Boiler running all the time even with the programmer off

Discussion in 'Plumbers' Talk' started by Old_duffer, Jan 16, 2018.

  1. Old_duffer

    Old_duffer New Member

    Woke up in the middle of the night rather hot. Felt the radiator in the bedroom and it was red hot. Checked the room stat (DT90E) on the landing and the temp was showing 25C set at 21C.
    Checked the programmer and both heating and hot water were off, the boiler was still running. Radiators cold downstairs and room stat 20C set 21.5C. Had to turn the power to the boiler off to stop it running.
    We had a short power cut in our street on Fri night 20.00 hrs. and it came back within 5 mins.

    Any ideas, heating has gone off this morning but boiler still running.
  2. Sounds as tho' you have two CH zones? Cooool - nice.

    These will be controlled by two 2-port motorised valves that look a bit like this:

    If you locate them and work out which one is for the upstairs rad circuit, try turning the boiler back on and waiting to see if the upstairs rads come back on as before, then turn the upstairs room stat down to below the air temp so it should tell the boiler to go 'off' and - when it doesn't - then (this is a bit technical, but bear with me) hit that valve with a lump of wood.

    Gently but firmly.

    Listen to it after it goes 'ouch' and you should hopefully hear a short 'whirrr' and it goes off - as it should have done before.

    It does sound as tho' it's sticking in the 'open' position, and this will turn on your boiler regardless of what your controls are saying.
  3. Old_duffer

    Old_duffer New Member

    thanks for the reply.
    I tried the technical part and did not hear the ouch or the whirr bit but I know what you mean as I hear the one on the hot water tank doing that. it's a Honeywell value with a lever, "what's the lever for".
    As everything is hot at the moment I will leave for an hour and try again.
  4. As you turn your room stat up and down beyond the 'click' position, does the motorised valve respond at all? It should go whirrrrr - click' as it opens, and 'click-whirrrrr' as it closes. (The click being the wee microswitch inside opening and closing - that's what then turns the boiler on and off).

    If the boiler simply comes on when not 'asked' to and the pipes to that valves become hot, that's a sure bet that it's stuck in the open position.

    You can try being more professional and remove the actuator - the grey metal box on top of the valve - and that should help diagnose what the cause is - ie a stuck actuator or a stuck brass valve. (Have a surf for info on removing motorised valve 'heads' - there's bound to be vids there too).

    Always do 'stuff' with the main CH power switch off. (Tho' you may need to turn it on again when doing tests).

    That lever on the side is to manually open the valve. This is useful when, for example, you are refilling or draining the system. With the valve 'closed' (ie no demand for CH) that lever should be firmly at the 'off' or closed position - away from the 'barb' that's in the slot. You can then gently-but-firmly push that lever towards the far end and the motor inside will go 'whirrrr' as it's being turned. When you reach the end of the travel, you should hear a 'click' as the switch is operated. When you release the lever, it should swing back firmly to the closed position. If you wanted to keep it open (for draining/filling), then you 'lock' the lever in that barb.

    When the valve opens, that lever goes 'floppy' and has no effect - I suspect it's like that now? That shows the valve is stuck 'open'.

    Ok, make sure the lever isn't caught in the barb, and give the brass body another clump. And another. (With CH demand 'off', of course)

    If that doesn't close it, then surf for info on removing its head - not as a punishment, but as a possible cure.
  5. Old_duffer

    Old_duffer New Member

    Got it to work at the moment, pushed the slider back a forwards and it started making whirring noise. The slider is at the end at the moment marked AUTO the other end is MAX OPEN. Will keep my eye on it and I have just found out that my gas service with BG has a month to run so I have made an early appointment (ha ha)for next Mon.
  6. Check that your service contract covers the whole system and not just the boiler :)

    But, if it does, then jobbie jobbed :D
  7. Mr Paul White

    Mr Paul White New Member

    Giving the unit a tap and then flexing the lever worked perfect for me. Boiler operating as normal. Thanks

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