Cross posted in the electrical area...Newb question

Gentlemen, I am about to purchase a 47 ft trawler and it doesn't currently have A/C or heat. I have perused the different types available on line and my question is : would an in roof 'RV type' system do the trick or would it be advisable to spend the extra and get a water cooled, ducted type deal ? My wife doesn't handle heat or humidity too well and the craft will be used in the Gulf mostly with the occasional longer voyage after I semi retire....hahaha...

Thankyou !!!

Water cooler? You talking about evaporative cooler like used in the desert and other low humidity areas where water drips down across a membrane and a circulating fan blows the cooled air into the cabin? Forget it!. You need something with a compressor and evaporator and condenser coils. Got to get the humidity out of the cabin if you want to feel the effects. Get the roof mounted, conventional refrigerated AC unit but ensure the roof will support the weight.

Water cooled Mark, not water cooler....as in an A/C unit that is cooled by a thru hull water flow...

AussieCraig said:

Water cooled Mark, not water cooler....as in an A/C unit that is cooled by a thru hull water flow...

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Ok. Not familiar with that. Water cooled meaning that the system is dependent upon the temperature of the surrounding water to cool a room? So you pump water through a finned coil and blow air across it........Yes?

Problem I have with that is still humidity in the room and temp differential.

On cooling, sit a glass of ice water on the counter in a humid environment. The condensation that drips from it is moisture in the air that you really need to get rid of. If there was no moisture there would be no sweating, to take it to a limit. Then sit a glass of cool water on the counter. Not much dripping. So not much temp differential doesn't result in dehumidification.

Second thing, if you are out in open water in the summer with the sun shining, the surface water temp isn't much cooler than ambient air. Refrigerated air systems use about a 30 degree temp delta to function properly. The evaporator coil that supplies the cold for air entering the room starts out at about 30 degrees cooler than the room temp before the refrigerant travels through the whole coil, picking up the heat in the room and departing.

Outside, the condenser coil is fed high temp pressurized coolant that is at or above ambient and the air outlet of this coil is about 30 degrees hotter than ambient.

I'd still go with the reefer. Besides it's a contained unit and no water pipes to route, leak, corrode, etc. Millions in use and costs are reasonable and replacement parts are abundant. Coleman is one mfgr. of such an item. Trusted name in outdoors here.

Mark

Easy answer, Spend the extra and get the marine a/c system. You can also get a keel cooler for the system.

I just googled marine water cooled AC systems and this is what I think I see.

You still have a refrigeration system like conventional domestic systems as the compressor is clearly visible, but no condenser (hot) coil. The compressor pressurizes the return freon gas from the evaporator (the cold coil) and as it is compressed and gives up the heat that it picked up in the living quarters. The system uses a freon/water heat exchanger to remove it.

The water circulating in that loop goes into a coil beneath the boat where the ambient water dissipates the heat, rather than blowing air across a condenser coil. This allows for multiple units in boats with no outside access. You don't need outside access for the condenser fan discharge. You just quietly take the heat away through a water pipe and this gives you an application anywhere on the boat. Makes sense.

So, yes you can freeze your twatsie off with that and remove room humidity also as both machines seem to be identical in that function. They have evaporators running 30 degrees cooler than ambient. The warm moist air blowing through them condenses on the cold coil and produces condensate liquid which just drains off just like domestic units.

If you have a nice unobstructed roof on your cabin that can support the weight, I think the Coleman RV would be your least complicated system and much cheaper than the marine. All you need is 115vac (probably as it is 15k BTU and 115 can handle that) a hole in your roof, and a drain pipe. Or just let it drain across the roof and fall where it may....but you probably don't want to do that.

Mark

Thanks Mark, I am thinking of a combination of rooftop for the stateroom and a water cooled, ducted deal for the main living areas....

AussieCraig said:

Thanks Mark, I am thinking of a combination of rooftop for the stateroom and a water cooled, ducted deal for the main living areas....

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I don't know your boat but sounds like a plan. Good luck,
Mark