Hi I am sorry if I have hijacked someones post here but it is something I am concerned about. It is not just the person using the installation, but family and friends and even passers by who can be affected (lethally).
Also do remember if you dont follow safety guidelines and something happens it is YOU who are liable and should an insurance claim be met your company will run a mile, do it once and do it right..............
The socket on the van needs to be linked as close as possible to the consumer unit inthe van. The length of the cable between what you are plugged into and the van is irelevant, although by LAW it should not be longer than 25 metres. With regards to what you might be plugged into DONT TRUST IT.
Firstly it might be a caravan site bollard with both RCD and MCB that have to be tested by law and have an installation conforming to both Part P legislation and to 17th edition regulations. However you cannot test the RCD yourself in most cases at the bollard, so how do you know it is working? In marinas they have to be accessable, in caravan parks they do not and often they are sealed to prevent you resetting the trip.
Secondly you may be plugged into a friends house, most of the above applies.
Thirdly you may be plugged into a generator, well nuff said.
Fourthly you may be on the continent where things electrically speaking are different, the European appliances tend to use double pole isolating switches so polarity of wiring is less important than here were we isolate more on a single pole switch. Most but not all experienced European campers carry something like a martindale tester
http://209.85.229.132/search?q=cache:da ... clnk&gl=uk" onclick="window.open(this.href);return false;
and a short hookup lead clearly marked "reverse polarity" and wired accordingly.
The link below shows how things should be done re motorcaravan or caravan wiring according to the sixteenth edition which has now been replaced by the seventeenth, however I have not yet looked into what differences the seventeeth edition makes to caravans, but only to fairground installations and marinas which is my main (professional) concern.
http://www.tlc-direct.co.uk/Book/7.9.2.htm" onclick="window.open(this.href);return false;
HTH