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Thermostat Hot Water Cylinder

Discussion in 'Plumbing and Central Heating' started by Breeno, 14 Nov 2019.

  1. Breeno

    Breeno

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    Hi

    Where would the thermostat be on my hot water cylinder?

    Would the immersion heater act as a thermostat?

    Thanks
     
  2. Hugh Jaleak

    Hugh Jaleak

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    Immersion will have its own integral thermostat. If a Cylinder stat is fitted to control a boiler, it should be around 1/3rd of the way up, strapped to the side of the cylinder. Gravity HW systems from an external heat source may not have a thermostat.
     
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  3. Breeno

    Breeno

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    mine is a gravity HW system and has no thermostat I take it!!

    must a an airlock as the hot water cylinder does not heat hot just warm when oil heating is on for 2 hrs or so!!
     
  4. The Novice

    The Novice

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    Cylinder will not heat just from central heating, Gravity maybe different. Take and upload a photo of cylinder and any motorised valves. Do you have a programmer?
     
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  5. Breeno

    Breeno

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    Yes programmer works twice a day
     

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  6. The Novice

    The Novice

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    Yes there's no thermostat on that cylinder. Depending on which zone valve setup you have, it's probably not sending the water to the cylinder
     
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  7. Breeno

    Breeno

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    there is no zone setup the heating is either on or off as in heats rads & water or nothing.
     
  8. stem

    stem

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    Are you sure that you have a gravity circulation hot water system, in that case your installation is like this. ie Gravity circulation of the hot water and pumped central heating. [Don't confuse gravity circulation with having tank(s) in the loft, that is something else altogether]

    [​IMG]

    Hard to tell in the photo, but the pipes supplying the hot water cylinder look to be 15mm to me.

    Capture.JPG

    If that's the case, for gravity circulation 28mm pipes are normally fitted. So, are you sure that it's gravity circulation? and if so has it ever worked?
     
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  9. Breeno

    Breeno

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    I have a water tank in the loft above the hot water cylinder and a pump at the heating boiler

    thanks for all responses
     
  10. Hugh Jaleak

    Hugh Jaleak

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    Can you have HW on without CH, but not CH without HW?

    Looking at that cylinder, you have a fairly ancient setup, I agree with Stem, and would have to question if it's ever worked properly. Gravity Primaries, (flow and return pipes from boiler to cylinder), need to be a minimum of 28mm diameter for a gravity system, 15mm is just not going to transfer enough heat, which may be your issue....

    Basic premise is, boiler heats the water, which flows up to the cylinder by gravity. Some control was used in a few cases with a 'C' plan system, by use of a cylinder stat and motorised valve on the Primary return pipe, but this was quite basic in the grand scheme of things. If CH was required, the pump was simply switched on to move heated water from the boiler around the radiators.

    What is the small copper cylindrical item in the last pic connected to?
     
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  11. JimCrow

    JimCrow

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    @Hugh Jaleak
    It's a Willis immersion heater connected to the dhw cold feed and the hot water draw off.
     
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  12. Breeno

    Breeno

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    Considering this is an old setup apart from a new CH boiler what else would be required to upgrade the system?

    Would a mega flow system be possible?
     
  13. The Novice

    The Novice

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    That can only be answered by a visit from an G3 registered engineer, unless you could provide pressure and flow rates with additional testing? Only advice we can give to upgrade is changing layout to an s plan or y plan (zone valves, thermostats and trvs)
     
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  14. Breeno

    Breeno

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    Costly?
     
  15. DP

    DP

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    There is me under the impression that HW cylinder should be upgraded when boiler changed to be BC compliant. Lovely big radiator is that cylinder
     
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