How Many Galvanic Isolators

[sail sfbay]

New 1984 boat to me has two (2) 30 amp and one (1) 50 amp shore power connections and NO galvanic isolator or isolation transformer. Planning to install one (1) 60 amp galvanic isolator (vs. isolation transformer due to lower cost, size and weight and no noise) on the "common" power line from the 30 amp/50 amp switch to electrical panel with the inension of only connecting either one 50 amp shore power cord OR up to two 30 amp shore power cords. Is that a safe OR do you recommend one galvanic isolator for each shore power connection and why?

 

[dlochner]

The GI should be on the green ground wire and should be between the shore power connector and any other connection. Whether you need one or three GIs depends I think on how the selector switch is wired. If it is possible for current to flow through an AC ground connection to the shore power ground regardless of switch position, then I think you need on each shore power connection.

If the selector switch breaks the connection on all three circuits, hot, neutral, and ground for each shore power connection then one big one might be sufficient. Depends on how the switch is wired.

 

[sail sfbay]

I think I am good as my marine electrician advised "as per the installation manual of your ProMariner, the ground lines from all three connectors come into your galvanic isolator and then there is one line going from the isolator to your AC ground system. Your selector switches don't switch the ground. They only switch the hot/hot or hot/neutral lines."