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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
     
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  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
  16. teecee90

    teecee90 Guest

    Because I've checked it myself.

    Must admit I don't understand the D1 issue - can anyone explain? As far as I know nothing has been changed since the property was built, other than replacement of the motorised valves, anode & TP valve a couple of years ago.
     
  17. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    From the safety valve the black tundish needs to be within 600mm

    So it wasn't right from day one
     
  18. teecee90

    teecee90 Guest

    I might be wrong, but looking back over previous versions of the regulations, at the time the house was built it seems that the requirements was for the tundish to be a maximum of 500mm from the valve measured horizontally and for a minimum 300mm fall after the tundish. There is no mention of a maximum pipe length between the valve and the tundish, although later regs set this at 600mm. So, it wouldn't meet current regs but was probably okay at the time it was built.

    [​IMG]
     
    Last edited by a moderator: Sep 6, 2017
  19. Best

    Best Trusted Plumber Top Contributor!!

    It was previously 500mm D1 maximum length to tundish, but recent years was changed to 600mm.
    The instructions and regulations description and drawings can be a bit confusing I must admit.
     
    • Like Like x 1
  20. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    I am intrigued, how have you done that ?
     
  21. teecee90

    teecee90 Guest

    This was the original wording: "..The tundish shall be located not more than 500mm horizontally from any valve discharging to it" which taken together with the diagram makes me think it was installed correctly at the time.

    The wording has now changed to: "..with no more than 600mm of pipe between the valve outlet and the tundish"
     
  22. teecee90

    teecee90 Guest

    With a pressure gauge on the shraeder valve on top of the vessel in the loft.
     
  23. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    :D
    So thats how you do it is it !!
     
  24. teecee90

    teecee90 Guest

    It's how I did it. Why, what have I done wrong?
     
  25. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Cant say , its a secret
     
    • Like Like x 2
  26. teecee90

    teecee90 Guest

    That's helpful. Thanks for your contribution.
     
  27. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Yea you done it wrong and will give a false reading
     
  28. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    My contribution is very simple my friend , working on an unvented cylinder requires a qualification that we have to pay for , it maybe your cylinder but you are not qualified to work on it , do you touch your boiler when you are not qualified to work on it ? , I hope not

    Thats why its a secret
     
    • Winner Winner x 2
  29. teecee90

    teecee90 Guest

    Nice attitude..
     
    • Like Like x 1
  30. teecee90

    teecee90 Guest

    All I said was that I had checked it was pressurised, not that the reading was correct. I checked it was pressurised the day before the engineer came to service it. He did go into the loft so I assume he checked the reading, although presumably he wouldn't have been able to get an entirely accurate reading himself with it still in situ?

    Anyway, its obvious this thread isn't going anywhere so this will be my last post.
     
  31. Best

    Best Trusted Plumber Top Contributor!!

    Other people could read this thread and use any advice to work illegally and dangerously on their, or others unvented cylinders, so that is why information given is limited
     
    • Like Like x 1
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