Non reset-able cut out on thermostats, how do you know if there?

Discussion in 'Electricians' Talk' started by MGW, Oct 21, 2021.

  1. MGW

    MGW Screwfix Select

    With a reset button on the immersion heater thermostat it is clear the thermostat is safe for use with thermoplastic water header tanks, with solid fuel we use thermosetting plastic or steel, and the reset on the thermostat is a pain as every time water boils in back boiler it needs resetting, there are models which don't have the reset built into the thermostat and instead have a completely independent reset and a button in the immersion heater casing so it can be reset without removing casing.

    Not seen one for years, but know my father's house had one, I needed to press it many times after the Aga boiled the water.

    But I note best practice guide shows a picture upload_2021-10-21_11-16-24.png seems odd as dad's house 1954 and he had a reset button. How old would it need to be not to have thermal cut-out?

    I would guess age is not the problem, it is the selecting of items for use with home with back boilers and for homes without, so if you find one of these upload_2021-10-21_11-21-10.png which does have a thermal cut out but no reset button, how do you tell it from one with no thermal cut out?
     
  2. Tony Goddard

    Tony Goddard Screwfix Select

    The thermostats with a built in cut out have a tiny button on them, either white or red (red normally on black ones, white on blue) near the setting dial. It sits flush to the casing when engaged and pops up when tripped.

    The Backer BT-7 stat you show is normally used in Backersafe immersions, so doesn't have a built in cut out, these have an entirely separate cut out fixed to the brass casting, you have to take the cover off to press it to reset - it looks like a tumble drier / washing machine mini thermostat but with a button in the middle.
     
  3. Tony Goddard

    Tony Goddard Screwfix Select

    There are more and more permuations of immersion thermostat now, some makes have a plug in stat that pushes onto spades on the element cold tails - this makes the interior much safer and neater, but weds you to a particular thermostat brand and means poor sparkies like me who used to just have 3 different length stats on the van now have to have a huge inventory!!

    Illustrated is Santon's effort, made for them by Cotherm, used on Santon/Heatrae Sadia
     

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  4. MGW

    MGW Screwfix Select

    Thank you, I had found a web site which said "Non Resettable" so assumed it had built in fuse, but reading further is did say "used with Manual Button Cut-Out Part No 13115" which I missed.
     
  5. The Happy Builder

    The Happy Builder Screwfix Select

    I hope you have thermostatic mixer valves on all your taps and showers.
     
  6. MGW

    MGW Screwfix Select

    Since I don't use my immersion heater getting the domestic hot water too hot is not really anything to do with the thermostat on the tank, it depends on central heating water temperature and time.

    However the question arose over doing an EICR and what should be checked, and I said in the main I use the Best Practice Guide but there were two points I did not agree with.
    1) Number of sockets, if the occupant decides to have adaptor plugged into adaptor then clearly the socket physical ability to take the weight may be a problem, and the occupant should be advised, however can't see how this should appear on the EICR, it would be like banning a car because it could exceed the 70 speed limit.
    2) Was the immersion heater thermostat, the main problem only exists with a thermoplastic header tank, with thermosetting or steel there is no problem, and even if there is how can the inspector know if that make of thermostat has a temperature fuse fitted or not?

    I read the non reset-able and thought Oh that's OK, seems it should have said no cut out. I got it wrong, and reading other web sites realised my error, but the question remains, remove cover from thermostat and see the reset hole or button great it's OK. But if no re-set is seen, how does one know if it has a thermal fuse built in or not?
     
  7. The Happy Builder

    The Happy Builder Screwfix Select

    I don’t think your dad had an immersion heater with a reset button, as dual safety stats weren’t made back then. So I’m not sure what you were pressing.

    Neither have I seen a new one without a reset button.
     
  8. MGW

    MGW Screwfix Select

    As a young boy at the time, no way was I removing the lid to reset, button was on outside, I am not sure if duel elements, the tank came out in around 1990 when the header tank started to leak, so a combi boiler fitted, I can't remember exactly how it was wired, except it was supplied from a 15 amp socket, odd one out, rest of house had 13 amp sockets.

    But I am sure there was a cut out, as was sent to press the button so many times after mother had been baking so had got the water to boil.

    There was a damper on the stove which in theory should have controlled heat to oven or side boiler, but as the song said, push the damper in or put the damper out, the smoke went up the chimney just the same.
     

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