In the UK its against regulation to supply caravans / campers / motorhomes from a PME (TN-C-S) supply according to Section 721 of BS7671. Section 717 of BS7671 also starts that PME supply would need to be under supervision to supply a mobile unit like a food truck and this is applied by organisation like the BBC on OB trucks, the supply earth is checked before connection.
In one of my days jobs (sound systems) we meter the mains before connection to ensure no broken PEN (loss of neutral) which could, although unlikely cause metal work to raise to dangerous voltages.
When we quote for a job we do some level of risk assessment to see if we need to add features to an installation to ensure all is good. For example someone who has a caravan on the drive long term with a PME install would maybe need the outside socket turning into a TT installation, although that is not that easy in built up areas due to underground services which would also raise to dangerous voltage levels close to the TT rod, so likely doesn’t remove the issue 100%.
After much google searching this topic does not seem to get discussed too much and we see food trucks and caravans on drives all the time with a trailing lead to the house, so am I been over cautious? I have a job coming up on a mobile bar and it will get plugged into anything from farms to houses to pubs and the operator can not be expected to check the mains. Therefore I see 2 options:
- Isolation transformer to make the bar an IT system (maybe also need insulation monitor too)
- Use an over / under voltage monitor between L-N to disconnect all 3 conductors entering the vehicle in case on a PEN fault
Both options obviously cost money, the voltage monitor is cheaper than the transformer option...
Any thoughts from installers in the UK?
Thanks,
Simon...
