Can i use the steel?

[Jas0n7]

Hey Guys,

I'm wiring a warehouse at the moment. I have the mains panels in one corner of the building. out of the mccb panel i have bonded the structural steel with a 25mm earth, bolted, lugged, labled everything.

Now heres my question, all the services come in the other end of the warehouse. instead of running a 10mm earth from one end of the building to the other cant i bolt, lug and lable a 10mm cable to the steel near where the water comes into the building and then earth clamp it to the water main?

I'm 99% sure you are able to do this but i can't find it in the regs book anywhere?

Please help!

 

[Paul.M]

Reg 411.3.1.2.... "shall connect to the main earthing terminal". How far away is your run? Has to go back to the main earth term I'm afraid. Unless, erm. Is it possible to give them their own earth rod? In thus case it would sound like a much easier option, is it possible?

 

[pevvers]

I disagree, there's actually a thread going on in the IET forums at the moment with the same question. As long as it's a sound structure unlikely to fail then it can be used as far as I see...

 

[IQ Electrical]

Nothing wrong with using the building's metallic structure as a protective bonding conductor, this is not often seen because it is misunderstood but in many cases, it is by far the best solution in commercial/industrial installations.

Yet another subject to add to that myths thread!

 

[Jas0n7]

I disagree, there's actually a thread going on in the IET forums at the moment with the same question. As long as it's a sound structure unlikely to fail then it can be used as far as I see...

I agree because the csa of the steel is massivly larger than a 10mm single core cable.

Do you have any links to this thread you are talking about?

ta

 

[Jas0n7]

Nothing wrong with using the building's metallic structure as a protective bonding conductor, this is not often seen because it is misunderstood but in many cases, it is by far the best solution in commercial/industrial installations.

Yet another subject to add to that myths thread!

can you back this up by any regs tho because thats the first thing my boss will say i i decide to do it this way!!

 

[IQ Electrical]

Well it's the way you interpret the regulations, as the ECA Guide to the 17th puts it 'if this technique is considered, it is obvious that the structure and metal services will form part of the bonding network whether you like it or not'

There is a diagram included showing 1 bond to the steel structure and numerous other services bonded from the structure, obviously a BS951 type label must be included at any such connection.

I'd scan the diagram but I don't have a flat bed scanner.

 

[Paul.M]

Try reg 542.3.1 and 542.3.2 with table 54.1. Not protected against corrosion 50mm in steel. I miss out the word "warehouse" in your question. Hope these regs help.

 

[Paul.M]

Oh and reg 542.2.1 iv. I think that is what your after.

 

[pevvers]

From the aforementioned thread on the other forums....

I'd go along with that - bond the steel near to the MET and then just loop off the steel frame at convenient locations for the water, gas and oil.

If the steelwork is together enough not to fall down then it's odds on that it has sufficient continuity and section to be a bonding conductor.

You could look at 543.2.2 (vii) and 543.2.6 for clarification

 

[Paul.M]

Yah, all the regs posted go hand in hand.542.3.1 gives csa minimum as per table 54.1.....542.2.1 iv gives you "underground structural metal work embedded in foundations....543.2.2 gives permission to use (vii) and 543.2.6 tells us what is prohibited for use as a protective conductor.

 

[Deleted member 9648]

Reg 411.3.1.2.... "shall connect to the main earthing terminal". How far away is your run? Has to go back to the main earth term I'm afraid. Unless, erm. Is it possible to give them their own earth rod? In thus case it would sound like a much easier option, is it possible?

That would introduce an earth potential to the building and totally defeat the purpose of main bonding.

 

[Paul.M]

But its what the regs say. I don't agree to it as well. Ok another question. Lightening conduit, if a person is stood outside having a cig resting against the conduit when the spike is struck by lightening, is this safe? I haven't looked into lightening protection yet.

 

[Jas0n7]

But its what the regs say. I don't agree to it as well. Ok another question. Lightening conduit, if a person is stood outside having a cig resting against the conduit when the spike is struck by lightening, is this safe? I haven't looked into lightening protection yet.

it is safe because the current will take the route of least resistance. which will be the copper lighting conductor.

 

[IQ Electrical]

Paul, I think wirepuller was referring to the "Is it possible to give them their own earth rod?" part of your post, that would certainly not comply with the reg's and would introduce different potentials on metalwork along with the dangers that that would present.

The lightning protection system is risk management and I haven't seen a single documented case of injury while in contact with a tape, can you imagine the odds of it happening?