DIY 6000 BTU AC install on a 43 ft Sailboat worth it?

[Tenedos]

Hi everyone,

I have started to casually consider installing an air conditioning unit on our Jeanneau 43 DS. If we do it, I plan to install it myself. We are in US PNW and don't need AC very frequently but it is occasionally needed and when it is needed it gets really bad. Also we eventually plan to sail south to Southern California and Mexico so want to have some options.

That being said, I have a bunch of limitations. I can only install a small unit. First of all, we only have a portable generator and don't want to use it for air conditioning. So planning to use it on shore power or in limited capacity on solar and batteries. We have 960 watts of rigid solar panels, which can pump in easily 65 amps on a sunny day when AC will be needed (controller is a Victron 150/70, so capped at 70A). We also have 600 Ah LifePo4, with an option to upgrade to 700 Ah. So a small unit, running either on shore power or for ~6 hours on anchor is the goal. We have a Magnum 2800 watt pure sine inverter. While planning to change it to a bigger Victron, it is not an immediate goal. So needs to work with this setup.

Size and space is also another consideration. We have a Webasto hydronic heater (more of a necessity in PNW) with 4 blowers and it takes a fair bit of space.

These are obviously some significant restrictions, the only practical option I found is a Webasto FCF-6000 (link). It is rated at 115V/ 4.7 Amps with a starting Surge: 21 Amps. The next bigger unit is FCF-10000 but starting surge is 34 amp, which is even exceeding our shore inlet of 30A, and the capacity of our inverter which is a no go. FCF-6000 would draw around 540W on average with a peak of 2415W. Average usage is acceptable for us and peak is within the limits of our inverter. We already have an unused thru hull previous owner installed, so want to take advantage of that.

Now obviously, 6000 BTU is a pretty small unit for a boat like 43 DS which has good big windows (which we love).

I have two questions: Is this worth the effort on my side? Or is 6000 practically useless? If we could bring the temperatures a bit down it would help. Also, is this something that can be a DIY install or will I be taking too much on? I am reasonably handy, having installed all electronics, lithium batteries with adjusted chargers, alternator protector, solar panels, Webasto forced air heater etc on our current boat (and the previous boat). But this is a more complex install and electrical wiring will be more complicated with grounding etc. Wondering how complicated this is.

Any thoughts, suggestions?

Thanks much in advance!

[ttex]

I just installed my AC a few weeks ago. I have the Webasto Platinum 12k btu.

The surge amps are not something you need to worry about as far as your breakers are concerned. In the manual for the AC unit it calls for a 20 amp breaker for both the compressor and the pump. This compressor has a surge amps of 37 but doesnt make any difference. Works perfect.

[Tenedos]

Originally Posted by ttex

I just installed my AC a few weeks ago. I have the Webasto Platinum 12k btu.

The surge amps are not something you need to worry about as far as your breakers are concerned. In the manual for the AC unit it calls for a 20 amp breaker and this compresssor has a surge amps of 37. Works perfect.

Thanks! Did you install it yourself? How challenging was it? And how much power does it draw?

[ttex]

I installed it myself.

It was not particularly difficult but I have an appliance installers license in Texas and I install things for a living in houses. Generally swimming pool equipment but sailboats are kinda like inside out swimming pools so it works out.

Hardest part is getting everything to fit in the tiny spaces and cutting a giant hole in my teak bulkhead for the duct. I also had to drill a hole for a new seacock while the boat was in the water. A bit scary but I got it done.

[Tenedos]

I am reading the manual and looks like the unit needs to be installed above the waterline which will be hard, if not impossible in my case.

[ttex]

Unfortunate. Mine went where the holding tank stuff used to be. We switched to a composting head. Luckily it is above the waterline under the vberth.

[GordMay]

One of the telling signs that your AC is undersized, is that it runs constantly. A properly sized unit will kick on and off periodically [a regular cooling cycle should run ±20 to ±30 minutes] to control the temperature. Undersized air conditioners will struggle to ever get the space cool enough, and therefore will fail to go through healthy on and off cycles.
This can lead to:
- motor overheating
- evaporator freezing up [but excellent dehumidification, until it does]
- excessive wear & tear
- higher energy use
- conditioned space too warm

But, life is full of compromises.
6,000 BTU/h A/C should cool a good sized berth [or small salon], nicely.

A rough "rule of thumb" for sizing marine air-conditioning (for use in sub-tropics) is between 14 (below decks) to 17 (above decks, glazed) BTU/H for each cubic foot of interior conditioned volume.

A (theoretically) perfectly-sized air conditioner will run continuously during the hottest 2.5% summer design (outdoor) temperatures.

See ➥ https://www.cruisersforum.com/forums...tml#post822698

[radsailor]

I do not think 6000btu is large enough. I had a free standing vented 6000btu a/c on a 35 footer in NC and it barely did the job. Of course NC is a lot hotter than PNW. Also, my boat had no significant insulation.

[Quadrille in JB]

Gord,
I’m sorry but I have to differ with your running all of the time being unhealthy for the AC unit. The hardest part of the AC cycle is when it starts up. This also uses the most power. A smaller unit that runs most of the time is more efficient than an oversized unit that starts and stops continually.
And to the OP, it’s not a big deal to install. Probably a lot easier than your heating system
Bill in JB

[DreaminFred]

Look at Emily and Clark on YouTube. He’s very creative and has designed a small tunable AC that can run on your solar/lithium easily.

https://youtu.be/rd__CXXygdY

[toddster8]

I installed the Webasto FCF 6000 on my 29 foot boat and it seems barely large enough. On a 43'er it would probably only cool/heat a portion of the boat that could be sealed off from the rest.
(Also being in the PNW, I wouldn't have considered it, except I got an unbelievable deal on a used unit.)

I think the "above the waterline" requirement is only due to the condensate tray drain, which is just a simple tray under the unit with a tube to drain off condensate. Instead of draining directly over board, it could for example, drain to a shower sump. The main heat exchanger loop is sealed, so its location depends only on the pump specifications. The pump that I got requires a location below the waterline.

Installation was fairly simple, given a scramble to find all the right sized tubing adapters on line - not available in small town stores. Because it was a bit of an experiment, and the demands of this unit are fairly small, I simply plumbed it in parallel to the head instead of installing new through-hulls in the boat. Water intake is from a tee (with check valve) off the same through-hull that serves the head. Discharge is to the lavatory drain, using a tailpiece with a dishwasher port. The 5/8" discharge hose from the FCF HX fits exactly on the dishwasher fitting. This does create a faint gurgling sound in the drain, but it is small compared to the noise of the pump and the fan. And almost eliminated if one remembers to put the plug in the lavatory drain.

{Note that the plastic tailpiece with dishwasher port is NOT a marine-rated fitting. I would only install this item above the water line. Though doubtless a functionally similar arrangement could be made with heavier-duty materials.}

Installing ducting to carry the output air to the desired location is potentially difficult. If the unit is installed in cabinetry or behind a bulkhead of the space to be cooled, a simple short straight run might work. You want the output as high as possible and the air return as low as possible for efficient cooling. (Another potential reason to put the unit "below the waterline.") My boat already had a chase running the length of the starboard side, so it was pretty simple just to add a couple of grills and a flange adapter to that.
FWIW, pics and such here.

[sailcrazy]

As a reference point, our Taswell 43 has a 10k BTU aircon installed in the aft stateroom, and a 16k BTU unit installed for the fwd stateroom, the saloon, and the galley area. We usually run only the 16k fwd unit, until it's time to turn in....then we shut it down and turn on the aft unit. That 10k unit cools the bedroom nicely, but because our thermostat is not the best, it often gets really cool before the morning-we usually wake up, turn it off, or just leave the fan on, or break out extra blankets??? But when it's hot and humid that 10k does cool the bedroom nicely! a 6k unit sound small to me.
Also...how well is your coachroof/ceiling insulated? your sidewalls? Do you use/have a sun shield/awning to keep the interior temps under control?

[Sailorlou]

I have a 36 foot boat and I used to have a 12K BTU unit and it was not large enough to cool my boat here in Mexico. I recently installed a 16K unit and it is just big enough to make my boat interior comfortable. I would suggest you install a larger unit or install two units as the person above did. I am familiar and have sailed aboard your model of boat and I really think installing a 6K unit would be a waste of time and money unless it is only used in the V-Berth.

[skipmac]

I have a 42' center cockpit/aft cabin with a single 16kBTU unit. On a hot day in Florida that will get the aft and main cabins to a little cool. For me definitely comfortable.

6kBTU on a hot day I think would make one cabin comfortable and maybe drop the humidity in two.

Have you thought about getting a reverse cycle unit that will heat and cool and replacing the heater with one unit?

[phillw]

Originally Posted by Quadrille in JB

Gord,
I’m sorry but I have to differ with your running all of the time being unhealthy for the AC unit. The hardest part of the AC cycle is when it starts up. This also uses the most power. A smaller unit that runs most of the time is more efficient than an oversized unit that starts and stops continually.
And to the OP, it’s not a big deal to install. Probably a lot easier than your heating system
Bill in JB

From my research you do not want an AC that stop/starts as they consume the most energy. You also do not want an AC that continually runs at high speed. The most energy efficient AC's have inverter compressors where the compressor speed is regulated to maintain the desired temperature. Having an AC that is too small for the area it is heating/cooling will result in the AC running continuously at max power. I also agree with the person that posted the link to Emily & Clarkes system. Especially for sleeping areas.