For those thinking of fitting a watermaker

[geem]

This again?

Schenker modular 30 (12V):
Power consumption: 96W
Current draw at 12V: 8A
Water production: 30L/h
Water production/Ah: 30/8 = 3.75L/Ah

Rainman (230V):
Power consumption = 2kW
Current draw at 12V (via inverter) = 2000/12 = 166A
Water production = 60L/h
Water production/Ah = 60/166 = 0.36L/Ah

The Schenker we've been using all the way from UK to NZ has let us down once with a cracked low-pressure hose. Across the Pacific it supplied enough water for 6 people to shower every day, and we never had to run the engine to generate power (we have a Watt and Sea towed generator). At anchor, we generate all our power with 700W of solar, and this has been sufficient, at all times except winter in Wellington. If we had to use 10x more energy for each litre of water, we would certainly have run the engine more often to keep up with power demands on board.

Or my watermaker. 1.5kw. water production 200litres/ hour.
Your watermaker makes so little water, it has to run for 3.3 times the time of our 220v model for the same production. It might only use a small amount of power but when they go wrong, and they do go wrong, fixing it is expensive and they require specific parts.
We also have 720w of solar and run our watermaker, cook, make hot water all on the solar. You can choose low amps or reliability but not both. You chose low amps and high cost. We chose low cost and high amps. Either is not wrong. It's just a different way of doing things.
We both do it all of solar so no difference there
Edit:
I just noticed your watermaker is only 30 litres per hour so you need to run it for 6.6hrs to my 1 hour for the same production. A Zen 30 costs about €5000 for 30 litres/hr. I built my watermaker for way less than that. We already had a diesel generator thst came with the boat, so it was a logical choice.
Now we have lithium we no longer need the generator as long as we are in the Tropics. We harvest 3.5kwh of solar on average, here in the Caribbean with 720w of solar. We just added another couple of hundred watts so now we are harvesting 4.5kwh of solar per day. Making our daily water needs is only 460Wh so about 10% of our daily solar harvest. Its less than making our hot water needs per day and less than our daily electric cooking load on the induction hob.

 

[roaringgirl]

Or my watermaker. 1.5kw. water production 200litres/ hour.
Your watermaker makes so little water, it has to run for 3.3 times the time of our 220v model for the same production. It might only use a small amount of power but when they go wrong, and they do go wrong, fixing its expensive and they require specific parts.
We also have 7202 of solar and run out watermaker, cook, make hot water all on the solar

At 1.5kW for 200L, you're running at 1.5L/Ah which is impressive, but still requires double the energy for the same volume of water. If you weren't so close to the equator, you would struggle! You know the membranes prefer to be run longer, right?

When mine went wrong, which it did once, I fixed it with a non-specific bit of garden hose.

 

[geem]

At 1.5kW for 200L, you're running at 1.5L/Ah which is impressive, but still requires double the energy for the same volume of water. If you weren't so close to the equator, you would struggle! You know the membranes prefer to be run longer, right?

When mine went wrong, which it did once, I fixed it with a non-specific bit of garden hose.

The membranes on my system run every day for 15 to 20 mins. Plenty of time to flush them through. We don't back flush with fresh unless we are going to miss making water every day. The flow through my membranes is high. The product hose runs like a garden hose. 3 litres per minute.
We normally make water whilst having breakfast and it's job done. The cost of my system was very ,ow as i built it myself. It has been installed for 11 years and never let us down. It's made thousands of litres of water. We used to run off the diesel generator but now it runs off solar just like you

 

[roaringgirl]

Unless you're parked permanently in the tropics, energy management is a big deal for most cruisers. Production speed is of no consequence, unless you're having a shower directly off the output of your watermaker. What is important is production efficiency - how much energy is each litre of water going to cost me?

Yesterday my 700W of PV made 620Wh of energy, which translates to 51Ah.
That's enough for me to make 180L of water (if I didn't also have to run the fridge, lights etc...)
It's enough for you to make 75L of water (if you didn't have to do the same).

If you've run your own 230V watermaker for the last 11 years, I presume all your experience of energy recovery systems has come from other people's broken ones? Have you considered that you only hear people complaining about the broken ones, not all the ones that are fine?

I'm glad that you're happy with your system, I guess what I object to is the sweeping generalisations that are so easily disproved by my experience.

 

[john_morris_uk]

Unless you're parked permanently in the tropics, energy management is a big deal for most cruisers. Production speed is of no consequence, unless you're having a shower directly off the output of your watermaker. What is important is production efficiency - how much energy is each litre of water going to cost me?

Yesterday my 700W of PV made 620Wh of energy, which translates to 51Ah.
That's enough for me to make 180L of water (if I didn't also have to run the fridge, lights etc...)
It's enough for you to make 75L of water (if you didn't have to do the same).

If you've run your own 230V watermaker for the last 11 years, I presume all your experience of energy recovery systems has come from other people's broken ones? Have you considered that you only hear people complaining about the broken ones, not all the ones that are fine?

I'm glad that you're happy with your system, I guess what I object to is the sweeping generalisations that are so easily disproved by my experience.

To add weight to your comments, Geems cost claims are wrong as well.

Our 12 volt Osmosea energy recovery water maker cost £3600 last year. No where near the alleged cost of £11000 for a 12 volt one he alluded to in his OP. It draws about 8 amps and makes 50 litres per hour. (Sometimes more as it’s more efficient in warmer water). I appreciate its only 9 months old but so far it’s performed faultlessly.

We’ve not got room for huge amounts of solar but even off the small solar panels that we’ve got hanging off the rails, we can run our watermaker. It’s also really quiet to use so a couple of hours a day making 100 litres of water keeps us showered and tanks full is not a problem. My experience of earlier generatio of water maker was that they were very noisy.

 

[Trident]

Like most things with boats there is no right answer. I've fitted lots of water makers professionally and fixed many too and fitted various models to my own boats and had very little go wrong with mine. I think there is a level of installation being an issue but also a lot of poorly conceived models. The Osmosea for example was notorious for very low life on some of the valves and a dreadful squeak on them after about 100 hours use. They fixed that a couple of years ago but had John had his 5 years ago he may well be less happy with it now.

I currently have the Zen 30 and I think its very good and Mactra who sold it to me a fantastic people to work with. I also have a PowerSurvivor 80 from Katadyn that does 15l/h for 6-7 amps as a back up and so far its been working on boats (came off another before I had it) with just a seal kit service for about 25 years - possibly on the same membrane. Yet my previous Power Survivor 35 could never be made to work properly. I rebuilt it twice, it went back to Mactra to rebuild and they literally swapped out every part, one at a time to test and it would still only make 2L an hour not 5 so it had to go...

I'm now looking at building an AC 100L/ hour until because I have more solar than I can use in a day (even in the UK latitudes ) so I may as well burn off lots making lots of water BUT I hate the noise of my current water makers and so having noise just for one hour instead of 2-3 a day now makes sense to me.

Ultimately most water maker makes will go wrong at some point though not every one of every make in the life time of the owner. The fewer hours the mechanicals run the better they last, provided that they do enough to keep the membranes happy etc. The Pardys did a study, interviewing long term cruisers, that showed that water makers and fridges were the two biggest reasons people got stuck in port whilst they waited for repair or parts. (Hence I have two)

I don't think there is a "best approach " - there is only the best for you and your circumstances and your usage but from my experience just don't ever be too smug and confident that your unit , be it 12v, 240 or engine driven, will always work and won't break down when you're in the least convenient place to repair it!

This thread has highlighted that AC production isn't just for boats with gen sets and that may have surprised a lot of people

 

[geem]

RO plants are not complicated. They have specific requirements regarding water cleanliness and maintenance which if ignored may result in unhappiness and expense, but are not complex.

Ro plants are not complicated since they use none energy recovery systems. 12v energy recover units are complicated until you strip them down. It's not super complicated but it is a lot of moving parts that wear with time. I have worked on both Spectra and Schenker energy recovery units with friends boats that have had problems. One needed a rebuilt Clarke pump. The other needed a rebuilt Clarke pump and a boost pump. Both due to failure after the components wore out.
They do a lot of hours because their production is relatively low so the wear rate is consequently higher than the simpler but power hungry none energy recovery types using a HP pump

 

[vas]

I agree re noise of the 230V pumps, it's a bit annoying, but I've got a decent solution for that: run the watermaker when I go swimming, turn it off 3/4h later when I come back job done

 

[dgadee]

One thing I just remembered to say. My 1hp motor operates at 50 cycles. By using a 3 phase motor and inverter (which I haven't installed yet) the output from the watermaker will rise by 20% (approx) if you set it to 60 cycles.

 

[vas]

One thing I just remembered to say. My 1hp motor operates at 50 cycles. By using a 3 phase motor and inverter (which I haven't installed yet) the output from the watermaker will rise by 20% (approx) if you set it to 60 cycles.

I also replaced the stock 1ph motor of my watermaker for a 3ph one and an inverter to soft start and stop the thing to put less stress on the membranes. Works fine, however never thought of upping the Hz on the inverter to 60!
maybe silly Q do all 3ph such motors happily work at 60Hz? and are pumps also happy running at higher rpm?
IOW, does the extra production could possibly mean earlier failures?

cheers

V.

 

[penfold]

Some motors are rated to run at either frequency, the data plate will tell you; whether an unrated motor will do so reliably depends on the load.

 

[geem]

I also replaced the stock 1ph motor of my watermaker for a 3ph one and an inverter to soft start and stop the thing to put less stress on the membranes. Works fine, however never thought of upping the Hz on the inverter to 60!
maybe silly Q do all 3ph such motors happily work at 60Hz? and are pumps also happy running at higher rpm?
IOW, does the extra production could possibly mean earlier failures?

cheers

V.

I am not sure how the soft start reduces stress on the membranes. When you first turn in the pump on, the needle valve is fully open. There is no back pressure created. The HP pump water can run unhindered around the outside of the membranes and out through your high pressure hose to drain. Once the pump is running, the needle valve is slowly closed and you build up pressure,to 800psi. Soft starting the pump does nothing other than reduce inrush current.
Motors need to be selected for 60Hz. Some can run at either 50 or 60 but you need to check with the manufacturer. Whether you can run your HP pump faster will also need checking out. Mine has a design speed or 1750rpm but we run it directly from a 1.5kw single phase motor at 1450rpm. From the pump calculation I did, to run it at 1750rpm, I would need a 2kw motor

 

[dgadee]

US motors all run at 60 cycles I thought and my pump fits onto the motor flange. In the version I reverse engineered the pump was fitted to a US motor.

But never trust my electricsa knowledge.

 

[geem]

US motors all run at 60 cycles I thought and my pump fits onto the motor flange. In the version I reverse engineered the pump was fitted to a US motor.

But never trust my electricsa knowledge.

It should be OK but worth checking the motor speed at 60 Hz against the rated speed of the pump

 

[dgadee]

Ps - I made the mistake of buying a US pump. That meant I had to get motors with the same flange from the US. Buy British and save yourself a lot of hassle!

 

[geem]

Ps - I made the mistake of buying a US pump. That meant I had to get motors with the same flange from the US. Buy British and save yourself a lot of hassle!

I am using a US pump. British motor. Its a standard flange pattern available world wide

 

[penfold]

That would be unusual, there's an international standard for motor flanges/casings, the cost of straying outside that is significant and a manufacturer wouldn't do it unless packaging dictates.

Ps - I made the mistake of buying a US pump. That meant I had to get motors with the same flange from the US. Buy British and save yourself a lot of hassle!

 

[dgadee]

I thought it would be easy to buy a flange adapter - have done it in the past - but not for this pump.

Edit: General Pump WM1516C. NEMA 56C flange.

 

[geem]

I thought it would be easy to buy a flange adapter - have done it in the past - but not for this pump.

Edit: General Pump WM1516C. NEMA 56C flange.

That's quite a small pump. Mine is rated at twice the flowrate.
What size motor do you use? Do you know what power the motor runs at?

 

[vas]

I am not sure how the soft start reduces stress on the membranes. When you first turn in the pump on, the needle valve is fully open. There is no back pressure created. The HP pump water can run unhindered around the outside of the membranes and out through your high pressure hose to drain. Once the pump is running, the needle valve is slowly closed and you build up pressure,to 800psi. Soft starting the pump does nothing other than reduce inrush current.
Motors need to be selected for 60Hz. Some can run at either 50 or 60 but you need to check with the manufacturer. Whether you can run your HP pump faster will also need checking out. Mine has a design speed or 1750rpm but we run it directly from a 1.5kw single phase motor at 1450rpm. From the pump calculation I did, to run it at 1750rpm, I would need a 2kw motor

not quite sure I follow geem.
My inverter is setup so that it starts at 1Hz and reaches 50Hz after 60sec (or 120 don't remember what I've programmed there!). Needle is not touched in the process obvs.
So monitoring what's happening, I can see on the boost gauge on the watermaker that pressure builts up nice and slow within this time from 0 to the full 800psi which I believe is what matters.
Don't really get the inrush current thing, care to explain please?

V.