Using extraneous metal as bonding conductor

[drzsta]

Hi,

Scenario, Oil service to a church boiler is at the furthest point to the distribution board. Rather than run a separate bonding conductor to the oil service I've decided to bond the 3" cast iron heating pipework local to the DB then take a fly lead at the boiler from the CH pipework to the oil.

543.2.6 seems to permit this and I'm not worried about somebody adapting the pipework in future with plastic being that it's a church and the run is all on show.

Anybody have a different opinion on this?

 

[Deleted member 26818]

As long as the pipe you intend to use is not a fuel pipe, it will comply.

 

[Deleted member 9648]

Might be tricky to show that electrical continuity is assured,as per note (i),and you will need to show that it's cross sectional area is equivalent to the required size in copper.

 

[Deleted member 9648]

As long as the pipe you intend to use is not a fuel pipe, it will comply.

There are a number of requirements that need to be met for it to comply, your statement is misleading. Read the entire regulation.

 

[drzsta]

Might be tricky to show that electrical continuity is assured,as per note (i),and you will need to show that it's cross sectional area is equivalent to the required size in copper.

Can't be much more "assured" than having heavy gauge screwed steel pipe. As for Csa equivalent pretty sure I'm good there too if 32mm conduit is equivalent to a 15mm2 copper cable.

 

[Deleted member 9648]

Can't be much more "assured" than having heavy gauge screwed steel pipe. As for Csa equivalent pretty sure I'm good there too if 32mm conduit is equivalent to a 15mm2 copper cable.

I'm sure you are right, you could measure the resistance of the pipes and record it on the cert, and your call on whether 'pretty sure' is good enough regarding CSA equivalent.

 

[Darkwood]

Personally I would be happy with using continuous structural steel as a bridge over long distances but from experience service piping is prone to alteration or removal, as this would break the bond I wouldn't entertain the idea, because you are not using a continuous unbroken bonding wire that may do more than one service you do leave the possibility of the installation becoming unsafe due to other trades who lack understanding of bonding reqiurements.

 

[drzsta]

Bit of a PITA to do it any other way. All of the run is exposed to the eye on natural stone walls. Micc would be the only decent looking alternative.

Interesting point, anything stopping me running a 2l2.5* micc as a bonding conductor and linking the inner cores and sheath together? Taking into account micc sheath Csa and conductor Csa I would be over the required main bonding size.

*because I have some in the garage

 

[davesparks]

Bit of a PITA to do it any other way. All of the run is exposed to the eye on natural stone walls. Micc would be the only decent looking alternative.

Interesting point, anything stopping me running a 2l2.5* micc as a bonding conductor and linking the inner cores and sheath together? Taking into account micc sheath Csa and conductor Csa I would be over the required main bonding size.

*because I have some in the garage

If they can stand the cost of it then I see no problem with it, and I have given a bit of thought to this exact idea in the past when trying to overcome such a situation.
Although I'm sure it would confuse a few people looking at it I think you could reasonably sweat a lug directly on to the end of the MICC sheath.

 

[PEG]

If your calcs are done,and MICC would be aesthetically acceptable,why not use one of the cables or tapes used in lightning protection?

You could shine it up like MICC,it would be commensurately smaller,for the same CSA,and there are a good range of sturdy,tidy clips,applicable to that product.

 

[davesparks]

If your calcs are done,and MICC would be aesthetically acceptable,why not use one of the cables or tapes used in lightning protection?

You could shine it up like MICC,it would be commensurately smaller,for the same CSA,and there are a good range of sturdy,tidy clips,applicable to that product.

That's a very good point, lightning conductor is available as a circular section solid bare copper conductor, although sizes probably start a bit bigger than 10mm!

 

[ruston]

There is two lightning conductor on our local clinic. one is the usual broad flat type , the other looked like 10 mm micro bore.
I believe it was stolen during the recent high copper prices.

 

[UKMeterman]

Circular lighting conductor is 50mm2

 

[ruston]

Circular lighting conductor is 50mm2

I wonder what concoction this was then. It ran parallel with the flat and was connected to it.

 

[Leesparkykent]

I wonder what concoction this was then. It ran parallel with the flat and was connected to it.

Maybe it was the bonding conductor to the lightning protection.