2 Room Thermostats work, the third seems to operate differently

Discussion in 'Electricians' Talk' started by ItWasAPub, Nov 12, 2013.

  1. Where the 'ell can that timer be?!

    Is it possible that the boiler has a built-in timer that hasn't been over-ridden? It's still working alongside the LP722 or summat?
  2. Lectrician

    Lectrician Screwfix Select

    It certainly sounds like there is a time clock lurking somewhere...
  3. ItWasAPub

    ItWasAPub New Member

    Thank you all, sorry about the delay in getting back.
    Outside of the two times when this zone works and with the LP722 programmer on for CH and HW, turning the thermostat in zone 3 up makes no difference. The flag on the zone valve is stiff. During the two times when the zone works, the flag moves freely. Also, during these times, turning the thermostat down turned the zone valve off i.e. it becomes stiff, and heating is cut to the radiators. Turning the temperature back up during these times turns the zone valve on and the flag moves freely and the radiators heat up again. I have had a look for a second timer/controller and can't find one anywhere. There is a joint box/wiring centre near the zone valves, I will open that up tomorrow and take some pictures of the exposed wiring. The boiler is downstairs in the utility room and the zone valves are all in the airing cupboard upstairs. The boiler is a Main 24 HE.

    I will try the following suggestion tonight:
    "IF you turn the 4200 stat (ok, long gorn...) down at, say, 11pm at night AFTER your LP722 has turned its CH off, AND that 3rd zone's rads COME ON, then - surely - that stat is being supplied by permanent mains power so is working COMPLETELY independently of the LP722 and other stats?"

    I will try the following tomorrow night:
    "Or, take your new prog stat off its back-plate and test for 'live' feed both before and after 11pm (when the LP722 goes off)."

    During the afternoon it is on 18C and at night 15C.
    What temp is your new prog stat set to that makes it come in the afa and during the night?

    Although I cannot locate another timer anywhere, I will have a good look in the loft(just in case).

    Thanks everyone, and I will post back with more information.
  4. What a mystery!

    I think you've done all the tests now, IWaP - it's pretty clear that, outwith the two times you mention, there is no power going to that 'stat. So, there is a timer somewhere. (How long does it stay on for at these times?)

    Does your Main 24 HE have the optional timer fitted to it - a clock on the front panel?
  5. ItWasAPub

    ItWasAPub New Member

    Certainly a mystery!

    The timer stays on about 2 hours in the afternoon and about 3 hours during the night. There is no clock on the front panel, just a square white plastic plate where one would go.
    I will carry out the other tests I said and post a picture of the wiring.

  6. You need to try and trace the cable from that 3rd stat.

    Odds on that, at the end, you'll find a mouse with a flick switch.
  7. ItWasAPub

    ItWasAPub New Member

    Sorry about the delay, that thing called work got in the way. I tried to trace the wires in the wiring box near the zone valves (picture attached) and noticed then traced a wire into the loft - not the extension loft but the original loft.

    Attached Files:

  8. ItWasAPub

    ItWasAPub New Member

    and I found (picture attached) in the loft. Why do people do this? So, I removed the pins so that it remains on all the time and I can now control the heating all the time via the thermostat. So, they did bypass the LP722 and had this timer in the loft - which suffered some power cuts so that it seemed to come on at obscure times.

    I would like to thank everyone who has helped.

    BTW - I have put programmable thermostats in the other two zones as well now and leave the LP722 on all the time.

    Attached Files:

  9. Well I'll be b.... :eek:

    Good to have a solution to it! Nice job.

    Now, we ain't gonna left you off that easy. You need to tell us which cable it is in the JB that supplies that timer so's we can by-pass it. Do you really want that stupid timer running around in your loft...?

    (Good move with the other Prog stats :))
  10. Lectrician

    Lectrician Screwfix Select

    I would like to see the stupid timer removed too :)
  11. ItWasAPub

    ItWasAPub New Member

    I will label all the wires this weekend and upload the image. You are both right, it should be removed. Thanks for making sure I don't get lazy and leave it, because it now works!
  12. unphased

    unphased Screwfix Select

    Is this the point where I say "told you there was another timer" ;). Well done for finding it.
  13. I'll hold my hands up, UP; I really thought it was unlikely; I reckoned the OP was just a bit 'confused' :oops:

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