galvanic isolator installation in catalina 320

[catalina453]

I own a 1997 catalina 320 and want to install a galvanic isolator. I am looking for a convenient place to install it. I plan to install a 30 amp DEI unit 2.6 in dia and 9.4 in long. I would appreciate any ideas as to where to install. I know it needs to be installed on the ground line from the shore power outlet. I could drill two screw holes for the mounting screws in the transom near the shore power socket but really don't want to drill through the transom. Any thoughts?

 

[centerline]

if you can easily get to the area that you speak of, take sandpaper or a small grinder and clean the paint off of an area so that you can glue a piece of wood or plywood there using thickened epoxy/putty.... use it as a mounting block.... no drilling at all.

if you fail to sand it bare fiberglass, the epoxied block will adhere nicely to the paint, but the paint will peel loose from the fiberglass leaving the block and isolator dangling from the wires. you can bet on it....

 

[njlarry]

Although I am hesitate to advocate it, when I installed my autohelm control unit, I simply hot glued a plywood base to the inside of a cockpit locker. I am sure I broke all kinds of rules but it has not budged and was ready to use instantly.

 

[centerline]

Although I am hesitate to advocate it, when I installed my autohelm control unit, I simply hot glued a plywood base to the inside of a cockpit locker. I am sure I broke all kinds of rules but it has not budged and was ready to use instantly.

its just another form of "epoxy".... as long as the paint doesnt peel loose.

one thing i will say about using hot glue... it WILL hold if the adhesion is good but usually the mounting surface is cold and the glue cools too fast to create the best connection. preheating the mounting surface may take a bit longer, but you will have a connection as strong as the plastic/glue itself...

 

[catalina453]

galvanic isolator

I installed a DEI 30 amp fail safe galvanic isolator. During the installation I measured the DC voltage coming from the shore side. I did this by shutting the shore breaker, cutting the 120 vac ground wire then measuring the voltage between the shore side and the boat side. This measured 0.47 volts. This does not seem like much but over time may be enough to erode the zincs to some degree. Does anyone know if this a significant amount? The shaft zincs were just about completely gone in 2 months before I installed the zincs.

 

[Charles Erwin]

Your description does not make clear exactly what you measured.

Try this: Once galvanic isolation is installed. Measure the boat DC voltage (your hull potential.) One meter probe (the +) at the motor block or shaft the other meter probe to your reference cell immersed in the water next to the boat. Then repeat the same measurement - only this time physically disconnect the shore power cord. Do these measurements match?

If everything is as it ought to be these readings should range between -550mv to -900mv DC - assuming you use a silver/silver chloride reference cell.

I use a pencil zinc instead of silver so the value is different. See attached - and note the values in that diagram are referenced to zinc.

 

[catalina453]

Thank you for the info. I followed the procedure using a pencil zinc. I measured 0.02 volts, so looks like my zincs are in good shape

 

[Donnybrook]

0.47 volts is way too high. While taking this measurement, was the shore power cord disconnected? With the cord connected and the breaker off, you are still connected to other boats and docks around you via the neutral and ground.

 

[njlarry]

I use a pencil zinc instead of silver so the value is different. See attached - and note the values in that diagram are referenced to zinc.

Thank you Cpt. Erwin! You just saved me a lot of money. Did not know one could use a zinc intead of a very expensive silver anode.
If you ever get to the Chesapeake I owe you a tall cool one.