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Old 06-02-2020, 10:46   #1
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Galvanic Isolators

The diodes in the Quicksilver 18478Ai galvanic isolator on my yacht have blown due to a lightning strike on a nearly boat. I can't easily fit another type as there's little space available so I'd like to replace the diodes. Does anyone have any ideas of a suitable substitute? A Google search for the type number on the blown diodes reveals nothing!

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Old 06-02-2020, 13:03   #2
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Re: Galvanic Isolators

I suspect that the mfg did not consider your GI reperable. Having said that, if you can access the internals and are handy with repair work might, have a chance.


When you here the phrase "they are just diodes" that is a bit misleading. They are actually rectifier diodes capable of 30 to 50 amp load for a significant time period. Get the picture of little black fingernail sizes devices out of your mind. These will probably be a couple of aluminum heat sinked devices the size of match boxes.


If your installation dates back to the days of just connecing the ZS/GI between the green AC ground and engine 12 V return then that is about it. If yours follows the newer guidelines of installed in series with the AC ground then there is supposed to be a integrity monitoring system or the design is supposed to fail safe (ie shorted). Always wondered how you assure that as my experience is that diodes usually fail open.

See if you can get inside. Even then you are playing a long shot game.


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Old 06-02-2020, 14:17   #3
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Re: Galvanic Isolators

@captainmikecoin:
These GI have not been manufactured in some time and certainly do not meet the latest requirements of being either fail safe or having a monitoring system installed to ensure the integrity of the safety ground wire back to the pedestal.
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Old 06-02-2020, 14:55   #4
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Re: Galvanic Isolators

I had already opened the box, looked inside and removed the diodes (rectifiers if you like) which checked out as short circuited. I need some new ones. I realise they need to be capable of 60 amps forward current (which is the rating of the galvanic isolator but am interested to know what the appropriate voltage should be. Do they need to withstand the peak voltage of full 240V RMS?

Mike
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Old 06-02-2020, 17:01   #5
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Re: Galvanic Isolators

I would expect that 240 VAC, 60 Amp as a minimum. These are typically bridge rectifier assys, so pay close attention to connection terminals. Should have two AC connections (normal not connected), and + and - terminals.


Proceed at your own risk, and those that may follow. Screwing this up may cause dangerous shock conditions, or dissolve your thru hulls in short order.


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Old 06-02-2020, 18:25   #6
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Re: Galvanic Isolators

240V rms would be about 340V peak, 120V rms would be about 170V peak; beware.

As CharlieJ said, current galvanic isolators are much better. The failsafe ones fail safe, and the monitored ones are monitored. The standard has moved on.

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Old 07-02-2020, 08:11   #7
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Re: Galvanic Isolators

Yandina has introduced the Galvanic Isolator PLUS - a 2.5 volt isolation which is twice as much as conventional isolators. Yandina Isolators have UNCONDITIONAL warranty, even for lightning.

The LOWEST voltage rating on the diodes is sufficient, they are never presented with more than 1.2 volts. On an AC current when the polarity reverses the diodes in the opposite direction turn on and limit the voltage.
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Old 07-02-2020, 08:22   #8
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Re: Galvanic Isolators

As the original poster I'm glad Ann-Marie has replied whatever the forum rules. Her post contains exactly the info I needed.

Mike
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Old 07-02-2020, 08:50   #9
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Re: Galvanic Isolators

I'm glad she posted as well. I have a Yandina GI and it is bonehead simple, completely potted and i now get double the life out of my zincs. Plus the least expensive option and lifetime warranty.

No leds on status, but with quarterly diving service I can tell it it it ever fails... my zinc usage will return to the pre GI days.
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Old 07-02-2020, 11:11   #10
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Re: Galvanic Isolators

Gi’s are small and can fit just about anywhere.

Replace it. Move it somewhere else if you have too. It’s only 2 wires to change.
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Old 16-02-2022, 04:01   #11
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Re: Galvanic Isolators

give me an offer, I have two of them
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Old 16-02-2022, 04:55   #12
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Re: Galvanic Isolators

Greetings and welcome aboard the CF, tijdverdrijver
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Old 23-02-2022, 19:29   #13
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Re: Galvanic Isolators

Just buy a new one.
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