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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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    DMB said:

    o I raised this problem quite some time ago with regard to a caravan camp site where the owner was having the local pitch MCB being replaced at random due to over heating of the neutral connection on the MCB.

    At the time I could not explain what was going on.

    Since then I have been involved in a more serious example of the same but devices were being burnt out, cables were melting and protective device were tripping randomly.

    The answer/ cause.............................................Harmonics.......................yep the one every body hears about but sometimes do not realise its a real world issue.

    At the moment, without further information,I can envisage two situations, either:

    (a) Perhaps I'm missing something, but if this is a single-phase RCD, that has been selected in accordance with BS 7671 (well, at least the latest version) ... If the issue is harmonics, that must present as a residual current at the RCBO ... or are we saying that the device ought to have been a Type F ?

    OR

    (b) The harmonics are on a "loop-in" (radial circuit arrangement) to the RCD, and it is on that ("line") side of the RDC that the burning occurs ?

    Could you be a little more specific ?

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  • 0
    DMB said:

    o I raised this problem quite some time ago with regard to a caravan camp site where the owner was having the local pitch MCB being replaced at random due to over heating of the neutral connection on the MCB.

    At the time I could not explain what was going on.

    Since then I have been involved in a more serious example of the same but devices were being burnt out, cables were melting and protective device were tripping randomly.

    The answer/ cause.............................................Harmonics.......................yep the one every body hears about but sometimes do not realise its a real world issue.

    At the moment, without further information,I can envisage two situations, either:

    (a) Perhaps I'm missing something, but if this is a single-phase RCD, that has been selected in accordance with BS 7671 (well, at least the latest version) ... If the issue is harmonics, that must present as a residual current at the RCBO ... or are we saying that the device ought to have been a Type F ?

    OR

    (b) The harmonics are on a "loop-in" (radial circuit arrangement) to the RCD, and it is on that ("line") side of the RDC that the burning occurs ?

    Could you be a little more specific ?

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