Spark from immersion heater switch

Discussion in 'Electrics UK' started by DiyNutJob, 26 Nov 2021.

  1. Harry Bloomfield

    Harry Bloomfield

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    A cheapy then. Better ones will have a snappier action and more robust contacts, both will help reduce arcing.
     
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  3. DiyNutJob

    DiyNutJob

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    OK, that's what I will look out for in the future. It's just the sparks scaring the family members. I have just replaced the central heating pump. There should be no more need for the immersion heater now.
     
  4. DiyNutJob

    DiyNutJob

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    Says 5 year guarantee. I will go see them when it melts.
     
  5. Colin Brenton

    Colin Brenton

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  6. EFLImpudence

    EFLImpudence

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    The sparking when switched off only happens when someone is looking at the switch; if no one is looking it doesn't spark.

    Either way, it doesn't matter.
     
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  7. Colin Brenton

    Colin Brenton

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    Haha, true. Time your blink reflex carefully :D
     
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  8. SUNRAY

    SUNRAY

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    But that isolator will also arc if switched of under load.
     
  9. RandomGrinch

    RandomGrinch

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    Yep, most will.
    Unless intrinsically safe, and even then, only when designed as part of an IS system.

    However, I would bet that the isolator would last a good deal longer than a cheap switch from wickes!

    ...and you would definitely not see the sparks in there ;)

    I may be wrong, but there seems to be a more positive 'break' in the contacts (and a greater travel distance), when turning a rotary isolator, compared to flipping a switch.

    Though as @Colin Brenton suggests, the 40A cooker switch would fit nicely without additional work, could cope better with the switching current and would look better if the switch was visible. I assumed, maybe wrongly, that the switch was in a cupboard! :)
     
    Last edited: 28 Nov 2021
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  11. Harry Bloomfield

    Harry Bloomfield

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    Yep - The contact is broken by a very positive spring action. They are not dependent on the operator flicking the switch, the operator winds up a spring, then the spring reaches a point where the spring flicks the contacts suddenly open. The are much better at dealing with inductive loads, such as motors, where there is even more tendency to arc, than a resistive load.
     
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  12. DiyNutJob

    DiyNutJob

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    Do you know that works for a fact, or are you merely speculating?

    From what I understand about the sparking issue is that the cause is the amount of energy present. Having a bigger or bigger-capacity switch does not reduce the energy present. The same size spark will be produced by the same energy. The only thing that would make a difference would be the contact material. Maybe some materials are better able to prevent arcing.

    Also, are you sure there are no regulations that says you are not allowed to confuse electricians who might be working on that switch?
     
  13. SUNRAY

    SUNRAY

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    Larger switches are obviously designed to cope with switching heavier loads, if we go to extremes (say a 1000A switch) the effect of a 13A load will be greatly reduced as the contact will open wider and quicker.

    Would it be more confusing if this has a cable going to an immersion heater:
    [​IMG]
    as opposed to this:

    [​IMG]
     
    Last edited: 28 Nov 2021
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  14. RandomGrinch

    RandomGrinch

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    ...and as we have said regarding isolators;
    Have you tried flicking the switch of a cooker switch?
    The action normally requires more force and is far more positive, than with a standard switch.
     
  15. DiyNutJob

    DiyNutJob

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    Yes, I have tried flicking the cooker switch. It is not connected. However, the 13A socket switch on it sparks.
     
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  16. DiyNutJob

    DiyNutJob

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    The spark size and strength is caused by the energy present. Bigger or smaller switch doesn't change the energy present. No matter how fast you flick the switch, the arc operates at the speed of light. As soon as the switch breaks contact, the arc charge begins.
     
  17. Harry Bloomfield

    Harry Bloomfield

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    There are no such regulations preventing the installation of a more robust than strictly necessary switch. The action of the switch will be brisker, the contacts more capable, therefore the resultant arc will be shorter and less obvious. Arc duration is a function of the speed with which contact is broken, which is why higher current and voltage switches, use a wind up and press a mechanical button to trigger make or break and/or oil submersion and/or an insulated barrier dropping into the gap to break the arc.
     
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