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Teddington pressure differential switches

Discussion in 'Plumbing and Central Heating' started by Mrmoo21, 28 Jun 2010.

  1. Mrmoo21

    Mrmoo21

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    Folks
    I have to rewire the controls for a large central heating system. I have most of the challenge covered but one thing is puzzling me. Fitted to the pipework are two Teddington pressure differential switches. One set at 15Psi with a diff of 10 and the other at 45 Psi with a diff of 30. I presume that these switches allow for safe operation but can anyone confirm this.

    Thanks
    Mark
     
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  3. D_Hailsham

    D_Hailsham

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  4. Onetap

    Onetap

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    It sounds like they are being used as low and high pressure switches.

    It is fairly common practice on BMS systems to use a differential pressure switch across a pump or fan to confirm that the device is running.

    A typical sequence might be supply fan enabled, dP switch confirms fan runs, extract fan enabled, dP switch confirms fan runs. Failure to run within a certain time would enable a stand-by fan or shut-down the system.

    I couldn't say what your ones are doing on a CH system, try operating them and seeing which lamps come on at the panel.
     
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  5. Mrmoo21

    Mrmoo21

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    Thanks for the feedback information guys.
    I should also have said that the switches are installed as part of a sealed heating system and they are sensing the pressure of water in the system. They are mouted on the primary heating loop. There is no control panel yet, I’m building that right now, currently it’s just a mess of connectors and every type of cabling system conceived.
    I did trace the cabling which is connected to the switches and it basically interrupts the supply to the whole system. When I get some down time on the system I’ll drop the pressure and possible increase it to see the effect it has on the switches.

    Cheers
    Mark
     
  6. Boilerman2

    Boilerman2

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    The Teddington Pressureswitches are Low & High Safety switches, Low pressure should be set at about 0-6Bar Min Diff High pressure should be ste 0-5Bar below the Safety Valve lift pressure, with Min Diff
    Low pressure should be wired between Common and N.O. High pressure should be wired between Com and N.C, with the switches looped in series, they should stop the Burner and quite often the Circulatrion pumps in the event of High or Low pressure occuring ;)
     
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  7. Biggles..

    Biggles..

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    Theyre still high and low pressure switches,more than likely used for system volume/pressure and pump proving.

    decrease in pressure will stop the boiler firing and pump running to avoid dry firing.Over pressure will also stop boiler firing incase the safety valves havent discharged.

    probably linked to pump and boiler failure indication on the BMS panel
     
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