supply to steel container/ necessary bonding

[leep82]

Recently went to a job that another lad on our firm had started to give him a hand.

A 3 phase supply has been installed to a steel container ( 16 mm2 4 core SWA , and separate 16mm2 earth ). The container is to temporarily house medical gas/ vacuum pumps that supply various wards on our local hospital, whilst the current building undertakes some refurb work.

After reading many threads on here regarding this subject and printing of bits of information as a reference, i was quite surprised to see no main bonding conductor to the new great big shiny copper vaccuum supply pipe that enters the container.

There is no rod being installed as part of this cabins installation and it is my understanding that as a result of this we need a main bond back to the MET.
Problem being the board which we are using to take a supply from is not at the origin. It is one of many sub mains situated on the hospital. My query, is it acceptable to take the main bond to where we are picking the supply up from, as running a bond back to the MET would prove to be an absolute nightmare.

My line manager is under the impression that the pipe in question doesnt even require a bond, but as i said reading various threads on here and doing my own bit of research i thought id question it. He may however already be aware that said pipe is infact already bonded.

 

[Richard Burns]

The key thing about bonding is it is required for extraneous conductive parts that may introduce an earth potential, even if it is a nice shiny copper pipe it may not be connected to earth, although the fact that it enters a steel container, that may well be at earth potential, could cause it to be inadvertently at earth potential. You would need to check before bonding it.

Using the sub board as an earth marshalling terminal for the bonding back to the MET is acceptable so long as the board itself is connected back to the MET by a suitably sized cable.

 

[davesparks]

The chances are pretty high that the steel container itself will need bonding.
And that the services joining it to the other building will be earthed in the other building.

There are some good diagrams in GN8 which show what should be done as far as bonding such services goes.

 

[Engineer54]

There is a more than a good chance that all medical gas pipework has been effectively bonded somewhere within the hospital building/complex. As stated above the metal container will probably need bonding down too, especially if it's sitting on bare ground or on concrete footings....