Trawler Air Conditioning

What do you guys use for air conditioning on a trawler? Is it the standard marine type sea-water cooled compressor type or do you go for the much much less expensive roof air mounted type?

I plan on an RV rooftop , we are not live aboard in FL, and try to travel in season.

The "look" is fine as we are not a "yacht" , and "what works" is the first key to a successful commercial vessel.

For months at a FL slip , the Cruise air , but with a very readily available sea cock (to remove jellyfish) would be first choice ,

esp if many cabins are required to be chilled.

I use the standard sea-water cooled system,* works well and has reverse cycle heating.

However the rooftop unit has an avantage because the return is always drawing the hot air off the cabin overhead.

A return high up in the cabin is an advantage for cooling, something that is not easy to do with a ducted system. ( without wasting space, or doing a lot of cabinetry and stuff)

JohnP

I currently have and have had the sea water cooled marine air conditioners and am very happy with it. I am also a Mermaid dealer. The boat I am looking at now has a roof mounted AC unit and is on its deathbed. I was wondering about replacing it with a roof mounted unit mainly for cost and ease of installation woith no ductwork required. This is over the main salon. I am not going to cut more holes in the roof for the V berth or the aft cabin roof. That just ain't gonna happen.
I currently have a 39' sailboat and my 16.5K unit barely can keep up with this heat in Houston area. The trawler has a lot more window area (probably like ten-fold) and also more cu. feet. to cool. I'm sure I will need 2 units. Just not sure yet how I will*do it that is why I am asking.

Thanks for the info and keep those posts coming.

*

Thanks

Tony B



-- Edited by Tony B on Sunday 7th of August 2011 07:37:42 AM


-- Edited by Tony B on Sunday 7th of August 2011 07:40:50 AM

Old Stone wrote:
....*I have 4 seperate marine systems on board ..... 'Would suggest using stand alone systems though, and not a single pump .....

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*Does this mean that each cabin has it's own AC unit? That's a sizable investment and was hoping it would not be necessary. Mermaid has a new 24K unit but it is 220V only and that wont work for me.

*

I too am in the Houston area with a 32' trawler. It has a 16,000 btu marine unit. I had to cover the salon windows to do a good job of cooling. I am about to install a "window" unit in the anchor locker for the v-berth area. I saw an artical in one of the diy boat repair magazines about the installation of a window unit in the anchor locker so I will let you know how it works soon.

I did think about installing a roof top rv model for the v-berth but thought i would try the economical window unit first. It should cost about $125 for the window unit and if that doesnt work then about $1,000 for the roof top. A marine unit would be over $2,000

"Sabi"
Bobby

It's been so hot this summer, I installed one of those portable AC units from Home Depot in the saloon. Kinda ugly with the big hose venting out the window, but sure helps! I had to run an extension cord out to the unused outlet on the dock power tower so it would run without tripping the boat breakers.

Gotcha. Good point.

Thanks

We have three Mermaids on our boat....two 5K's and one 16.5...one of the 5's cools the V-berth and galley, the 16.5 cools the salon and galley, and the other 5 cools the aft cabin....and is vented to supplement the salon AC. We're quite happy with them. All three units are reversing heat pumps.

a keel cooled, reverse cycle, central chilled water air conditioning system is going into mine...don't know how it will work - hoping for the best.

Keel cooling removes the problems with clogging the intakes so the pump should not have problems. My unit has twin compressors so if one fails, the other takes over.*

It's a new build Diesel Duck (and slow build) - metal hull, keel cooler on one side for hydraulics + aircon combined into one system and a keel cooler on the other side for the engine. Very much like Delfins systems....

The aircon has an "heating option" to chose either reverse cycle or heating through a diesel heater.

The pipes will be welded onto the hull.

The aircon is a Webasto chilled water cooler - the pipes that delivers the chilled (or heated) water are routed through the bulkheads to each "fan-unit" in each cabin.

A Webasto diesel heater is connected to the aircon, that way the same pipes are used to either cool or heat the cabins....

the thing about "don't know how it will work" is because the company that dellivers the aircon says that it will not work with keel cooling - I will give it a try though......

The company that delivers my aircon says it will not work - so I am setting up a back-up delivery pipe from the raw water delivery + setting up a return drain thru-hull for the waste water. That way - if the guy is correct - I will be able to switch over to raw water cooling....and then I will probably have some strainers that will have to be cleaned on regular intervals........


-- Edited by Singleprop on Thursday 18th of August 2011 07:11:31 AM

Singleprop wrote:
The company that delivers my aircon says it will not work - so I am setting up a back-up delivery pipe from the raw water delivery + setting up a return drain thru-hull for the waste water. That way - if the guy is correct - I will be able to switch over to raw water cooling....and then I will probably have some strainers that will have to be cleaned on regular intervals........

*

Click to expand...

*Mine is coolant circulating through half pipes welded on the hull - basically one side of the original plumbing for the engine, now replaced with a Walter keel cooler.* The other side is used for cooling the*hydraulics.*Seems to work fine, although I admit that here in the NW it is not exactly worked hard.

Why does the vendor think keel cooling won't work?* Not enough heat exchange through the pipes?


-- Edited by Delfin on Thursday 18th of August 2011 10:10:47 PM

Don't know why he says so, there is plenty of cooling area...

Was discussing this the other day and someone came up with a crazy thought. Why not extend an intake pipe down to a deeper layer where the incoming water would be cooler? I sort of immediately poo-poo'd the idea, but it's kinda stuck in my head. Not for cruising of course, but for folks mostly sitting at the dock. Just posted as an out-of-the box idea.

The freon in the system gets to quite a high pressure , and therefore temperature .

Cooling with 60 deg water or 80 deg water will not change the Delta T by very much.

A larger heat exchanger would be better if the system is distressed.

I wonder why on a new cruising boat why internal box coolers which have no drag or external dangers was not chosen.

The math is easy in one of Dave Gerrs books.

Keith wrote:
Was discussing this the other day and someone came up with a crazy thought. Why not extend an intake pipe down to a deeper layer where the incoming water would be cooler? I sort of immediately poo-poo'd the idea, but it's kinda stuck in my head. Not for cruising of course, but for folks mostly sitting at the dock. Just posted as an out-of-the box idea.

Click to expand...

*Not a crazy thought up here in the NW.* While an extreme example, in Desolation Sound the surface temperature of the water might be 75 degrees but 5 feet down its 52.

TonyB, You said you were a Mermaid dealer and you are thinking of using a roof top unit. Are you out of your mind? Put in a Mermaid AC, they're very good units.

"you are thinking of using a roof top unit"

These are had at an RV dealer for $500-$600 , with a low amperage and soft start feature.

Mounted on a cabin top they seldom see much salt spray .

They are very efficient as hot air rises , so special oversized return ducts need not be built into an existing boat.

Most will last over a decade dockside , sometimes much more, 2x that .

Like most AC systems their death is from low voltage .

$50 a year for a maint free air cond setup, that could be installed in 10 min with an existing hatch , doesnt seem baf to me.

For the cruiser who may only need it for a season or two its beyond ideal! AS it has resale value.

Fred, Please not on that pretty Yankee boat of yours! I guess it's a personal thing. I just think roof top air conditioners look awful on boats.

"I just think roof top air conditioners look awful on boats."

Perhaps on Yachts , but commercial looking boats usually look fine when practical solutions are used.

Where does the condensate go on those unit? A tube led over the side?

Keith wrote:
Where does the condensate go on those unit? A tube led over the side?

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*I plumped mine into a small shower bilger located in the E/R that also drains a utility sink below the waterline and the pressure relief from the boiler and water tank.* If it fails, it would just overflow into one of the bilges.

Where does the condensate go on those unit? A tube led over the side?

Yes,

Many dump any excess right into the mounting pan , where a 1/4 inch hose or tubing tales it down with no mess.

Both of our marine a/c units do not work. I figured until I get around to fixing then I would buy two 99 dollar window units. They work good and I see no need to hurry and fix the marine units.

One boat here built a stand on the pier to hold the window unit, and ducted it into the boat. Looked real trailer park but seemed to work fine while he was at the dock.