Immersion heater unvented cylinder - help!

Discussion in 'Plumbers' Talk' started by sophiel55, Sep 12, 2014.

  1. sophiel55

    sophiel55 New Member

    Hi all, this is my first post and I'm very much clueless about these matters but I'm getting desperate so hoping someone may be able to help!

    I have an unvented hot water system in an all electric house. Heat is supplied by two immersion heaters, one at the bottom and one in the middle. The bottom heater appears to be the one that is controlled by the timer.

    For a couple of weeks I have been getting only a few seconds of hot water before it goes stone cold (although for months the water still hasn't been great). An electrician has changed the safety thermostats in both heaters but it's still not working. He says the element may have gone in the top heater (apparently it is also corroded around the stat). Despite this, when I press the boost button I can hear what I assume is the water heating.

    My main question is, could the top heater not working prevent the bottom one from working too, even though the bottom one is the only one I use? Is there anything else that could be wrong?

    Thanks in advance!
     
  2. tom.plum

    tom.plum Screwfix Select

    If your not getting hot water then BOTH of the elements are faulty, if the top one only is working you'd expect enough hot water to fill half a bath, if the bottom one is working you'd fill the bath these are just approx measurements cos I don't know how big you cylinder is, but thats how it should work, top one some HOT water, bottom or both lots of HOT water,
     
  3. sophiel55

    sophiel55 New Member

    t

    So if I'm getting next to no hot water it must be the bottom one that needs replacing?
     
  4. tom.plum

    tom.plum Screwfix Select

    No, hot water rises to the top of the cylinder, the water from the taps draws off from the top, so niether element is working how it should, otherwise you'd have at least half a cylinder of hot water,
     
  5. G&W Plumbing & Heating

    G&W Plumbing & Heating Active Member

    Check fuses & Breaker, check supply from clock, test voltage across stats, then replace immersions
     
  6. Crowsfoot

    Crowsfoot Screwfix Select

    :/

    Yes, I do think that is the problem.
    The bottom Heater heats your full tank overnight at a cheaper rate of electricity that hopefully lasts you the full day.
    If it doesn't the top one is just for a daytime boost (at the FULL price mind you).
    Might be a good idea to change them both though whilst the cylinder is drained.
    Tappy,
     
  7. G&W Plumbing & Heating

    G&W Plumbing & Heating Active Member

    That's best bet, change the clock £10 & both immersions £25 each + labour
     
  8. sophiel55

    sophiel55 New Member

    Thanks all for your help. Happy to fork out for new heaters etc, just didn't want to do it unnecessarily!
     
  9. G&W Plumbing & Heating

    G&W Plumbing & Heating Active Member

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