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colemj · 13-01-2013, 07:21

I don't have the bandwidth right now to multiquote or respond to many postings, so I am going to try to catch many points in one post.

My debate points on higher/lower capacity units have mostly defined low capacity as <3gph. I cannot see how these make any sense at all. The 8-12gph DC systems fill a much more usable middle ground (we have been cruising 4+ years with a 6gph system). However, I have found that these systems do not make sense for full time cruising in the tropics with no marina visits UNLESS they are an energy recovery system (and that means Spectra/Schenker). I have purposefully set these aside in my points because their price makes no sense. If one is buying new, it still makes sense to me to get a 20-30gph AC system for half the price of a 8-12gph DC system.

The issue regarding output and power is the terminal voltage, not the battery capacity. LiFePO4 batteries make no difference here because their voltages are the same as any other battery type - regardless of how long they hold that under-spec'd voltage. You will still need a running charging source to meet output specs because these units are spec'd at 13.8V.

There is no way to make a DC system more efficient other than buying an energy recovery unit. I am assuming proper wiring, plumbing, etc.

I agree that if one has sufficient solar/wind, one can run a lower output DC system for long periods of time. However, this isn't really practical unless one has an energy recovery system. These are VERY expensive and another debate altogether. It really is about amps per gallon, but the price wall makes the decision complicated. If money is no object and one has enough wind/solar to provide daily energy PLUS water (and you know this is true from actual experience with your usage and systems and not a paper calculation), then I agree that a Spectra/Schenker makes sense.

A larger capacity DC system either uses as much, or more, energy as a higher capacity AC system or, if an energy recovery one, costs as much as a moon landing. And at this size it will be less energy efficient because you will be trying to charge the battery at the same time as pulling 100 amps out of it instead of simply running it directly off the AC of the generator. It will be a rare boat indeed that can supply enough solar/wind to power a 1000gpd system, let alone meet daily energy demands - energy recovery or not.

Automatic flushing, etc adds complication and mucho cost. Nothing wrong with that, but cost has been one of the major debate points of this thread, and many people I meet with these systems are constantly fighting them and jumping over the automated parts to keep them running. If you are leaving your boat for a long time (many months), it makes more sense to simply pickle the membrane. If you are only leaving for a couple of weeks at a time, a single good freshwater flush will last that long.

I disagree that the smaller systems have reduced operating and capital costs. The facts are easy on the capital costs - the larger AC units are the same price, or less expensive, than the smaller DC units. The AC units all use common parts found anywhere in the world. The membranes are standard sized and easily ordered inexpensively. Go ahead and price a membrane from Village Marine or PUR. Then price a HP pump from any maker of your choice. Then see about getting that HP pump repaired in Columbia or Venezuela. Now do the same for a standard sized Filmtec membrane and a common CAT or General HP pump. Operating costs in terms of $/gallon may or may not be reduced depending on how it is operated and how much cost went into the alternate energy systems running it. An AC system run off an inverter while motoring is essentially free since you needed to motor anyway. However, even dedicating a Honda generator to a watermaker is less upfront cost than a large wind/solar array.

It is not just polluted anchorages that are a problem. Try running your watermaker in beautiful Thompson Bay Long Island Bahamas. Or almost any other bay on Long Island Bahamas. These are fantastic cruising grounds, but they are full of silt and your filters will completely plug within 20 minutes. Same at Crooked and Aklins. We are often anchored behind beautiful reefs with excellent snorkeling and fishing during tradewind season where the sand is washing over so much that the filters clog fast. We are also often anchored in beautiful fun places in the summer months when the algae and microscopic jellyfish (hydras?) are thick and will clog your filters in no time. Now let me tell you about anchoring near mouths of rivers that provide excellent exploring and wildlife. Guess what happens there...?

In other words, we too leave polluted anchorages as fast as we can, but regularly encounter excellent cruising grounds that we wish to spend time in that are not amenable to making water. In these areas, we are finding our 6gh system to be a pain.

In tropic waters, the system cannot set more than 3 days without flushing or using.

To summarize my opinion and experiences, the <3gph systems make no sense at all. The 8-12gph DC systems make some sense depending on your water needs, your cruising grounds, energy usage and supply, and if they are a Spectra/Schenker make much more sense if you ignore the cost of these units. 20-30gph AC systems make the most sense for those who wish to use live and use water comfortably, cruise in tropic climates, do not have a military-sized budget, have a generator of some sorts (even a suitcase Honda) and an appropriately sized inverter coupled with a reasonable alternator (60A).

Mark

Auspicious · 13-01-2013, 08:44

Quote:

Originally Posted by noelex 77

There are small differences in the Ah/gal figures across the Spectra range, but the differences are small in the sizes that yachts would use.

25 - 30% total energy savings isn't small to me. The 300 gpd sweet spot is very real.

wolfenzee · 13-01-2013, 10:34

Quote:

Originally Posted by goboatingnow

Great post Mark, a voice of experience. I would agree with u 100 %. Wolf misses the point. I built a watermakers , its way cheaper to use industrial components and standard HTCI vessels and a Filmtec membranes. I used an Italian piston pump typically used in farm power washers.

Dave

It seems people are missing my point too (not grasping the points of someone with a different opinion is common place here anyway). I never said to get the smallest watermaker you can find......I was trying to say that unlike what that salesman says, you don't need the largest watermaker you can find (or biggest most expensive anything for that matter). I have talked to alot of people that were happy with the Survivor 40.....I will probably go one step up, the 80. I am not concerned about power draw, a wind generator will give me all I need. The main point I was trying to get across was just sail awhile to see what your water consumption would be. You should have enough tankage so if you watermaker breaks down any point in your passage you will have enough water. A smaller watermaker can be used to top off tanks, a really big watermaker will have to be flushed between uses (unless you use it the way you would a smaller water maker).

sailorboy1 · 13-01-2013, 11:23

Quote:

Originally Posted by wolfenzee

The main point I was trying to get across was just sail awhile to see what your water consumption would be.

I bet that comes out parallel to "cruise a while to determine your budget"! In both you will use what you have.

mcarling · 13-01-2013, 11:23

Quote:

Originally Posted by colemj

LiFePO4 batteries make no difference here because their voltages are the same as any other battery type - regardless of how long they hold that under-spec'd voltage. You will still need a running charging source to meet output specs because these units are spec'd at 13.8V.

Lithium phosphate (LiFePO4) batteries (4 wired in series) hold about 13.3 to 13.4 volts through the range of 20% to 95% SoC. That's a huge difference compared to lead acid batteries in any application where 13.8 volts is optimal.

Quote:

Originally Posted by colemj

To summarize my opinion and experiences, the <3gph systems make no sense at all. The 8-12gph DC systems make some sense depending on your water needs, your cruising grounds, energy usage and supply, and if they are a Spectra/Schenker make much more sense if you ignore the cost of these units. 20-30gph AC systems make the most sense for those who wish to use live and use water comfortably, cruise in tropic climates, do not have a military-sized budget, have a generator of some sorts (even a suitcase Honda) and an appropriately sized inverter coupled with a reasonable alternator (60A).

For those who do not have or want AC on their boat, it should be easy enough to get an AC system and replace only the pump motor with a DC motor. The electronics would be DC anyway, so finding an appropriate power supply for them should be even easier.

**noelex 77** · 13-01-2013, 12:14

Quote:

Originally Posted by Auspicious

The 300 gpd sweet spot is very real.

I just don't see any "sweet spot" for efficiency at 300gpd like you claim, at least in the Spectra range. The most efficient model is the 1000gpd model.
These are the figures from Spectra on the AHrs per gallon @ 12v (the lower the number the more efficient)

150gpd. 1.43 AHr/gal

200gpd. 1.20AHr/gal

300gpd. 1.20AHr/gal

1000gpd. 1.17 AHr/gal

The energy required for the non energy recovery watermakers is much higher.

wolfenzee · 13-01-2013, 12:21

Quote:

Originally Posted by mcarling

Lithium phosphate (LiFePO4) batteries (4 wired in series) hold about 13.3 to 13.4 volts through the range of 20% to 95% SoC. That's a huge difference compared to lead acid batteries in any application where 13.8 volts is optimal.

For those who do not have or want AC on their boat, it should be easy enough to get an AC system and replace only the pump motor with a DC motor. The electronics would be DC anyway, so finding an appropriate power supply for them should be even easier.

There used to be a watermaker powered by a tow behind prop, like a knot log....name brand was "Water Log"......no electricity needed.

wolfenzee · 13-01-2013, 12:46

Quote:

Originally Posted by noelex 77

I just don't see any "sweet spot" for efficiency at 300gpd like you claim, at least in the Spectra range. The most efficient model is the 1000gpd model.
These are the figures from Spectra on the AHrs per gallon @ 12v (the lower the number the more efficient)

150gpd. 1.43 AHr/gal

200gpd. 1.20AHr/gal

300gpd. 1.20AHr/gal

1000gpd. 1.17 AHr/gal

The energy required for the non energy recovery watermakers is much higher.

That may be the most efficient in gpd, but if you have a watermaker which keeps up with a logical water usage, it is not the most efficient in cost, figuring purchase price, cost of installation, cost of maintenance, filters etc. Of course figuring on a crew of 2...if you figure on the size crew that they were designed for then the others would not work anyway.

mcarling · 13-01-2013, 12:47

Quote:

Originally Posted by wolfenzee

There used to be a watermaker powered by a tow behind prop, like a knot log....name brand was "Water Log"......no electricity needed.

Good for an emergency back-up if crossing oceans -- or as the primary water maker if circumnavigating in this.

**noelex 77** · 13-01-2013, 12:57

Quote:

Originally Posted by wolfenzee

That may be the most efficient in gpd, but if you have a watermaker which keeps up with a logical water usage, it is not the most efficient in cost, figuring purchase price, cost of installation, cost of maintenance, filters etc. Of course figuring on a crew of 2...if you figure on the size crew that they were designed for then the others would not work anyway.

Those figures are only for electrical efficiency and only for one brand. They don't include rinsing which will tend to push up the efficiency of the smaller watermakers.
In terms of cost, both initial purchase cost and running costs then smaller is cheaper if you are comparing like with like.

The hardest thing to factor into the decision is reliability which seems to vary enormously between the brands.

Don't forget noise. A noisy watermaker will need to be a more expensive high capacity model to avoid having to run it for long periods, unless you can soundproof it in the engine bay.

wolfenzee · 13-01-2013, 13:08

Quote:

Originally Posted by wolfenzee

There used to be a watermaker powered by a tow behind prop, like a knot log....name brand was "Water Log"......no electricity needed.

Found it (after the time limit for editing was over). The are made in the UK, cost is 1200GBP/$1936US, they produce 24gpd with a permanent filter. This is more than adequate to keep up with the water needs of a crew of 2 (manufacturer says 2-4), experienced cruisers I have talked to use 3-5gpd/person tops, you can just tow this till your tanks are topped of. This is just a very simple, inexpensive alternative.
Waterlog the only water-powered watermaker in the world

**noelex 77** · 13-01-2013, 13:14

Quote:

Originally Posted by wolfenzee

Found it

It's second hand information, but users seem very unimpressed with this unit.
Has anyone on CF got one?
It would be a great option if it works.

Albro359 · 13-01-2013, 13:27

We flush our watermaker with 5 litres of fresh water every time we use it....we generally run it everytwo days to make water and keep the tanks full.
Last year when stuck in a marina for a week, we just rinsed / flushed with fresh water every two days and that kept everything fine without having to pickle it.