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Two Faults.

I went to explore the reason for a failed immersion heater. The element tested out o.k. The rod 'stat had its main operating contacts welded together and the safety trip had operated and switched the element off. I renewed the rod 'stat. Then upon turning on the 20 Amp D.P. switch with neon it flickered the neon momentarily then it died. There was a supply in from a good old 60s M.K. 20 Amp switch down stairs, still operating perfectly, but its neon is a little dim. But the newish 20 Amp D.P. switch by the immersion heater had failed after about 2 years use from new. So I found one fault, and by operating the switch by the heater that switch then failed. You couldn't make it up, and then trying to explain that to the customer isn't easy.

Has anybody else had similar experiences?

Z.

  • All the time. Part of how it is on the tools.

    Smile and wave.

  • The old saying was that faults always came in threes ... what have you overlooked?

       - Andy.

  • Well, presumably while the stat was stuck on and before the safety cut-off at 90c or whatever, the element was on full blast for quite a while, and the switch in the cupboard was running hotter than planned, and in a hotter place then normal, for longer than planned. I suspect the 3rd fault will be that this over-running event has taken years off the life off the element , and you will be back in a few months to change that as well.

    Unless the switch  is low down in the cupboard, it is quite possibly running in a higher than room temperature environment, and should be de-rated a bit. Same reason badly sited 13A fused spurs in airing cupboards often fare badly.

    Mike.

  • Possibly Mike. But the 20 Amp switch was overrated for its 12.5 Amp load in the first place and should have coped well.

    Z.

  • So, just what is the maximum permitted ambient temperature allowed for domestic wiring accessories by a standard please?

    Z.

  • So, just what is the maximum permitted ambient temperature allowed for domestic wiring accessories by a standard please?

    MK seem to say "Ambient operating temperature: -5 °C to + 40 °C" but "not to exceed an average of more than 25 °C in any 24 hour period" for both their 13A (BS 1363) and 20A (BS EN 60669-1) ones:

    https://www.mkelectric.com/Documents/English/EN%20MK%20Technical%20Specifications/Wiring%20Devices/Logic%20Plus/Connection%20Units.pdf

       - Andy.

  • The airing cupboard has a well insulated copper tank with the minimum of hot pipes showing. I don't think that it gets very hot, even with the door closed.


    Z.

  • Then it's not much of an airing cupboard! Laughing

  • I don't think that it gets very hot, even with the door closed.

    25 degrees isn't that hot - only a few degrees above many people's idea of ordinary room temperature.

       - Andy.

  • Saw one recently where the client kindly emptied all the towels and blankets beforehand for access. Loads of stuff in piles around the room. Accessories can quite easily be subject to additional insulation in "normal" use.

    But i take the point about the well insulated tank, building regulations also stipulate insulation of hot water pipes so hopefully not too much lost heat to the local environment.