Earthing structural steel

kramer1

On my last inspection , the inspector wanted to know if I had bonded any structural steel on the job, there was none. How are lads doing this , alright to drill an RSJ and stick a nut n bolt with earth lug?

Risteard81

To be pedantic you mean bonding, not Earthing.

kramer1

Risteard81 wrote: »

To be pedantic you mean bonding, not Earthing.

Fair enough

2011

Risteard81 wrote: »

To be pedantic you mean bonding, not Earthing.

Not only can structural steel be bonded, it can also form part of the earthing system. In many larger buildings this forms part of the lightning protection system too which is of course connected to earth rods, see link:

http://apqi.org/pdfs/Aneesh-OBO-Bettermann.pdf

2011

There are a number of ways of connecting to RSJ's, these include:

1) The simplest is when they come supplied with a threaded earth boss welded to the RSJ, like this:


2) As suggested you could drill and insert a bolt (M10 or M12) with star washers to ensure a "good bite". This can result in corrosion so Denzo type tape.

3) Exothermic weld which can be complicated and expensive but provides a great connection.

The use of 25 x 3mm copper tape has become increasingly popular for this purpose in recent years.

kramer1

2011 wrote: »

There are a number of ways of connecting to RSJ's, these include:

1) The simplest is when they come supplied with a threaded earth boss welded to the RSJ, like this:


2) As suggested you could drill and insert a bolt (M10 or M12) with star washers to ensure a "good bite". This can result in corrosion so Denzo type tape.

3) Exothermic weld which can be complicated and expensive but provides a great connection.

The use of 25 x 3mm copper tape has become increasingly popular for this purpose in recent years.

Appreciate the advice , personally I think it's a bit much to have to bond it in the first place, it's going to be slabbed and plastered , but the reci man says bond it , then by God it shall be bonded

Risteard81

2011 wrote: »

Not only can structural steel be bonded, it can also form part of the earthing system. In many larger buildings this forms part of the lightning protection system too which is of course connected to earth rods, see link:

http://apqi.org/pdfs/Aneesh-OBO-Bettermann.pdf

It could be used as an Earth electrode, but that isn't what was being discussed.

2011

Risteard81 wrote: »

It could be used as an Earth electrode, but that isn't what was being discussed.

Incorrect, read the title of the thread.
What was being discussed was “earthing” of structural steel. You stated in the 2nd post that the OP should consider it “bonding” instead of “earthing” of structural steel. This is not necessarily correct as this implies that structural steel would not be earthed when in fact it frequently is. An example I gave is for lighting protection. Earthing of the structural steel can be achieved by connecting the steelwork to earth electrodes / earth pit.

Bruthal

Risteard81 wrote: »

It could be used as an Earth electrode, but that isn't what was being discussed.

So structural steel can only be bonded, but not earthed? Is that an EU or UK thing?

Andrea B.

kramer1 wrote: »

Appreciate the advice , personally I think it's a bit much to have to bond it in the first place, it's going to be slabbed and plastered , but the reci man says bond it , then by God it shall be bonded

There are numerous dangerous scenarios that could present themselves by metalwork not been equipotentially bonded and connected to system earths. Personally sick of finding unconnected earth wires under steel sinks in certified installations.

Bruthal

Andrea B. wrote: »

Personally sick of finding unconnected earth wires under steel sinks in certified installations.

Two copper pipes come to a standalone piece of metal(sink). Pipes bonded.

Does the sink need bonding....

Im more curious than anything.

corkgsxr

Ask a electrician and a block of wood needs to be earthed/bonded if it has a nail in it.

kramer1

Andrea B. wrote: »

There are numerous dangerous scenarios that could present themselves by metalwork not been equipotentially bonded and connected to system earths. Personally sick of finding unconnected earth wires under steel sinks in certified installations.

Agreed, sinks should be bonded , not so sure about an RSJ that s going to be slabbed and plastered, but if that's the way they want it then that's what I'll do. Only brought this up as I was curious to see if anyone else had come across this issue and if so , how had it been resolved. I'm wary enough of drilling any structural element of a build , even if it is just for a small hole

Bruthal

kramer1 wrote: »

Agreed, sinks should be bonded

That might not be as clear cut as simply saying it should be earthed/bonded. Metal structures such as pipes or RSJs may be earthed somewhere by the nature of their structure, so bonding all may be wise to ensure equal potential at all times(not necessarily 0v in some fault conditions). A sink however, can possibly be an isolated metal part where bonding wouldn't offer any advantage, and in theory could be a disadvantage.

In the cases mentioned above about sinks not being earthed, that's more likely because its difficult in many cases, rather than the contractor thinking its unnecessary.

2011

kramer1 wrote: »

Agreed, sinks should be bonded , not so sure about an RSJ that s going to be slabbed and plastered, but if that's the way they want it then that's what I'll do.

With the greatest of respect, sometimes "they" need to be challenged.
In order to present a risk of electric shock the RSJ must be at Earth potential and must be accessible. Is this the case? assuming that the installation has a 230V supply if the resistance between the RSJ and the MET is >7.667 kΩ then it can be argued that it is not extraneous conductive part and as such may not need to be bonded. In fact connecting a bonding conductor to some conductive parts such as this can make the an installation more dangerous. Why? Because under fault conditions these parts may become raised to the level of the fault voltage. Under these conditions a person touching this part could receive a shock (at touch voltage) that they would not have received if it had not been bonded.

Look around you and it will become obvious that many items such as the raised computer floors, metal shelving, filing cabinets, metal tables (like those that a butcher uses), metal frames for suspended ceilings, metal window frames are not bonded (in most cases) and nor do they need to be as they are considered to be sufficiently insulated from earth.

kramer1

Rang the engineer on the job , asked him if it was alright to drill the RSJ s , gutter bolts n lugs . Cheers for the replies and the refresher courses on earthing/ bonding