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Old 10-06-2019, 17:56   #1
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Stray current in 220v water heater?

Last month, after three years of use, I replaced the magnesium anode in my Quick Nautic water heater, which was completely gone. The element and thermostat looked pretty ugly, but it appeared everything was working.

I've since discovered the while the heater still works, the thermostat is shot, and it runs until the water approaches boiling. Even turned all the way down, it is scalding hot.

In discussions with Quick USA, they suggested I replace the element and thermostat, but also suggested that there is stray current somewhere in my boat.

Without stray current, they claim the anode should last indefinitely.

I've done limited wiring since the boat was new. No electrical issues or other signs of corrosion. Other anodes are holding up. Boat has an isolation transformer.

Questions for the group:

Anyone have any luck tracking down stray current that resulted in water heater issues?

Any suggestions on where to start?
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Old 10-06-2019, 18:53   #2
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Re: Stray current in 220v water heater?

take your vom and measure for voltage between neutral and ground and hot to ground. If there is voltage, unplug everything in the boat and turn inverters and chargers off and measure again.

My guess if there is stray current, it might be from a battery charger or inverter. That is from how its wired interally.

if there is no voltage between either leg to ground, it's not stray current. make sure that the wiring to the water heater is correct in that ground and neutral was not swapped at the factory.

Then the cause would be anode reaction to farrous metel of heating element base metal and any brass valves. That is normal. Anodes do need replacing now and then. Though three years is pretty quick.

Edit: I have known anodes that needed replacing after 4 months. But that was in glass lined tanks. Yours is ss so should last a while.
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Old 10-06-2019, 19:12   #3
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Re: Stray current in 220v water heater?

One other thought. Do you have a watermaker. Depending on purity, the ro water could cause the anode to exchange ions and fail faster.
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Old 10-06-2019, 20:21   #4
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Re: Stray current in 220v water heater?

While stray current is a possibility, it's also possible that some Chinese factory that built the water heater substituted different metals to save money. I once saw a hot water heater from a well regarded US company where the stainless steel tank had been welded with mild steel rod. Was leaking in a year. Surprised the manufacturer too.
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Old 11-06-2019, 03:35   #5
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Re: Stray current in 220v water heater?

Thanks for all these suggestions.

No water maker, but I was in the Bahamas for awhile each of the past three winters, and the RO water there is quite salty.
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Old 11-06-2019, 06:32   #6
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Re: Stray current in 220v water heater?

See “Leakage currents, Kirchoff's law” ➥ https://www.fluke.com/en-ca/learn/bl...at-a-boat-dock
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Old 11-06-2019, 16:28   #7
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Re: Stray current in 220v water heater?

You have stray current creating marine electrolysis corrosion. Do a Google search for Marine Electrolysis and click Conquer marine corrosion.
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Old 11-06-2019, 18:27   #8
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Re: Stray current in 220v water heater?

Quote:
Originally Posted by Corrosion-Eng View Post
You have stray current creating marine electrolysis corrosion. Do a Google search for Marine Electrolysis and click Conquer marine corrosion.
Assuming the water heater is installed on a fiberglass Hull, or isolated from a metal hull and the piping to the water heater is all hose or pex, the only path for electrolysis is through the 3 power wires.

That the heating element and thermostat were cooroded, it's possible that the anode sacrificed itself to protect the non-stainless metal. just as probable it's one of the other appliances on the boat has an internal connection between neutral and ground. Very common to see with inverters on the secondary side.

To the op, C.E. makes a rather expensive galvanic meter, which appears to be mostly idiot lights and not any actual voltage readings. He posts on every corrosion thread.

A good VO meter will work better or at least as well. But that's just my opinion. I'm just an engineer (retired PE). I have some experience with corrosion, but a ton of experience with water heaters.
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