Raw water air conditioning?

Status
Not open for further replies.
bcollis

bcollis

.
Apr 16, 2010
79
88 Hunter 30 Solomons, MD
Has anyone made their own sea water air conditioning unit? I found a small radiator, attached some 12V .35Amp fans with a small 12V 2 Gal/m water pump, and will get a couple of hoses to run overboard. Since the water five feet below the surface is around 70 degrees or so here in the Chesapeake, how well should I expect this to work, if at all? Anyone have any experiences they'd like to share?
 
Delezynski

Delezynski

.
Jan 22, 2008
551
NorSea 27 Az., Doing the To-Do list
When we were cruising in the Sea of Cortez, the surface water was in the 95 Degree F range or above.

Our washdown pump is on deck and I use an overboard hose for the pickup water. I extended the hose and added a weight and filter to the end and drew water from about 10 to 15 feet down.

It was WAY cooler and I would spray the deck every 15 to 30 min. It kept the inside of the boat a LOT cooler! And an occasional splash on us helped also.:)

Greg

 
DeniseO30

DeniseO30

.
Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
Not worth the effort I'm sure. Water, to cool air would have to be cold enough to reach "due point" Like the ice cubes in your glass on a hot humid day unless you can get the water from down deep at 55 degrees.and even then it's doubtful.
Even 60 degree water would not cool the air much at all.
 
B

Benny17441

.
May 24, 2004
7,164
CC 30 South Florida
Ahhhh? Is not going to work. A few CFM of 70F air will be gobled up by the volume of air at 100F inside the cabin and the heat that radiates into it. I like Greg's method; we have found that by hosing the cabin top and deck down we can reduce the temperature inside the cabin by 5-8 degrees. An awning that keeps the direct sunlight from the deck and allows ventilation to flow in between can give you another 5 degrees so instead of having a temperature of 100 F inside the cabin you may get a much more comfortable 90 degrees. We do this at the dock but having a pump to draw sea water could allow similar benefits at anchor. The real benefits are more noticeable at night as it allows the boat to cool down a lot quicker.
 
Delezynski

Delezynski

.
Jan 22, 2008
551
NorSea 27 Az., Doing the To-Do list
The evaporation of the water on my deck also lowered the themp a lot. like what Benny said, we have a shadetree cover that funnels air at anchor. So the system works better than when the aire is still.

I once worked in the Middle East and the company put in a pool with a cover. We had to install a pool heater! The evap lowered the pool temp so much it was not usable until the heater was put in.

Greg
 
TFrere

TFrere

.
Oct 1, 2008
144
Morgan 382 Mandeville, LA
I have a friend that claims he took a window unit a/c and converted it to water cooled. He said he had to replace the pan with aluminum but it was a simple job. Sure beats the cost of buying a marine unit. I'll find out more and post another comment later.
Tommy
 
Delezynski

Delezynski

.
Jan 22, 2008
551
NorSea 27 Az., Doing the To-Do list
A/C at dock v at anchor

When we spent a few summer months in Mazatlan Mexico (SOOOO HOT), we use a small room A/C unit I mounted in our forward hatch. No mods to it. Lowered the humidity so much that any cooling made the boat like a meat locker. ;)

But no A/C unit I know of is practical on a small boat at anchor for any length of time.:cry:

Greg
 
Bob J.

Bob J.

.
Apr 14, 2009
774
Sabre 28 NH
Chilled water systems have a leaving water temperature of 45 degrees. The air side of the unit has a leaving air temperature of 55 degrees. Using 70 degree water would give you a leaving air temperature of 80 degrees.
 
kloudie1

kloudie1

.
Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
T Frere.. a couple of the machinists that I worked with had done that.. taken a 8000 btu window unit and replaced the condenser with a little shell/tube exchanger that had a high enough working pressure I think it may have had a former life as an oil cooler in a compressor?.. we cog-belt drove a small pump off the shaft that used to have the fan for the air cooled condenser. Both units went into 26 foot boats, one sail and the other a little cabin cruiser.. both worked fine..
 
A

alexco38

.
Sep 25, 2008
1,096
CS 30 Toronto
Yeah I am thinking of the same.

You can get a 5,000btu window AC from Walmart for $98. Ditch the condenser and replace it with a tube-in-tube heat exchange. I am thinking of brazing together a 3/8 copper tube inside a 3/4 copper tube. A low volume water pump can be used to pump raw water through it.

You can't even buy a compressor for that price. Most likely made in China;-(

The evaporator coil is about 12 inches square. I can just use a squirrel cage fan for it.

The replacement refrigerant is about $16 a can.

That may be my winter project this year.

Yes, Denise030 is right. You need "dew point" in order to cool.
 
S

SVCarolena

.
Oct 17, 2007
40
- - Washington, DC
alexco38 said:
Yeah I am thinking of the same.

You can get a 5,000btu window AC from Walmart for $98. Ditch the condenser and replace it with a tube-in-tube heat exchange. I am thinking of brazing together a 3/8 copper tube inside a 3/4 copper tube. A low volume water pump can be used to pump raw water through it.

You can't even buy a compressor for that price. Most likely made in China;-(

The evaporator coil is about 12 inches square. I can just use a squirrel cage fan for it.

The replacement refrigerant is about $16 a can.

That may be my winter project this year.

Yes, Denise030 is right. You need "dew point" in order to cool.
Click to expand
If you are going to go to all that trouble, why not just mount the AC unit in the companionway like a lot of people do? All you would need is to fabricate a couple new hatchboards. For the past few years, we have been using one of the floor AC models with a hose that we vent out of one of our ports (in a house, it would go to a regular window). However, we are now intalling a standard marine AC, mostly to get the cabin space back and so we don't need to worry about rain coming in at night.
 
Delezynski

Delezynski

.
Jan 22, 2008
551
NorSea 27 Az., Doing the To-Do list
As I said, we used a small $100.00 window unit in our forward hatch. I built a mount using an $8.00 piece of the pink insulation board and a box cutter. Worked GREAT. Did not lose any deck/cabin space.

Greg
 
Gunni

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Have you seen the Mayor of New York's solution ?

OK, you don't want to sweat. And as we know, nothing evaporates in the Chesapeake Bay this time of year - it boils off. I suggest some 12vdc cabin fans immediately and a shiny new marine heat pump install over the winter. They provide a low energy "dehumidification" mode while away, and pump heat during the shoulder seasons. You know you want one... and you can't take those boat bucks with you! They are babe magnets my friend! :evil:
 
A

alexco38

.
Sep 25, 2008
1,096
CS 30 Toronto
(1) a standard marine AC = $1,500+, nice but not in the budget
(2) I don't like a window unit sticking out the front hatch which is slanted, the boat will look a bit strange
(3) A floor unit takes up way too much cabin space
(4) The admiral won't like a thing sticking in the companion way
(4) Too heavy to lug around when racing

I figure hacking up a "new" window unit may cost around $200 with a new water pump. It worth a try.
 
S

SVCarolena

.
Oct 17, 2007
40
- - Washington, DC
You should be able to get a marine unit for less than that. We got one for much less than one BOAT unit during a sale from a merchant I won't mention out of respect for the store on this site. Also remember that most marine units also provide heat when the hot weather passes.
 
Bob J.

Bob J.

.
Apr 14, 2009
774
Sabre 28 NH
alexco38;938643I figure hacking up a "new" window unit may cost around $200 with a new water pump. It worth a try.[/quote said:
When selecting the water pump just keep in mind that 2.5 GPM @ 45 degrees equals 1 ton of ac (12,000 BTU's)
Click to expand
 
kloudie1

kloudie1

.
Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
Denise.. yes, the normal ones are coax exchangers.. but they don't have to be.. We used a little shell and tube, much like the one on an engine, only smaller and rated for much higher pressure.. The coax ones are a lot cheaper to build.. we "found" the little shell and tube unit as part of a wrecked industrial gas compressor.
EDIT: maybe the correct word today is "Re-purposed" the exchanger..
 
anchorclanker

anchorclanker

.
May 27, 2012
1,152
Oday 222 Beaver Lake, Arkansas
The system described would work, its just a hot water heating system in reverse, something thats been around over 100 years. Dew (not due) point has no effect on it, unless your talking about a swamp (evaporative) cooler. It would be quiet, and consume minimal power (at least a 10th of any AC unit). The question is its efficiency. If the radiator isnt large enough or is inefficient, you wont get enough cooling. If you can get the efficiency up high enough, you should be able to get return air close to water temperature. Also, you could drop a line all the way to the bottom to get into even colder water. Though the line may need some insulation to keep it from heating on the way up.
 
Status
Not open for further replies.

Top Bottom