I don't feel Isolated anymore!

[Snotter]

I recently installed a galvanic isolator. (I am writing this post away from my boat and I don't remember what brand isolator I bought.) The isolator was built to the old ABYC standard that mandated a monitor to determine polarity and grounding faults and to determine if the isolator is working. The problem is when I first activate the my monitor, the 3 warning lights are green. After 5 or so seconds, the warning light that indicates a fault in the isolator goes red.

I read the section in Nigel Calder's book "Mechanical and Electrical Systems" (or something like that) that tells how to check the capacitors and diodes in a galvanic isolator. My unit checked ok. Also, I put an amp meter between the shore electrical box and the ground wire of my shore cable (the cable was otherwise unplugged). No galvanic current was detected.

Now for the million dollar question: is my galvanic isolator working?

 

[Don S/V ILLusion]

Sounds like you answered your own question when you said the unit checked okay. If the continuity checked as per the procedure in Calder's book and you have no current flowing across the diodes, I'd go back to the manufacturer and ask what the "idiot" lights do and why they contradict testing.

 

[Bill Roosa]

No current does not mean it is working correctly

Just because your unit is on a boat with no galvanic currents flowing does not mean that it is OK.
You have to check the diodes for short and open conditions. If you are seeing a 1.5ish voltage drop across the diode going in either direction you can be sure they are working ok. There is no easy way to test the cap except to unsolder it.
To measure the voltage drop across a diode you need to have some current flowing unless you can plug it into your "diode test" slot on the multimeter, which most will find imposable. So unplug the unit, get a 12 volt light that draws a couple of amps and connect it in series with the unit. Measure the voltage from one terminal of the unit to the other and see what the voltage drop is. Reverse the unit's wires in the circuit and remeasure. You should get 1.5ish volts when the light is lit. If the light does not light up you have a bad unit. If you get no or less than 0.5ish volts drop across the unit then it is bad.

 

[Snotter]

My digital meter has a diode checker. I checked the diodes per Calder's instructions. They checked OK.

 

[Don12364]

Maybe the boat?

It is known that 'galvanic' voltages are less than the 1.5 volts forward conducting voltage of two diodes in series.
But impressed voltages of greater than this will cause the LEDs to come on.
I suggest you have a galvanic isolator which is okay and a boat which is not.
Somewhere something on your boat is leaking current to earth and this needs to be found and corrected.
I guess there was a reason for buying the isolator in the first place.

Perhaps try disconnecting mains powered items one at a time until these LEDs go out.

Tip:- To meet modern Radio Interference standards many mains powered units have a balanced filter across their mains input circuit. This uses capacitors which are connected to each power wire and the centre of the filter is taken to ground. This means the hot wire passes a significant current into the ground wire but the neutral wire, having very little voltage difference, passes virtually none so does not cancel out the hot side current - hence an induced overall leakage.
Big battery chargers or combo inverters can be a major contributor here and I suggest this is the first place to look if you have one.
With my Freedom Inverter/charger it was necessary to open the unit and disconnect the filter centre point from ground.

 

[Rick D]

Re: Maybe the boat?

Don: did you get your Freedom repaired?