Which Watermaker To Choose

[Auspicious]

Originally Posted by noelex 77

I have a spectra 150 watermaker.
I don't want a bigger watermaker, if I needed more water I just run it for longer, or more often
I get 90-95% of my power from solar.

I think the different views come from different forms of power generation. If you get most of your power from a generator, or running the main engine then you need a much bigger watermaker, which will make all your water during the engine run time. Energy recovery is not important and a bigger watermaker will give you more water to use.

If running the watermaker on solar power energy recovery is vital. The gallons per watt becomes vital. Bigger watermakers do not make more gallons per watt so is little practical benefit in increasing size.

Bold added.

There is a sweet spot in small watermakers at around 300 gpd. The Spectra 150 consumes 1.5 Ah/gal of water. The Catalina 300 consumes only 1.2 Ah/gal. Larger watermakers consume more power. Sea Recovery, HRO, and Village Marine demonstrate similar characteristics.

If running off renewables (solar and/or wind) a 12 VDC (or 24 VDC) watermaker sized right around 300 gpd will be most efficient.

[noelex 77]

Originally Posted by Auspicious

Bold added.

There is a sweet spot in small watermakers at around 300 gpd. The Spectra 150 consumes 1.5 Ah/gal of water. The Catalina 300 consumes only 1.2 Ah/gal. Larger watermakers consume more power. Sea Recovery, HRO, and Village Marine demonstrate similar characteristics.

If running off renewables (solar and/or wind) a 12 VDC (or 24 VDC) watermaker sized right around 300 gpd will be most efficient.

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. If you factor in the rinse cycle (which favours a smaller watermaker ) the differences become very small.

There is a big jump in energy consumption for the non energy recovery models. If you are are running the watermaker from a generator the difference between an energy recovery, and non energy recovery models not very important, but it becomes critical when operating the watermaker from solar power.

If you are running a watermaker from a generator its important it makes all your water during the daily run, which should be as short as possible. This means a large watermaker is mandatory.

If operating from solar a longer run time of several hours + is fine. Even a small watermaker will make a lot of water in this time.
The smaller watermaker has reduced capital and operating costs, which helps compensate for the higher cost of the energy recovery technology.

[twistedtree]

To me, the advantage of a DC watermaker is that it can take care of itself while you are away, doing weekly automatic flushes. An AC unit can't do that unless you are on dock power, and at least the Village Marine units reset and discontinue their auto flush if the power is ever lost, and that's a common occurrence in my experience. And an engine-driven unit has similar issues.

If you are a full time live aboard then monitoring and flushing a system manually is no big deal. But if the boat gets left for weeks to months at a time then the auto flush is a real winner, and I think DC is the most reliable way to do it.

And the same logic about when to make water with an engine driven maker also applied to a DC maker. The best place is to make water while out at sea and underway. If you are a power boat your engine is running anyway and DC is plentiful. If you are a sail boat just make water while motoring which is what your would do with an engine driven unit.

Another consideration is that although there are low power, low output DC water makers, DC power does NOT mean that it HAS to be low power and low output. Spectra, for example, has DC units that make 700 and 1000 gal per day. That's just as good as an AC unit, but still uses about 1/2 the total power of an AC unit.

[daddle]

The point about being stuck in a polluted anchorage is a good one. A slow watermaker will not be any fun there. But nothing else will be fun their either. Otherwise the above arguments for a large watermaker are flawed. Any size watermaker could be made efficient with proper design. It's Energy per liter that is important, not size.

[sailorboy1]

Originally Posted by daddle

It's Energy per liter that is important, not size.

I don't agree.

If you are powering with a generator or using an engine driven unit you don't care much about efficiency, you care about capacity! In these cases you have energy to burn and the biggest energy loss has to do with burning the fuel for the engines.

Nothing probably is less efficent than running an engine to power a watermaker, just as it is very ineffective to use 1 to charge your batteries.

[daddle]

Originally Posted by Don Lucas

If you are powering with a generator or using an engine driven unit you don't care much about efficiency ...

I completely agree with you. That is exactly my point. Some of us care about efficiency.

[goboatingnow]

The issue of efficiency is separate to the issue of capacity. Efficiency only matters, ( other then an ideological concern) when you have a limited supply of power or an expensive one.

Dave

[downunder]

Originally Posted by daddle

I completely agree with you. That is exactly my point. Some of us care about efficiency.

If you do have a genset aboard and it might be for AC use in some conditions or to run a scuba compressor it makes sense to ensure you load your genset for efficiency. It makes sense to plan your genset use. depending on capacities etc run watermaker at time your are washing/battery charging. Generator use can be planned for efficiency also.

Mark (colemj) your summary of practical use of a watermaker in the tropics was excellent.

Cheers

[nigel1]

Carsten, if considering a Spectra unit, these people may be worth a call.
Ex demo & pre owned watermakers for sale - Sailfish Marine - Watermakers, Marine Generators, Solar Panels and more..

Appear to be UK dealer for Spectra, and sell re-conditioned units (although the reconditioned units seem to sell very quickly. The site suggests there is a 3 month warranty

[mcarling]

Originally Posted by Don Lucas

I don't agree.

If you are powering with a generator or using an engine driven unit you don't care much about efficiency, you care about capacity! In these cases you have energy to burn and the biggest energy loss has to do with burning the fuel for the engines.

Nothing probably is less efficent than running an engine to power a watermaker, just as it is very ineffective to use 1 to charge your batteries.

All this depends on unstated assumptions which are true for some cruisers and not true for others. The battery technology, AC v DC generator, battery bank capacity (watt-hours), fuel capacity, etc. are all factors which vary from boat to boat.

[carstenb]

Originally Posted by nigel1

Carsten, if considering a Spectra unit, these people may be worth a call.
Ex demo & pre owned watermakers for sale - Sailfish Marine - Watermakers, Marine Generators, Solar Panels and more..

Appear to be UK dealer for Spectra, and sell re-conditioned units (although the reconditioned units seem to sell very quickly. The site suggests there is a 3 month warranty

Thanks nigel, I'll check it out.

Re watermaking at anchorage: I have about 280 liters total in two tanks. So using say 20-30 liters per day I can go ten days before having make water. A 30 liter per hour watermker fills them in ten hours.

I haven't sailed in the carribean, but I just can't see that it will be a problem having to leave a dirty anchorage once a week. We will probably do that anyway. We actually do like to sail.

[noelex 77]

Originally Posted by carstenb

Thanks nigel, I'll check it out.

Re watermaking at anchorage: I have about 280 liters total in two tanks. So using say 20-30 liters per day I can go ten days before having make water. A 30 liter per hour watermker fills them in ten hours.

I haven't sailed in the carribean, but I just can't see that it will be a problem having to leave a dirty anchorage once a week. We will probably do that anyway. We actually do like to sail.

To keep the watermaker in good condition running it more frequently is much better.
In hot weather think about running every few days. 10 days is too long IMHO. You can flush the watermaker, with fresh water instead of running it, but this uses quite a lot of water, even flushing a small watermaker.

[carstenb]

Noelex, I expect to run it every day actually. My mail was inresponse to the " yeah but a small watermaker is a PITA when you are in a dirty anchorage" folks.

[noelex 77]

Originally Posted by carstenb

Noelex, I expect to run it every day actually. My mail was inresponse to the " yeah but a small watermaker is a PITA when you are in a dirty anchorage" folks.

I understood that, i just wanted you to factor a 5 day freshwater flush into your calculations. Also after running the watermaker it also needs a freshwater flush at this stage which means your water tank wont be comeletly full, when you have finished your watermaker run.
You should still manage 7-10 days, but not with much reserve.

Running out of water is worse than running out of beer

[sailorboy1]

Originally Posted by mcarling

All this depends on unstated assumptions which are true for some cruisers and not true for others. The battery technology, AC v DC generator, battery bank capacity (watt-hours), fuel capacity, etc. are all factors which vary from boat to boat.

Is, but that's a different discussion!