Bonding Structural Steelwork

[equitum]

A friend runs a business from a typical commercial premises, single storey, say 100sqM, on an industrial estate. A recent PIR identified the absence of main bonding conductor(s) to exposed structural steelwork. (The premises is essentially a steel frame of RSJ type steelwork bolted together and then clad in sheet material, so its exposed in lots of places!)

My question is: Would one 10mm bonding conductor from the MET be adequate, I propose a hole drilled into a suitable point and a lug bolted to the steelwork. If after continuity testing around the building any points on the framework were found to be not connected to the rest by the bolts holding it all together then I propose additional bonding conductors back to the MET. (or could I link them in a similar way with short links of 10mm?)

Whats the usual bonding approach/method ?

 

[Spark123]

How are the building girders joined together? Do you have access to guidance note 5?

 

[equitum]

As I recall, bolted together. Don't have access to GD 5, had a search on the net but only update sheets available

 

[RF Lighting]

The CSA of the earth cable required to bond the steelwork depends on the earthing system provided by the DNO, and also the CSA of the main neutral conductor.

 

[equitum]

The CSA of the earth cable required to bond the steelwork depends on the earthing system provided by the DNO, and also the CSA of the main neutral conductor.

Thanks, thats the basis on the choice of 10mm. I can see my post was not clear - My uncertainty in summary was around whether I could daisy chain elements of the structure found not to be electrically connected together but nevertheless deemed to be extraneous conductive parts, and also what method of termination should be used on the steel girders.

Having thought more about it, this is no different to taking one (continuous) cable from the met, to, for example the gas service and then to the water supply, and therefore should be permissible.

I guess the difference in steel work to gas or water services is that it could be earthed in several points and does not necessarily form a continuous electrical circuit.

 

[securespark]

The good news is, once the frame is bonded, you can tap off for the meb's to service pipes & ducts.

 

[Spark123]

From what I can gather it is more or less if the girder connections are electrically reliable then only the one connection is required. GN5 shows labels placed at each joint on the structural steelwork!! If doubt exists over electrical continuity then continuity checks should be carried out. Advice should also be sought from the DNO re sizing. As the building framework is an extraneous conductive part, supp. bonding may also be required in special locations.