OP
Search the forum,
E
H
B
And the reg that tells you not to?
Not saying you have to include it in the CPC size above the cable conductor CPC size but there is nothing stopping you using it ...... reg 543.2.1
E
Why would anyone be bloody daft enough to include a CPC in earthed trunking containment system?? lol!!
B
Strangely enough I have come across a few cases in the past where the 'electrican' was taught on his course that as good practise you should run a seperate CPC to the conduit/trunking ...... new type "apprentice" electrician not a short course!
H
I agree but if you're carrying out EICRs then you will come across it - there have been instances in the past (80s ish) where it has been required for installations in military establishments (if I remember correctly).
P
Is that right eng, u should include a cpc if only for good working practice. What happens if the trunking continuity fails! We'll all be buggered if we scrimp on safety. Lol!!!
H
But you could say the same about cpc cables...
The benefit to using trunking as cpc is the very favourable R2 values you achieve, to add cable cpcs is just a waste of time, money and the world's resources - don't you care about the environment??
P
E
If you are still arguing that you can combine a copper CPC and a steel CPC to make up the required minimum CSA you are WRONG!! Which ever one you do choose, it must be capable of taking the full fault current on it's own, not as a combined entity. A fault will always choose the easiest route to earth, so it will be the copper conductor (with superior conductivity) that will take the hit in a combined copper/steel arrangement!!
E
What would you know about ''Good Working Practice''?? lol!!
E
Also, all you will achieve, is filling up the containment systems with pointless CPC's, that can't come close to matching that of the containment system they are enclosed in!!
P
P
H
Looking at the part of my post you highlighted, then your reply, I am guessing you perhaps 'speed read' it lol
B
Have to disagree with you there.
A fault current will split itself between the two with a ratio depending on resistance of the conductors. It will not all just flow down the one conductor. The steel has an equivalent copper x-sectional area (less than copper because its resistance to current flow is higher) so provided the two together meet the minimum x-sectional area required for the fault you satisfy the requirement.
That is my understanding of why reg 543 permits the mixed use of conductors.
P
Nice edit.
E
You would also swear that black was white if it suited your purpose!! ...lol!!
Oh i most certainly will, and actually am. There is not a single ''SEPARATE CPC'' in any of our metal containment systems throughout this project (which is around 85% overall, metal containment systems), and our Zs values will be far superior than anything you install with your superfluous CPC's...
E
I was agreeing with you Hawkmoon, i just added the containment fill factor
E
Think about your electrical training, and you'll see that it doesn't and can't work like that!!
Discuss recorded cpc size in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
OP
Hawkmoon
If you have circuits run in metal trunking (with cpcs) you don't include the trunking when determining/recording the cpc size...
SWA sheath is no different if you are using a core as cpc
SWA sheath is no different if you are using a core as cpc
OP
Badged01
And the reg that tells you not to?
Not saying you have to include it in the CPC size above the cable conductor CPC size but there is nothing stopping you using it ...... reg 543.2.1
OP
Engineer54
Why would anyone be bloody daft enough to include a CPC in earthed trunking containment system?? lol!!
OP
Badged01
Strangely enough I have come across a few cases in the past where the 'electrican' was taught on his course that as good practise you should run a seperate CPC to the conduit/trunking ...... new type "apprentice" electrician not a short course!
OP
Hawkmoon
I agree but if you're carrying out EICRs then you will come across it - there have been instances in the past (80s ish) where it has been required for installations in military establishments (if I remember correctly).
OP
pepparz
Is that right eng, u should include a cpc if only for good working practice. What happens if the trunking continuity fails! We'll all be buggered if we scrimp on safety. Lol!!!
OP
Hawkmoon
But you could say the same about cpc cables...
The benefit to using trunking as cpc is the very favourable R2 values you achieve, to add cable cpcs is just a waste of time, money and the world's resources - don't you care about the environment??
OP
pepparz
Haven't got time to answer that, got to go to market to buy a pig.
OP
Engineer54
If you are still arguing that you can combine a copper CPC and a steel CPC to make up the required minimum CSA you are WRONG!! Which ever one you do choose, it must be capable of taking the full fault current on it's own, not as a combined entity. A fault will always choose the easiest route to earth, so it will be the copper conductor (with superior conductivity) that will take the hit in a combined copper/steel arrangement!!
OP
Engineer54
What would you know about ''Good Working Practice''?? lol!!
Last edited by a moderator:
OP
Engineer54
But you could say the same about cpc cables...
The benefit to using trunking as cpc is the very favourable R2 values you achieve, to add cable cpcs is just a waste of time, money and the world's resources - don't you care about the environment??
Also, all you will achieve, is filling up the containment systems with pointless CPC's, that can't come close to matching that of the containment system they are enclosed in!!
OP
pepparz
Ive been to conduit and trunking jobs with no cpc that suffered with poor zs, if there had been a cpc this wouldn't have happened. So you do it your way eng and I'll do it mine, ok.
OP
pepparz
Please stop loling ur messages it doesn't make the offensive ones less offending. Saying "what would you know" is childish.
OP
Hawkmoon
Looking at the part of my post you highlighted, then your reply, I am guessing you perhaps 'speed read' it lol
OP
Badged01
Have to disagree with you there.
A fault current will split itself between the two with a ratio depending on resistance of the conductors. It will not all just flow down the one conductor. The steel has an equivalent copper x-sectional area (less than copper because its resistance to current flow is higher) so provided the two together meet the minimum x-sectional area required for the fault you satisfy the requirement.
That is my understanding of why reg 543 permits the mixed use of conductors.
OP
pepparz
Nice edit.
OP
Engineer54
You would also swear that black was white if it suited your purpose!! ...lol!!
Oh i most certainly will, and actually am. There is not a single ''SEPARATE CPC'' in any of our metal containment systems throughout this project (which is around 85% overall, metal containment systems), and our Zs values will be far superior than anything you install with your superfluous CPC's...
OP
Engineer54
I was agreeing with you Hawkmoon, i just added the containment fill factor
OP
Engineer54
Think about your electrical training, and you'll see that it doesn't and can't work like that!!
Reply to recorded cpc size in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
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