Galvanic Isolator or Isolation Transformer Question

[boatpoker]

Originally Posted by GordMay

Indeed.

I think you'll need a Galvanic Isolator for each Main Breaker.
If all your shore power inlets supply (through some sort of selector sw) a single main breaker, you'll only need one isolator.
Otherwise, you'll need an isolator for each Shore Power "Service".

The ground does not go through a breaker.

[GordMay]

Originally Posted by boatpoker

The ground does not go through a breaker.

Indeed.
The cable that goes from the Inlet(s) to the Main Breaker (Service Panel), has it's ground connected at the Isolator.



FWIW:
I'm agreeing with you, and only extending your accurate advice, to the rarer application, when a boat has two separate services:
1) Service with Inlet, Isolator, Main Panel /w Main Breaker serving general house loads,
and a second Separate Service for (say) Heating/AC loads, with it's own Separate Inlet, Isolator, Main Panel /w Main Breake.

[sail sfbay]

Thanks for all of your replies!! I should have clarified that I only plug in one (1) shore power connection at a time and I am working with an electrican.

ProMarina technical service advised: "Yes, you can use the Promariner 60 amp model #22074 (common for all shore connections) by connecting the two incoming ground wires at one post and use the correct 60amp rated wire to go from the second post to your circuit breaker panel."

[mvmojo]

Originally Posted by boatpoker

A lot of misinformation here.

Yes you can run multiple shore grounds through one Galvanic isolator as long as it is appropriately sized.

One 60amp isolator for the two 30amp lines
+
One 50amp isolator for the single 50amp line.

Best you talk to an ABYC Certified Marine Electrician or Certified Marine Corrosion tech.

Check ABYCinc.org , they've been running free on-line mini seminars lately

This is the pretty much the correct answer. The galvanic isolator sits between the boat ground wire(s) and the shore ground wire(s). As long as it's rated to handle your max load you're fine. I suspect (a guess!) that you boat is set up to EITHER use two 30 amp/120v cords OR one 50 amp/240v cord. It's unlikely that you have three different circuits on a boat that size. You probably (another guess) have a transfer switch that allows you to select either the 50 amp cord or the two 30's. If that's the case, one galvanic isolator between the boat's grounds and the shore ground's is all you need.

[sail sfbay]

ProMariner techical serice just advised: "If only one AC input is connected then the 60amp isolator would be fine. However, if more than one could be plugged in at the same time, you would want a 60amp isolator for the 50amp line and one for the two 30amp lines for safety."

[sail sfbay]

Originally Posted by mvmojo

...............This is the pretty much the correct answer. The galvanic isolator sits between the boat ground wire(s) and the shore ground wire(s). As long as it's rated to handle your max load you're fine. I suspect (a guess!) that you boat is set up to EITHER use two 30 amp/120v cords OR one 50 amp/240v cord. It's unlikely that you have three different circuits on a boat that size. You probably (another guess) have a transfer switch that allows you to select either the 50 amp cord or the two 30's. If that's the case, one galvanic isolator between the boat's grounds and the shore ground's is all you need.

You are spot on.....that is how my 2 30amp and 1 50amp shore power are connected to the panel with a transfer switch. Thanks again!! Surprised the PO's never installed either an isolation transformer OR galvanic isolator in 36 years (1984 boat). Just ordered the 50/60 amp ProMariner #22074 galvanic isolator and requested my ABCY certified elelctrician to install it as soon as I get it next Tuesday as a priority.

[manitu]

Did'nt realise that all inlets supplied the same panel.

A question to you chaps familiar with the american split phase 120/240v system: The 50 amp socket are two phase 120v+neutral+120v (240v), right?
Does that mean that if using 2x30amp inlets, and you have 240v consumers on board, the two 30 amp sockets has to be the opposite phases?

.manitu

[David B]

Originally Posted by sail sfbay

New to me 1984 Symbol 44 Sundeck has two (2) 30 and one (1) 50 amp shore connections. I am guessing the boat will need one galvanic isolator (or isolation transformer) for each shore connection. Is that correct?

Two isolation transformers (one for each circuit) or one galvanic isolator (in the common earth circuit).

[mvmojo]

Originally Posted by manitu

Did'nt realise that all inlets supplied the same panel.

A question to you chaps familiar with the american split phase 120/240v system: The 50 amp socket are two phase 120v+neutral+120v (240v), right?
Does that mean that if using 2x30amp inlets, and you have 240v consumers on board, the two 30 amp sockets has to be the opposite phases?

.manitu

Yes, in the US a 240v service consists of a neutral and two 120v legs 180 degrees out of phase with each other. Voltage across the two legs is 240v, voltage between either leg and neutral is 120v. If you have a 240v consumer then the two 30amp/120v supplies must be out of phase with each other. That's typically how shore pedestals are wired... if there are two 30a outlets they are typically out of phase with respect to each other.

[smac999]

Originally Posted by manitu

Did'nt realise that all inlets supplied the same panel.

A question to you chaps familiar with the american split phase 120/240v system: The 50 amp socket are two phase 120v+neutral+120v (240v), right?
Does that mean that if using 2x30amp inlets, and you have 240v consumers on board, the two 30 amp sockets has to be the opposite phases?

.manitu

yes. but more and more marinas are starting to install GFI / RCD / ELCI 30a dock breakers. so some places you can no longer feed a 240v boat with dual 30s. and likly in the future no where.

most boats don't have a lot of 240v stuff on them. the 50a 240 is gernally just running more 120v stuff. giving 100a of 120v

[millsie]

A Galvanic Isolator or Isolation transformer is required for each shore power connection.
If you don't need all the shore power connections, remove the ones that are not being used ( need a licensed electrician) .
If you are unsure or unqualified please don't offer advice.