Caravan hook up

With respect, I think that Gino needs to learn a bit more about earthing.


I don't understand why SWA is proposed as a cable type - it does not appear to be exposed to any environmental hazards.


The problem with using the DNO's earth is, as Andy pointed out, that it is unlawful. It is unlawful because of the rare, but potentially lethal issue of a broken 'PEN' (= protective earth and neutral) conductor.


If it happened indoors, everything stops working, but the voltage of everything which is electrically connected can rise to mains voltage. Now if you touch your bright shiny kettle, you have the voltage across yourself to the kitchen floor; but you are wearing shoes and the kitchen floor also insulates you from the ground. If the same happens in a caravan, the whole thing including the chassis and other metal structural parts go up towards mains voltage. That may include a rail or handle by the door. This time, when you step out, your hand is at mains voltage and you may step onto wet ground so the resistance of the circuit can be much lower. If you aren't wearing shoes and the caravan site is bare (wet) ground, the problem may be a lot worse again.


So that's why you need a separate earthing system, which includes an earth rod.


HTH.

Good afternoon, thank you for everyone's posts. I really do understand this but caravans on sites hook ups are earth roded. But caravans are not from the hook up to the caravan. So for 100% protection caravans should have an earth rod fitted and connected to its chassis to make it safe at its parked postion in a field. Not just at the site hook up point.

Hardly practical.

Good afternoon, thank you for everyone's posts. I really do understand this but caravans on sites hook ups are earth roded. But caravans are not from the hook up to the caravan. So for 100% protection caravans should have an earth rod fitted and connected to its chassis to make it safe at its parked postion in a field. Not just at the site hook up point

Nothing's ever 100% safe. With TT systems the RCD is the weak point - research has showed that something like 7% of installed RCDs won't trip properly when required to (either not tripping at all, or too slowly). Earthing alone - without disconnection (at least with the sort of impedances a simple rod can offer) - doesn't provide foolproof safety.


Normally we say safety is adequate if two separate faults have to occur before danger arises - say a broken c.p.c. and an insulation failure, or (in the case of double insulated equipment) two separate insulation failures. Within an installation, a broken c.p.c. doesn't of itself give rise to danger - as long as there isn't also an insulation failure - the system is still unable to give anyone a lethal shock. On that score the approach for caravans is the same as for anything else - unless there's an expectation of high protective conductor currents a single c.p.c. or means of earthing is deemed adequate.


In fact not all caravan hook-up points have their own earth electrode (rod) - it's commonly done that way as that allows PME earthing to be used for the distribution cables and so avoids the complexity, cost and possibly reliability issues that can go with having multiple tiers of RCDs that would be needed for TT distribution. But where the distribution system is TT anyway (e.g. because it's fed from an Agricultural site or difficulties keeping earthing systems separate - e.g. where metallic piped services are used for static vans) then the hookup points can use the installation's earth facility with no extra rods are needed at each hookup. Very occasionally where it can be guaranteed that the earthing system is pure TN-S (say on a large site with its own transformer) caravans can be supplied from the main earthing system with no consumer's rods at all.


   - Andy.

Andy I thank you for your response. I actually now am thinking of looking at the new devices on the market used for EV chargers called a pen fault unit. Ones that measure and detect earth issues which in the event of a loose they isolate the supply to a charging point. I think this would work well as its designed for issues like this. I see that an amendment was issued with regards earthrod in bs7671. Also newer EV chargers are coming out with built in 18th edition with pen.

looking at the new devices on the market used for EV chargers called a pen fault unit.

As I mentioned earlier - BS 7671 doesn't currently recognise their use for caravans (the requirements for charging electric vehicles are a little different) - and is probably unlikely to while the law of the land (the The Electricity Safety, Quality and Continuity Regulations) prohibit the use of PME earth with caravans. You certainly wouldn't be able to certify the installation as complying with the wiring regs if you did rely on such a device.


  - Andy.

When I first saw this I thought it was April 1st, not Jan 1st. I like to pop into the forum occasionally to see what is on offer but recently I have noticed an ever increasing number of 1st timers. Nothing wrong with that, but many of them have little if any electrical knowledge. From the "EICR" testers who dont know a dangerous situation from further investigation, to the DIY self builders who think they know better than long established DNOs, this one is particularly interesting. Having come onto the forum for advice, and against overwhelming evidence that caravans are prohibited from utilisation a PME terminal, the writer insists on "looking at the new devices on the market used for EV chargers called a pen fault" "also newer EV chargers are coming out with built in 18th ed with pen" 


The "18th ed" cannot "allow"  a CNE network to be disconnected by any "gadget". Only the DNO can authorise variations in earthing requirements and this wouldnt happen. The EV rules for PME were set out by the DNO years ago, and this idea isnt in the requirements. 


My advice to this poster is to engage the services of a qualified, experienced electrician.


Regards, UKPN.

Thank you ukpn, maybe I am not explaining myself. I am not talking about a device cutting out anything with DNO. I was looking at a Viridian EV pen loss connection centre. New to market. A solution to not using an earth rod. I have never quoted my self as an fully qualified electrician, but know you guys are as I have an huge interest in this area.

I think the Wiring Regulations are written with the thought that caravans will be set up and used in the middle of a field, rather than on a house driveway that may have metal water and gas supply pipes running buried under it along with electricity cables as well as possibly telephone and other cables.


So simply hammering a rod in may create more problems than it resolves unless carefully  considered.