Singles

[ban-all-sheds]

Presumably if wiring a circuit with singles in conduit it's OK for the cpc to be the size that it would be in T&E, e.g. 1.5mm² with 2.5mm² or 4mm² L&N, 4mm² with 10mm² L&N etc?

 

[andy]

i would have thought so. but a few month ago when re-wirin a boiler house, all the cables for each part were all the same CSA (mostly all 2.5)

 

[Lectrician]

Yea, but its good practise to wire the same size.

You can also share CPC across circuits, say if you had a row of lights and a row of sockets, you could link the earth to which ever came next etc etc. You would have to use 2.5 CPC for the lot.

 

[ban-all-sheds]

Hmmm..

Wonder if my new shower is designed to accept a 10mm² earth, or if it was only designed with the expectation of T/E....

 

[brown-nought]

If I recall correctly, the CPC can be smaller than live conductors provided it complies with the adiabatic equation.

 

[Lectrician]

If I recall correctly, the CPC can be smaller than live conductors provided it complies with the adiabatic equation.

Very true. But rings and the like, we all generally use the same size cables. Always have, always will. I was taught that way.

The adiabatic can give some strange figures for cables that are oversized due to volt drop. I seem to remember a cct that was fed via 95mm, but a 10mm CPC would do, that seemed pathetic, and a 50mm was installed.

BAS - who would wire a shower in conduit and singles? Even in a commercial property etc

 

[ban-all-sheds]

BAS - who would wire a shower in conduit and singles?

Err.... Me. I would.

I needed to use flexible conduit buried in the wall (non-insulated, plaster depth) to get the cable to the shower. I didn't fancy trying to pull 10mm T/E through it...

 

[Lectrician]

Ah, thats a little different from an industrial system with hundreds of meters of glav trunk and conduit

Yea, I can see you would want to down size the CPC - Hope you bonded aswell

 

[ban-all-sheds]

Don't have to use a smaller cpc - 3 x 10mm² singles fills the conduit to less than 45%.

And yes - I will be connecting the cpc to the supplementary bonding, but there are no E-C-Ps on the shower to bond, fortunately.

In fact - I ought to do a final check - I think there might be no E-C-Ps left in the bathroom now - it's all plastic pipes within the room, apart from short lengths of chrome where they're visible.

 

[jimi]

i think plastic pipes are a waste of time, any pro plummer would always use copper. you may have done it but you should have used copper.

 

[dw3101]

I disagree with the above comment, any pro plumber would use whatever was appropriate at the time!

 

[plugwash]

The adiabatic can give some strange figures for cables that are oversized due to volt drop. I seem to remember a cct that was fed via 95mm, but a 10mm CPC would do, that seemed pathetic, and a 50mm was installed.

the adiabatic is NOT the only consideration you must consider the earth fault loop as well (must be low enough to take out the breaker)

iirc the adiabatic gives the size or earth cable that won't be destoryed in a short not the size needed for good disconnect.

 

[jimi]

my dad is one off the bosses of trasco and before that was a old school plummer he will never think of plastic pipe cheap and tacky. copper pipe is the best way forward long lasting and makes a perfect job if done right and even if you cant see the work its pride and peace of mind

 

[securespark]

I know several pro plumbers - one has been in the game since leaving school at 15 and he's now 65....and he uses plastic all the time.

 

[plugwash]

they seem happy enoough with plastic for outdoor gas piping....