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Caravan Site - Overheating supply neutral connection on pitch RCDs

DMB

Hi,

Am presently staying at a farm caravan park in south of England and the owner has shown me a problem he is having with some individual pitch electrical devices. Apparently, over time a number of the Type C  16A RCD devices have been affect by the INCOMING supply neutral connection overheating. Seems unlikely to be loose connection on so many devices and device are not tripping. 
site is served by overhead 2 phase connection with single phase distribution to at least 3 sepeate areas built at different times. Pitches are served by buried SWA and marked up as “ring”. RCDs are British supplier and all other connections on the 30mA device are clean and unaffected. Are we looking at an harmonics problem or distribution system fault. All suggestions welcome (It won’t spoil my holiday) Thanks

Dave



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  • 0

    I doubt that harmonics are a problem on relatively small and single phase loads.

    I also doubt that a distribution system fault is to blame, no common or likely fault would increase the supply current, but not trip the overload protection.

    Probably poor connections leading to simple ohmic heating. Either poor workmanship by the installers, or poor manufacture of devices resulting in poor internal connections. Possibly not helped by frequent overloading and repeated re-setting. Damp may have corroded connections and resulted in heating.

  • 0 in reply to broadgage

    We have mused this sort of thing before, and wondered last time for water heaters I think.. Unless the supply loops through the incoming terminals onto the next it is hard to see how more heat would be created in live than neutral - presumably they are within 30mA of each other...
    So we have to conclude the heating curretn is similar but cooling is not as good, either because the layout of the cables in the box is assymetric, or because inside the device that terminal has less metal attached to it to act as heatsink.  I do expect the two sides to be different, as in the RCBO, the live connects to the current sensing part with its heater and coil, the neutral has a contact and passes the sensing coil.
    It may be an age thing, but I preferred traditional terminals with round cable tunnels and double grub screws - a rectangular cage only sort of hits where it touches, and that is not really an all-round contact.

    M

  • 0 in reply to mapj1

    Why is the RCD dirty?  Could there be enviromental factors

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