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Old 02-26-2018, 12:39 PM   #81
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Yes, I have learned about the new docks and the breakers. I would think that this is something that can be tested prior to having an issue. I still think I have an issue with my shore power cord. 1st guy tested it somehow and said that it is shorting out I guess? Put a MM to it and showed me current returning through....the ground maybe? Something like that. Said I needed a new cord. Forgot to ask the second guy. How do you test a shore power cord for integrity?
This you can definitely do yourself if you have a multimeter. If you don't, get a cheap one online and play with it a bit. Watch a few online videos. You don't need to become an expert on this stuff, but it feels good to at least be able to find out when a wire is energized or not, whether something is shorted to ground, etc.

Set the meter on the OHMS setting...this is a continuity test, or a test to determine if one wire is connected to another. Touch the two test probes together and see how the reading goes to zero...this means zero resistance in the circuit...total continuity between one probe and another.

So you coil up the cable, both ends unplugged. Insert one probe (doesn't matter which) into one of the connections, making sure that it's in contact with the metal inside. Do the same with the other probe in each of the other connections AT THE SAME END of the cable. The resistance should be infinity, i.e., there should be no continuity between any two of the wires in your cable. Repeat this so that you check all the combinations of conductors in your cable (whether 3 or 4). If at any time the reading between two of the connections goes to zero, as it does when you touch the probes together, that means a "dead short" exists between those two wires in your cable.

Much more likely, however, would be some partial electrical leakage between two wires, in other words, some resistance value other than infinity and zero. Oftentimes it takes some flexing of the cable to reveal this.

Then check continuity along each wire within the cable by inserting the probe into the same wire's connector at both ends of the cable; the resistance should be zero.

If this were my boat, I'd focus on the items that the second outfit identified and go from there. Unless your shore power cable is quite old and worn out, it's the least-likely source of any problems. Please note that I am NOT an electrician.

Thanks for sharing your experience with us!
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Old 02-26-2018, 12:53 PM   #82
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The recommended continuity test is ok, and certainly better than nothing, but it will just show that there are no wires adrift in the cable ends that are touching.

The best way to test your shore power cord and the internal connections at the connectors is with a megohmmeter (aka; megger). A good electrical shop/technician will have one. This device places a selectable high voltage on one conductor and checks the resistance reading on the parallel conductor. The shore power cords are rated at 600V so I test them using the 500V setting on my megger. As insulation ages, it looses its insulating properties until, under high voltage, the insulation will break down and there will be a short circuit between the conductors. A reading > 1 Mohm is acceptable.
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Old 02-26-2018, 12:59 PM   #83
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The recommended continuity test is ok, and certainly better than nothing, but it will just show that there are no wires adrift in the cable ends that are touching.

The best way to test your shore power cord and the internal connections at the connectors is with a megohmmeter (aka; megger). A good electrical shop/technician will have one. This device places a selectable high voltage on one conductor and checks the resistance reading on the parallel conductor. The shore power cords are rated at 600V so I test them using the 500V setting on my megger. As insulation ages, it looses its insulating properties until, under high voltage, the insulation will break down and there will be a short circuit between the conductors. A reading > 1 Mohm is acceptable.
I just bought one of these, got it in today.



It measures to a few GigOhms at 1000 Volts.
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Old 02-26-2018, 01:02 PM   #84
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...The best way to test your shore power cord and the internal connections at the connectors is with a megohmmeter (aka; megger)....
Excellent information.
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Old 02-26-2018, 08:37 PM   #85
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This you can definitely do yourself if you have a multimeter. If you don't, get a cheap one online and play with it a bit. Watch a few online videos. You don't need to become an expert on this stuff, but it feels good to at least be able to find out when a wire is energized or not, whether something is shorted to ground, etc.

Set the meter on the OHMS setting...this is a continuity test, or a test to determine if one wire is connected to another. Touch the two test probes together and see how the reading goes to zero...this means zero resistance in the circuit...total continuity between one probe and another.

So you coil up the cable, both ends unplugged. Insert one probe (doesn't matter which) into one of the connections, making sure that it's in contact with the metal inside. Do the same with the other probe in each of the other connections AT THE SAME END of the cable. The resistance should be infinity, i.e., there should be no continuity between any two of the wires in your cable. Repeat this so that you check all the combinations of conductors in your cable (whether 3 or 4). If at any time the reading between two of the connections goes to zero, as it does when you touch the probes together, that means a "dead short" exists between those two wires in your cable.

Much more likely, however, would be some partial electrical leakage between two wires, in other words, some resistance value other than infinity and zero. Oftentimes it takes some flexing of the cable to reveal this.

Then check continuity along each wire within the cable by inserting the probe into the same wire's connector at both ends of the cable; the resistance should be zero.

If this were my boat, I'd focus on the items that the second outfit identified and go from there. Unless your shore power cable is quite old and worn out, it's the least-likely source of any problems. Please note that I am NOT an electrician.

Thanks for sharing your experience with us!

Thanks for the instructions. The cable was sort of a side issue, tested because he happened to think about it while we were standing there. Was a simple test, what you described so I can do it again. Definitely not the top of the list of fixes but too easy to ignore. Not dying to buy a new 50' 50amp cable I can tell you that. Ouch. Actually have 2 of them to reach my bow. Double ouch. But....they both have some definite age. Did smell the connections but couldn't detect any burn smell and there is no blackening anywhere. Have a digital multimeter will check it tomorrow while they are installing my brand spanking new Fail Safe Galvanic Isolator. I have my wife convinced that the boat will ride much smoother with it installed. She almost believes me.
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Old 02-27-2018, 06:46 AM   #86
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Originally Posted by CharlieJ View Post
The recommended continuity test is ok, and certainly better than nothing, but it will just show that there are no wires adrift in the cable ends that are touching.

The best way to test your shore power cord and the internal connections at the connectors is with a megohmmeter (aka; megger). A good electrical shop/technician will have one. This device places a selectable high voltage on one conductor and checks the resistance reading on the parallel conductor. The shore power cords are rated at 600V so I test them using the 500V setting on my megger. As insulation ages, it looses its insulating properties until, under high voltage, the insulation will break down and there will be a short circuit between the conductors. A reading > 1 Mohm is acceptable.
Thanks Charlie. A piece of equipment I have no business buying and have no idea how to use (I have a duffle bag full)!!! Not being very well versed in marine electricity it seems the megger would have very limited use for me but it does sound much simpler than some of the other equipment I have. As I mentioned I have the install of the isolator today so I will ask the electrician if he has one and can test. If not I can start with the MM I have and go from there.
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Old 02-27-2018, 09:31 AM   #87
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Visually inspect the cable foot-by-foot over its entire length.
Do a test as described in Sabre's post with a simple DVM on each cable. Set the ohm scale on the highest scale. Write down the result of each point to point check.
The good news is either a fault in a cable will usually be an obvious chink or lump in the insulation or corrosion at the cable connectors. Connectors can be replaced to save the rest of the cable.
The bad news is if at some point in its life if the cable end was dropped into the water, the water will wick up the copper strands over time. While not absolutely terminal, you may have to cut off several feet of end to get to clean copper again.
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Old 02-27-2018, 10:15 AM   #88
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Thanks. And I do know that one end of one cable was dipped in saltwater a few months back. I mean I heard that happened, someone told me it did, I would never let that occur of course. Lie.
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Old 02-27-2018, 02:11 PM   #89
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"Connectors can be replaced to save the rest of the cable."

The hassle is folks tend to purchase cheaper cable with molded ends , rather than say Hubbel with removable ends.

A few bucks more at the start can save , later.
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Old 07-01-2018, 05:44 AM   #90
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To sort of close this out, ends up that I had 2 problems. First was in my inverter. I don't pretend to understand but there was a problem with something on the circuit board that was causing a ground/neutral issue. It was supposed to close the ground or neutral or whatever at a particular time and it was staying open. Or the other way around. Man I hate electrical stuff. Second issue was a ground/neutral problem with my stove top. Pinched wiring due to bad install. Supposedly fixed now, will see how the zincs do. Still haven't touched my power cords to check them but...that moved up the list one place.
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