Domestic central heating help please

Discussion in 'Tech/Mech General' started by pappajohn, Jan 4, 2016.

  1. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    I have a bit of a problem and need advise.

    It concerns an S plan heating system.

    The problem is the heating run continuoisly even with the programmer removed from its back plate.
    The room stat has no effect at all.

    From what i can see the power is first supplied by the grey wire to both ch and hw port valves (single port spring return) then when either valve is opened via the brown wire (room stat or tank stat) it closes a contact in the respective valve and energises the orange wire which in turn powers the boiler and pump.

    If im correct that would constantly power the boiler regardless of stat or programmer if the valve was stuck open.

    Am i correct ???

    I havent had a proper look at the zone valves yet to see if they have a manual lever due to poor access.

    [​IMG]
     
    Last edited: Jan 4, 2016
  2. olley

    olley Funster

    Joined:
    Jul 29, 2007
    Messages:
    3,709
    Likes Received:
    2,098
    Location:
    Ipswich
    Hi papa, yes looking at that schematic I would agree.

    Ian
     
  3. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    Thanks Ian.

    Its the only thing i can come up with.
    I changed the programmer tonight thinking it could be a stuck relay but it continued to run even with the programmer in my hand.

    The only thing shutting it down is its own internal stat but that simply cycles as the water in the boiler cools slightly below pre set temp so the boiler runs all day and night.
     
  4. mitzimad

    mitzimad Funster

    Joined:
    Jan 28, 2008
    Messages:
    2,963
    Likes Received:
    3,301
    Location:
    walthamstow east london
    if yours is wired as per that drawing yes if the valve is open or the micro switch is stuck it will continously run
    the blue and brown wire actuate the motor in the valve once it has opened a cam operates a microswitch the grey and orange wire are either side of this switch
    to check which valve is causing the problem switch off power take the two orange wires out of their connector in the junction box and seperate switch power on but with clock of the back plate the one thats live is the problem depending how old and what make the valves are you maybe able to just change the head but check theres no leaks and the spindle is easy to move with your fingers putting a new head on a partially seized valve will burn it out in no time
     
  5. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    Thank you.
    That was my thinking as well but nice to be confirmed.

    Hopefully the head can be changed as its really hard to access the zone valves thanks to British Gas fitting all the electricals and plumbing THEN fitting the boiler as close as they could.

    I have a gap between boiler and wall of maybe 7" with everything sqeezed in except the pump.
     
  6. Electraglide

    Electraglide Funster

    Joined:
    Jul 27, 2010
    Messages:
    330
    Likes Received:
    361
    Location:
    Farnham Surrey
    If you turn the power off first you can remove the cover and
    check. If I remember correctly there is a bolt that holds the.spring return and microswitch in place. It would not be.the first one where the screw has loosened and left the contacts closed.
     
  7. mitzimad

    mitzimad Funster

    Joined:
    Jan 28, 2008
    Messages:
    2,963
    Likes Received:
    3,301
    Location:
    walthamstow east london
    if you post a picture of the valves i might be able to tell you if heads are changeable
     
  8. mitzimad

    mitzimad Funster

    Joined:
    Jan 28, 2008
    Messages:
    2,963
    Likes Received:
    3,301
    Location:
    walthamstow east london
    profesionally i dont mess about with the internals as its not cost efective but on your own valve its possibly worth a look you can get the motors seperately so if its a motor gone you could change just that but when im working its always a new head or complete valve
     
    • Like Like x 1
  9. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    Thanks, worth checking if i can get at the valve head.
     
  10. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    I have fitted S plans (electrical side) before but never actually took any interest as to how they worked.
    I simply followed the diagram for whichever plan....S or Y plan and switched on.
    If it worked it was right, if it didnt i made a wiring mistake and sorted it.
     
    Last edited: Jan 4, 2016
  11. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,460
    Likes Received:
    16,888
    Location:
    YO11 2BD
    This is at my MIL's house, before i got involved she got a plumber in who simply turned down the thermo rad valves to reduce the room temperatures :doh:...served its purpose but it didnt cure the boiler running day and night....i dont think he was very good as a plumber. :rolleyes:
     
    • Like Like x 1
Loading...

Share This Page