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Service cable and cut out too hot.

broadgage
I was called by a local hospice to investigate "overheating" and found the DNO service cable and cut out to be alarmingly hot, I would estimate the surface temperature of the service cable to be at least 60 degrees. Definite smell of hot PVC.

Enquires suggested that the supply was originally 60 amps, single phase and was upgraded to 100 amps by fitting a larger fuse.


Measured load was just just under 100 amps, it probably exceeded 100 amps if anyone used a kettle.Service cable looks like only about 10mm. Voltage is rather low at 221 volts, but just within tolerance.


Is it worth calling the DNO, or will they simply say "supply working, do not worry" I suspect that the service cable is very undersized, but am aware that DNOs work to different rules.


I have moved combustibles away from the cable and advised reducing the load a bit,


  • 0
    Cables that run at 70 degrees, run with that as the metal core temperature, and certainly  the inside of the insulating jacket is at that temperature but the outside of the jacket where you touch it will be a few degrees cooler, though quite how many degrees will depend on airflow and mounting arrangements. If the outside is at 70 degrees and the cooling is good, then inside it will be a little bit warmer, so it if you are  looking at external temp and trying to push the insulation temperature right up the limits, this needs to be allowed for.

    Equally, all that happens if you overheat a cable is that it stinks,  and the insulation lifetime is somewhat shortened, it does not blow up immediately, rather a  few years are taken off the lifespan.
  • 0
    The 60 degree cable temperature was only my estimate, it might have been hotter. It was certainly hot enough to concern me, and I am not easily alarmed.

    The DNO have replaced the service cable because "it looked a bit cooked" and also replaced the cut out on grounds of age and general condition.

    The new cable looks like 50mm copper single core concentric and is run directly to the replacement pole mounted transformer, which is nearby. The existing overhead distribution is retained for the other 4 customers, but no longer serves the hospice.


    I was impressed by the speed with which the transformer was replaced.

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