CPC in steel conduit

[redman]

Hi all,

Am I right in thinking that when installing wiring in steel conduit, there is no need to run an earth wire along side the line & neutral.

So... If I was installing lighting, would I just terminate the supply earth at the start point of the conduit...

then connect an earth wire from each metal back box to each switch ?

Does this sound right ?

Cheers

 

[Zeespark]

Redman its ALWAYS better to run a seperate earth inside trunking/conduit, as it would guaruntee an earth, it cant be guarunteed if run via conduit.

AndyGuinness

 

[redman]

Nice one mate.

Its something that Ive got to do for college.

I thought I`d read somewhere that you could use the steel as the cpc,

but I suppose it is better to have a guaranteed earth by running a cable.

Cheers

 

[sparkytim]

Metal conduit and trunking IS acceptabe as a CPC and was for many years considered normal practice in Industrial installations, many still do.

However with increased risk of corrosion causing high resistence at poor joints etc it is deemed good practice to include a CPC within the conduit/trunking to provide a more reliable conductor.

Metal Flexiable conduit such as used for final feeds on to Motors was never acceptable as CPC and always had to have seperate CPC enclosed.

 

[netblindpaul]

redman,

It is still allowed to use the stell conduit as a cpc.

HOWEVER, Zeespark is correct, a seperate earth is always better!

Some of the steel conduit i've seen as cpc would make your hair stand on end.

Also as per my other conduit post, who these days uses or even has a high current earth continuity tester?

Can't remember the correct name now!

 

[batty]

Not sure if its a reg but I will always have a cpc in all metal conduit, trunking and tray. The reason being you are not then reallying on metal as your protective conductor so to speak and if a joint fails its not the end of the world. The reason conduit stopped being used for cpc was in schools and similar establishments were temperature would go up and down corrosion would occur on joints so would then fail loop tests.

 

[Lee321]

many still do..

thats a bold statement

 

[kme]

Perfectly true, though, in my experience......

 

[Mr Sworld]

Steel conduit is still allowed as a CPC however it requires a rather expensive bit of kit to test the conduit's earth resistance.

However 'best practice' nowadays' is too run a CPC with the phase's.

Conduit will rot over time and you are relying on 'mechanical joint' to provide earth.