In what context do you use a CPC?

[not_today]

Gentleman,

Im reading through the forums, especially the fault finding threads in this sub and there are a lot of talk about CPC's. when someone has time could you please explain what a CPC is and when it is used?


im sorry if this sounds like an amateurish question but its because at this point i am!

Sam

 

[shanky887614]

Gentleman,

Im reading through the forums, especially the fault finding threads in this sub and there are a lot of talk about CPC's. when someone has time could you please explain what a CPC is and when it is used?


im sorry if this sounds like an amateurish question but its because at this point i am!

Sam

go start an aprentaship.

if you don't know what a cpc is you shouldnt be playing with electrics

 

[Marvo]

A CPC (circuit protective conductor) is included in a circuit for safety reasons. It allows a low impedance (low resistance) path for fault currents to flow because it is connected to earth in the CU. If a fault occurs whereby the chassis of an appliance comes into contact or partial contact with the live (low IR fault) then the low resistance of the CPC ensures the chassis stays as close to 0Volts as possible meaning anyone coming into contact with the faulty appliance doesn't receive a serious electric shock. Secondly the low resistance of the CPC to earth ensures the fault current can become high enough to trip the OCPD (over current protective device) which might be a fuse or an MCB.

 

[shanky887614]

earth to ccu (customer consumer unit) then cpc (circuit protective conductor) from ccu to circuits e.g. lights,sockets

 

[Baker1988]

Its basically there for safety incase of a fault in the circuit, you use it basically in every circuit in a installation if a fault occurs it should trip the over current device which would make the circuit dead so the person who is getting the shock or going to touch the live parts does not become dead

 

[not_today]

thank you chaps,

for the record. i am not touching any electrics. as stated in my OP i am just looking through the threads to try and learn as much as i can.

sam

 

[trev]

go start an aprentaship.

if you don't know what a cpc is you shouldnt be playing with electrics

Shanksy, when this section was set up it was agreed that there were no questions too stupid for it. It was also agreed that every question would be answered and no trainee would be flamed for asking it. This one could be in the very early days of his training for all we know mate

 

[MDJ]

Agree with trev, out of order this time IMO

 

[shanky887614]

Shanksy, when this section was set up it was agreed that there were no questions too stupid for it. It was also agreed that every question would be answered and no trainee would be flamed for asking it. This one could be in the very early days of his training for all we know mate

didnt read title, just clicked new posts as usual

 

[Baker1988]

Shanksy, when this section was set up it was agreed that there were no questions too stupid for it. It was also agreed that every question would be answered and no trainee would be flamed for asking it. This one could be in the very early days of his training for all we know mate

I totally agree that was not a very constructive answer this section is too help people I didnt know what a cpc was before I started going to college I just called it a earth

 

[shanky887614]

I totally agree that was not a very constructive answer this section is too help people I didnt know what a cpc was before I started going to college I just called it a earth

i hold my hands up, i made a mistake i thought i clicked on another diy thread as i didnt pay much attention to the location of the thread

 

[trev]

Nothing more to see here, move along

 

[Marvo]

It's great to see everyone is on the same page regarding basic questions. Shanky, no harm done mate if it was an honest mistake.

 

[not_today]

dont worry lads. its all cool! thanks for the replies everyone. plenty more silly questions to come!

going to be chasing up that apprentiship tomorrow. i had a dream on friday night that i rang on monday and it had gone!

 

[shanky887614]

if you dont get given a course book and end up buying one yourself make sure it's for

city and guild 2357 not 2330

there is still some old stock floating around since they ended the 2330 course

 

[not_today]

i have both i think. a very helpful chap on here sent me a load of pdf books. currently uploading them to my google drive so i can read them on my phone.

 

[Floody]

go start an aprentaship.

if you don't know what a cpc is you shouldnt be playing with electrics

Shanky, as a student yourself... you don't want to be jumping down people's throats like that

 

[trev]

Shanky, as a student yourself... you don't want to be jumping down people's throats like that

Guys come on, he screwed up and has acknowledged it. Let's not have a witch hunt

 

[MDJ]

Agreed not in this forum, it's the only one left on the site which is a safe haven, it needs to stay that way or the trainees won't come onto the site.

 

[not_today]

can anyone please link me to an image of a CPC please ...

 

[trev]

You know when you strip a bit of twin and earth mate and you've got that bare copper wire in the middle? That's your CPC, it is short for circuit protective conductor. They come in many different formats eg the armouring of a steel wire armoured cable, the metal sheath of a MICC. They're normally referred to as earths.

 

[shanky887614]

can anyone please link me to an image of a CPC please ...

in most cases it is one of the cores in the cable.

except with armoured cable, its common to see a green+yellow(cpc) tywrapped to it

 

[not_today]

Oh my god my face is red with embarrassment!

i was reading a thread in one of the other subs and someone was talking about CPC's but i think they were using the term out of context to the confuse the OP. i dont think i'll bother reading that section for a while (there's a lot of sarcasm)

i know what your talking about now. cheers chaps.

 

[trev]

I've always said this place is like a site cabin mate, there's a lot of **** taking goes on. The trick is to know who are the **** takers
It's also easy to get confused by terminology you're not used to, as an example I have no clue what the proper name for Zebs is. I will have done once but having called them Zebs for so long that pushes the real name out of my head.

 

[Marvo]

Zebs?? That's a new one for me, no idea what they are but they sound pretty mysterious. We have zebras around here but no zebs...

 

[trev]

Zebs is short for Zebedees Andy, remember the magic roundabout? The guy with the sprin up his butt? Time for bed said Zebedee and all that old malarkey.
Well they're the nuts with a spring on them, you'll know the ones I mean

 

[Marvo]

Ahh, makes sense. Like unistrut spring-nuts I assume.

 

[trev]

Ahh, makes sense. Like unistrut spring-nuts I assume. View attachment 17762

They are the very chaps I was talking about.

 

[Baker1988]

Ahh, makes sense. Like unistrut spring-nuts I assume. View attachment 17762

They are zebs lol

 

[not_today]

cheers chaps. it'll all part of the steep learning curve i am on at the moment.

 

[Baker1988]

can anyone please link me to an image of a CPC please ...

this is a twin and cpc used mostly in domestic/houses the middle connductor without its own insulation is the cpc


This is swa (steel wire armored) cable used in places where you need protection to your cable like industrial/commercial/supply cables, you can buy this with a extra core and use that as the cpc but normally you use the steel armorings of the cable by useing the gland, here is a pic the outer steel is the cpc


Then there is mi (mineral insulated) cable also known as micc (mineral insulated copper clad) cable this is used where you need to maintain the circuit integrity during fire and stuff like on a fire alarm system as it can with stand a really high temp, it is the copper clad on the outside under the sheath that is used as the cpc


Hope this helps clarify a few things pal

 

[Floody]

Lmfao Trev, I never knew what the ral name for Zebs were either, also heard people calling them zebedees but no idea if that's the real name? Been using them for 9 months of 2012...

 

[KWCFC]

Why is the earth left bare in T+E out of interest? Why not insulated like the others and why smaller?

 

[trev]

1 To protect the cable if it's damaged along the run.
2 To save money

 

[Baker1988]

Why is the earth left bare in T+E out of interest? Why not insulated like the others and why smaller?

im not sure to be hones i think it is probily to save money in production as it is not designed to carry current all the time like the other too it is only there for fault current bus as i say not sure

 

[Baker1988]

1 To protect the cable if it's damaged along the run.
2 To save money

haha 1 is obvious but it did not even come into my head haha think its getting late haha

 

[not_today]

1 To protect the cable if it's damaged along the run.
2 To save money

Sorry trev im a bit confused, how does leaving the CPC or earth uninsulated protect it from damage? i can understand the need to save money and the fact it wont be carrying current very often if not at all.

 

[Baker1988]

Sorry trev im a bit confused, how does leaving the CPC or earth uninsulated protect it from damage? i can understand the need to save money and the fact it wont be carrying current very often if not at all.

well it doesnt protect it from actually being damaged but if it gets damaged like it gets cut or part of the insulation is removed as the cpc is connected to earth at one point in the circuit the live/neutral conductor will touch the cpc which wil create a fault path for the circuit and trip the mcb/rcd

 

[not_today]

i thin ive got it!

so it if the live or neutral are damaged inside the cable somehow, they will touch the bare wire and send the current to earth?

if it was covered then it would not go back to earth and could cause someone to have a nasty shock?

Sam

 

[trev]

well it doesnt protect it from actually being damaged but if it gets damaged like it gets cut or part of the insulation is removed as the cpc is connected to earth at one point in the circuit the live/neutral conductor will touch the cpc which wil create a fault path for the circuit and trip the mcb/rcd

Thanks for saving me some typing again mate