Doubling up on cables to increase csa.

[Tillywolves]

Hi everyone. Im a fire alarm guy, who was qualified as a spark, over 27 years ago, to the 15th edition.

Just fitting a new alarm system into a kids nursery school, and noticed that a new consumer unit had been fitted since I first quoted the job. The spark has doubled up two 10mm earth singles to make it over the 16mm needed.

Can this be ok, or does it have to be a single cable only.

cheers in advance.

Tilly


(any questions on fire alarms I'd be happy to answer)

 

[lj.l]

I can see nothing wrong with this .I have done it myself as long as continuity is proved .is it the main earth or a bond?

 

[Tillywolves]

main earth from incoming supply sheath, to consumer unit.

 

[i=p/u]

im only in 2nd year with little expierience , but id say is ok.. cant wait to someone else awnsers nowww

 

[Darkwood]

Yes but only if both cables are identical follow the same run hence the same length, if for any reason you suspect the load isnt balanced between them then it not ok.

 

[lj.l]

agree ,I just assumed that the guy didnt want to rip out the existing cable so just improved on what was there, but he might have took a diferent route

 

[Darkwood]

agree ,I just assumed that the guy didnt want to rip out the existing cable so just improved on what was there, but he might have took a diferent route

Has to be same length usually same route as this makes sure loading is split equally the calculations of having same csa but different lengths isnt recognised by regs thus not allowed although it might be mathematically safe.
I will stand corrected but i do recall the regs have a clause about paralleling cables up and that they must follow each other and be the same length.

 

[Tillywolves]

They are only 2 mtrs in length, and follow the same route.

Cheers for everyone taking time to reply...

 

[malcolmsanford]

The regs do comment on parallel conductors in chapter 43 section 433.4, which then refers you to other parts of the regs. Though they are really aimed at LIVE conductors, under fault conditions you need the earthing conductor to be capable of carrying the possibilty of high currents.

Technically nothing wrong with doubling up on an earthing conductor, it's like so much in the industry it's deemed not good practice. I suppose if a connection broke at a termination on the MET then it could leave the remaining smaller conductor to carry those high fault currents.