Sorry for being so late in answering your very interesting, professional and detailed reverse engineering on water maker.
I live on my boat, presently sailing in south Pacific Islands, often very far off an internet connecting point.
As I already said, mine is a Duo 60 which seems to be a lousy quality by-product very different of yours; amongst others: no BP primary feed pump, degraded HP pump (I opened it to confirm: 2 pistons removed out of the 3 installed by CAT and which are, they say, essential for the balance), no electrical protection….etc….
I looked again in the so called “control box” in the cockpit locker; NO CIRCUIT BREAKER at all (neither motor nor distribution curve); only relays to make clic clac after ~3 min. That confirms that there is no electric protection of the motor, against all safety standards. That is why I nearly got fire and I think I have no other choice than putting a slow blow fuse to protect the HP pump motor.
Incidentally, I know very well the CB’S you are talking of: I was with this company quite a lot of years, in charge of all types of CB (EHV to LV) all over the world.
Thank you again for your very factual and detailed approach of the problem which is of great help to all of us.
Yves MARTIN d'AIGUEPERSE
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