Trunking or seperate cpc???????

[Jay Sparks]

Hi Guy & Gals,

So, I was reading a very interesting thread earlier where the OP was asking whether to use SWA or singles in trunking/containment for a supply to a sub main.
The responses the OP got were different to say the least!!!!!!!

Anyway, some were saying SWA and some were saying singles with a seperate cpc and others were saying use the trunking as cpc.

Now Ive been on installs where the architect/designer has requested/insisted that a seperate cpc has to be used for every circuit. Ive also been in a factory, not so long ago, where the install was over 40/50 years old and the trunking was used as the cpc. Now this trunking was battered and some sections were rusty but I got a brilliant Zs at every point I tested.

So, I am happy to run a seperate cpc if Im told too and I am also happy to use the trunking/containment as the cpc (nice fence this.lol). Now obviousley cost has to come into it but what I want to know from you guys (without starting any arguments), is which method do you prefer and why???????


Jay

 

[VoltzElectrical]

I prefer separate CPC, as have always done it, and you can be a bit less stringent on making sure everything is tip-top tight, but maybe that's just laziness! Also if 'someone' moves or alters anything with the containment, you know the circuit should still be sound.

I dunno, perhaps I deserve the flaming I'm no doubt to get over this lol!

 

[cogsey133]

I have used both methods. The containment can be used quite satisfactorily as the cpc however designers do quite often ask for separate cpc,s so i do what i am asked...end of!

 

[Guest55]

for a submain swa every time.
quicker to install than containment + wiring.
less likely to be tampered with after installation and swa is protected for its lifetime , trunking lids go missing all the time.

 

[Engineer54]

Now Ive been on installs where the architect/designer has requested/insisted that a seperate cpc has to be used for every circuit.

Must be very young Deign Engineers, that knows no different. An Architect would not request something he knows little to nothing about. Either that, or they just don't trust today's electricians to install a metal containment system to the standard it needs to be installed too. I can't think of any other possible reason.

Ive also been in a factory, not so long ago, where the install was over 40/50 years old and the trunking was used as the cpc. Now this trunking was battered and some sections were rusty but I got a brilliant Zs at every point I tested.

And that my friend, should answer any question you have on installing separate CPC's on a metallic trunking/conduit containment system. eg, It would be a pointless and costly exercise, ...end of!!!

 

[Jay Sparks]

Must be very young Deign Engineers, that knows no different. An Architect would not request something he knows little to nothing about. Either that, or they just don't trust today's electricians to install a metal containment system to the standard it needs to be installed too. I can't think of any other possible reason.


And that my friend, should answer any question you have on installing separate CPC's on a metallic trunking/conduit containment system. eg, It would be a pointless and costly exercise, ...end of!!!

I get were your coming from but when Im subbying for a company and they tell me to do it and its not illegal or dangerous, I tend to do as they say, after all, its there money and profit at stake.




I only tested one section of the trunking and the readings where fantastic, even where the trunking was rusty. There where lots of lenghts that had been hit with the forktruck and where dented and twisted and in some parts only connected to the next length by one link/screw.
I have advised them to have the whole installation I & T but they said "it will be ok", "it has worked fine up to now".

Anyway, thats why I have no problem in useing the trunking as a cpc or running a seperate one for each circuit. Both do the job and neither are dangerous.


Jay

 

[moddeydhoo]

Old time trunking with copper links was and is ok for normal circuits for a cpc. 17th edition does not allow 16mm twin & earth sub main because of the 50mm depth so in trunking is ok. Singles with own cpc ok in trunking as mechanical protection. Swa can be run on its own

 

[Engineer54]

Old time trunking with copper links was and is ok for normal circuits for a cpc. 17th edition does not allow 16mm twin & earth sub main because of the 50mm depth so in trunking is ok. Singles with own cpc ok in trunking as mechanical protection. Swa can be run on its own

Its more than just OK, it's by far superior to any separate circuit CPC. And copper links, is only a relatively later requirement on trunking and tray work. Why would anyone be daft enough to install a metallic trunking containment system for mechanical purposes only???

The very original metal containment system within the factories of the company i did my training with, had no such copper links, but i bet if you were to go there today and test it, ...it would still be giving exceptional Zs values after 60+ years...

 

[telectrix]

...it would still be giving exceptional Zs values after 60+ years...

i still work fine after 60+ years, so why shouldn't trunking?

 

[moddeydhoo]

But regs require copper links if trunking is being used as cpc, if not no copper links

 

[Engineer54]

But regs require copper links if trunking is being used as cpc, if not no copper links

Were talking about metal containment installations that were installed probably before you were born. There was no requirement at that time for copper links. What i'm saying is that links or not, metal containment systems (correctly installed) is a far superior CPC than a any separate circuit CPC. Which frankly is a complete waste of time, unless your running in a so-called clean earth for any specialised equipment...

 

[moddeydhoo]

I know i worked in a factory which still has 1955 metal trunking zs still ok.

 

[telectrix]

1955.... still settling in then.:rockon:

 

[Engineer54]

I know i worked in a factory which still has 1955 metal trunking zs still ok.

I bet not just OK, ...but still excellent!! lol!!!

 

[Knobhead]

But regs require copper links if trunking is being used as cpc, if not no copper links

Here we go again. There was electricity BEFORE the 17th you know. We had the 14th when I started.