- Reaction score
- 1,512
yes-i know,but otherwise there is no reason why they can't be paralleled is there? on pme
No reason.
Discuss Can we use the armour of an SWA as the CPC??? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
yes-i know,but otherwise there is no reason why they can't be paralleled is there? on pme
If you are exporting PME earthing out to an outbuilding that HAS extraneous metalwork (=<22000ohms between metalwork and main earth terminal) and you are intending to use the armouring only as an earth conductor then for a:
TNCS system you will need 8 x the required equivalent in copper e.g 10.00 copper required = 80.00mm armouring.
TNS system you will need 4 x the required equivalent in copper.
If after installation it is found to require external CPC it should be a minimum of 25% csa of phase conductor.
"ECA guide to the wiring regs."
Hello everyone just been reading this thread and i find it very interesting......
I must admit i´m a little surprised that only one person has mentioned using the adiabitc equation for calculating the size of a cpc... It doesnt take long and i have found i have never needed to run a seperate cpc when making calculations for distribution cables. As a general rule though, if the cable is to be run outside or where other external influences are present then i always run a copper earth (not a seperate single core cable, an extra internal core) due to corrosion.
I undertook the 2391-20 design course where a lot of cable calculations were made and i always used the adiabatic, as by using the table at the start of this thread you will generally find that you run in an earth that frankly is oversized. If you want to price a job competitively (im talking larger commercial, industrial jobs) then using the adiabatic is alot more accurate, if were talking about large SWA cables from say 95mm upwards you will find a seperate earth costs a fair bit... 50mm BS6491x say 150m.... NOT CHEAP! a simple calc.. oh its not required so why bother....?
If anyone wants a bit more clarity on this like exactly how the calculation is made (can show examples) then let me know as i would be more than happy to help....!
cheers Dave
Show me the calcs Dave!
Seriously though lately i've been trying to gen up on using the adiabatic more lately as like you say the cost can differ massively on some jobs
Cheers
I'm supprised that no one has mentioned that running a separate CPC contravenes BS7671.
Specifically Regulation 521.5.2.
Reply to Can we use the armour of an SWA as the CPC??? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.