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Discuss Unvented system - hot water not very hot. in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. teecee90

    teecee90 Guest

    We have an oldish Tribune Premier TP150B unvented indirect hot water cylinder. It has two tank thermostats - I think the upper one controls the 1.5kw immersion heater and the lower one controls the gas boiler. When relying solely on the boiler, the water never seems to get very hot. This evening the water was barely luke warm so I hit the boost button on the controller to fire the boiler up, but it did not fire. I checked the thermal cut-out buttons on the thermostats and neither appeared to have tripped. The temperature setting on the upper thermostat was set to maximum and the lower thermostat was set very slightly below maximum. I turned the lower thermostat to maximum and the 2 way valve promptly opened and boiler fired up. Looking at the instructions for the tank it says that the 'low' setting on the thermostats is 43 degrees and the high setting is 70 degrees. There is no way that the water was even at 43 degrees but the boiler only fired when I set the thermostat to the maximum setting. Does this indicate a faulty thermostat(s)? The system is probably about 20 years old.

    Do thermostats degrade over time or do they just completely fail (all or nothing)?

    Would it help to remove and clean them?

    Any advice greatly appreciated.

    [​IMG]

    [​IMG]
     
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Best to get a G3 engy to have a look at the system and maybe service the cylinder

    You need to be G3 registered to be able to work on unvented cylinders

    Put the thermostat settings back as they were
     
    • Agree Agree x 1
  3. teecee90

    teecee90 Guest

    The system was serviced last week. The only thing I've changed is to move the lower therm setting about a millimetre to the right.
     
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    The cylinder or the boiler ?

    If boiler cylinder needs to be done and checked by an unvented technician
     
  5. teecee90

    teecee90 Guest

    Both were serviced.
     
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Call them back as it's one of the points to check store water is reaching the correct temperature to prevent legionella
     
    • Like Like x 1
  7. teecee90

    teecee90 Guest

    I have no faith in them. This isn't the first time Ive had problems with them. Would be helpful to have a clue what the problem might be so I can get someone else in if necessary. Could an electrician deal with the thermostats?

    [​IMG]
     
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Any chance of a pic of the whole cupboard? Eg whole cylinder and pipes

    And no anyone working on an unvented cylinder needs to be G3 registered
     
  9. teecee90

    teecee90 Guest

    Yes of course... there are two 2-way valves at the back of the tank - both were replaced 2 years ago. There is an expansion vessel in the loft.

    [​IMG]
     
  10. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Who ever serviced that wasn't G3 registered

    D1 should be no more than 600 mm and yours is listed at 1200mm

    So it makes you think what ever else they missed
     
    • Like Like x 1
  11. teecee90

    teecee90 Guest

    Okay, well I think I'll get the thermostats replaced. It's a pretty simple system really and I can't see what else could be the problem.
     
  12. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Good look on locating the stats , sorry you may struggle , but good luck .
    I havnt read everything above but has there been water running through the tundish ? , did the engineer go into the loft ?
     
  13. teecee90

    teecee90 Guest

    Seems to be plenty of those thermostats available online - S6211

    There is no leakage from the TP valve and the expansion vessel is properly pressurised
     
    Last edited by a moderator: Sep 6, 2017
  14. Best

    Best Trusted Plumber Top Contributor!!

    How do you know the expansion vessel is properly pressurised?
    The engineers you said yourself you had no faith in them, plus you have faults unrectified
     
  15. Best

    Best Trusted Plumber Top Contributor!!

    Strange the engineer wrote 1200mm D1 length, but then didn't correct it or note it on the Observations part of form. o_O
     
    • Agree Agree x 1
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