Marine AC using fresh instead of raw water?

[bensolomon]

I have a stand up portable AC unit that I place the exhaust tube vent through a port hole. It does a good job.

[boat driver]

Originally Posted by S/V Illusion

It's amazing the imaginative ways people find for not doing something correctly.

what's wrong with reaching out with an idea?
Marine recreational A/C systems that cool via open water loop are a poor designed device.
prone to plugging up, noisy, power hungry.

Following up on the water cooling- it is all about the quantity of water vs BTU (simple mathematics followed by experience) followed by (if a closed water tank loop) control of the warm water critters.

The ideal small boat system would use an external closed loop integrated in the hull below the waterline. A large hull/keel skin water tank might have enough heat exchange but it requires more information.
If your conversation suggests this is a simple temporary program for when the vessel is unattended at the dock, then make a 1" diameter copper coil and drop it overboard at the dock, connecting it to the in/out circ water on the unit. This will keep the raw water debris out of the system and eventually you can hard install with seacock.
There is no reason not to share a thruhull with another intake (like the head or sink) provided the water flow is adequate.

[Cwens]

Originally Posted by SeeMonstrEd

I didn't do the math when we were on the hard in a boatyard in GA. I got a 64 gal. trash can a filled it with fresh water from the tap. My 16K BTU AC had it so hot I could not put my hand in it within 15 minutes.

If you really had to do this longer term, and you really wanted to do it in a funky, junkyard-chic style, you could probably MacGyver together an improvised cooling tower: big plastic trash bin half full of water, bunch of holes punched in the top half to let air circulate, recirculating pump that would suck up the water and discharge it through a spray nozzle near the top of the bin, where some would evaporate and the rest would fall back into the tank. Maybe you'd need a fan to boost circulation. And a float valve to keep resupplying with fresh water to make up for evaporation.

You could get bonus style points if you build the whole thing out of stuff you picked up from the recycle pile, including toilet innards for the float valve, etc.

[Idaho]

If the boat is at a marina with running tap water, just run the hose to cool the a/c and dump the warmed water over the side.

Yes. It is not PC. It is not Green. It is a "waste" of fresh water.

It will work.

[CaptTom]

Originally Posted by boat driver

...
Marine recreational A/C systems that cool via open water loop are a poor designed device.
prone to plugging up, noisy, power hungry.

Everything on a boat is a compromise. A properly designed and installed marine air conditioner is efficient, quiet and reliable, compared to the alternatives. Yes, bio-fouling is an issue which requires maintenance.

Originally Posted by boat driver

...The ideal small boat system would use an external closed loop integrated in the hull below the waterline.

This isn't too far-fetched. Many lobster boats around here use "keel coolers" for their diesel mains. Google that for pictures, it's exactly what you're thinking.

That said, you'd still need to do the math. The water around here is pretty cold, and dumping heat from a big diesel is going to be very different than the few degrees difference an air conditioner operates on. My guess is you'd need smaller tubes, and more of them, to be effective.

Originally Posted by boat driver

...make a 1" diameter copper coil and drop it overboard at the dock, connecting it to the in/out circ water on the unit.

Another lobster boat item: "Hot tub coil"

Again, the heat exchange math isn't going to match. With all the air conditioner system fouling issues in southern waters, I imagine someone would have tried this already. Since it's not commonly done, I assume there's a reason why not.

[sailjumanji]

I owned a Seawind 1000 for about 12 years, and now have an 1160 Lite. You already have a thru-hull for raw water, associated with the head (port, stern). You could "T" into that and bring a hose forward to your A/C unit location. But the challenge is going to be around the steps. In both hulls, that area doesn't have any cabinets or walls to hide the hose in - it's basically hull. Even the wiring on the starboard side is in a small channel behind the top step. I don't think there is enough room to run a 5/8 or 3/4 in hose forward to your air con pump.

On our 1000, we installed a Dometic Turbo 8k unit under the v-berth in the starboard hull. Brought the duct work up thru the cabinet between the v-berth and the master berth. It worked well to cool the sleeping quarters, but was probably oversized for that hull even when we cooled all the way back to the head. Would get the temp down to 65 deg, but then came on infrequently, so didn't get the humidity down as much as you'd like. I would probably opt for a 6k unit, if having to do it again.

You could also drop a hose overboard for an intake. But depending upon where you install the air con pump, it would probably have to be very long (coming up and out thru a hull hatch, or thru the front windows in the saloon.

And no disrespect to this group, but there is a Facebook group specifically for owners-only, that is also participated by the factory. You could ask your question there, and get answers from people who own the same boat and might have already addressed this question.

[Audeamus]

Well since you asked we were imaginative/stupid enough to try this (without engineering design calcs) - Could have got some buddies who design heat exchangers to calculate it for me but really there was nothing to lose apart from a few valves and a bit of pipe in our refit. We have an aluminim hull with integral tanks so I thought there might be enough duty in the tank walls to dissipate the heat - there's a large area!
Well on the hardstand the chiller having cooled the main cabin on 54ft mono and running at about 18000btu 200 gallons of water in the tank is hot enough to bath in after 3 hrs. Coolng the "bedroom/cabin" the same result overnight.
We tried in the water with better results - not viable for whole boat but could do small cabin overnight however keeping our main water tank luke warm to hot all the time doesnt appeal. So for a short period of desperation on the hardstand yes - otherwise not really.

[sailjumanji]

Before we installed permanent A/C unit on our Seawind 1000, we used one of the CruisAir hatch units to cool the port hull. It worked well enough, but I got tired of lugging it topside onto the hatch above the berth. And then having to put away when done. It would also alleviate having to install shore power on the boat if you don't already have it.

[jhulmer]

Originally Posted by Cheechako

While in the boat yard in the tropics I thought maybe I could hook up a 5 gallon bucket and run the onboard AC now and then through the bucket and back to the bucket.. NOPE! The water is very hot in 5 mins or less! My guess is an entire water tank wouldn't work.

I tried this also with the same results. I hung the bucket under the discharge thru hull and put a hole in the bottom of the bucket added a hose that would fit the intake thru hull. This continuous loop worked for about 15 minutes before it got too hot and shut down the A/C.

I eventually stuck a water hose in the bucket and added a small flow of cold water until the water spilling out of the bucket was only warm. This worked well and I am still using it in this heat today.

BUT, This is on my property and my water bill. I'm sure a yard manager would nix this idea right quick and in a hurry!
My next experiment (JUST FOR SNITS AND GIGGLES - DON'T BE HATING ON ME) will be with a roll of copper tubing plumbed in a loop in the shade and see if this can dissipate the heat fast enough.
I do have a 5000 BTU window unit that I use when in the yard. I just cut out a piece of plywood to fit the companionway and mounted the unit in it. This works to cool the saloon but barely. And, it is a pain to come and go thru the companionway.
I'm with the OP it's fun to try things and find something that works.

My surveyor came to do the insurance survey a couple weeks ago and was amazed and pleased he had a cool boat to survey.
Cheers!

[aybabtme]

Originally Posted by sailjumanji

And no disrespect to this group, but there is a Facebook group specifically for owners-only, that is also participated by the factory. You could ask your question there, and get answers from people who own the same boat and might have already addressed this question.

I actually asked about where and how people install their AC over there and I think you answered . But the overall "fresh water" thought experiment is more generic and I think works well if addressed to a larger audience.

[aybabtme]

Originally Posted by Audeamus

Well since you asked we were imaginative/stupid enough to try this (without engineering design calcs) - Could have got some buddies who design heat exchangers to calculate it for me but really there was nothing to lose apart from a few valves and a bit of pipe in our refit. We have an aluminim hull with integral tanks so I thought there might be enough duty in the tank walls to dissipate the heat - there's a large area!
Well on the hardstand the chiller having cooled the main cabin on 54ft mono and running at about 18000btu 200 gallons of water in the tank is hot enough to bath in after 3 hrs. Coolng the "bedroom/cabin" the same result overnight.
We tried in the water with better results - not viable for whole boat but could do small cabin overnight however keeping our main water tank luke warm to hot all the time doesnt appeal. So for a short period of desperation on the hardstand yes - otherwise not really.

Amazing! Glad you tried this out!

[dannc]

I am pretty sure that the Dashew's used their fresh water tanks on one, or some, of the early FPB models for the AC system. The FPBs have huge fresh water tanks which are integral to the hull so there could be quite a bit of heat absorbed. Since the FPBs hull and tanks were AL, the tanks were a giant keel cooler.

As I remember it, the problem was that heating the fresh water ran the risk of creating an environment for Legionnaires disease and other nastiness.

Later,
Dan

[Squanderbucks]

I see this quite often on the forum - not wanting a thru hull fitting. I just can’t get my mind around what the big deal is. It’s not like it is something that requires a lot of service or is trouble prone.
If you want to run AC while away I would not recommend using your marine water cooled AC anyway. Get an air cooled window unit and make a temporary mounting. I do this for my boat when it docked at my home dock. I remove it when going offshore.
Marine circulating pumps have a definite not so great lifespan and are not cheap. The raw water pump costs is more than a window unit.
Leave your costly marine AC unit for use while you are on the boat.

[aybabtme]

I'm sure you can stretch your mind a bit and guess why someone might think that no hole is better than a hole. The best way to not have a problem with something is to not have it in the first place.

[sailjumanji]

Originally Posted by aybabtme

I actually asked about where and how people install their AC over there and I think you answered . But the overall "fresh water" thought experiment is more generic and I think works well if addressed to a larger audience.

True. Another thought that I think someone else had as well, is to install a window unit in a replacement companionway board. For the SW1000 specifically, it would be a PITA to step over it, maybe even impossible to get into the port hull that way. OTOH though, it's cheap. And just toss it when it no longer works. The bow hatch is pretty big, and you could use that for going in and out the port cabin.