Use of SWA armour as protective bonding conductor?

[Deleted member 26818]

Yes that's exactly what I'm suggesting.
To my mind, a conductor can be both a bonding and a CPC at the same time.
Just waiting for someone to disagree and state that the 10mm² has to be a single condutor, or that both conductors have to have the same CSA or something.

 

[Guest123]

Yes that's exactly what I'm suggesting.
To my mind, a conductor can be both a bonding and a CPC at the same time.
Just waiting for someone to disagree and state that the 10mm² has to be a single condutor, or that both conductors have to have the same CSA or something.

Lets have your reasoning then.

 

[SW1970]

Thinking that the protective bonding conductor may have to carry large fault current in the event of failed incoming neutral or neutral of the distribution circuit. In this case, the distribution circuit is protected by RCBO so it should trip anyway?

 

[Deleted member 26818]

Lets have your reasoning then.

I was assuming that the 6mm² CPC was adequately sized.
With PME, the CSA is chosen so the conductor can withstand diverted neutral currents for long periods of time, rather than earth fault currents for short periods of time.

 

[netblindpaul]

There has been research and testing provided to the "industry" that goes along with the idea that the fault current will be shared acceptably by an internal core & the SWA, & / or an external cpc, the internal core & the SWA.
So you can do any of the above.
Also if you check GN1 you will get armour csa's for compliance with table 54.7, from this you should be able to assess your suitability.

Also you can use the adiabatic to size bonding conductors.

 

[Guest123]

I was assuming that the 6mm² CPC was adequately sized.
With PME, the CSA is chosen so the conductor can withstand diverted neutral currents for long periods of time, rather than earth fault currents for short periods of time.

My view is that we cannot guarantee how much fault current will flow in which conductor so one should be sized to carry out the function solely.

 

[alli]

if its any help, there is a good background reading on using earthing/bonding at
steel wire armour as the earth conductor

 

[johnboy6083]

There has been research and testing provided to the "industry" that goes along with the idea that the fault current will be shared acceptably by an internal core & the SWA, & / or an external cpc, the internal core & the SWA.
So you can do any of the above.
Also if you check GN1 you will get armour csa's for compliance with table 54.7, from this you should be able to assess your suitability.

Also you can use the adiabatic to size bonding conductors.

Not sure about being able to size main bonding by adaibatic with TNC-S paul? i think your allowed to on TNS & TT.

 

[Deleted member 26818]

My view is that we cannot guarantee how much fault current will flow in which conductor so one should be sized to carry out the function solely.

Both as I understand it are sized adequately to carry the fault current.
The armour apparently is equivalent to 15mm2, with regards to k2/k1.
It's just the conductance equivalence that doesn't meet the requirements.

 

[netblindpaul]

Lenny,
I understand your point, but one of the major players has commissioned research, and it has been done & published, it states that you are fine with the scenario I describe.
The research is on the internet somewhere, I think I also have it on my disk, but I can't look now sorry guys.
Wife's car has just broken down, why when we are skint!
Running on 3 cyls by the look of it, that's only half the engine, so big problems.
May be back later, or if I'm not around for a few days, sorry but I may be doing car mechanic type things!!!

 

[Deleted member 26818]

I believe this is the item you are referring to Paul:
http://www.wiley.com/legacy/wileychi/eca_wiringregulations/supp/Appendix_16.pdf

 

[Guest123]

Thanks Spin, looks like an interesting one.

 

[Engineer54]

Thanks Spin, looks like an interesting one.

A Very interesting one Lenny!!
In fact, ....Can you include this report into the the sticky relating to the use of SWA as a CPC??

 

[netblindpaul]

Non new info guys this has been around quite a while!

Blocked fuel pump inlet/stuck fuel pump, question is, will it happen again....

(referring to earlier post!)

 

[Deleted member 26818]

Non new info guys this has been around quite a while!

Blocked fuel pump inlet/stuck fuel pump, question is, will it happen again....

(referring to earlier post!)

Might, might not, who knows?