Water Cooled Marine Air Conditioner

This video shows how to convert a window air conditioner to cool using lake water. Shout out to You Tube user Nobox7 for secret on bending copper and stainless tubing. I was hesitant to try water cooled AC because I never found a proper solution for bending tubing. This worked perfectly from the start. I even came up with a few improvements myself.
If this is a bit too technical I have another video showing how to convert the same unit using duct work and a boost fan.
Video link
• Marine Air Conditioner

[@SethRocksYou]

Well done. I did a very similar setup, although somewhat different. Maybe a little easier depending on someone's personal skillset. I used a 10k BTU unit and it's able to keep my 28' flybridge cruiser's cabin in the mid to high 70ºF range in 105ºF-ish outdoor temperatures. Details below.
I'll share and maybe it helps someone out or sparks some other genius thoughts. Mine's been going strong for five summers now. Absolute life saver! (Well, sanity and sweat saver anyway)
I run the water directly through the condenser, instead of copper coils. I used 1/4" plywood, sealed with polyester fiberglass resin as my condenser encasement material.
One inch wide strips of ply, the height of the condenser were applied on the left and right side of the condenser, both front and back, with thickened resin to create a space between the condenser fins and the ply that would eventually cover/sheath the entire area.
Then used thickened resin to attach a strip of ply to the top and bottom of the condenser, the entire width of the condenser (including the U-turns on the ends), and deep enough to extend slightly past the surface of the to-be-installed-later front and back panels.
Front and back panels height measured and cut, width the same as the top and bottom, and secured in place with thickened resin. Prior to installation, the front and back were drilled and hose barb fittings were secured in place with resin, INPUT on the BOTTOM corner of the front, OUTPUT on the TOP and opposite corner of the back. Filling from the bottom and discharging from the top is important, it allows the cavity to fill completely with water. DO NOT fill from the top.
I used a router to flush the top and bottom panels to the front and back and applied a single layer of medium weight fiberglass over the top and sides to better secure the joints and prevent cracking and leaking at the seams. Same for the bottom.
So now, there's a top, bottom, front, and back encasing the condenser, with 1/4" space between the front and back for water to fill, bottom up, and flow across the condenser. But, what about the ends of the condenser, where the copper U-turns are? I simply tilted the unit on one side and poured about 3/8" of resin into the end to seal them and keep them from leaking. Then did the other side once the first side cured.
In the place the unit is installed I've shimmed the base of the AC unit so the collected condensate from the evaporator runs to one corner , which I've drilled a hole that provides a friction fit for silicone tubing that directs it into the bilge.
I tapped one of the existing through hull water intake hoses (for the toilet, in my case) with a T fitting for my water intake. It goes from there to an inexpensive sea strainer to catch larger junk that gets sucked in (lake weeds mostly), then the same style filter in this video to filter out the finer debris then to my pump, all of which is located in the bilge.
I've gone through a few pumps over the years. A couple 12v diaphragm pumps, which were repurposed from other duties. I didn't like them for this particular use. They're pretty noisy, I had to turn them on and off manually, and I always worried if the condenser somehow became clogged, that the relatively high pressure capabilities of a diaphragm pump would break the plywood casing apart and spew water everywhere. What I've settled on and really really like so far is a 120V centrifugal pump (marketed and sold for Home Brewing on Amazon), which is nearly silent. It is not self priming, but it's location in my boat is in the bilge, below the waterline and I've experienced no priming issues.
I wired the pump to the AC unit's compressor leads, so when the compressor is running the water is flowing. When the compressor cycles off or I turn the unit off altogether, the water pump and flow through the condenser is off.
The pump does not have an integrated check valve, so I added one designed for bilge pumps. So now, when the pump shuts off, water stays and doesn't drain out of the condenser.
I simply run the water output from the condenser into a sink, which drains overboard. Although, one could certainly T into an existing overboard drain hose or drill and install a dedicated through hull discharge fitting.
One thing I haven't done yet, but am considering doing is putting a cooling coil on the compressor. I don't seem to get any over temp shut off's, but that sucker get's too hot to touch and is releasing a lot of heat energy into the space that could potentially be captured and released overboard, increasing the overall efficiency of the system. I'd personally probably use 3/8" aluminum tubing for this purpose.
I REALLY liked the method this video shows, to fill and pressurize the tubing with water to keep it from kinking while coiling and/or bending. Might give it a go and cool my compressor for this reason alone! just to try it out!
Thanks for the great video Bob! I enjoyed it!

[@nickd5943]

Very interesting! Thanks for sharing. This has given me some ideas on making a heat exchanger for a chill water style a/c for my shop using a chest type freezer. Thanks again.

[@rlbob1]

interesting concept. I am not sure if feasible. As you know a window AC sitting on cinder blocks in the boat cabin would produce more heat than cool. Its the physics and dynamics of the device. Same is true of a freezer. However a freezer uses same principal as a refrigerator or AC. So heat from the freezer condenser would have to be removed. Preferably locate it outside or place in separate room or duct the exhaust.. Only worry is the cooling capacity. I suspect compressor would run constantly. But maybe not if you achieved the desired balance. Sounds like a fun project!

[@prasantamedhi]

COP will be very great.. had the same idea in my mind. glad that you have done it already

[@rlbob1]

The Secret is obviously coiling the copper tubing using a grease gun. It turned impossible into easy.

[@trilexcom]

welcome back sir

[@rlbob1]

thanks

[@rlbob1]

System update: I added 33% Propylene Glycol to the water jacket to prevent freezing and slow the compressor cycling. Yes it was actually cooling to good! It purred along all summer with no issues even during July-August.
Winterizing was also a snap! I just opened the intake line in a bucket of boat antifreeze and turned the ac on for a few seconds.

[@orangezeroalpha]

Thanks for the update and the original video. I just picked up a $10 window AC and was planning something similar, but you've given me some other ideas. Do you happen to have any idea of the temperature difference of the water intake vs output?

[@rlbob1]

It is mildly warm to the touch. 15 to 20 degree difference from intake.

[@orangezeroalpha]

@@rlbob1 Thanks for the reply

[@mustangandfrankenstein]

thats badass.a bunch of smart people still on earth tgat gives me hope in mankind and i love to make stuff rather than go and buy it from corperate america off grid apocoliptic shxt is where the fun is and eventully with be the new america after the world resets it self again like it does million of yrs at a time...question what or how can i kool my minivan down in no shade 100 degree sc day living inside it with a pitbull frankie and myself ?i do access to a power outlet..without putting an whole ac unit sticking out the window like a billbily..or spendng 300 on a 12 volt eco cold air blaster conditioner which id love but am not wealthy and money snd food are scarce...any good suggestions..im pretty handy with stuff so not a complete lay person..thanks and love the vid..

[@rlbob1]

I did it years ago with a Ford E150 van. The van had 2 rear doors. So I took some thin plywood a couple of 2 by 4s and blocked off the opening leaving a cutout for the window AC at the vans floor with a hinge. All of this was on the inside so the door could still close and lock. Worked Fantastic! Pull up to campsite open back door, hinged plywood drops down then slide the AC out and plug it in. The only improvement I made was to cut out a similar hinged piece so I could see out the back windows while driving.

[@rockyhighwayroad7365]

Is the heat exchange just from that copper coil going around the air compressor? Do you cut into the refrigerant line at all?

[@rlbob1]

The heat exchange is the double wound coil inside the aluminum exchanger box surrounding the condenser. If I recall its about 38 feet coiled to 9 inch diameter. Be aware the exchanger box is filled with 66/33 water/propylene glycol mix. The compressor coil, cut down fan and side vents provide adequate ventilation for compressor. The refrigerant line is not cut and one should be careful not to damage it.

[@sto2779]

5:01 - Why do we have to fill the flare caps with grease? Can you explain more on how to do it? Thanks. Interesting, nice modification. Would it be possible to cool the water by radiating it away using fan blown radiators?

[@rlbob1]

The grease is what applies thousands of PSI pressure to the water filled tube. This keeps the copper tubing from kinking. Think of it as an internal core of water exerting 1000 Psi against the sides of the tubing evenly. That's a lot of internal core pressure which until now was not possible.

[@sto2779]

@@rlbob1 Thanks for the reply. I realized it later on. I tried doing this for a different project using sand and didn't work.

[@mahalkasi]

Any issues or is it still working as shown?

[@rlbob1]

Yes It's working better than expected. Only improvement was I added Marine Antifreeze 33% to the heat exchanger to avoid having to drain it in the winter. Good now for -6F. Although this tends to reduce efficiency the exchanger was cooling better than anticipated and the compressor run was very short. Water cools far greater than air. This will become most important this summer as temps hit 100F while the lake temp remains relatively unchanged.

[@haydenc2742]

Do a tube in tube heat exchanger...(aka tube in tube condenser)
ruclips.net/video/vh5dkvXjhZk/видео.html (ex. on how they run a tube inside a tube, braze fittings on the end for the cooling fluid inlet outlet, then the freon inlet/outlet w/ pressure testing) TONS more efficient

[@rlbob1]

YES It is more efficient. I do not see the the inner spiral like in this video. ruclips.net/video/uH-la_eI3mc/видео.html that increases efficiency even more. Unfortunately the tools and skills required would exceed most DIY people. It also would add expense and not fit the existing window unit. It kinda explains why Water Cooled Marine units cost thousands. Thanks for sharing!

[@josephparaskevas7375]

Coaxial water condenser connected to either open or closed loop geothermal.

[@rlbob1]

I also have a simpler video converting the same type unit using duct work and a boost fan.
Video link
ruclips.net/video/BufNIXANedc/видео.html