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Hot water cylinder thermostat fault?

  • 28-06-2017 11:33pm
    #1
    Champ
    Registered Users, Registered Users 2 Posts: 677 ✭✭✭


    Hi all,

    Basically I have one of these attached to my boiler to control the hot water temperature (borrowed from Berty's post in 2013, thanks Berty http://www.boards.ie/vbulletin/showthread.php?t=2056914158).

    BFE79929-3774-441C-B72F-36E197FC226C-3203-000003368C1A1BF5_zps2c0f9af3.jpg


    I suspected my boiler was running too continuous so I did a little experiment.

    (1) Remove the thermostat and let it cool off and keep it off the cylinder until the last part in step (3).

    (2) Setting the thermostat <= 40 and the hot water will never heat (the valve / actuator doesn't open). This setting also makes a distinct click in the thermostat itself which I can feel, pretty odd?

    (3) Setting the thermostat >= 50 and the hot water will heat non stop (the valve / actuator opens and doesn't shut). After letting this run for a while I manually attached a digital thermometer to the thermostat spot on the cylinder and got back a reading of 55. I reattached the thermostat (which was set to 50) and the hot water still didn't shut off.


    So... definitely the thermostat I think?


Comments

  • #2
    froshtyv
    Registered Users, Registered Users 2 Posts: 225 ✭✭froshtyv


    The cylinder stat is basically a switch that is operated by temperature.

    For a cylinder stat it should be wired normally closed.
    Lets say you set it for 60 degrees.
    When wired normally closed (N/C) the stat should keep the motorised valve open to heat the cylinder until the cylinder stat becomes satisfied 60 degrees or above reached.

    I have seen these cylinder stats wired normally open (N/O). In this scenario if the cylinder stat is to 60 degrees the boiler remains off unless someone turns down the cylinder stat to below whats its currently reading. (you will hear the cylinder stat click)
    If this happens, the valve will remain open until some turns up the cylinder stat.

    So you could have this scenario rather than a faulty cylinder stat.


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