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HIGH LIMIT / LOW LIMIT / OVERHEAT STATS

Discussion in 'Plumbing and Central Heating' started by jackecole, 30 Oct 2010.

  1. jackecole

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    WHat's the difference between a high limit stat, a low lmit stat, overheat stat etc? I know some boilers use a combination of the above but what's the difference?
     
  2. kevplumb

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    all the same just trip/switch at different temps :p
     
  3. jackecole

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    Thanks for the quick reply kev

    I take it a low limit stat is just your normal user stat/thermistor then?

    High limit being same as an overheat?
     
  4. kevplumb

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    low limit stat is usually found on solid fuel
    it stops the pump running till the boiler is warm enough to stop condensation forming

    frost stat is sometimes called a loww limit stat as well

    yeah high limit / overheat same animal ;)
     
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  5. spraggo

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    These high and low limit stats were used on the old Thorn Apollo etc. They were activated by a rocker switch on the control panel marked high and low. The purpose of these, where to enable the user to select low in the mild weather and high in the cold weather. These two button type stats were fitted to the flow inlet side of the primary heat exchanger and were marked with a coloured dot to indicate their temperature at which they opened, which ranged between 135F and 190F.

    The overheat stat shuts the boilers down if the water temp goes to high if either of these two stats failed
     
  6. namsag

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    Wee bit mixed up there Spraggo a low limit stat is different from a lo stat that was on appollos.
    In domestic situation a low limit stat is what you get on warm air units ,burner comes on and the unit has got to get to a certain temp before the fan kicks in so that its not blowing cold air to start with
     
  7. spraggo

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    Thankyou for your correction namsag and I apologize, I was refering to high and low stats, not high and low limit stats.

    spraggo
     
  8. spraggo

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