Shore Power Ground Alarm

[Marc14857]

For the past few years I have had an intermittant problem with the ground alarm on my ProMonitor Unit that is getting worse.When I connect the Shore Power Cable Main 1, I often get the ground and galvanic isolator alarm on the ProMonitor unit. Sometimes I can reset the alarm but more recently I can not reset the alarm. Sometimes just the ground alarm clears but the galvanic isolator alarm remains in.The alarm comes in even though the main #1 AC distribution breaker is off, i.e. no loads on the bus. I do not have the problem when I connect the second shore power cable for the Air Conditioning unit. Both lights for cable #2 remain green "Normal" even when the Air Conditioning starts. I have switched the two cables but the alarm remains on line #1 indicating that the problem is on the boat.When I can reset the alarm, the circuit runs fine unless I start a large load like the water heater. When I switch on the water heater both green lights for line #1 on the Pro Monitor system get very dim and after a few minutes both change to alarm.Do I have a ground problem on line # 1 or can the Pro Monitor be faulty. How can I tell?Thanks in Advance

 

[Chris]

I don't know your

specific setup, but if the lights dim when you connect a heavy load, then you are overloading the existing circuit. I say existing because you probably have a bad connection somewhere in the line, on either the positive or neutral side. backtrack the wiring with a light load applied and check every connection with a votage meter to see if you have a drop across any connection. Connect the meter on the line either side of a connection. If it's bad the meter will register. If good, the meter will read '0'.Good luck.

 

[chuckwayne]

356 ground faults

I think Chris is on the right track-check the connections at the ac shore power connector on the stern-the wires are retained by screws which can loosen-and check for corrosion on the socket and possible salt buildup on/in the socket forming a conductive bridge between the terminals. the next place to check is the master ac breaker in the port lazarette. After that, check the power panel and galvanic isolator connections. on our 2002, the galvanic isolator unit is tucked up in the corner of the nav station

 

[Paul]

I have a similar problem on my 356

This has occured on my 356 since she was new. I havn't completly isolated the problem yet, but have made a couple of observations:1) The ground fault error has never occured at my home slip, only at other marinas.2) When visiting other marina's, the fault only occurs about one in 5 times.3) The fault will occur regardless of load. we usually notice it when first hooking-up, However, the fault has occured after several hours.4) We only use one shore-power cord and Parallel the air-cond to the house AC.5) We have a dedicated shore-power cord and a dedicated travel cord. My first suspicion was the travel cord, but continuity, resistence and short testing proved the cord was fine. Just to be sure, I swapped the cords which proved the cords were both fine. I now suspect recepticles at some transient slips do not provide a solid connection and have begun bending the prongs open (just a little). I also ensure the terminals are very clean by removing any tarnish.Paul