Prosafe FS30 Fail Safe Galvanic Isolator Question

[Kaptajnen]

A year ago i installed a Prosafe FS30 Fail Safe Galvanic Isolator on our boat. As I understand it (from the Prosafe installation manual) the purpose of the galvanic isolator is to allow the bonding system to be isolated electrically from the dock.

Our harbormaster insists that the galvanic isolator is for prevention of galvanic caused corrosion, it does nothing to prevent AC leakage as noted by the 40mA leakage current that the marina is registering.

Is this correct or not?

 

[TBates]

Hi Claus,

The main purpose of the galvanic isolator is to block low voltage DC currents coming onboard your boat on the shore power ground wire, which could cause corrosion to your underwater metals (thru-hulls, prop, shaft etc).

I've attached a link below, which you mind find useful:

https://abycinc.org/blogpost/1653087/331366/Galvanic-Isolators

Thank you,

-Tim

 

[Kaptajnen]

Thank you Tim.

But that does not answer the question whether the harbormaster is right or wrong. The link you sent me says “ The diode assembly has two sets of diodes and a capacitor that block the movement of low-level DC current on and OFF (emphasized by me) the boat”.

Anyone else?

 

[Wee Venture]

Claus, your Harbormaster is right. The galvanic isolator blocks low level DC current on your green ground wire in order to prevent other boats on the same dock from “borrowing” your anodes when their own are insufficient. It does nothing to block AC currents on that ground wire which is very important for safety reasons. Therefore, if your boat has an AC leakage current either to the ground wire or to the water, it will trip the ELCI or the GFI and/or show up on leakage tests.

John

 

[Wee Venture]

Here is a good article on what a galvanic isolator is and how it works.
https://www.boatus.com/expert-advice/ex ... -explained

 

[Kaptajnen]

Thank you very much for the link. I learned that the galvanic isolator isolates me from other boats on the dock.

 

[Kaptajnen]

Here is the information from my ABYC Certified Electrician:

Customer indicated marina found his Ranger Tug leaking 50+ mA AC back through green grounding wire. * First test performed found 70mA AC leak. Turned all power off to boat with all breakers turned off and reading went down to 60Ma AC. This indicates 60mA AC leak coming from an other boat or leak from dock using customers boat as a path back to shore power ground not originating from his vessel.
* Did confirm a 10mA AC leak coming from customers boat. Appears to be coming from inverter. Customer is having a isolation transformer installed to solve this 10mA AC leak and protect his vessel from other boats or dock.
* Connected an ELCI 30mA breaker to customers boat and breaker did not trip with all systems on indicating if vessel is leaking AC in water or back to shore grounding it is less than 30mA AC. Confirmed 10 mA AC leak through boats safety ground to water.

 

[Wee Venture]

Claus, an isolation transformer is certainly the “gold standard” though many of us haven’t installed them because they are expensive, bulky and heavy. (And there is a bit of loss, your 30A power from the pedestal might be down to 28 amps.)

But even if you go ahead and install the transformer, I think the Marina should be notified of the electrician’s findings. If I understand correctly, the electrician is saying that another nearby boat (or the dock) is leaking AC current to the water, and some of that current is finding the underwater metal of your grounding system and hitching a ride on your green ground wire as an easy path back to earth ground through the marina wiring. If this is so, then it should be a high priority for the Marina to identify the original offender and take care of it. If you share the electrician’s findings with the marina they should recognize the need to track it down.

Not sure what is causing the small leak with the inverter but that is not enough to trip your ELCI or the dock pedestal ground fault breaker. An isolation transformer wouldn’t technically fix the leak at the inverter but it would render it harmless and keep it from migrating to the dock wiring.

John

 

[Kaptajnen]

The Marina owner was at the boat, when the electrician briefed me and him. He agrees and will take neccessary action to fix issue.

I am installing a Marine-Puck Isolation transformer manufactured by Bridgeport Magnetics. It is very compact and weighs 45 lbs. Cost with Fedex delivery and taxes around $900. (Ouch!). However, the cost will be somewhat offset by keeping zinc changes to a minimum.

 

[Kaptajnen]

After installing the Bridgeport Magnetics Isolation Puck, my ABYC Certified Marine Electrician found that the red Reverse Polarity light on the 120 volt panel was ON. However all 120 volt outlets still had correct polarity and my 120 volt dehumidifier is working.

He spent several hours trying to troubleshoot this, including calls to Bridgeport Magnetics technical guy, but was not able to solve this conundrum.

Any suggestions would be most welcome.

 

[BB marine]

I would have the electrician look closely at this wiring. download/file.php?id=731. If the electrician has not looked at the wiring to and from the inverter/charger it would be a good idea to make sure it is wired correctly. Make sure the neutral/ ground connection at the inverter is isolated when on shore power. He probably has already done that but just a thought.