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Old 07-05-2017, 04:56   #1
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Advice & opinions on type of power source for water maker

I am moving aboard my yacht in 4 months to live and am wanting to install a water maker. The hard decision that I am having is what power source to go with. I have three 175 watts solar panel and 2 wind generators and 750 amps of batteries storage, so 12volt power is not a problem, but I also have a Fischer panda 8kva generator so 120volt power is plentiful as well. I know I have to run the water maker roughly every three days to keep it clean and going, so I'm assuming the 12volt one would have to run for a couple hours where as the 120Volt water maker I can probably just run for half an hour and make plenty of water. I am just a bit worried if the generator broke down I wouldn't be able to make water but I would always have 12 V power available. Any opinions from people who have got different power sources on board their yacht and how they feel about relying on a generator to make water. I am not after opinions on different sorts of water makers there's heaps to choose from it's that just the power source reliability that I'm worried about and asking opinions on. Your opinions would be much appreciated

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Old 07-05-2017, 05:17   #2
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Re: Advice & opinions on type of power source for water maker

Cruisers & Sailing Forums - View Profile: SV THIRD DAY (Rich Boren) would advocate for 120VAC


Cruisers & Sailing Forums - View Profile: Tellie (JT) would advocate for 12VDC

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Old 07-05-2017, 06:18   #3
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Re: Advice & opinions on type of power source for water maker

We opted for a 120V option and purchased a Honda 2000 as well. This gives us the ability to make water from our diesel, Honda or in very rare cases 3000W inverter.

However, running through the inverter kicks the hell out of our 12V numbers. It draws like 80A when running. Even on a super sunny day our 900W solar array has trouble keeping up with that.

The Honda 2000 has been one of our best purchases. We use it way more often than our diesel for a couple of reasons. Number 1 is shear operating cost. The Honda cost us $850 so we never stress about racking up hours on it (plus no worries about impellors, zincs, ect). Two is fuel cost. It takes about the same amount fuel as the diesel generator (it produces less watts though). Gasoline is more often cheaper down here. Personally I would have bought a Honda 2000 anyway.
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Old 07-05-2017, 08:56   #4
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Re: Advice & opinions on type of power source for water maker

We used a 12V unit (Spectra) that got fired up everyday just after the solars topped up the bank (about 13:00 LT, on that boat). Small sub 40' boat & two crew.

So rather than let the solar energy waste past noon, we converted it into fresh water. It was the best watermaker set-up I ever used. Would go this way on my own boat.

I have also used and maintained a big AC unit run of an inverter/genset on a bigger yacht (72ft, 40t). It was great too as it churned out huge amount of water very fast. I think this is the way to go in a big boat with many crew and big water needs.

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Old 08-05-2017, 08:13   #5
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Re: Advice & opinions on type of power source for water maker

It depends on your fuel and water budget. It may also depend on your rainfall. Do you catch rain water? Do you save gray water? Do you flush your heads with fresh, gray or salt water? Does your crew insist on long showers? These things determine your water budget.
We are quite frugal with water so we have lots of options. If you use a lot of water, then you have no options. Just buy a big 120V water maker and run your genset and water maker as needed. Or buy water. QED.
If you don't need much water then you have the option of getting a small water maker, say 8 gph, 12 V, and running it an hour or two each day. It sounds like you have more photovoltaic power than you can use most days. That's our situation, too. If we don't make water for a couple of hours in the morning, our batteries are topped off by early afternoon and the excess PV energy goes to waste. For that reason, I like our little 12V water maker. We easily make enough water for our crew of 2 to 4 people to bathe, cook, and clean daily, and do a load of laundry every week or so. And we rarely need to use our genset; we can do it all with solar. Your needs may vary.
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Old 08-05-2017, 09:17   #6
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Re: Advice & opinions on type of power source for water maker

I have a 3000 watt inverter that will use the 12v and handle most 120v AC watermakers. It's also useful for power tools, computers, coffee maker, and (of course!) microwave.
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Old 08-05-2017, 09:44   #7
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Re: Advice & opinions on type of power source for water maker

It all depends on your water needs and the size of your watermaker to determine required run time and frequency. Almost every cruiser I know that has a 12vDC watermaker complains about how it runs all the time. We have built our boat around running the genset every day, and we depend on it. With just the 2 of us on board we make water every 3-4 days-with a 1-1.5 hrs run time.....we bought a 30gph watermaker for that reason, and we make water while doing other things that require the genset (we have an electric cooking stove, an electric refer, etc). And if your genset does crap out, all you need to do is Fresh Water Rinse your unit every 3-5 days to keep it healthy....and that just takes the 12vDC boost pump, not the hi press pump (ours is a Cruise RO unit). But-the choice is yours-just weigh all the pros and cons of each. While some complain about the run time and the power use of their 12vDC watermakers-they still have them.
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Old 08-05-2017, 10:12   #8
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Re: Advice & opinions on type of power source for water maker

I went with the 12Vdc Spectra, but i don't have an AC generator and didn't want to buy one. If you don't really use the AC generator and plan to live on the 12V, then I would stick to the 12V. For one, you won't have to worry about getting fuel for the AC gen, maintaining as much or breakdowns. 2nd, you are doing us all a little favor by not burning fuel when you can use the sun for power. Now I'm assuming your water needs are modest. There's a practical limit to how much water you can make with 12V. My family of 4 uses 10-12gal a day, but I've heard of couples using four times that! Of course if you plan to run the generator anyway then adding more load has a negligible environmental impact and IF you have a large enough inverter, you could use 12V as a backup. So IMO, it comes down to how often you use your generator for other purposes
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Old 08-05-2017, 10:23   #9
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Re: Advice & opinions on type of power source for water maker

Run it from your inverter if needed.
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Old 08-05-2017, 10:40   #10
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Re: Advice & opinions on type of power source for water maker

Like you, we have reliable and plentiful AC and DC power available.

Our boat came with a 12 VDC Spectra watermaker already installed and it has been flawless. It makes 10-12 GPH for about 1AH 12VDC/gallon. From what I have read, that is about as good as it gets for DC watermakers.

For the two of us we run it once or twice a week to top off one of two, 110 gallon potable water tanks. That covers laundry, showers, freshwater deck and anchor chain washdowns, etc.

I mention all this as background. If I had to replace this unit, and since I already know our needs and have power options, total cost of new would be an important selection criteria.

Without analysing what is currently available [or even looking at current prices] my casual observations give me the sense that comparable AC watermakers cost about half or less of their DC counterparts.

Therefore, since we have reliable AC power, total initial cost would factor heavily into my decision when choosing a new watermaker for our current needs. [e.g., Do I want to spend $4k or $8K for a unit I need to operate once or twice a week to meet our demands? We run the generator that often, or more often as well...]

I am not concerned about the reliability and availability of our DC and AC power sources. We have many dependencies on both.

The worse case scenario might be choosing an AC watermaker and then having the generator inoperational for a period of time in a situation where no other source of water is available. We could get by with the AC inverter until the generator was repaired/replaced. And we could go for weeks [without alternate sources of potable water] without needing to run the watermaker if we had to- potentially providing enough time to get the genny going again.

Since we can go either way for power choice, it therefore becomes a secondary consideration for us.

That makes $ saved [for the same outcome] more important [for us.]

I say all this assuming suitable/comparable AC and DC watermakers are being evaluated.

In case this strategy helps with your personal evaluations.

Cheers! Bill
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Short on opinions; focused on research, facts & experience [yours and ours...]
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Old 08-05-2017, 21:49   #11
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Re: Advice & opinions on type of power source for water maker

The figure of merit for watermakers is amps (@12V) per gallon of fresh water. Spectra is 1.1A per gallon (due to patented technology), most DC watermakers are around 3-4A and most AC watermakers are 6-10A per gallon. The second consideration is initial cost.

If you are running a generator then it probably makes sense to with an AC watermaker. If you need to run the watermaker off the inverter, it will be half as efficient as an equivalent DC version. It has to do with the AC/DC motor efficiency. If you are running a mostly DC boat then a DC watermaker makes more sense. The size of the watermaker is determined by your consumption and tolerance to noise.
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Old 08-05-2017, 23:34   #12
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Re: Advice & opinions on type of power source for water maker

Watermakers are about convenience, it's much more convenient to Not have to depend on and start a generator to make water unless other things depend on it as well.
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Old 09-05-2017, 03:54   #13
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Re: Advice & opinions on type of power source for water maker

We have a DC generator and inverter so a DC watermaker makes more sense to us. It produces 20 gallons per hour - at 24 amps like the Spectra - but it has patented technology that reduces the current needed, but at a cost. It also automatically backflushes with fresh water after each use and again every 7 days if not used, so you can leave the boat for as few months without having to chemically winterise it. The cost has been worth the convenience.

We have been in the Med for 10 years and motor a lot because of winds. We only ever make water when motoring off shore so with a large alternator the batteries don't get drained. We never make water behind another boat in case they empty their heads, and never at anchor with other boats around!!!!!
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Old 09-05-2017, 19:15   #14
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Re: Advice & opinions on type of power source for water maker

Your 120v generator can also make 12v power. Your alternator produces 12v power. Your solar panels produce 12v power. What was the question again?
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Old 10-05-2017, 04:32   #15
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Re: Advice & opinions on type of power source for water maker

For three years we spent living aboard we ran a 12v / 7gph spectra either when the motor was on, the Honda was running, or on rare days the wind generator was over producing. If I did it again I'd go with a 120v system.

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