1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Hot water cylinder not getting to temperature

Discussion in 'Plumbing and Central Heating' started by starfire, 21 Sep 2013.

  1. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi,

    Hoping someone can help.

    Have recently moved into new house with a glowworm Ultracom 18Hxi boiler/

    Issue I have is the hot water is not getting to temperature of 60C set on cylinder stat - the cylinder stat is new, I measured the tank temperature with a temp probe on my multimeter and it reads around 50C and if I move the stat to 50C the boiler and pump turn off as expected.

    So, with just the HW turned on at the timer the pump runs continuously for hours as I guess the HW stat is constantly calling for heat, but tank never gets to 60C...

    The boiler is set to 75C, I notice when it fires up it only burns for say 30 seconds, quickly hits 75C on the display and turns off however measuring the inlet and outlet pipe temps it doesn't seem to be 75C.

    If I turn the CH on as well at same time the boiler burns for much longer and the temp display on it climbs much slower.

    Any ideas? Is this a boiler issue?

    The system has been powerflushed as well and its had a new 3 way valve as that wasn't working correctly either. Tried pump (also new) set on 1 and 2 same issue.

    Thanks!
     
  2. Sponsored Links
  3. twgas

    twgas

    Joined:
    26 Oct 2007
    Messages:
    4,900
    Thanks Received:
    426
    Location:
    Kent
    Country:
    United Kingdom
    Is there a balancing valve on the HW circuit, if there is try opening it a bit.
     
  4. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    Sorry don't know, what would a balancing valve look like and where would it be positioned?
     
  5. twgas

    twgas

    Joined:
    26 Oct 2007
    Messages:
    4,900
    Thanks Received:
    426
    Location:
    Kent
    Country:
    United Kingdom
  6. CBF

    CBF

    Joined:
    15 Oct 2012
    Messages:
    2,165
    Thanks Received:
    363
    Location:
    Hampshire
    Country:
    United Kingdom
    put the pump on 3 & see if that makes any diff sounds like a lack of circulation to me
     
  7. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    There is a gate valve on the lower pipe that comes out from the cylinder, presumably the return from the heat exchange loop (the top pipe goes in about half way up and has a bleed valve on it also).
     
  8. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    OK will try that, presumably I just need to make sure it doesn't cause venting into the HW feed tank in the loft?
     
  9. CBF

    CBF

    Joined:
    15 Oct 2012
    Messages:
    2,165
    Thanks Received:
    363
    Location:
    Hampshire
    Country:
    United Kingdom
    if it does then the pipework isn't installed correctly or you have a restriction somewhere
     
  10. Sponsored Links
  11. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    OK, I will separately try pump on 3 and opening the cylinder return gate valve a bit - anticlockwise I presume.
     
  12. twgas

    twgas

    Joined:
    26 Oct 2007
    Messages:
    4,900
    Thanks Received:
    426
    Location:
    Kent
    Country:
    United Kingdom
    Yes, anticlock
     
  13. leakydave

    leakydave

    Joined:
    2 Nov 2005
    Messages:
    959
    Thanks Received:
    102
    Location:
    Gloucestershire
    Country:
    United Kingdom
    Is there any trapped air causing poor circulation?
     
  14. xr4x4

    xr4x4

    Joined:
    1 Oct 2009
    Messages:
    3,159
    Thanks Received:
    290
    Location:
    Hampshire
    Country:
    United Kingdom
    As been said, open the gate valve a bit more, count the number of turns so you can put it back if needed.

    You will know when it's working as the flow pipe to the cylinder will get too hot to hold.

    Is the bleed valve manual or auto? If manual, open and check for air, should just be water coming out.
     
  15. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks all, I will try the suggestions.

    Yes, the system is quite noisy so I suspect a lot of air may be trapped then.

    Do you bleed the pump when its running and the same question about the bleed valve on the cylinder HW feed ?
     
  16. xr4x4

    xr4x4

    Joined:
    1 Oct 2009
    Messages:
    3,159
    Thanks Received:
    290
    Location:
    Hampshire
    Country:
    United Kingdom
    Both when off.
     
  17. starfire

    starfire

    Joined:
    14 Jun 2006
    Messages:
    61
    Thanks Received:
    0
    Country:
    United Kingdom
    Waking up this thread, thanks to all the previous help which partially sorted the issue but in the end I moved my tank thermostat down to 55C so the boiler and pump eventually stop.

    Can I ask, I find whenever the system has been drained and then refilled it seems to get completely full of air and this problem reoccurs, as its an open vented system shouldn't the air just dissipate up the vent pipe ?

    Pictures here http://www.diynot.com/network/starfire/albums/

    Thanks
     
Loading...

Share This Page