Is the caravan plugged in, or is it more like fixed wiring, and if the latter, what sort of cable ? There are caravans that are really static and more permanent than some houses, wired in SWA or with ducted cables, and then there are those that are more mobile, where the lead is a flex and trails over the grass for the lawnmower. I'd be more worried about the latter.  Its an odd choice anyway - I'd either expect 100ma time delay ('S type' ) or 30mA instant.

Mike.

I can see the dilemma. The definition of a caravan park is an area of land that contains two or more caravan pitches and/or tents, so a park consisting of only residential park homes, would seem not to be covered directly. Is 10 acres of statics "similar" to 9.9 acres of statics plus one tourer pitch? I'd probably assume yes, but I can certainly see the argument either way. It's similar to being allowed to use PME for a caravan on the drive or front lawn of a house (according to BS 7671, if not the ESQCR) but not on a camping site - even though the risks must be very similar.

I'd argue it was certainly good engineering practice to use the same rules as for a caravan park, but I would be wary of claiming t'other bloke was wrong.

   - Andy.

A residential park home is there and listed within the scope of the section and yet. Of a time some time ago a decision was made that the external supply point to a caravan (or similar) requires a 30mA RCD. A decision was made yet what is of more interest and indeed offers more understanding is the reason for the decision. The answer is almost always in the reason for the decision. Now I am not privy to any such discussions, oh if only we had a wiring regs equivalent of Hansards it would be wonderful. Yet consider what we know.

Is the concern for compliance with the letter of the regulations or some other issue? Mobile or static, A static in which folk reside, lets call them all one and the same for the sake of this response. Usually limited to 16A connection perhaps we may see a 32A connection. If so the external supply position as supplied is fitted with either a 16A or a 32 A 60309 socket. By this the supply is usually connect to the accomodation by a flexible cable. Be nice if it was HO7-RNF. What do we know about sockets?

In this case you have a 40A connection which would suggest a 'hard wired' connection to the accomodation. Is it a flex, swa or some other? Does the cable run from the external supply point to the internal consumer unit within the walls of the caravan? If it does and it's flex well, caravan site, or similar, or not, the general body of the regs still apply.

WHat about that 6A circuit does that require a 30mA rcd?

What is the earthing system on the site? Is this of relevance in the need for the dual RCD's.Why make a point of grouping all such under the 'or similar locations' banner well the possibility of dual earthing systems at play TN-C-S and TT would be one reason for such.

Then we have the manufacturer who wires the caravan / mobile home. They can only cater for what they know. They do not know the details of the site on which  the unit will in time be sited. For this reason they can only record the results of the 'dead' tests on the van at the time of the electrical install. Why 30mA rcd backed up with 30mA rcd, well the internal rcd can be easily explained.

Engineering decisions. In this case what purpose would replacing the 100mA rcd with a 30mA serve? Are there any factors, aside from a debate on a definition of a location, that by their impact would make life so much easier and require that the 100mA RCD be replaced with a 30mA rcd? That is after all the essence of the question.

Conjecture yes of course. What if the resident was an elderly person and on a dark wet winters night they trip. No lights. A nusiance trip is a nusiance ever more if you slip and break a hip. Electrical safety is paramount and as part of that we look to minimise nusiance and unwanted loss of circuits.

Hi, personally I would prefer to have a 100mA time delay RCD. But I was more after the definition of what was meant by similar locations. They are all fixed connections here wired in SWA and all had a 30mA RCD at the external meter enclosure which would have  met req 708.415.1 under residential park home. Not sure i would have changed a 30mA RCD with a 100mA RCD without knowing what actually was installed in the home. 

708.1 relates only to the distribution circuits. And it is the distribution and the associated earthing arrangments that I believe is the reason why residential park homes (which are not leisure accomodation or caravans) are in that paragraph that reads: 'In caravan parks , camping parks and similar'.

The similar being the distribution system feeding them. Only my understanding of course

No such thing as a "static home", although I would be surprised if mine moved.

If you have a peep below them, all those "mobile homes" have wheels beneath them to satisfy the planning conditions.

Yep got to have wheels, jacked up and bricked in certainly not going anywhere. 

@Colin Haggett 

What are the requirements for 30 mA RCD protection for the circuit supplied from the B6 MCB?

That does the street light outside. 

Have 411.3.4 and/or 714.411.3.4 been considered?