Central heating only working with hot water

Discussion in 'Plumbers' Talk' started by Neil Murray, Oct 21, 2018.

  1. Neil Murray

    Neil Murray New Member

    Morning,

    I’m in need some advice. We live in a 7 year old new build with an ideal logic heat 15 boiler with iflo controller and thermostat in the hallway. Hot water tank with expansion tank in the airing cupboard upstairs - no cold water tank.

    Trying to preempt questions from what I’ve read elsewhere - although it sounds like a problem with the 3 way switch??

    Our central heating will only come on when the hot water is active.

    The thermostat only “clicks” when the hot water is switched on - although it will still “click” after the water has been switched off (doesn’t “click” if the hot water hasn’t been switched on at the same time)

    HW on - heating works as expected
    HW off - heating doesn’t work and there is no “click” when I turn the thermostat up/down

    HW on, heating on at the same time then HW off - heating works as expected

    Hopefully this makes sense.

    Do I need an electrician or a plumber? Or any other suggestions as to what the problem is?

    Thanks in advance

    Neil
     
  2. Peter208

    Peter208 Active Member

    Do you mean a 3 port valve.
    A picture of the valve might help.
     
  3. Neil Murray

    Neil Murray New Member

    Sorry yes you are right (read too much last night and brain isn’t working fully yet) I’m only guessing from reading across the internet about heating only working when hot water is on.

    I don’t know what the problem is but I can’t find any information about the fact it all works fine when hot water is active (and then switched off.)
     
  4. Peter208

    Peter208 Active Member

    Try this little DIY test.
    Have the room stat at max.
    Does your heating come on, it should but if it does not then;
    Go to the stat on the hot water cylinder.
    Note its setting.
    Turn the cylinder stat up, you might/should hear it click and your boiler should come on. OR you could run off some hot water and see if the the boiler now heats the cylinder AND the heating.
    If it does do both, then the problem looks to be with the 3 port valve.
    If it is this valve, it could be a couple of things.
    Could be just sticking and failing to move to the required position.
    Might be the valve head motor, cost about £20 from SF ( part No. 28670 )
    Good luck.
     
    Last edited: Oct 21, 2018
  5. Neil Murray

    Neil Murray New Member

    Before I start the tests, On the control unit should I have either hot water or heating active?
     
  6. Peter208

    Peter208 Active Member

    Hot water
    Then if your rads start to get hot, it points to the valve
     
  7. Neil Murray

    Neil Murray New Member

    3DFE65F1-0879-4E52-BBEC-6B52D2B6C891.png 577D7AD2-D4F8-4FEB-BAB0-05739B5D5C65.jpeg 9624848B-B9C1-49D9-AB8C-459F9C4E8DC7.jpeg
    Thank you for your help so far...

    Hot water on, boiler firing up and tank making noises. Radiators are not warming up.

    I’ve taken some pics and the only cold pipe is below the iflo zone valve actuator, everything else was hot.
     
  8. Mike83

    Mike83 Screwfix Select

    Could be a faulty microswitch inside the heating zone valve.
     
  9. Mike83

    Mike83 Screwfix Select

    It’s a basic s plan system.
    A multimeter is probably required to diagnose the fault.

    When you turn the heating on by itself does the black plastic bit on top of the iflo valve retract inside the valve?
     
  10. Neil Murray

    Neil Murray New Member

    With just heating switched on, thermostat up to full, the black plastic bit is still out.
     
  11. Mike83

    Mike83 Screwfix Select

    Turn hot water on itself. What does plastic bit do now?
     
  12. Mike83

    Mike83 Screwfix Select

    Just for info.
    The silver metal box is for the hot water.
    The white plastic one is for heating.
     
  13. Neil Murray

    Neil Murray New Member

    Hi Mike, thanks for the help.

    Had to wait for the kids to have a bath for the hot water to fire up.

    The black plastic bit hasn’t moved with just the hot water on.
     
  14. Mike83

    Mike83 Screwfix Select

    If you turn both on (heat/hw) does the plastic bit move.
    If would move leftwards and down a few mm
     
  15. Neil Murray

    Neil Murray New Member

    With both on, the black bit moves and moves back when I turn the thermostat down to minimum.
     
  16. Mike83

    Mike83 Screwfix Select

    Is this a new fault or did you inherit it.
     
  17. Neil Murray

    Neil Murray New Member

    We’ve been in the house for years. Only just noticed it since trying to turn on heating this winter.
     
  18. Mike83

    Mike83 Screwfix Select

    If it's a new fault it could be the electronics inside the programmer.
     
  19. Neil Murray

    Neil Murray New Member

    Thanks! Is there a way I can test this? Or would it just be a switch out and see if it works
     
  20. Mike83

    Mike83 Screwfix Select

    Turning the heating on by itself at the programmer does nothing. But turning the water on whilst the heating is on somehow jolts the heating side to life.
    Plausible.

    Multimeter would confirm.
     

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