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Old 27-01-2018, 07:44   #1
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Sizing Air Conditioning Units

I am purchasing a Lagoon 380 S2 and am considering adding air conditioning. Are there published values for the area of the living space in the hulls and saloon (or has anyone calculated them)? Knowing this will help me to properly size the unit(s). I am trying to minimize the electrical and weight loads of this project.
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Old 28-01-2018, 01:17   #2
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Re: Sizing Air Conditioning Units

Where are you sailing that you need AC? We are in the eastern Caribbean and see charterers run their generators 24/7 and stay inside to keep cool never to be seen outside!! Isnít the point of being here, to enjoy the outdoors?!

Not to mention the cost and maintenance having it on your own boat.

Anyway Iím not trying to judge your reasons, just something to consider and you might want to try living on your 380 for a while to see if you really need AC or not.

Cheers!
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Old 28-01-2018, 04:15   #3
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Re: Sizing Air Conditioning Units

Greetings and welcome aboard the CF, datfoos.

A “rule of thumb” recommendation for sizing marine air-conditioning is about Ī 14-to- 15 BTU/h per cubic foot of cabin volume.
More glazing, pilot house, etc = more heat gain; so perhaps up to 17 BTU/h per cu. ft.

Lets Talk Air Conditioning - Size Matters

Sizing the right air conditioner for your boat
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Old 28-01-2018, 04:24   #4
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Re: Sizing Air Conditioning Units

Quote:
Originally Posted by krafthaus View Post
Where are you sailing that you need AC? We are in the eastern Caribbean and see charterers run their generators 24/7 and stay inside to keep cool never to be seen outside!! Isnít the point of being here, to enjoy the outdoors?!

Not to mention the cost and maintenance having it on your own boat.

Anyway Iím not trying to judge your reasons, just something to consider and you might want to try living on your 380 for a while to see if you really need AC or not.

Cheers!
Actually you are judging. Everyone I see down here in the Caribbean that says they don't need A/C on there boat either can't afford to buy it or spends all there time on the hook where there is no way to run it. Unless you want to spend all your time sweating, and smelling bad buy the A/C.
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Old 28-01-2018, 08:06   #5
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Re: Sizing Air Conditioning Units

Krafthaus: That's the dilemma. I don't expect that we would use A/C too much, and we expect to be between NYC and the Caribbean. The reverse cycle units also provide heat, when necessary and that would extend our useful enjoyment of the boat. Therefore, I am trying to understand what size/power/weight considerations there would be if we were to install.
GordMay: Thank you for the links. Again, we're trying to weigh all options, including possible propane-based heating systems in lieu of the reverse cycle heat/cool electric systems. As always, it's a compromise.
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Old 28-01-2018, 08:49   #6
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Re: Sizing Air Conditioning Units

I would start by checking with Lagoon to see what size unit(s) they installed as option on your Lagoon. This should also give you insight as to where they put the unit, thru hull, pump, and supply and return grilles and ducting. For reference, Seawind puts a single 18k BTU unit on their 1160 (38 ft) catamaran. The single unit has the advantage of taking up less space that multiple units.

We have an 8k BTU unit on our Seawind 1000 (33 ft) cat. It is installed in the port hull - which is the primary sleeping quarters and head. It's a bit too much AC for that space, but was the smallest Dometic Vector Turbo unit sold at the time. It gets that hull down to frigid conditions, and heats well too. Its really nice to pull into a marina, close everything up and run the AC, and really dry out all of the bedding, clothes, towels, etc. Plus, nice to close up and be secure while at a marina, with the AC running. That's really the only time we run the AC - at marina - because the boat has good hatches and air flow. But sometimes marinas spaces are not aligned with the wind for ventilation, plus again we feel more secure with the boat closed up.

At anchor, we can run the AC with a Honda 2000 generator. We've only done that a few times - August in Texas can get dead calm and temps in high 90's. A friend has the same boat with a Dometic 16k BTU unit, and it also can be run from the Honda 2000. He cools his entire boat - not to frigid levels - but comfortable enough. There is a lot of cooling lost to zip up salon enclosures, so not real efficient. Not comparable to closing up your Lagoon. And the Honda 2000 is relatively easy to stow, and runs about ten hours on 0.9 gal of gas.
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Old 28-01-2018, 08:49   #7
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Re: Sizing Air Conditioning Units

I added AC on my ex L450 because I thought it could be useful. I cruised 4 season in S. Pacific and I never turned it ON once... I anchored almost exclusively.

If you have enough ventilation you should be fine. My wife and I did not want to be closed inside the boat with the AC ON and generator running. Also, it was hotter at night. We did not want to run the AC and generator all night.

On my new boat I am ordering a diesel heater only. I do not like the cold.
In my opinion, with the AC you add expense, maintenance and you loose storage space.

This has been my experience.
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Old 28-01-2018, 10:10   #8
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Re: Sizing Air Conditioning Units

Most times we have liked to use Air con is when at a dock in East Coast USA in mid summer with the boat either not facing the breeze or there is no breeze.

A very simple solution is to buy a portable domestic air conditioner(s) that are very cheap in Walmart etc. and plug into shore power. We did not use the boats main air con as we have European voltage, so bought a portable (8000 BTU) - but next time would buy the biggest portable possible (or a second) as the 8000 only just took a few degrees off - to make it bearable..

Anchoring out there is nearly always breeze, but when there is none inevitably the mosquitoes come and the screens block air flow. So that is when we run the boat's main AC on a generator. It is a big investment though for just a few nights of discomfort.
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Old 28-01-2018, 10:34   #9
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Re: Sizing Air Conditioning Units

One of my boats had ac installed when I got it. I never used it at all in the Caribe. Maybe if I was at a dock that had power I would have. If you get AC, you need a generator... and the weight and cost just keeps adding up and up.
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Old 28-01-2018, 21:16   #10
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Re: Sizing Air Conditioning Units

We just installed AC on our 400S2.
That said the install was a single unit not 3 and it works very well.
The ducting supplies the owners cabin and the main salon.
It gets used in the marina where the wind is usually not so great.
If we want to use it at anchor we can run it on our Honda 2000 with inverter assist for the start up loads, that said we have never needed AC at anchor.
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Old 28-01-2018, 21:27   #11
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Re: Sizing Air Conditioning Units

Quote:
Originally Posted by Scottster View Post
We just installed AC on our 400S2.
That said the install was a single unit not 3 and it works very well.
The ducting supplies the owners cabin and the main salon.
It gets used in the marina where the wind is usually not so great.
If we want to use it at anchor we can run it on our Honda 2000 with inverter assist for the start up loads, that said we have never needed AC at anchor.
What size did you install, and where did you install it?

Thanks.
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Old 29-01-2018, 07:22   #12
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Re: Sizing Air Conditioning Units

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Old 29-01-2018, 08:22   #13
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Re: Sizing Air Conditioning Units

Quote:
Originally Posted by datfoos View Post
I am purchasing a Lagoon 380 S2 and am considering adding air conditioning. Are there published values for the area of the living space in the hulls and saloon (or has anyone calculated them)? Knowing this will help me to properly size the unit(s). I am trying to minimize the electrical and weight loads of this project.
Use the following for the living areas of the boat:
For below deck areas:
Multiply Length x Width x Average Height x 14 BTU's
For above deck areas:
Multiply Length x Width x Average Height x 17 BTU's

Example: 12 x 8 x 7 = 672 cubic feet x 14 BTU's = 9,408 BTU's Needed
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Old 04-02-2018, 21:32   #14
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Re: Sizing Air Conditioning Units

Have a 380 and have considered this as well. 1. Do you have a genset to run it away from shore power. 2. I am most interested in this for sleeping, so I have considered a smaller unit just for the owners side. 3. I also considered putting a larger single unit in the main salon, and just the principle of letting the cooler air fall down to the sleeping areas. I would use fans to suck the air down at bedtime.

Lagoon factory option had multiple units. You need this if you want to make it like your house. I figured I just wanted to cool down but really just get some of the stickiness out of the air to sleep more comfortably. I don't need it to be 70 Dec. 75 with a fan and less sticky would be great and save me money and less weight. My 2c.
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Old 04-02-2018, 21:43   #15
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Re: Sizing Air Conditioning Units

Iíve always wondered about buying a cheap Home Depot portable AC unit exhausting it thru a porthole. Powered by the Honda generator. Or shore power when at marina or in the boat yard.
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