I recently moved my Grady to a new dock that has a regular 3 hole outlet. I think when I turn on the water heater the reverse polarity light comes on and the power shuts down. I say think, because I believe it comes on without turning anything on. An electrician says the problem is either my cord or on board. It never did this at the old dock. Any ideas?
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Shore power reverse polarity
- Thread starter Hookster57
- Start date
JeffN
Well-Known Member
When you say regular three hole outlet I assume you are saying you have a standard 15 amp 120 volt recptacle you are using and not a twist lock of some sort. See if you can borrow, or puchace one they are inexpensive, one of the plug in testers with the three lights on the back. They will diagnose reversed polarity - bad ground etc. Plug it into the dockside receptacle and see what it tells you, if that is OK you will need to check the female end of your dock power cord to see what is live there. If that end is a twist lock you will need a simple votage tester to ID what is live. The dock power should be GFI protected, is that functioning? When you say the power shuts down is it on the dock or some device on board? Was the receptacle on your old dock GFI protected? If the problem is aboard it might well be in the water heater but I would suggest starting your troubleshooting at the dock.
Thank for the reply. An electrician said the dock power is correct and yes, there is a functioning GFI. When the light comes on the voltage meter drops to zero.
JeffN
Well-Known Member
Well the shore power system on my boat is not very sophisticated so I at somewhat of a loss as to how to narrow it down. Does the polarity shutdown reset itself or does it require a manual reset ie will it reset when the water heater is not calling? I would guess the polarity shut off protects the entire AC system, would that be correct? If the water heater breaker is off do you still have a problem? If you don't experience an AC shut down with the water heater off then you have isolated the problem to that circuit assuming the polarity shut off protects the entire AC system and not just the water heater circuit. Good luck.
Found the problem. I cant have the main batteries turned on when hooked up to shore power. That causes the reverse polarity light to come on, though I'm not sure why.
JeffN
Well-Known Member
Glad you found a solution. Do you have a rectifier or inverter aboard to power equipment when on shore power?
JeffN
Well-Known Member
On my boat, which is primitive compared to today Grady's, I have two separate systems. My 120 volt shore power feeds the water heater and a couple of 120 volt outlets, everything else is powered by the boat batteries with no connection between. I would think your two auto style receptacles are powered by the 12 volt boat system and the GFIs and water heater by the shore system. What I am curious about electricly, if you do dig into it further, is I'm thinking that because you are getting the reversed polarity shut down there must be some sort of interconnect between the two systems and I wonder where. If you do find out any more I would like to know.