Probe Thermostat

Discussion in 'Plumbers' Talk' started by MarkyBoy, Jan 6, 2005.

  1. MarkyBoy

    MarkyBoy Member

    I have just fitted a new hot water cylinder that requires a probe thermostat to measure the water temperature instead of the standard cylinder stat. The main difference is that the probe stat is inserted into the cylinder via a 1/2 " female thread mounted at the bottom of the cylinder.

    The problem I have found is that the thermostat never seems to reach temperature and stop the boiler firing (when set to 60 degrees) even though the water temp at the taps is almost 70 degrees.

    When I turn the stat dial back, it clicks at about 38 degrees and turns the boiler off (so not a wiring problem). Is it just a faulty thermostat or could it be something else ?

    The thermostat is new.
     
  2. doitall

    doitall New Member

    How about installing it in the right place.
     
  3. MarkyBoy

    MarkyBoy Member

    As stated in my original post, the probe stat is fitted to the cylinder by a 1/2 female boss located at the bottom of the cylinder (about 1 1/2" up). I know thermostats should be approximately 1/3 up but the cylinder was supplied with the 1/2" boss located in this position.

    The cylinder is an Albion Superduty as shown on this link
    http://www.albion-online.co.uk/.
     
  4. doitall

    doitall New Member

    The one drawing shows the correct possition whereas in reallity it's in direct conflict with the cold feed.

    I would expect at least a 30° temperature difference in that possition.
     
  5. MarkyBoy

    MarkyBoy Member

    I struggled to understand the logic behind it and have sent Albion an email asking for an explanation.

    If you download the Superduty installation guide it re-confirms the position of the probe thermostat as being at the bottom. It recommends the use of a probe thermostat for quicker temperature response and to assist the economical and efficient running of the system.

    How can that be when the thermostat never reaches the dialed-in temperature and therfore never turns the boiler off !
     
  6. doitall

    doitall New Member

    Do post their reply it make no sense whatsoever.
     
  7. MarkyBoy

    MarkyBoy Member

    I spoke to someone in Albions technical department today and their comments were as follows :-

    Since the new Part L Building Regs of 2001 the primary heater coil of hot water cylinders has been moved to the bottom of the cylinder. This increases efficiency, ensures a full cylinder of hot water is available at all times, prevents corrosion and greatly reduces the chance of legionnaires. A probe thermostat reacts much more quickly to temperature change than a standard cylinder stat and therefore, the boiler will require less firings because the probe stat will kick-in instantly a reduction a temperature is detected rather than the delayed reaction of standard stats.

    There was more but I can't remember it all.
     
  8. Stoday

    Stoday New Member

    The heat sensitive part of the probe must be above the bottom of the heat coil because the heated water will not flow downwards.

    Maybe there is a special probe that is bent up inside, although the only ones I've seen are straight.
     
  9. doitall

    doitall New Member

    just as well MB one good laugh a day is more than enough.

    Did they mention scale build up over 60°C, and the energy that would be wasted above the recommended hot water temperature.

    Only thing I agree with that little lot is the probe stat reacts quicker than a normal stickon jobbie, but that assumes the boiler is on 24/7 waiting patiently for client to open a hot tap.

    Their taking rubbish tommorow I will tell them so :)

    And what about secondary circuit
     
  10. doitall

    doitall New Member

    Another good point Stoday, the probe is below the coil ??
     
  11. MarkyBoy

    MarkyBoy Member

    Sounds like Albion have told me a load of old B**s*t then !
     

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