Servowarm Elite 50 shut-down problem

Discussion in 'Plumbers' Talk' started by Barnster, Oct 19, 2010.

  1. Barnster

    Barnster New Member

    I have a Servowarm Elite 50 boiler. I can light the pilot light and it stays lit, so I assume the thermocouple is working OK. However, when the boiler fires-up, sometimes after about 10-20 minutes of operating, the flames simply go out, and then about 5 minutes later the pilot light goes out. I can then re-light the pilot and it stays lit again.

    Could anyone suggest why it seems to be "shutting down" in this way?

    Many thanks.


    Is this quite an old boiler. So, from memoery. Boiler is cutting out correctly on 'stsat. There should be a pump over run to clear residual heat. If this is not working, maybe due to faulty sensor, the o/h stat will kick in.

    Are you an RGI?. If not then you will need help
  3. Barnster

    Barnster New Member

    It is an old boiler, yes.
    From what you explain, would it be worth trying draining the system to remove any sludge? Is there an easy way to tell if the pump is working properly, because from your explanation, I guess that could also cause this problem? The pump is definitely making a noise, but I don't know how fast it is actually pumping, and it certainly does over-run after the flames have gone off. Would it help to check whether it ever fires back up after cutting back in normal operation when it is trying to modulate the heat? Is there any way it could be the thermocouple (or would the pilot never stay alight if that had failed)?

  4. G Brown

    G Brown New Member

    Is the pump working?
  5. tomplum

    tomplum Active Member

    the thermacouple on these is interupted by a overheat stat, so i would start with these two parts, if you can get them, and don't even think of looping the overheat out, these are a low content water boiler, a low amount of water can soon change to steam, and you might join the " i put an elite boiler on the moon " club :^O



    You are on the right lines. A failed pump, though, would be evident, with similar symptons, much quicker. Sludge in the boiler certainly would present the synptons you describe. I don't think it is the O/H stat faulty, it is doing what is intended, likewise the thermocouple. There is a sensor/stat ( I am 99.98% sure of that), that will allow the pump to run after the valve has closed down. If this sensor is faulty, the pump may be cuttting off as soon as the boiler closes down, OR there may be scale or sludge. However, it would be making quite a rumble, and you haven't mentione that, to date.
  7. tomplum

    tomplum Active Member

    you're 99.98% right,these had a modulating flame, the stat phial gave juice to the pump to overrun, but if this failed the overrun would't work at all, the op said the runs when the flame goes out,
    if its a blocked h/x these screamed their bludy heads off,
    to test the t/couple turn the grey knob and wait for it to drop out, should take at least 20 secs, if less then 10 secs its either t/couple or o/heat stat,
  8. Barnster

    Barnster New Member

    Thanks... I'll try out the test you suggest for the thermocouple.

    Regarding noise - it's strange - sometimes it does make a lot of rumbling noise but it only lasts for about 5-8 seconds and doesn't happen all the time, but when it does it is loud.

    The thing I have just noticed by experimenting is if I just do hot water, it seems to continue working ok. It seems to be whenever I choose water+heating or just heating that the problems seem to start. Further to this, once I have been trying it in heating mode, the next time on hot water sometimes cuts out. This may not be 100% accurate, but it seems to be more "reliable" on water than heating.

    If it was sludge or scale, what is the best thing to do? - Drain the system and use some chemical?

    Thanks everyone.
  9. midlands heating

    midlands heating New Member

    are we right in assuming this boiler has been serviced properly ?
    if not and heat exchanger is partially blocked you can get symtons your describing through lack of oxygen to keep flames burning. its an old beast (like me ready for retirement) LOL.
    As for sludge problems 2 options powerflush or replacement of rads etc.
    I prefer 2nd option powerflush expensive (it causes its own problems) £500 plus and that buys a lot of pipe and rads and mains flushing is effective to JUST ASK TOM


    Sorry, MH, but replacing rads isn't gonna shift carp from boiler. Powerflush (properly) the way to go.
  11. midlands heating

    midlands heating New Member

    agree EG but I was not thinking of powerflushing the boiler it would probably explode knowing servo warm stuff LOL
    no replacement best option !!


    replacement best option !!

    Defo can't argue with that!
  13. doitall

    doitall New Member

    The problem is the gas valve is worn or clogged up.

    Not all Elete 50 had an interupt on the thermocouple, some were on the gas valve itself.

    I would suggest you get explosive ignition sometimes as well, (boiler comes on with a bang.)
  14. doitall

    doitall New Member

    As for the pump noise, check the header or whatever it has, has water in it.

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