Water Heater Ground

[Ray Stacey]

My 6 gallon Atwood water heater in my 1990 Hunter 30 has a problem with it's 110 volt system circuitry. Even with the water heater circuit breaker off, the shore breaker will trip when I make the onboard 110 volt general circuit breaker.I had an electrician quickly diagnose the problem as a "common ground". I disconnected the water heater heating element and the problem went away. I'm getting 10 ohms resistance across the heating element, the same as a new one gives. If anyone can help me diagnose the problem further I would be most grateful.Ray

 

[Ray King]

My Guess

I think the "common ground " may mean the reading you may get if you connected your meter from the heating element to the case of the heater. You should read "open circuit" RegardsRay

 

[daveM20557]

i don't get it. when you shut off the breaker to the heater it shuts off the power. the neutral is still connected,110v, but the neutral and ground are tied together at the shore so how could that trip the shore power main breaker.unless there's a open neutral somewhere and its using the heater neutral to complete the boat's circuit.

 

[Trevor - SailboatOwners.c]

Water heater and AC input ground connection

Hi Ray -I believe the challenge will be a connection between the case of the waterheater and the ground wire on the AC input. This is a commong setup on home and RV water heaters but causes problems on boats. You will need to remove the AC ground to case ground connection. To provide shock protection you will need to connect the case to ship's ground and test periodically to insure there is no AC voltage or current on this wire.Hope this helps,Trevor

 

[daveM]

but with the breaker shut off going to the heater the main should not trip. if the element in your house shorted out,with the water heater breaker off ,it wouldn't trip your main breaker. i would love to get more information from the electrician, i'm a marine electrician myself.