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Hot water tank - Element problem!

Discussion in 'Technical Discussion' started by Mikeyessir, Dec 31, 2014.

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  1. Mikeyessir

    Mikeyessir New Member

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    Hello, first post as i'm new here.

    Currently working on a brand new boat that has had approximately 10 months running now.

    We developed this problem about 2 months ago now where our hot water tank elements would trip on the breaker. We have two tanks Port and Stbd and each contains 3 elements each.

    The elements would trip, I would then remove the backs of the elements to find that there was dripping into the electrics through the thermostat sleeves.

    Anyway with the boat being under warranty I was awaiting new elements as eventually all 6 elements failed in this way.

    I went on 2 weeks leave from the boat and whilst away the yacht manufacturer replaced 3 of 6 elements giving us one good tank. Upon my return I inspected the backs of the elements and once again we had 2 out of 3 defective leaking water.

    Here are the pictures of removed elements.

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    Okay so this is a new boat, it ran all summer no problems and has only become a problem since being sat in our winter berth.

    I have traced the system on the same boat which is 3 years old and has never had a problem with their heaters and all wiring is the same.

    I'm getting 240v which is the correct voltage for these heaters.

    The Manufacturers seem to think the elements are boiling dry, but i've proved that there is no air in the tank (air bleed valve.)

    Myself, the boat manufacturer and Howdens the element manufacturer are all scratching our heads now.

    I've been thinking along the lines of the tanks bonding, if the tank wasn't bond properly would electrolysis cause the elements to become the cathode/anode?

    Can anyone help, it would be really appreciated by all of us.

    Regards,

    Mike.
  2. TeKeela

    TeKeela Member

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    Let me first say, I have never had an element problem. That said, when I saw your first photo, I thought electrolysis. Not having experience in the area I was not going to comment until I saw your last sentence about bonding.

    If the tanks were cooking dry, I would think you would just have mineral deposits. But you show elements that have been "eaten" by something. Maybe you are on the right track with bonding or some other voltage leak.
  3. Capt Ralph

    Capt Ralph Senior Member

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    Is there (or supposed to be) a Anode or zinc rod in the tank? I'm not familiar with your tanks design but smaller heaters have them.
    While you're away, is water pressure still applied?
  4. Mikeyessir

    Mikeyessir New Member

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    Thankyou Narwhal and Rcapps,

    There is no anode or zinc sacrificial anode in the tank its not part of their design.

    When i left the boat both tanks were completely stripped and drained ready for the warranty engineer to come aboard and fit new ones. When we flood up the tanks the air escapes through a bleed valve and then we have a hot water circ pump which just circulates the water in a big loop around the boat and back to the tank.

    We run a water softener onboard which is correctly setup using the guide in the manual and hardness test kit supplied by the manufacturer. We also dose our water with chlorine which is done via an automatic dosing system whilst filling the tanks. We have used a different supplier for our chlorine since arriving in our winter berth but i am not sure if chlorine can have this effect on the elements.

    Thankyou.
  5. Capt Ralph

    Capt Ralph Senior Member

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    I'm guessing but are those thermostats and pumps on the element ends? Leaking current from them to the elements could be possible.
    I would assume any other equipment (remote, outside the case) stray currents would be shunted by the heater case if bonded correctly.
  6. dennismc

    dennismc Senior Member

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    If all 6 have failed in two separate tanks I would suspect the water as a source, have it analyzed.
  7. Capt Ralph

    Capt Ralph Senior Member

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    Hummmmm,, Radioactive water? High minerals? high carbon or acids?
    OP has stated he injects chlorine and the system cycles the water as like a sister ship. I'm missing a page?
    I'm not sure how water Q can eat up water/food quality metals., And nobody has died yet?
    I'm not trying to be an overly SA (much) here but don't think water Q is an issue.
  8. Capt Ralph

    Capt Ralph Senior Member

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    I'm still thinking stray currents causing runaway thermostats & then stray currents on damaged/open elements.
  9. Capt J

    Capt J Senior Member

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    Does your water system have air in it? The recirculating system on a yacht is a little beyond what I've ever seen, but if air is somehow getting into it, the air could be accumulating in the hot water tanks causing the elements to run partially submerged causing the distortion of them. But, I'll take a stab at it. The green on the elements looks like electrolysis, but could also be too much chlorine. The elements look like they've overheated, or run with air in the water tank.
  10. Mikeyessir

    Mikeyessir New Member

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    I don't believe the tanks to be running with air in them as we do not get any air through the system and we have auto air bleed valves at the top of the tanks which function correctly as you hear the air escaping as the tanks are filled.

    I have cracked elements before whilst draining the tank and got water out of all levels.

    Does anyone know of a test I can do to confirm whether there is stray currents effecting the elements?
  11. Capt Ralph

    Capt Ralph Senior Member

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    Guessing out loud here; Unstrap all bonding and green (green/yellow) wires from the tank. Measure for any voltage from the water heater to ships green (green/yellow) wire. Now be careful here, if there is a leak, you could get zapped.
  12. v10builder1

    v10builder1 Senior Member

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    Looks like 2 problems to me. First: The element tubing is THIN SS. SS will rapidly corrode in water with high chlorine concentrations. Verify the chlorine concentrations are correct (check/recalibrate dosing and be sure the new chlorine supplied is correct concentration (using a new supplier was stated). If practical, stop the dosing for a while - I suspect it is not possible to dose the water after leaving the heaters, but that would eliminate one suspect possibility. The element tubing is also suspect - SS type may have inadvertently changed by the manufacturer to a type with significantly less corrosion resistance. In industry, SS is not listed a suitable for tubing/tankage in chlorine solutions. Some poster might know the chemistry - not I.
    Second: Looks like the elements are being operated at too high a voltage - if you are sure they are continuously immersed. Suspect wrong voltage elements supplied or incorrectly wired. The nameplate wattage can be verified by measuring the voltage on the element and the current to the element (clamp on ammeter) and multiplying the two values (this is resistance only). From the photos, like other posters, I have never seen elements this bad. I do not think the FRESH water quality is the problem, or bonding, unless bonding is incorrectly done and is resulting in excessive voltage (thus current) on the elements. Have you verified that the thermostats are operating correctly? And you are sure the elements are immersed at all times?

    All I have. Good luck.

    Joe
  13. milo12

    milo12 Member

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    If it never happened until you placed it in its winter berth maybe a neighboring boat or bad wiring at the dock is causing the electrolysis.
  14. Capt Ralph

    Capt Ralph Senior Member

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    Any updates?
  15. Mikeyessir

    Mikeyessir New Member

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    Nothing yet awaiting new elements from Manufacturer as we are down to one out of six now.
  16. K1W1

    K1W1 Senior Member

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    The only time I have seen multiple short time failures it turned out to be a manufacturing defect, a different manufacturer was found and problem went away.
  17. ddw1668

    ddw1668 Senior Member

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    Being in the plating business for thirty years, I am sensitive to water quality. This looks like BAD water to me. Had it analyzed yet?
  18. Capt Ralph

    Capt Ralph Senior Member

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    Please keep us up. I (and many) would like to learn from this and it's positive outcome.
    ,rc
  19. Capt J

    Capt J Senior Member

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    Have you checked the Chlorine content of the water? What level is it?
  20. NEO56

    NEO56 Member

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    I really don't mind being the village idiot here...but why not toss the water heater and put in a Tankless water heater. There is a brand made called S.E.T.S. It's manufactured in Florida and was designed along with NASA's help. After six water heaters, I'd take a different road. At this point what could it hurt?