runniing single core tails in trunking

james king · Mar 20, 2011

hi all just reading through and i have come across a post.

it was about running single core 16mm tails to 5X CUs only 2way 5 sockets and 1 lighting point per CU. as if one trips it wont take the other 4 rooms out with it.

i know you have to put an isloator on any tails lengh over 3m but from then on could u use trunking and protection??? so u dont have to run SWA cable to each CU?

malcolmsanford · Mar 20, 2011

jiga said:
hi all just reading through and i have come across a post.

it was about running single core 16mm tails to 5X CUs only 2way 5 sockets and 1 lighting point per CU. as if one trips it wont take the other 4 rooms out with it.

i know you have to put an isloator on any tails lengh over 3m but from then on could u use trunking and protection??? so u dont have to run SWA cable to each CU?

Sorry up until then I understood what you were asking.

james king · Mar 20, 2011

do u have to run SWA as its not protected by an RCD, only the 60A islotor? if the tails are run in trunking (not SWA) then would this be ok not to use SWA?

nickblake · Mar 20, 2011

The best way of doing it would to be install a 5 way CDU at the point of the incommer and run 5 16mm TWE to each of the CDU's protected by a 50 or 63 amp mcb , you may have to install an additional CPC as well s for each of the CDU's , if you install these in a metal trunking thats earthed then there is no need for additional RCD protection , or instead of TWE use 16mm singles if the trunking is continuos to each of the CDU's , but would be alot cheaper and quicker to use 16mm 3 core swa

james king · Mar 20, 2011

5 way CDU?

nickblake · Mar 20, 2011

Sorry 5 way consumer unit CDU = Consumers distribution unit , by using this you can protect the tails to each CDU and provide the required single point of isolation , and protect the tails from over load via the 50 or 63 amp MCB this is as long as its installed in an earthed metalic trunking

james king · Mar 20, 2011

ohh rite got me a lil confused then.

i am trying to imagine what would be the best way

eg,

henley block - tails - islotaor 60A DP

then from there run the SWA to the CU

but do u think 5 of them would be a little to much? can u even get a henley block with 7ways?

malcolmsanford · Mar 20, 2011

At the origin of the installation run a set of 25mm^ tails into a proper CU. Then to the 5 rooms run a radial final circuit on a RCBO in 4mm to an adaptable box with klippons and din rail. From the box feed your sockets and your lights via a FCU.

But why you would even want 5 x 2 way CUs one to each room is beyond me.

somersetsparks · Mar 20, 2011

Just put a metalclad DB at the point of the incomer with 5x C40 MCBs and run SWA to each unit as Nickblake says, No RCD needed on the Sub-mains.
Or have a 5 way placcy at the incomer and run 16mm twins in 2x2 placcy trunking to the Fuseboards with C40 breakers, No RCD Required for the submains.

As malcolm says, you could use a 30ma RCBO on each circuit at the incoming DB and then not need RCD protection at each board.

You wouldn't want to run tails and then have 5 switchfuses at the incomer though.

nickblake · Mar 20, 2011

malcolmsanford said:
At the origin of the installation run a set of 25mm^ tails into a proper CU. Then to the 5 rooms run a radial final circuit on a RCBO in 4mm to an adaptable box with klippons and din rail. From the box feed your sockets and your lights via a FCU.

But why you would even want 5 x 2 way CUs one to each room is beyond me.

thats a great idea think i was a tad over the top , opps look its sunday and im looking forward to a few glasses of wine later ,

somersetsparks · Mar 20, 2011

Looking at the question that has been posted though, I think Mr. Jiga actually means could you do it whilst staying within the regs, The answer to which is YES, as long as you had correctly fused each submain down, you could use tails.