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 23, 2020
pianotuna wrote:
dclark1946 wrote:

I don't understand how any kind of evaporative cooler can function to lower temperature in a closed environment regardless of where it is located. The cooling process adds moisture to the air raising the interior humidity and if it is just recirculating it keeps adding more humidity to the air reducing the cooling. To me it seems somewhat similar to operating a window A/C unit totally inside your closed RV with the cooled evaporator air and heated condenser air both being blown into your RV.

Then you don't understand that when water evaporates the temperature is lowered.

It is NOT at all similar to a window A/C operating inside.

I must be doing a terrible job of communicating on this post. I was trying to use an analogy with the window unit substituting temperature for humidity. I fully understand that when water evaporates the air is cooled. The lower the relative humidity the greater the cooling. I used that principle in the A/C assist evaporative cooler I designed, built and used successfully for years. However when the air is cooled by evaporation the air moisture content is increased. If you keep recycling the air through the evaporative cooler in a closed environment (no outside air brought in) the relative humidity will continue to increase and the evaporation process will give you less and less cooling. I hope I have explained it clearly.
C_Schomer
Explorer
Aug 23, 2020
In the 70s and 80s I added sub coolers... water cooled exchangers and Penn head pressure control valves in the liquid lines of condensing units that were in hot equipment rooms and overworked ACs and that worked terrific to increase NRE - net refrigeration effect.
I remember seeing swamp cooler frames and pads that could be added to the face of condenser coil's and it dripped water over the pads just like a swamp cooler and cooled the air before it went thru the cond. coil. I thought that was a great idea but I was working at a plant with well over 100 RTUs and I had a bunch of large ones, up to 80 tons, with horizontal coils and swamper pads wouldn't have works. We had excellent water with very low hardness and I ran lawn sprinklers under those coils until I could add liquid line subcoolers, cooled with plant chilled water, to them.
I've been thinking about adding something to my home condensing unit. Swamper pads require staying on top of the maintenance. If the water were to stop, there would be a big air restriction in front of the coil, but the liquid line subcooler with a Penn control valve is fully automatic and will maintain a preset liquid line temperature no matter what the conditions are. Also, there's no negative effect if the water stops.
I also added a water subcooler to my recovery machine and it cut recovery time to a fraction of the time. Craig
dclark1946
Explorer
Aug 23, 2020
Craig,

Thanks for you comments on the commercial application of evaporative cooling to assist A/C operation. I found it informative.
whjco
Explorer
Aug 24, 2020
We have a 34' Cherokee with a 15k BTU Dometic AC unit. We've had it in high humidity 98 degree weather in Alabama and it keeps up just fine. There may be some issue with the AC unit or, if it's ducted, it might have a leak that's blowing cold air into the attic area.
PatJ
Explorer II
Aug 24, 2020
I like the idea and would love anything that would make RV AC more effective or efficient, and wish you the best of luck overcoming the issues with using water to assist the condenser in an RV.

In the meantime, it seems to me the effort is best spent just using a much larger condenser and much larger condenser fan for increased efficiency. Of course then we would need a variable speed condenser fan and compressor to keep the pressures in check, maybe an electronic TXV, and a computer to run the whole thing. This is starting to sound like a modern mini-split!.

Most current RV roof air conditioners use 1960s/1970s window banger technology. They could make a rooftop RV air conditioner with a very superior performance and efficiency to what's available now, but it would be $4500 instead of $800. You and I may buy one for that, but unfortunately we are the minority RV buyer at the moment.
time2roll
Nomad
Aug 24, 2020
whjco wrote:
We have a 34' Cherokee with a 15k BTU Dometic AC unit. We've had it in high humidity 98 degree weather in Alabama and it keeps up just fine. There may be some issue with the AC unit or, if it's ducted, it might have a leak that's blowing cold air into the attic area.
I think 90% have this issue. Some worse than others.
dclark1946
Explorer
Aug 24, 2020
PatJ wrote:
I like the idea and would love anything that would make RV AC more effective or efficient, and wish you the best of luck overcoming the issues with using water to assist the condenser in an RV.

In the meantime, it seems to me the effort is best spent just using a much larger condenser and much larger condenser fan for increased efficiency. Of course then we would need a variable speed condenser fan and compressor to keep the pressures in check, maybe an electronic TXV, and a computer to run the whole thing. This is starting to sound like a modern mini-split!.

Most current RV roof air conditioners use 1960s/1970s window banger technology. They could make a rooftop RV air conditioner with a very superior performance and efficiency to what's available now, but it would be $4500 instead of $800. You and I may buy one for that, but unfortunately we are the minority RV buyer at the moment.

We do have the Coleman Mach 3 PS 13.5 which has a higher efficiency compressor (scroll I think) and larger condenser compared to their standard 13.5 Mach 3. Currently only have 15A service in our back yard where our trailer is parked and that works well except in the middle 9f Aug. in full sunlight.
dclark1946
Explorer
Aug 24, 2020
PatJ wrote:
I like the idea and would love anything that would make RV AC more effective or efficient, and wish you the best of luck overcoming the issues with using water to assist the condenser in an RV.

In the meantime, it seems to me the effort is best spent just using a much larger condenser and much larger condenser fan for increased efficiency. Of course then we would need a variable speed condenser fan and compressor to keep the pressures in check, maybe an electronic TXV, and a computer to run the whole thing. This is starting to sound like a modern mini-split!.

Most current RV roof air conditioners use 1960s/1970s window banger technology. They could make a rooftop RV air conditioner with a very superior performance and efficiency to what's available now, but it would be $4500 instead of $800. You and I may buy one for that, but unfortunately we are the minority RV buyer at the moment.

We do have the Coleman Mach 3 PS 13.5 which has a higher efficiency compressor (scroll I think) and larger condenser compared to their standard 13.5 Mach 3. Currently only have 15A service in our back yard where our trailer is parked and that works well except in the middle 9f Aug. in full sunlight.
C_Schomer
Explorer
Aug 25, 2020
Our rv ACs and existing compressors would benefit GREATLY with larger coils and more airflow to bring the DTs down and that would automatically increase efficiency... N.R.E. The evap. would bring the sensible load down better and not so much the latent load. But, we only get cheapo engineering/design in our rv junk. Craig

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