Galvanic Isolator test how far apart can the numbers be?

[johnnyv49]

I have a GI Zinc Saver (looks pretty old) and is rated for 100 Amp or less. I did a diode test on it and get 1025 and 1055 (after shorting out the terminals between the two tests). Is this GI working?

Also I don't leave my boat plugged in and my marina has no 30A service so I don't use this very often. Only a few times a year when I go to some travel docks. Do I need a GI at all?

 

[Thalasso]

Re: Galvanic Isolator test how far apart can the numbers be?

If you have it it's best it works properly.Your metal could get hot at one of those marinas.
if one or both of those diodes get blown? NO SAFETY GROUND....! AC green/grounding wire is bonded to the ships DC grounding bus and this means metallic parts of AC devices could become "hot" in the event of a fault. Hot cases and metallic parts of your boat spell the potential for electrocution.
The readings can vary, depending on the multimeter used. For a successful test, it is essential that both readings, with the probes reversed, are virtually the same.e.g. 1032-1029, 783-786.

Galvanic Isolator Explained
Galvanic Isolator Explained

 

[UncleWillie]

Re: Galvanic Isolator test how far apart can the numbers be?

Instead of measuring the Resistance, measure the voltage across the isolator.
If your Electrical panel has a Voltmeter, Turn it ON.
The Panel Voltmeters are commonly wired to return through the ground instead of the common.
This will cause you to get ~1mA of current through the Galvanic isolator.
If you see ZERO Volts, it is shorted, ~0.7 to 1.5 volts AC will be normal operation.
50 to 125 vAC indicates One or Both sides are open.

The Electrical Panels Voltmeter will also NOT indicate the full 125 volts and your Ground Fault lights will come ON.