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Old 16-09-2016, 04:18   #16
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Re: how much air conditioning

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Originally Posted by b-rad View Post
Three units and give up a hanging locker, I hope not. Major issue for me for 3 units besides cost, have to have power and water in and out of each unit that would be 6 through hulls, 3 pumps and 3 strainers. I would need to add another 30 amp service to the boat. Talking about a 8-10k commitment, not sure I'm ready for that. I'm not concerned so much with the front cabin at the dock. Just need to cool the pilot house and galley (down galley ) and head and freeze the aft cabin. Thinking about trying the 24k for the boat with a smaller unit for the aft cabin, not sure where to hide it though.

Actually it would be 1 pump, 1 strainer, and one or three overboard through hulls.

With only one 30 amp shore cord you'll be upgrading your shore power no matter what you do. From experience the Mac continuous draw on anything but a shiny new 30a cord is about 20 amps. More than that and you start burning cord ends.

More economical I believe would be to upgrade the 30 amp shore supply to 50 amps. No more dual shore cord worries!!


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Old 16-09-2016, 04:23   #17
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Re: how much air conditioning

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Originally Posted by zboss View Post
We used a 16,000 BTU AC unit in our hatch last summer (covered by our boom tent) and a 5000 BTU unit in our companionway this summer. We found basically no difference.

Then there was something wrong with the 16k unit. I run a 5k unit, not adequate for most people during the heat of the day, but works for my purposes. If I had a 16k I could hang meat at noon in August.


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Old 16-09-2016, 04:36   #18
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Re: how much air conditioning

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Originally Posted by b-rad View Post
New to me boat, it's a 43 foot very beamy pilothouse, lots of windows, lots of surface area. Need to install ac to make it a little more comfortable to liveaboard here in sunny south fl.
Currently have a 15k portable in one cabin that turns the room to a meat locker but does nothing for the rest of the boat. Trying to decide how big of unit (s) I need. Just found a 24k unit that I think could do the whole boat, or should I pony up and do a 16 and a 12 or 2 16s. Other issue is I only have a 30 amp service to the boat so if i do 2 units I will need to add an additional 30 amp power for the ac alone.

We probably have more window surface than you do... maybe more overall space... and we get by with two 16K BTU units. One handles saloon and galley, the other does two staterooms, head, and shower.

If we moved back down there, I think I'd add some more effective window tinting, but other owners already down there say that's about all that would be necessary. (Edit: actually there's an improvement in the installation they have recommended too: blocking supply access so that air is actually only coming from the area to be cooled, not the area between interior bulkheads/hull liner and the hull itself. A minor detail in our case.)

Can you tap off your existing 15K unit to spread some of that wealth into other areas? If so, one more unit could do the trick. And I'm told the newer versions of our units are much more efficient, too... so you could perhaps realize some improvement that way, too.

If you set your relay so that both units don't start at the same time, and depending on the units you select (and their current draw)... I think you should be able to run both on a single (existing) 30-amp service, and with a single (existing, maybe) water pump serving both units.

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Old 16-09-2016, 06:25   #19
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Re: how much air conditioning

Regardless of what everyone says you will need more btu's than you think. A boat is a fiberglass box with no insulation, and in a climate like Florida with a lot of direct sunshine every day it spends its time absorbing heat and radiating it into the boat. I have a 44' sailboat and added A/C from scratch. Two staterooms and a salon/galley area. I installed two 16,500 btu units and I am in a similar climate down here in St Maarten. I run both units continuously during the day and only one at night. The units run without cycling just to keep up, but they do cool the boat to the right temp. If you try and save money, or buy units a little smaller than you think you need you will never get the boat cold enough and will have wasted money on a partial solution. With a pilothouse I would guarantee you will need more btus than I have. I had to add a second 30amp supply to accommodate the addition of the A/C, washer/dryer, etc which required a second 110v panel. DO NOT upgrade to single 50amp service as 30amp cords are $100 each, and 50amp cords are $500 and you will pull in to a marina at some point and burn up your cord with crappy wiring or plug and the cost to replace will really piss you off.
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Old 16-09-2016, 08:39   #20
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Re: How much air conditioning?

There are calculators on the internet that will help point you in the right direction as per size for a given space. Question is, how segregated is your interior? How hard to run ducting from one spot to another? (6" duct for a 24K BTU unit) It may be easier to have multiple smaller units. It would also have the benefit of being able to set the temperature differently in the various sections. Con would be multiple thru-hulls would be required. (Intake and output) You can also get units that are a separate condenser and evaporator, much like your home unit. I would assume these would require a professional to install.

We have a 30 Catalina and added a 24K BTU unit. It turns the main cabin into a meatlocker and does a fair job in the V-berth. A 20K would have been the best fit, but they only have 16K & 24K units. It also has reverse heat so in the winter it is still comfortable.
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Old 16-09-2016, 08:50   #21
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Re: How much air conditioning?

To echo an earlier comment....consider a compressor located in the engine room. Then your air handlers in the bottom of various lockers. Don't overlook the power of shade. Deck and cockpit awnings are the key to A/C efficiency in our small spaces.
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Old 16-09-2016, 08:53   #22
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Re: How much air conditioning?

I live just north of Ft Lauderdale, (Lighthouse Point, Hillsboro Inlet). I have a KP 46 which is a center cockpit, no pilothouse, aft cabin boat. I have a Cruiseair 16K in the main salon, ducted to the fwd cabin, which does not do much in the fwd cabin but keeps the main cabin nice and cool. I also have a Cruiseair 12K in the aft cabin with a duct to the aft head. Keeps the aft cabin very cool.

Hopes this helps,

Michael
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Old 16-09-2016, 09:33   #23
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Re: How much air conditioning?

Might try ducts to circulate the cold air throughout the boat. Do not have to be large, nor visible. Your unit should be capable of cooling the entire boat if you install ducts and funnel the cold air into them. Its a dyi or hire an a/c specialist. We used pvc pipes attached to the cabin roof on both sides of the boat fore and aft from the vee berths to the cockpit entrance and back to the aft stateroom. 15k was more than enough on the hottest days. If we had to do it over again, would have installed a 6k unit to save energy.
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Old 16-09-2016, 09:41   #24
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Re: How much air conditioning?

I rarely disagree with GordMay as I have yet to find him wrong, but I would oversize a little, cause you can always turn them down to low and enjoy the much quieter cabin with the blowers on low, or tirn off a unit for awhile, but if your even a little undersized, then the heat in the boat begins to build in the middle of the day and it really doesn't get cool until the middle of the night, so you have a tendency to over cool hoping that will give you a head start on the next days heat.

Tougher to oversize a boat than a house, cause it seems the R value of a boat isn't very good, and we of course are usually out in direct sunlight, as has been said, shade can make a HUGE difference, on a hot sunny day I can feel the heat on the hull from the inside.
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Old 16-09-2016, 10:37   #25
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Re: How much air conditioning?

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I rarely disagree with GordMay as I have yet to find him wrong, but I would oversize a little, cause you can always turn them down to low and enjoy the much quieter cabin with the blowers on low, or tirn off a unit for awhile, but if your even a little undersized, then the heat in the boat begins to build in the middle of the day and it really doesn't get cool until the middle of the night, so you have a tendency to over cool hoping that will give you a head start on the next days heat.

Tougher to oversize a boat than a house, cause it seems the R value of a boat isn't very good, and we of course are usually out in direct sunlight, as has been said, shade can make a HUGE difference, on a hot sunny day I can feel the heat on the hull from the inside.
If you oversize, the unit may start freezing up. Assuming the hull is reasonably insulated, the square footage is rather small on 40 footers and the air circulation minimal with ports closed up. Plus below water line is a heat sink anyhow. On our 43 footer the 18k system was way too much even at the equator, even with piping cold air into the engine room.
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Old 16-09-2016, 10:55   #26
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Re: How much air conditioning?

We're out of Kemah, TX so the weather is similar to Miami's for heat and humidity. Our Nauticat 43 sloop has similar constraints for area, window exposure, and a single 30A supply. We have a single Marine Air 16K BTU system installed with ducted air vents to the aft master cabin, pilothouse, and galley. The cabin and galley vents are louvered so the airflow can be modulated somewhat (e.g. to stop cooling the galley late nights and direct more air to the cabin). This single system works well off shore power or our genset. There is no ducting forward to the bow cabin, but the (unimplemented) plan is to have an air handler move the air from the galley forward (this is a low amp fan solution). I think this system works because we use a boom tent and also cover windows receiving sun with a removable, tailored cut sheet of interior reflective insulation.
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Old 16-09-2016, 10:59   #27
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Re: How much air conditioning?

Reed

You must have a much better insulated boat than I do, cause with me 21K is barely enough, and if I'm in and out of the companionway much on a hot day, its not enough.
But then I am not warm weather adapted either, last few years I usually work and live in air conditioning, give me awhile to adapt, and I hope I won't want so much cool air?
So hot to one person, may be cool to another.
Biggest issue with being over-sized is you don't dehumidify, unit comes on and slams the temp down to the set point and turns off, to dehumidify you want continuous airflow through a surface that is cooled well below the dew point, that way of course water condenses and you dehumidify.
A humid cool room isn't nearly as comfortable as a room that is the same temp, but low relative humidity.
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Old 16-09-2016, 11:14   #28
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Re: How much air conditioning?

I have a center cockpit 51. Recently installed a domestic 16 btu with smart start draws 17 at start runs at 11. Boat came with 3 inch pluming for air circulation I connected the 7 inch main air exit in the back to the 3 in hole hoping it would cool the forward cabin. Nothing forward or aft stays hot. Galley and saloon 79 afternoon 74 at night. Starting Instalation of a 8 btu in aft now.
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Old 16-09-2016, 11:19   #29
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Re: How much air conditioning?

KISS KISS KISS

The first thing to do before buying or installing ac is to tint the windows.

i have beneteau 50. called in an automobile window tinter and used 10 or 20 % limo tint on all portals and hatches. insanely effective in reducing interior heat and you and can see outside perfectly while no one can see inside.

check interior temps before and after the tinting. you will be amazed!

i may call the tinter back in to add a bit more tint (second layer over first) perhaps another 50%.

i purchased 2 flagship marine ac/electric heat units 9k + 16k. the 9k feeds the 2 aft berths. the 16k feeds the crews cabin in the bow (where the 16k unit is installed), the very large master stateroom forward and aft of the crew cabin and finally the saloon and galley.

the key is lots of vents. usually they are found at the base of cabinets, under seats etc. i am also adding 2 adjustable vents that point upward to the coach roof.

with 840 amps of lithium batteries, 680 watts solar, a 2000 watt inverter to 240 volt - the units are insanely efficient and can be run off the dc/inverted power system with no generator or shore power.

since i purchased the yacht in croatia, i use European 230 volt 50 cycle ac shore power. but of course 120 volt is standard for them.

so, after all the window tinting, you should be able to use flagships 2 units like i do 1 x 9k + 1 x 16k. they are light reasonably small
very efficient and easy to install without professional assistance to keep costs down. tech support is very good.

one last thought if you want to go the extra mile. check out self adhering insulation panels from dynamat, gt sound and a few other automotive sound and insulation barriers. there are 2 types of panels - insulation and sound barrier. the insulation ones are normally used for the engine hood, headliner and firewall. max thickness is 100 mil (about 5/16" i think)

have fun!

captain ron.
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Old 16-09-2016, 11:51   #30
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Re: How much air conditioning?

Quote:
Originally Posted by b-rad View Post
New to me boat, it's a 43 foot very beamy pilothouse, lots of windows, lots of surface area. Need to install ac to make it a little more comfortable to liveaboard here in sunny south fl.
Currently have a 15k portable in one cabin that turns the room to a meat locker but does nothing for the rest of the boat. Trying to decide how big of unit (s) I need. Just found a 24k unit that I think could do the whole boat, or should I pony up and do a 16 and a 12 or 2 16s. Other issue is I only have a 30 amp service to the boat so if i do 2 units I will need to add an additional 30 amp power for the ac alone.
B-Rad,

Our boats appear to be somewhat similar.

Ours came from the tropics and the POs installed AC since they cruised hot climates for 15 years before we bought the boat.

What they set it up is similar to what many have advised on this thread: 3 separately controlled AC units sized for the area(s) they are cooling [and heating don't forget...] All share one March pump [and associated raw water strainer] and coolant loop with one above waterline discharge through-hull. [We are sometimes asked on hot days why our bilge pump never shuts off...]

More details with links to related discussion on this forum are available on this blog post if you are interested.

Best wishes sorting out what is best for you.

Cheers! Bill
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