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Old 04-10-2014, 23:41   #1
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Small AC units

We are in the process of buying a 47' used catamaran. The idea is to sail predominantly in the trades. I was hoping it would have AC but the boat we love does not. Does anyone that has a unit or two that does not have piping throughout the boat have a suggestion or input on what brand or size will cool off a salon, cabin etc? I've heard there are good portable ones. We will use as much solar power and wind power as possible so not looking at running the generator very much.
Starting from scratch here and I know some of you will say get used to it but no, I grew up in the tropics and I don't feel like sweating when it's hot, muggy, raining, buggy, and especially when it's all of the above!
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Old 05-10-2014, 07:59   #2
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Re: Small AC units

Originally Posted by sail2travel View Post
We will use as much solar power and wind power as possible so not looking at running the generator very much.:
Its a BTU Laws of Physics problem that just can't realistically be solved by wind and solar....if you want the comforts of AC then you will have to run a generator to get it. Oh sure you can find small DC AC systems but they are really designed for small sleeping cabins and even a that who can sustain a 30Amp DC load from their battery bank all day and night? No one I know and I have 1380w of solar with a 400AH liFePO4 battery bank and wouldn't try it. AC take power baby....Honda 2000 type of power or a diesel genset.
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Old 05-10-2014, 08:19   #3
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Re: Small AC units

Rich is quite correct. Theoretically it is possible to run an air conditioner on batteries, DC or inverter but practically it isn't practical. It would come down to using an ac unit so small it would almost cool a closet or adding so many batteries and so many solar panels you would have to double the size of your boat to carry them.

Air conditioning equals generator or shore power.

That being said there are lots of fairly compact units that are pretty efficient and would run on a Honda or very small diesel genset. However to cool the main salon of a 46' cat, especially in the tropics with all the windows letting the sun in you will need something a bit larger than the minimum size unit.

If you want to avoid long runs of ducts around the boat you can go with two units or more units, one for the main living area and one or two smaller ones for the sleeping areas. That might be more energy efficient as well since you cool only the areas you are using; sleeping cabins at night and the main salon in the day.
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Old 05-10-2014, 14:07   #4
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Re: Small AC units

We run an 800w unit only when we have shore power. It is one of those self contained mobile units for small rooms. anything over 30 degrees outside and it struggles to keep the temp at 26 and that is trying to cool a small saloon only. I had to put a 100 mm hole to out side to shift the heat away. It's closed off for cruising. I don't know if I'd want it open under any circumstances when we're at sea.

On A large cat 2400w might work but that's 200 amphours on 12 volts. Given that you can't reclaim a lot more than 50% charge, you need 400+ amphours of storage for an hours running. To keep the system running on solar/wind you would need to be pumping in over 3000w every hour without fail. Mosrt solar units will never consistently give you their rated wattage and wind is even more unreliable. I wonder how cool it gets in the middle of the ocean when the sun goes down.
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Old 05-10-2014, 14:16   #5
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Re: Small AC units

OK Got it. No way to do this without the genset. Anyone have recommendations for the portable units at sea? Durability and strong enough to cool the salon?
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Old 05-10-2014, 14:28   #6
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Re: Small AC units

I was skeptical of portable AC units, but four weeks of experience has changed my mind. An LG 8K BTU portable AC unit can cool the master cabin of a Nauticat 43 with daytime temperatures approaching 100F. I can run off either the engine or 30A shore power. However, a second LG 14K BTU can't be run off the same 30A shore power without blowing dockside fuses (when one of the compressors kicks on). So, a second 30A shore power line is needed for the second portable AC unit. The second one cools the pilot house and galley areas. While on the hook, our 5KW diesel gen can power one or the other units, but not both.

The LG unit has some technical advantages. Water is collected by the system into a catch tray that needs to be emptied periodically. So, the system isn't trying to do the impossible: lower ambient humidity and automagically get rid of the water. Also, the systems come with a small section of tubing for hot air exhaust. In the master cabin, this is exhausted out one of the portholes. In the pilot house, the exhaust goes out one of the hatches.

Eventually, we'll get a central unit. But, in the interim, these portables have been very pleasant and effective. Please, note that, for the price, I would not expect great longevity of the portable units.
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Old 05-10-2014, 15:12   #7
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Re: Small AC units

Get a 2 hose unit if you can work out the routing of hoses. Our 2 hose unit went out this summer and we bought a new one hose unit, it sucked in a ton of hot air from outside. I have a new 2 hose one coming next week with a drain hose.

This is the one we just ordered:
EdgeStar Extreme Cool 14,000 BTU Dual Hose Portable Air Conditioner & Heater - AP14001HS
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