Caravan hook up

Is the caravan fixed or moveable. How far from the socket is it likely to be .



Gary

Andy thank you for taking your time. Wow so complex, funny as I was actually going to by a ev chrager pen device which monitors earth and will disconnect the supply. My thoughts were because my new hook up box will be connected next to the incomer box and all the wiring swa would be inside and very short that I could install without a rod as the risk of loose of earth would be very reduced as its so short, not like a caravan site where the hook up is in a field.

The complication with caravans is that the ESQCR prohibits the use of a PME earth connection for a caravan (or boat) - and since UK DNO's are liable to interconnect N and PE during network alterations the only safe policy is to assume that every DNO supplied earth terminal could be PME (unless there's been explicit assurance from the DNO otherwise). So generally the caravan socket will need to be connected to a TT system and separated from any DNO's earth facility. If the installation is already TT, then it's simple and no extra rod is required - it can just share the installation's.


Driving in a new rod will of course require a lot of care - not just from the risk of hitting exiting buried services (quite likely if you're next to a meter box and the supply is underground...) but really you should keep the rod well away from any underground metalwork that's connected to the PME system (old gas and water pipes, or lead sheathed cables for instance) otherwise you still have the same problem of the caravan's earthing system being taken to hazardous voltages should the supply CNE go open circuit. Ideally it should be subject to the same potential as the ground the caravan will be stood on, but that isn't necessarily straightforward when buried metalwork can have an influence over a much shorter distance than the length of a caravan.


Electric vehicle charge points have the same problem - and for them there is an option of using the PME earth together with a device that disconnects everything (L, N & PE) if an open-CNE is detected. They are a little controversial however (especially the single phase L-N voltage monitoring types) and as far as I know aren't recognised by the regulations for use with caravans.


   - Andy.

repost this in the wiring forum, and you will get a better informed set of answers, it is a perfectly sensible question but in the wrong place.

But please first find out how is your house earthed now -

TT

PME

TNS

?

you will need to know that as it affects the answer.

Also how is RCD protection afforded for the new circuit?


best regards Mike.

This is not a great question for a forum, you should really consult a professional who can provide the relevant calcs/testing and insurance.


Earthing is predominantly to provide an equipotential path that is common, as far as possible across the entire supply network so that faults that connect directly and indirectly to the physical earth will cause a large enough current to operate a protective device and disconnect the fault. Using an earth rod or not depends on the fault-loop impedance, as measured from a suitable test device (or calculated), the type of supply provided by the distributer and the types of protective device that are used. Because there are several variables, it is not a simple question of "yes use one" or "no, don't bother".