineering so yes I have completed college level chemistry. I was inspired to investigate this technique to improve residential A/C efficiency after discussing this with mechanical engineers that worked on the same government DOD program I did. They were building their own version of this type of cooling system.

Key words: Home (residential) system, not motorhome. (there is a difference) Hey look, bang your head against the wall. Make evaporative cooling work in a motorhome and you could be the next Bill Gates, Elon Musk, etc. Good luck to you!

Chum lee
dclark1946
Explorer
Aug 21, 2020
Chum,
Yes which is why I am soliciting inputs to see if anyone else has adapted this approach to an RV A/C system. I have two specific scenarios where I would use this. Every summer we prep our trailer for trip to the mountains. Usually temps are in upper 90's to mid 100's and we are operating our A/C to assist the RV fridge during a 2-3 day prep period. The trailer sits in full sun so the A/C is at its limits and runs nearly continuously during the hot part to maintain 83 deg. The other scenario is in case of a neighborhood power outage during a heatwave. In this case we plan on moving to our trailer since it is parked in our back yard and can easily power it and A/C with a pair of EU 2000's.
pianotuna
Nomad III
Aug 21, 2020
Chum lee wrote:

Key words: Home (residential) system, not motorhome. (there is a difference) Hey look, bang your head against the wall. Make evaporative cooling work in a motorhome and you could be the next Bill Gates, Elon Musk, etc. Good luck to you!

Chum lee

Chum Lee,

There is, or was, a commercially available evaporatetive cooler designed for use in an RV. However, it was about the same price as a regular roof top unit.
Chum_lee
Explorer
Aug 21, 2020
pianotuna wrote:
Chum lee wrote:

Key words: Home (residential) system, not motorhome. (there is a difference) Hey look, bang your head against the wall. Make evaporative cooling work in a motorhome and you could be the next Bill Gates, Elon Musk, etc. Good luck to you!

Chum lee

Chum Lee,

There is, or was, a commercially available evaporatetive cooler designed for use in an RV. However, it was about the same price as a regular roof top unit.

Hi Don: IMO, there's no reason why you couldn't put an evaporative cooling system on any MH. They WORK. BUT only in hot dry climates (0-20% relative humidity) where you have a readily available supply of fresh water. (like 10 gallons per day) In my Class A MH with an 80 gallon fresh water tank, that simply doesn't work. (especially while boondocking in the deserts SW) Now if I'm staying in an RV park with full hookups, I just use the regular rooftop AC unit which works fine. I'm not interested in adding the complexity of an evaporative cooling system to an HVAC system that already works fine without it. IMO, excessive moisture inside a motorhome is always a bad idea. If you look at the RV industry, in general, they seem to agree with me. (well more accurately, ego set aside, I agree with them)

I've been designing/building things for over 50 years now. Evaporative cooling systems are an economical solution and definitely have their place. IMO, a motorhome is NOT one of them.

Chum lee
pianotuna
Nomad III
Aug 21, 2020
Chum lee,

Where I live--I do on occasion run a humidifier in my RV. But never in the summer. Our relative humidity goes from 4% to 84% on a yearly basis.

Even with our relatively low humidity I found the swamp cooler I bought, rated for 500 square feet, did just about nothing for the 241 square feet in my class C.

Here is the one I was referencing: https://www.turbokool.net/product-p/2b-0001-turbokool-swamp-cooler.htm

They don't allow sharing the picture--how odd of them.
dclark1946
Explorer
Aug 21, 2020
Chum lee,

The evaporative cooling system I am proposing raises the humdity only of the outside air passing through the condenser unless the RV A/C is not sealed properly and allows leakage between outside and interior (conditioned) air. It should function like the home central A/C system I referred to in my original post. Not only does the humidified cooled air benefit the condenser because of the lower temperature but the denser humid cool air is more efficient in removing heat from the condenser coils.
dclark1946
Explorer
Aug 21, 2020
pianotuna wrote:
Chum lee,

Where I live--I do on occasion run a humidifier in my RV. But never in the summer. Our relative humidity goes from 4% to 84% on a yearly basis.

Even with our relatively low humidity I found the swamp cooler I bought, rated for 500 square feet, did just about nothing for the 241 square feet in my class C.

Here is the one I was referencing: https://www.turbokool.net/product-p/2b-0001-turbokool-swamp-cooler.htm

They don't share the picture--how odd of them.

Did you open a window to allow the outside air pulled into the evaporative cooler to push the trailer air outside? These systems are commonly used for interior cooling in dry climates where the cooling is greater and increase in interior humidity is a desired benefit. We used evaporative cooling in Dallas when I was a kid with cooler pads in three windows and a centrally located attic fan that pulled outside air through the wet pads and exhausted interior air out through the attic.
Chum_lee
Explorer
Aug 21, 2020
dclark1946 wrote:
Chum lee,

The evaporative cooling system I am proposing raises the humdity only of the outside air passing through the condenser unless the RV A/C is not sealed properly and allows leakage between outside and interior (conditioned) air. It should function like the home central A/C system I referred to in my original post. Not only does the humidified cooled air benefit the condenser because of the lower temperature but the denser humid cool air is more efficient in removing heat from the condenser coils.

I understand what you are doing and I agree with you. It will work. However, how much time have you spent traveling/living in an RV? Most who have realize that water is always at a premium when they are out and about. (boondocking/camping/fishing/hunting/etc.) If you prefer to stay in an RV park, generally, water/electricity/sewage are no big deal. IMO, you are trying to solve a problem that doesn't exist.

I don't know what else to say to you other than "live and learn."

Chum lee

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