Ask PYS: Power

Peter, on Feb 17, 2010 asked:

The AC grounding connection on my Uniflite 36' is no more. What is going on here? Shouldn't the AC (green) grounding wire be continuous between the AC shore power socket and the AC grounding bus?

Hi Peter,

First off, we would like to emphasize why AC grounding connections are absolutely crucial on boats or homes. Without a grounding connection, if you have a device that develops a faulty AC neutral path, the electrical energy will find the next best path in which to flow.  If you are unfortunate enough, it could be you, resulting in painful or even deadly electrocution.

Now, galvanic isolators are commonly installed on the AC grounding connection to prevent galvanic corrosion while safely allowing the AC ground currents to flow.  But they also limit your ability to confirm the connectivity of your AC ground using a standard Ohm meter or "tone generator."  When a galvanic Isolator is present, you need to use a multimeter in diode test mode to confirm connectivity.

So, Peter, it’s possible to have a perfectly functional galvanic isolator installed but not be able to properly measure the continuity on your AC ground wire with certain metres. If you know you do have an isolator, you can perform a diode test to confirm the galvanic isolator hasn’t failed (search online for galvanic isolator testing instructions). Otherwise you need to get this problem resolved expediently.