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Discuss Horizontal cylinder indirect immersion heating element burnt out in the Plumbing Forum area at

  1. diybazza

    diybazza New Member


    We recently had a horizontal cylinder installed with a main hot water supply from a gas boiler. The immersion heater was hooked up to a solar panel diverter to utilise excess power generated by the panels. This worked great for the first few months, but suddenly the diverter was reporting a problem with the immersion heater.

    After sending the diverter off for testing and three new thermostats the issue was still not resolved, so I eventually convinced the heating engineer that the heating element must be at fault and he replaced it the other day.

    The old element was completely burnt out and the engineer said that diverter must be supplying too much power which cause the burn out. During the replacement I noticed that the engineer has rotated the cylinder so that immersion unit is now at the bottom of the tank whereas before it was at the top.

    So would the diverter have burnt out the element, as the engineer suggests or would the fact the heating element was near the top of the cylinder (and possibly not submerge) have been the cause?


  2. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    I highly doubt your solar panels have enough power to burn out an immersion heater.

    I don't think the element been placed towards the top would burn it out either, the position of the element is to give you maximum hot water usage, not prolong the life of it.

    If anything I would say that if your in a hard water area, the wrong immersion had been used or possible faulty thermostat or maybe set too high.
  3. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    What manufacturer?
  4. Ben-gee

    Ben-gee Plumber

    Is the cylinder actually designed to go horizontally? I have come across a similar problem where someone had installed a regular unvented cylinder in a horizontal position, the main problem being that the cylinder is not able to fill properly and some of the element can remain not fully submerged.
    Whatever the cylinder, the orientation is critical when fitted horizontally- get it checked by someone who knows what they are doing or you will have problems.
  5. Chuck

    Chuck Well-Known Member

    Have you got a photo of the burned out element?
  6. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    If its the standard elements it wont last .
    On solar PV they are a different element, ask the manufacturer for the correct part no.
  7. diybazza

    diybazza New Member

    Thanks all for you replies.

    The cylinder is designed to be horizontal and was installed by heating engineer and the solar diverter by an electrician, so it's not something I have attempted myself.

    The diverter is the Apollo GEM-C and it does state that it works with any standard immersion heater. The immersion is rated as 3kw and the diverter supplies variable power from 50w - 3kw depending on what the panels are generating, so not sure why it would need a special element.

    I have attached a picture of the element.



    Last edited: Feb 21, 2019
  8. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    How old is that immersion? Definitely signs of corrosion and where in the UK are you?
    • Agree Agree x 2
    Last edited: Feb 21, 2019
  9. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    I’d still be checking with the manufacturer that the immersion is suitable for solar. Manufacturers guidance wins out and all that
    • Like Like x 1
    • Agree Agree x 1
  10. diybazza

    diybazza New Member

    At the time it stopped working it was only 3 months old and when it was pulled out a couple of days ago it had been in about a year.

    I live in North Yorkshire, which is a soft water area (30 ppm).
  11. diybazza

    diybazza New Member

    The new immersion heater is a Tesla TIH550.
  12. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    Well the new immersion heater is inncoloy which has better corrosion resistance then the copper one that was removed.
    I presume you are on a gravity system and not unvented?
  13. diybazza

    diybazza New Member

    Hi, yes a gravity system.
  14. Chuck

    Chuck Well-Known Member

    To me, that photo looks like a copper immersion heater that's failed due to electrolytic corrosion. (The corrosion seems to worsens as you get towards to the flange, which is closest to the tank.) If so, the replacement needs to be a type recommended by the cylinder manufacturer.
  15. diybazza

    diybazza New Member

    No it is a copper cylinder. Attached a photo

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