mcymabm@voila.fr <mcymabm@...>

Dear Gary

Sorry for answering late, but I am not so often near an internet

I confirm that I nearly had fire in my boat due to Dessalator 220 V. motor by end 2005.

My equipment is a Duo 220 V. / 24 V given for 60 L./h.
Equipment and electrical cabling are strictly original.(20A. 2 poles Diruptor, low breaking capacity C.B. )

The Facts: how it happened

One day, I started the water maker on 220 V. as usual, from the galley with gen set running.
I was waiting for the “good quality” green light to switch on, which, of course happened after 2/3 min.
When I turned the pressure up, it was not rising. I then understood that the 220 V. motor had not started and switched the CB on the panel board in the galley off.
This circuit breaker had not tripped ( see further why). I thought I would have a look at it later.

Then, I could smell a strong odour invading the boat. When I opened the engine compartment, I understood the odour was coming from there.

The Diagnosis : why it happened

Examining the motor, I discovered that the capacitor on the motor was damaged, leaking, probably having been mounted too close to the motor. Which I had not noticed before.

Since, without the capacity functioning, the motor didn’t start when I turned the water maker on.
But the Circuit breaker remained in ON position (didn’t trip), nevertheless the short circuit, and nothing told me that the motor had not started. A blocked rotor motor is exactly the same as a short circuit.
The motor was completely burned and I had to have it rewired at my next port of call (Panama). Should have it lasted longer,… you can imagine the possible disaster.

The electrical facts are as follow:
· in order to allow the motor to start and pass the starting peak of current, the breaker is calibrated much higher than the nominal current of the , motor ( 20 A for 5.4 A. nominal current of the motor).

· This setting makes that, in case of blocked rotor, the current, which is the same than the starting one (~16A. for this type of motor), is not high enough to trip the breaker….leaving the motor burn.

· A circuit breaker is designed to protect lines, and not appliances, with exception (see further).

· There is no fuse on the motor to back up the CB.

The professional installation could be in two ways (twofold):

· Use a “motor CB”. This is a special type of CB with special tripping curve to let the peak pass, although being calibrated for the motor nominal amp.
· Use CB + Fuse (a slow blow one) . This is called “line starter” in the US. The CB protects the line (which is the normal aim of a CB) and the fuse protects the motor, but being slow, let the peak pass as long as it last only a very short time (normal starting delay).
· Never protect a motor with a standard CB. A slow blow fuse should have been set on the Dessalator motor.

I made my utmost to be clear, but if not, don’t hesitate to come back.

As to the Watermaker, the responsibility problem is not easy ( see my recent post on this forum):
· I have in hand a letter from Dessalator stating that it was together with Amel that they had decided to do so; Wagner sent a copy of this letter, and others, to J.Y. Selo, at that time after sales director.
· On the other hand, I know other boats, non Amel, having the same problem.
· I am glad that, after having been very doubtful, Ian is now becoming very active on this big issue.

Take care,

Blue Marine
SM 311


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amelliahona <no_reply@...>

23 June 2006

Dear Yves:

Thank you for more details on your system and on the type of near fire
that you suffered. Your description has led me to do some additional
research on my watermaker.

Does your water maker have an electrical control box similar to the
one depicted in the photo section of this web site under Watermaker Service?
You access the box from the port cockpit lazarette. See the photos on this
web site. I would quess that it must have a similar box.

This box on my water maker (160 liter per hour 220 volt sytem)
contains two circuit breakers. They are Merlin Gerin multi 9 C60N D5A and
D25A ciruit breakers (see photo) The D before the 25A or 5A indicates
that these are D curve rated circuit breakers that are motor circuit breakers.

The circuit breaker (20 amp) on the 220 volt panel in the galley is not a
motor rated circuit breaker but does supply feed power to this control
box (see photo).

The 220 volt power to the motors (both low pressure "BP" feed pump
and high pressure "HP" pump), are controlled by stacked relays on the
control circuit board and in the control box and the pumps
are protected by the above circuit breakers.

Everything you have said about protecting the pumps is correct. They
must be protected by motor circuit breakers or dual type fuses. I was
initially confused by the 5 and 25 amp breakers in the electrical box.
However,on my system, and based on reading the complete data sheets
for the manufacturer of these circuit breakers they meet all US and EU
electrical codes for both overcurrent and overload motor protection.

The US codes require the fuse or motor circuit breaker be rated at
125% of the motors data plate current rating. These CBs are D curve
breakers which means that they are appropriate for external motor
protection per the following US electrical Code UL 489, and EU Code

I will have to check the data plates on my motors to verify their rated
current draw to be absolutely sure the breakers are appropriately
sized but my first impression is that Dessalator did provide proper
motor circuit breaker protection for the motors. The specifications
for these circuit breakers say that they are marinized and rated
for at least 10,000 operations, so they are well made. They are
also expensive (about $117 USD each).

Additional protection for the motor could indeed be provided (and
redundant) by appropriate slow blow dual type fuses located at
the motor but neither of the the above noted codes require that.

I am sorry to hear about your electrical failure. I believe your
experience should serve as a warning to us all that we should
shut the system down immediately if either pump does not start
in sequence in their usual fashion.

I am not sure yet which circuit breaker from the 24 volt panel
protects the 24 VDC feed to the Dessalator water maker. Some
day I will complete my schematics, parts list, and parts diagram
for our water maker and post those on the files section.

Kindest regards,

Gary Silver