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Vokera Excell Help Me Please - Hot Water strange problem

Discussion in 'Plumbing and Central Heating' started by aims, 18 Mar 2010.

  1. aims

    aims

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    Can someone pls suggest anyting.....Hot water till today worked a treat. Now if I switch on just the hot water tap, i get hot water for about a minute before it goes cold - the boiler shows no red light and if i switch the tap off and back on again after 10 seconds or so i get hot water again for about a minte before it goes cold again HOWEVER if i turn on the hot water and cold water taps then i get luke warm hot water without any problems and the bolier keeps working. Any ideas ?
     
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  3. Andygasman2010

    Andygasman2010

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    possibly the DHW diaphragm worn. Are you able to drop the front down and do any checks?
     
  4. tamz

    tamz

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    Don't encourage him ;)
     
  5. aims

    aims

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    Only replaced the DHW diaphragm about two months ago - made sure I cleaned away all the old crap inside before I replaced it with the new one. I have also found if i run the hot water tap at max output then it does not switch off however the water is only ver mildly warm.
     
  6. aims

    aims

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    To add.....checked the 2 micro switches and they are ok. Noticed the 3 port arm disengages to off position completely however if i turn the hot tap off and wait ten seconds and turn back on again the port arm fully engages.
     
  7. Andygasman2010

    Andygasman2010

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    So it's that arm dissengaging that's causing the problem?

    That arm is operated by the DHW diaphragm and a good flow of water, if the diaphragm is new then maybe the flow is too low. How about checking the flow rate? Find out how many litres of water it passes in a minute, post back.
     
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  9. aims

    aims

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    The arm disengages back to it's 'off' position as if no demand for hot water is being made rather than not fully extend becuase the diagraphm is worn. The mains water inlet to the boiler is turned to maximum input. How do i check the litre pressure of water passing through the boiler ? I first thought it might be some sort of overheat control problem BUT now I find if the hot tap is turned on full of about 3/4 full then the boiler works fine (though hot water fast flow makes it luke warm water). If I run the tap at slow rate then the boiler goes to idle mode as if no demand for hot water is being made (after about giving 30 seconds or so of piping hot water).
     
  10. Andygasman2010

    Andygasman2010

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    That's typical of a worn diaphragm.

    Use a measuring jug or something, see how many litres of water it passes in a minute.
     
  11. aims

    aims

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    Thanks for the help. Just ordered a new diapraphm and bearer. Guess I did not clean off all the crap as good as I should have done last time. Can I ask another stupid question - if i measure water from a tap that would be dependent on how much water is flowing? Shall I get a bucket and measure the flow over a minute with hot tap turned to max output ?
     
  12. Andygasman2010

    Andygasman2010

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    That's right. The flow rate is altered as you turn up and down the tap
     
  13. Boilerman2

    Boilerman2

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    Some Vokera Excells can muller a Diaphragm in 6 months they are notorious :cry:
     
  14. aims

    aims

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    Man it's taking the ****. Only changed it just under two months ago and now have to do it again. I did give the inside a good clean down before replacing the diaprahm. Will post back once done to say if that was the problem. Just seems that the hot water arm does not function till tap water is turned quite high otherwise it goes back to off position.
     
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