EARTHING and BONDING ! construction site

[YOUNG4R]

new at this guys, excuse the lack of equittte

I have a question if anyone can help.
Designing a construction site install with feed from a TN.s Mains supply. I am planning to install 230 volt RCD Protected feeds to supply office porta cabins. I have been told, as part of the install I should Bond all the extranous metal workwork that is around the compound sorrunding the portacabins (i.E harris fencing). however, not sure how this works, Cos surely,If I Bond this metal work does this not create a different potential to the ground creating a shock risk for any one in contact with them both? Or am I being thick Any one put me straight?
:mrgreen:

[solo3uk]

Hi Young4r. The answer to your questions is to be found in BS7671 Regs as usual.

Reg 604-01-03 (i) says that, "the special requirements of construction sites shall not apply to construction site offices, cloakrooms, meeting rooms, canteens, restaurants, dormitories and toilets, where the general requirements of the regulations shall apply".

This means that you treat them as a domestic installation because it doesn`t say they are to be considered as caravans or anything like that. However many of these portacabins are made of metal and for that you apply Reg 413-02-02 (v). "In each installation main equipotential bonding conductors complying with Section 547 shall connect to the main earthing terminal extraneous conductive parts of the installation including the following, (v) exposed metallic structural parts of the building".

So besides all pipes of all services you should bond exposed structural parts. It is up to you to interpret if Harris fencing is a exposed structural part, but I would say no, other people will have other opinions.

All answers are to be found in the Regs, and remember they are written in legal language, that`s why it is very important to refer to them, because in case of trouble the electrically ignorant barristers will read them when trying to nail you, and will check you complied with them, however as they are trained in turning and twisting words, even if one complies, they always get you!!!.............that`s why I am training myself to like porridge for breakfast............