Spark from immersion heater switch

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

  1. DiyNutJob

    DiyNutJob

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    I had an immersion heater switch that sparked intermittently. So I replaced it with a new one. The new one sparks even more when switching off. The new one from wickes is ASTA approved, etc.

    I understand the why's of the spark. But, I still prefer no spark. Is there such a thing as a non-sparking switch? Another switch at that location was overheated once, and burnt out. Is that an indication there is something wrong with the immersion heater?
     
    Last edited: 26 Nov 2021
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  3. sparkwright

    sparkwright

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    If the switch is a good quality, and wired correctly, safely, with sound connections, you can still get 'arcing', where you get a small flash showing round the switch itself.

    I do not know of a switch that is guaranteed not to do this.
     
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  4. RandomGrinch

    RandomGrinch

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    Hi,

    This may be slightly over the top, but could it be worth considering a 2-pole isolator?
    Something like this:

    19b9779d-9e66-4905-a651-058e873f8aff_704x832.jpg

    https://www.sparkswarehouse.com/col...ducts/bg-cprsd220-rotary-isolator-2p-20a-ip65

    They are significantly 'beefier' than a standard switch, and easy to turn on and off.

    Edit: although it wouldn't be a straight swap, cable glands and a fused outlet would have to be considered.

    The problem is, when arcing occurs, the switch contacts are damaged. This causes higher resistance within the contacts, eventually causing even more heat damage.
    A destructive feedback cycle!

    ...and yes, it is possible that there is something wrong with the immersion!
     
    Last edited: 26 Nov 2021
  5. winston1

    winston1

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    An immersion heater typically takes 3kW and when breaking such a load you will get a spark and switch wear. Nothing wrong with the immersion heater, just laws of physics.
     
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  6. DiyNutJob

    DiyNutJob

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    My understanding is that arc'ing always happens with conventional switches. I am just curious if there are any non-conventional switches for domestic use. So, there aren't.
     
    Last edited: 26 Nov 2021
  7. DiyNutJob

    DiyNutJob

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    You are pulling my leg. The heater is protected by a fuse at the consumer unit. There's probably nothing wrong with it. When I asked the question, I was still thinking the broken heater overloading the switch.

    Now I am thinking the heater is overloading the worn switch caused by arcing. So the heater is OK, but the worn switch has to be replaced or the diminishing contact will cause a melt down.
     
    Last edited: 26 Nov 2021
  8. RandomGrinch

    RandomGrinch

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    Yes, not a conventional switch; but again as I said, there is nothing wrong with using a small industrial switch, that won't have issues with arcing, in a domestic environment.
     
  9. Harry Bloomfield

    Harry Bloomfield

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    They always do spark/arc, but the amount can vary depending on when during the 50Hz cycle the switch is triggered - worse near one of the voltage peaks. If the arc persists longer than a fraction of a second, or it can be triggered by touching the switch - that suggests the switch may be faulty or that the switch operator is using the switch wrongly. A switch should be flicked quickly with a finger tip, rather than gripped and moved gently.

    Arc visibility can appear to be worse in thin or white coloured switches, plus when it is dark - brown or black plastic hides the arc better.
     
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  11. RandomGrinch

    RandomGrinch

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    Well anythings possible! ;)

    It will take a good while for a switch to be destroyed by arcing, so don't panic! But, yes, that could be the failure mechanism :)
     
  12. DiyNutJob

    DiyNutJob

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    Something that fits directly will be OK. We are not all builders and electricians. It would be too involved to set it up. They should make a domestic version that are more domestic looking.
     
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  13. DiyNutJob

    DiyNutJob

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    Both the new and old switches are conventional white. The new one sparks more, giving the rocker piece a surround-light kind of look.
     
  14. terryplumb

    terryplumb

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    What type of switch do you currently have ,is it double pole ? Rated at 20 amp ?
     
  15. DiyNutJob

    DiyNutJob

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    Are you quite sure? Maybe cheap switches use cheap metals and wear out after 5 switches. If they do a four-pronged iridium version, that would be OK. Those are known to last 100k miles on the car.
     
    Last edited: 26 Nov 2021
  16. Harry Bloomfield

    Harry Bloomfield

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    When it is turned on and you feel the switch, does it feel warm? If not, just ignore the arc - assuming as above it is marked 20amps.
     
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  17. DiyNutJob

    DiyNutJob

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    Yes, 20a, DP. New one is from wickes for £3.x. The old one, I can't quite make out the brand.
     
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