Dessalator Water Maker Issues

amelliahona <no_reply@...>

2 April 2006

I continue to investigate the watermaker issues. But Olivier Beaute, of Amel, has
confirmed to me the following: (at least for watermakers of about my vintage,
mannufactured about July 2001, Hull # 335),

If everything is working as originally installed the salinity sensor should divert high
salinity water if detected. However, if the salinity sensor or the circuity that senses the
salinity fails the watermaker will start up and operate as if everything is normal even if
high salinity water is being produced. Furthermore, there is no indication on the machine
to indicate whether or not the salinity sensor is working properly.

Thus my previous statement stands. If you want to avoid the failure scenario that I
experienced (i.e. salt water being pumped into the fresh water tank when a membrane
failed despite a green good quality water light) then you need a back up secondary salinity
sensor with an alarm.

Dessalator says that they do not have schematics or logic diagrams for their circuit board
because it was manufactured by a sub-contractor that is no longer in business. They do
say that they have about 50 spare circuit boards available if anyone wants theirs replaced.
However, it still isn't clear how to best know if you circuit boards is working.

I suggest the following:

1. Inspect the four fuses on the circuit board to make sure all are ok
one fuse protects the circuit board
one fuse protects the relays
one fuse protects the solenoid
one fuse is the main power to the circuit board fuse.
I will post a picture - parts diagram with fuse sizes etc in an upcoming post.
2. Verify that the green LED on the circuit board is lit (it indicates that the DC power
supply on the board is working
3. Verify continuity of the wiring to the circuit board from the salinity sensor at the
membranes. I had a corroded wire inside a connector.
4. Verify there is continuity of the wiring from the circuit board to the solenoid.
5. Finally test the salinity sensor as I described in my previous post using salt water bath
to see if the high salinity is detected and diverts the water.

I am reverse engineering the circuit board and will have those details available after my
upcoming trip to the boat. At this point I do not believe that there is a 400 hertz signal on
the salinity sensor. It appears that it is a simple DC voltage on a Schmitt trigger buffered
logic gate. More infor with schematics and a logic diagram in about 3 weeks.

Gary Silver

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