Plastic conduit

ianmacd · Mar 25, 2009

Hello.

I am planning on rewiring my garage for my assessment with elecsa and am having trouble confirming the correct size with the OSG when in conduit. With a type B 32A cb I can use 2.5 t&e with ref methods A,100,102 & C. AIUI conduit is B. This suggests that t&e should not be used in conduit (I was planing on using 2.5 singles for L&N and 1.5 singles for CPC) but there doesn't appear to be any mention of ref B in any of these tables or any tables for singles.

Does anyone know where (if anywhere) it is stated that 2.5/1.5 singles are ok in conduit for a Final Ring Circuit protected by a 32A type B cb?

I was also planning (until I couldn't find the tables) to use 1.5/1.5 singles for the lighting in conduit too.

Thanks.

Ian.

Gforce · Mar 25, 2009

Its a strange one that-doesnt seem to be a precise explanation for singles-though using the spec you have said would suggest using 4mm t and e to allow for enough ampage for 32 amp due to thermals in the conduit.

I cannot see any harm in using 2.5 singles for this as thermals will be far lesser and it doesnt give any exact answer to singles.

Though it does say the overall diametre of cables should not exceed 45% of the od of the conduit-so really depends on the size of the conduit used.

Though im in the same boat as you and still learning.

But many posts on here have said that singles is often used in conduit-as for one thing saving on costs as protection isnt required.

But im sure someone will clarify this for you

Martin

Think i just found the answer-it says single core pvc insulated-not multicore which t and e would be. The singles are still insulated in pvc are they not. As I think you may have been thinging single core as in solid and not stranded?

So if im right just work out the cable factor of the number of cables to be used and if 3metre run or greater and then use the conduit to give you enough factor.

Apache · Mar 25, 2009

It's going to cost you more to use singles rather than T&E.

SF 100m 2.5mm T&E

Gforce · Mar 25, 2009

Not always though-if your limited to the length and are not going to use hundreds of meters you could just use one colour and label the wires as needed with either l n e or their respective colour sheath-that way could do it all for under

Evans Electric · Mar 25, 2009

You never use T/E in conduit , there is no point , its not intended for conduit, 6242Y is insulated and sheathed so use for clipping surface, 6491X is insulated only , the conduit becomes the sheathing. So your socket would be Brown-Blue- G/Yell all 2.5. your lighting in 1.5 6491X.

20 amp MCB for socket . I presume there is an RCD somewhere downstream ?

Good luck with assessment.

Deke

ianmacd · Mar 25, 2009

No RCD in the house currently but there will be one in the new CCU for both circuits. The cable out to the garage is existing though.

Would you normally use 2.5 for CPC in the sockets too? I only ask becasue I ordered 1.5 CPC for both already (as thats whats in T&E) so should I order some 2.5 CPC too?

Ian.