RCD's and vibration

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

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.

I'm inclined to agree - unless you know it will be towed over the Ural mountains first or something, it is not likely to go wrong between dispatch and arrival, and then there are loads of things that might go adrift where  an electrical test may not show it anyway. RCDs are not high on that list.
If folk are that bothered then having a plug in socket tester plugged in permanently and a 'please try the RCD test  button on first switch on and call this no if anything funny happens' is as far as due diligence needs to go, and pretty much anyone can handle that.

Mike.

PS I have worked on something that considered 1,000 hours transport on a sponson on the side of  a tank to be a reasonable re-inspection interval for vibration damage.  A few hours on tyres down the motorway is nothing....

Mind you it had no RCDs ;-)
Mike.

I have a similar problem with our brand new Swift caravan.

The DB is fitted on it's back and everytime its moves to a new location, it switches off and I have to reset it. No one sems to have an answer but the dealer has suggested he orders a new one but I feel the result will be the same.

I would not consider a 'trips and has to be reset' to be a serious failure mode. Might be best to transport it 'tripped' anyway so that on arrival someone has to bother to find the thing to turn it on.

Would it be too much to require that the test button be tested on arrival? (And then recorded along with any other checks before the cabins are put to use.)

+1 for the caravan comparison - and in that case it's not always a nice smooth ride even with pneumatic tyres - many a camp site is down what's effectively a farm track consisting of potholes separated by randomly orientated bricks - quite enough to fling anything that's not fixed down from one end of the caravan interior to the other. Ordinary crockery doesn't last a single journey - yet even the cheap never-heard-of-at-the-wholesaler brands of RCCB seem to survive for years without issue.

   - Andy.

Isn't this covered by suitable lower recommended inspection periods, for example GN3 recommends the maximum period between inspections and tests for caravans is 3 years.

There are other factors than just road vibration. My experience tells me the environment in which a mobile installation is used can be a greater factor than the transportation between locations. For example, welfare cabins used in construction sites, the switchgear suffers with the dust on those sites, which, especially with dampness in use and storage causes all sorts of problems including corrosion that can cause mechanical problems, or increase the resistance of breaker or RCD contacts (to the point the device overheats) etc. - so perhaps in that environment we might be edging periodic verification down to the 3 months recommended in GN3 for construction sites (if that is where the unit is used every day) ... but whilst this might be valid for a unit that's dumped on some construction sites, it might not be for all construction environment welfare units, so for example a highway maintenance team's unit might not be subject to the same dust, especially if the maintenance team is only looking at lighting or signals/communications as a stand-alone activity.

Duty Holder's Risk Assessment I guess is the answer.

Thank you for the opinions and feedback to all.