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Dessalator Duo watermakers - energy saving tip: don't use 230v if you can avoid it

Scott SV Tengah
 

We have a Desslator Duo 100 that runs on either 24v DC or 230v AC.

According to the specs and our own measurements, the 24v motor draws 600watts and the 230v motor draws 1100watts! The AC motor draws 83% more energy, so I asked Desslator if it produced more water per hour. Here's their response:

"It is the pulleys ratio which make both motors turn at the same speed at the axis of the pump, even if the electrical consumption is more important with the AC motor.  

Consequently, both motors produce the same liters per hour (around 100 liters with a 25° sea water)."


I've been trying to "balance out" the motor wear by using both DC and AC, as I'm acutely aware of the problem of DC motor brush wear on my fridge pumps. But it seems if you're trying to do your part to save energy, running the AC motor is not a good idea.

Related question - what are people's experiences with DC and AC motor longevity. My research on DC motor brushes seems to indicate 2000-3000 hours of life is typical. What about the AC motor? I recall hearing the capacitors being the first things to go?

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

Oliver Henrichsen, SV Vela Nautica
 

Hello,

We got the same Duo 100.
It was compleatly falling apart after only 300h of use when we got Vela Nautica. 
We gave it a compleat refit what included an one DIN grade stronger AC Motor because CAT PUMP Germany said the build in AC Motor is not strong enough. And the motor shaft was worn out. 
It was also needed to replace the soft pulley discs to industrial grade ones and change all bearings to high quality SKF. 
The selenoid previously munted on the device did not cope with the units vibrations and was then wall mounted. 

Since that its working flawless and has now about 900 hours. The unit is now almoast vibration free and is not to be heard anymore.

We use AC only when the Genset is working anyway. Otherwise we use the 24V motor. We like this oportunity to switch AC / 24 V, I think its a clever design. Only it might be wise to use higher grade spares than the original brand. 

An replacement of the 220 V AC motor is not really expensive (industrial grade about 160 €) so its not worth to level motor wear. 


Oliver from Vela Nautica Amel54#39 
Martinique 

On Tue, Jun 30, 2020, 16:29 Scott SV Tengah <Scott.nguyen@...> wrote:
We have a Desslator Duo 100 that runs on either 24v DC or 230v AC.

According to the specs and our own measurements, the 24v motor draws 600watts and the 230v motor draws 1100watts! The AC motor draws 83% more energy, so I asked Desslator if it produced more water per hour. Here's their response:

"It is the pulleys ratio which make both motors turn at the same speed at the axis of the pump, even if the electrical consumption is more important with the AC motor.  

Consequently, both motors produce the same liters per hour (around 100 liters with a 25° sea water)."


I've been trying to "balance out" the motor wear by using both DC and AC, as I'm acutely aware of the problem of DC motor brush wear on my fridge pumps. But it seems if you're trying to do your part to save energy, running the AC motor is not a good idea.

Related question - what are people's experiences with DC and AC motor longevity. My research on DC motor brushes seems to indicate 2000-3000 hours of life is typical. What about the AC motor? I recall hearing the capacitors being the first things to go?

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

Jamie Wendell
 

Almost wish I had the duo system after looking at those numbers. I only have the 230 VAC version.,,,,,,,
The good news is that it has been pretty reliable - the only issue I had was the mounts for the low-pressure pump (replaced in Martinique) and the high-pressure switch failing (also replaced). I also replaced the HP hoses, as the covering seems to go bad pretty fast.
I am due, though, for a membrane replacement (second time) - not a fun job for sure. I have the new ones ready to go.
Jamie
Phantom, A54 #44

Denis Foster
 

Hello,

Concerning the Dessalator DUO 100, the information I have gathered :

- the 230V motor is more efficient and the good flow in the membranes keep them in good conditions for longer (4000h versus 2000h with the 24V flow)
- a good feeding pump allowing sufficient flow through double 20 and 5 micron filters are good for the CAT pump. Avoiding cavitation is crucial for longevity.
- Reading Oliver of Vela Nautic who is very knowledgeable the Dessalator duo 230V motor can be improved to an industrial grade with excellent bearings and shafts.
- A lot of electronics can look good but is prone to more complex failures difficult to fix.


This research also led me to have a look at Aquatec German made water maker that advocates 230V when generator is fitted. But I like the redundancy of the DUO that has also 24V motor in case the generator fails. (Which does happen). They indicate the use of a high quality Stainless Steel high pressure pump.

The ideal water maker would be a combination of both concepts allowing reliability and redundancy.

As I am not an expert of this field I would like to have your real world feed back on the ideal Blue Water Cruising water maker.

Thank's 

Denis

Ex Madinina Meltem 

Scott SV Tengah
 

Thanks! For energy saving purposes, going forward, we will try to use the 24v DC motor whenever possible but it's good to have the 230v AC as a backup. We replaced the entire water maker not too long ago and have about 350 hours on it and only maybe 20 hours on the AC motor, but I'm sure others would love to improve their older units.

Do you have the part numbers for all the changes you made to the water maker?

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

Scott SV Tengah
 

Jamie - how long do your membranes last? I presume you're replacing once TDS goes above a certain limit?

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

Scott SV Tengah
 

Denis -

I am a little confused. Desslator said that both motors turn at the same speed on the pump due to pulley differences, so I'm not sure how the 230v motor flows more water than the 24v? Maybe I'm not understanding the system?

In any event, even if the membrane life is somehow 2x, by using the AC over the DC motor, you're using an additional 500 watts, which is roughly 20 amps. Over 4000 hours of using the 230v pump vs. the 24v pump, you're using 80,000 extra amp hours of energy. If you're running genset to run the 230v AC motor, that's 4,000 extra hours of genset usage and all the fuel and maintenance that entails.

If you have lithium and a big inverter then you won't need to run the genset during usage, but could rather charge the batteries later.  Even with my two chargers feeding 200Amps, that's an extra 400 hours of generator usage and all the fuel and maintenance that entails. This ignores the environmental cost of all that genset usage, which is not zero.

I can't see the AC pump being anything more than a backup, assuming your electrical system can handle 600w, which it should even on lead acid.


--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

Jamie Wendell
 

I replace my membranes when I see the TDS tests showing higher than "normal" levels or the water tastes a bit salty. I have found it important to actually test with a meter vs. relying on the built-in sensor. That sensor always seems to show a green light after a few minutes running and I am not sure how it is calibrated.
I have never seen the numbers exceed approved standards (I believe 500), but I like to err on the side of caution if I see TDS numbers rising say above 300. Hence, I replace about every 2 to 3 years, particularly if I do not use the watermaker routinely (winter storage for example).
In 5+ years of being an Amel owner, this will be my second replacement.
Jamie
Phantom, A54 #44