I'm Installing Air Cond. in 51' s/v in Panama

[Geoff H.]

Hi to All. Un Mundo is in Panama swinging at Balboa Yacht Club. I'm in LA working on ELEMENTARY for CBS, but will be back on my baby at Christmas. I'm going to install central air. The Dometic rep in Fla wants to know what cubic size is.
Funny haha, but I've never measured the interior for anything like this -- anyone have an idea what a 51' Formosa Ketch measures out as in CF???
(AREAS TO COOL: I don't care about the fwd v berth cabin much, but the mid (fwd) guest cabin, and going aft, the galley and dining cabin, then upper salon, then aft master stateroom, are all important for cooling.)

Lastly, does anyone love or hate Dometic? Anything better?

THANKS!!
GEOFF

[DSDman]

looking at all the venders at the boat show it seems like you have a few options. Do you want AC 110 or 220 units or DC 12 or 24 V units? how and when will you use them? On the hook with generator or just at night on battery power, or all the time plugged into the dock? According to how you answer those questions will lead you to battery bank size, charging methods, generator size, etc etc, all that will probably point you in one direction or manufacturer. I currently have 4 220 v units in my 60 footer. I'm working through all these questions now as I will have to start replacing them soon.

[DSDman]

For the tropics each guest cabin should have 8000 to 12000 btu worth of cooling. The main salon area should have 16000 min probably. That is how my boat is set up 220 v = smaller wire. each cabin has it's own unit. Not sure how that would work out with a central system. All mine still work, they are just getting very old...sometimes they take a little mechanical encouragement to get the squirl cage going. I'm thinking I would like to go all dc next.

[Sailorman375]

If you can run some ducts considering the cabins you want to cool, you should be able to get by with two 16K units. If you have 220V power you can go up to 20K or 22K for main cabin and another at 16K. 16K is about the limit for 120V power.

[Geoff H.]

Thanks very much to all. I'm thinking 110 at the dock and at anchor will be running the 5K Kohler gennie. I was hoping with ducting (I have plenty of room), and not needing things cold but just comfortable and not too humid, that two units, kind of split fwd and aft, might work. I've got 12v fans everywhere. For last cpl of yrs. I ran a home "window" unit sitting in the companionway hatch, which worked fine for my needs, except it was always in the way, and was noisy,) so this will be a big improvement..... I hope.

[DSDman]

I would be interested in what you finally decide on and which way you go and how well it works once you do it!

[sailvayu]

With 120 30 amp service you will not be able to run much more than 12k on a single shoreline, Add another 120 30 amp line and you could do 24k safely. A boat this size you will want 24k min. The generator is another limitation. It really boils down to what your power supply will handle, do not push it or you will burn up shore cords AC units and maybe your boat. You may do the calculations and think you can run more but I know from experience this is about the max you can do safely. The sales reps want to sell units based on volume but they never consider power supply. Almost all brands use the same compressors so it boils down to cost and features. Domatic is the big name and there are tons of dealers not a bad product either.

[btrayfors]

Geoff,

With a 5K generator, I'd think about installing two 16.5K BTU A/C units, since the generator could quite handily take care of these, including the AC water pumps.

That should be enough to cool your 51' with no problem. I have a 16.5KW BTU unit and a 12K BTU unit. The larger one alone keeps my 42' boat liveable even in 100-degree F weather. My 3.5KW generator won't quite run both; it will start them and run them for a few minutes, but quickly overloads. A 5KW genset would do better.

My A/C units are by Flagship Marine. I chose these because they have a large coil -- the diameter of your thumb -- which is used for heat, rather than a heat exchanger such as the Dometic A/C units use. This avoids any moving parts, and any ingress of water in wintertime. Just one of these 2,000 watt heater coils keeps my boat warm in even the worst winter weather conditions.

FWIW,

Bill

[Ex-Calif]

Originally Posted by Geoff H.

to know what cubic size is.
Funny haha, but I've never measured the interior for anything like this -- anyone have an idea what a 51' Formosa Ketch measures out as in CF???

As a conservative estimate I calculated the volume of a cylinder assuming a 7 foot diameter and 45 foot height which is a guess about your headroom and interior length.

It is about 1750 cubic feet.

Cubic Volume
V = π×r²×h = π×D²×h ⁄ 4

Of course I didn't crunch the math - I just found a calculator.

Calculating the Volume of a cylinder

You can adjust using different assumptions.

In nosy parker mode - If it were me I would consider a couple of smaller units over one bigger unit. Then you can cool the areas you want cool more efficiently while not cooling others. On my brother's boat it made a big difference on sleeping to knock the temperatures down only a few degrees making a big difference in sleep comfort. We ran the genny an hour or so and then turned off the aircon at lights out.

[bobconnie]

In our 51 ftr we have a 5kw genny and a 16000 btu in the main salon, galley, and the BIG head and shower room. and a 6000 btu in the aft master cabin. We run the 6000 unit for sleeping and only use the 16000 at the dock or if theres no breeze at the anchorage. It works for us but then we don't melt easy! and if we can sleep well and cool we are happy ! just our 2 cents And we second the flagship marine set ups !

[Geoff H.]

I thank you all again! I had a sales guy at Marine Warehouse in Fla. helping me (I thought) but he's disappeared. We had been talking about the Dometic equipment. But I'm going to look at the Flagship name. Thanks for the tip.
I had thought one unit would be way to go, but looks like there's some logic to having two systems; will figure out that too!!

[Beausoleil]

In our Formosa 51, we installed two Dometic/Marine Air units - a 16kBTU and a 12kBTU (both 120Vac), running off our 7.6kW genset. The 16k unit handles the salon and aft cabin, and the 12k unit handles the galley and the port cabin (no ducts yet run to the starboard and forward cabins). This is the minimum for a boat this size.

When we bought it, she had a 12k and a 9k unit, but you could see that there was also a unit in the aft cabin at one time, and possibly a fourth unit for the port and forward cabins as well. A previous owner had the boat berthed in Ft. Lauderdale (when she was known as China Lady), so I can understand the need for more cooling there.

Out here on the hook, we rarely run them - sometimes just to put a load on the genset.

[Geoff H.]

Dear Capt Jon on Beausoleil,
Interestingly, my 51 Formosa is also a 79' aft cabin. Bought her in Mazatlan Mx in 2000. Restored her in Los Angeles and am transiting the globe (very very slowly), currently mooring her at Balboa Yacht Club in Panama while back in LA to do a little TV stint. We'll be heading E, back on the boat in May. I'm looking at Dometic but also hearing good things about Flagship. Thinking about their 16,5k btu, and their 9k. Or alternatively, what about a single 24,000 unit? Anything wrong with one larger unit to cover all?
Best, Geoff

[colemj]

Originally Posted by sailvayu

With 120 30 amp service you will not be able to run much more than 12k on a single shoreline......The generator is another limitation.

We run two 16kbtu AC units just fine on a 30A service and a 5.5KW generator.

The Dometic 16kbtu AC units only draw 8-12A (model dependent) full load. That is a very large safety factor you are using for a 30A service.

A 5.5KW generator is rated ~43A continuous load.

Mark

[Sailmonkey]

Originally Posted by Geoff H.

. Or alternatively, what about a single 24,000 unit? Anything wrong with one larger unit to cover all?
Best, Geoff

The only drawback to a single large unit is that it will always need a compatible power supply. If you have two or three smaller units, chances are good that you'll be able to, at the very least, cool the sleeping cabin when you're someplace with less than adequate power.