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RCD's and vibration

Paul Brewerton

Where RCDs are installed in areas such as mobile welfare units, caravans, towable catering units, etc)

After being transported from A to B, are they likely to have suffered any detrimental effects (particularly due to vibration) caused during transit?

Case in question is self powered mobile welfare units we have on site, which are tested prior to delivery and found to be functioning correctly. 

Cabin manufacturers have stated that there is no need to test again, after every time the unit is moved, and indeed would be impractical and overkill in many instances, yet I have someone claiming that RCDs fail due to vibration. 

My gut feeling is this is nonsense, if an RCD is tested at any time and found to not function, how would it be determined that the root cause was transit vibration anyway? 

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  • 0

    It rather depends, road transport on a vehicle withe pneumatic tyres is likely to be very gentle. If you had in mind cross country transport in a tracked vehicle like a tank or a JCB then it is a different game. (in the past I have had to consider the latter, and then the switch gear is mounted on something like engine mounts so it can bounce about without coming to grief, and wago type connectors are everywhere.)

    In the end wiring frets and rubs through the insulation, terminal screws loosen and some kinds of fittings may come undone, but not on a timescale that will be missed by annual inspections.

    The RCD is not much  more likely to fail than a light switch, and the  mechanism is the same.

    Far more likely on a caravan type unit is that on arrival the shore power supply is not the same as at the point of testing, and genset neutral earth bonds are either duplicated, so the RCD won't stay on, or missing, so the ADS does not work as it should.

    Mike

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  • 0

    It rather depends, road transport on a vehicle withe pneumatic tyres is likely to be very gentle. If you had in mind cross country transport in a tracked vehicle like a tank or a JCB then it is a different game. (in the past I have had to consider the latter, and then the switch gear is mounted on something like engine mounts so it can bounce about without coming to grief, and wago type connectors are everywhere.)

    In the end wiring frets and rubs through the insulation, terminal screws loosen and some kinds of fittings may come undone, but not on a timescale that will be missed by annual inspections.

    The RCD is not much  more likely to fail than a light switch, and the  mechanism is the same.

    Far more likely on a caravan type unit is that on arrival the shore power supply is not the same as at the point of testing, and genset neutral earth bonds are either duplicated, so the RCD won't stay on, or missing, so the ADS does not work as it should.

    Mike

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  • 0 in reply to mapj1

    Thanks for the reply mapj1,

    Indeed in our case the cabins have travelled on pneumatic tyres. I get that electrical connections in general may work themselves loose in time, but the point my 'colleague' is making, is the RCD itself will fail. I cannot see it myself, but am willing to be educated if this is the case. I have just spoken to technical at a well known manufacturer and supplier, and they also have never heard of a case of RCDs failing specifically because of transit caused vibration. 

    I maintain that it is a good idea to do our own checks and due diligence which is simpler if we have electrical knowledge, but when the cabins are delivered to other trades such as road workers, the cabins are ready to operate as soon as they land. Two manufacturers of the cabins have separately stated to me that the cabins do not need testing upon arrival as they are pre-inspected and tested prior to delivery and come with certificate as good to go.

    This thing about RCDs failing after transit is a red herring in my view, but again, I'm happy to stand corrected if anyone can show me otherwise.

    Thanks again.

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