Doubling up conductors

[Amp David]

Is it an exceptable method to double up conductors in a 4 core cable to increase the CSA and then put in a seperate CPC?

If so, then as there are no tables for doubled up sizes eg. 5mm, 8mm squared etc, would it just be a case of doing the calcs for the single core size then dividing by 2

 

[High Tower]

someone told me that as long as they are exactly the same length then you can but please dont take that as gospel, i dont know how reliable it is

 

[tonys]

Do you parallel them up?

 

[johnboy6083]

Yes. In some situations its the only way, because it means smaller cables canbe used, with smaller bending radius ect. As for calcs, current carrying capacity is doubled, voltdrop and resistance is halved. Don't think though that you can use the values given for a 50mm2 cable for 2x 25mm2 for example, as the 50mm values may take other things into account, ie capacitance.

 

[topquark]

I would say that it's fine for cpc but for phase conductors no. If you dropped one of the connections for a cable in parallel then you'd run a very high risk of overheating.

Even if it's a distribution circuit only terminated at either end, I still wouldn't risk it, with what device would you protect the cable?

 

[johnboy6083]

In my experience, it's only ever used with distribution circuits, or radial circuits, that are wired with SWA. Both cores of each phase and neutral must be terminated at the same place, and the cables must be the same length, so the load is split evenly across the cores.

 

[topquark]

I guess if you took each core into a separate MCB/RCBO then that would be safe but definatley not both cores into one protective device.

 

[johnboy6083]

I've installed parallel cables onto the same Acb before. Most large incomers are parallel cables installed onto the same fuses or mccb/Acb. I was looking at one today. It would something pretty violent that would cause the loss of one phase conductor, and IMO, the kind of condition that causes that would probably be more likely cause a short, causing near instataneous operation of the protective device.

 

[Mr Mike]

Hi Amp David,
As johnboy has, so have I have installed SWA in parrallel, again into an Acb.
At the time the MEB (Midland Electricity Board) were required to certify the installtions at the job; it was for public use and they had no problem with the parrallel cables.
Hope this helps some
Kindest regards
Mike.

 

[Engineer54]

Hahaha, Running parallel cables is standard practice, it can increase current carrying abilities enormously. Example a 300mm csa cable is required for say a given load or sub-main. If you run in 2 x 120mm cables the cost of cable is reduced, the current carrying ability is increased, volt drop halved etc etc.... I've been on projects where each phase from a transformer was run with 9 single core cables on tray to the Main Distribution Board.

paralleling distribution cables works, and it works VERY well!!!!

 

[mogga]

Is it an exceptable method to double up conductors in a 4 core cable to increase the CSA and then put in a seperate CPC?

If so, then as there are no tables for doubled up sizes eg. 5mm, 8mm squared etc, would it just be a case of doing the calcs for the single core size then dividing by 2

IM unable to answer your question and IMO others answering havent read correctly that its not PARALELLING your talking about but using 2 cores for Live n 2 cores for neutral within the one 4 core SWA ?? Thats how Iv read the question please correct me if Im wrong ??

 

[Engineer54]

IM unable to answer your question and IMO others answering havent read correctly that its not PARALELLING your talking about but using 2 cores for Live n 2 cores for neutral within the one 4 core SWA ?? Thats how Iv read the question please correct me if Im wrong ??

So what would you call that then, if not PARALELLING???

 

[mogga]

Id define paralelling as taking 2 equaly sized SWAs eg 125mm running in parallell not 4 cores within the same swa

 

[Engineer54]

What's SWA cables got to do with paralelling, you can parallel any cable, multi core or single core?? All you would be doing in the original OP case is turning a 4 c cable into a 2c cable, ....So what's the problem with that??

 

[RogertheBodger]

Is it an exceptable method to double up conductors in a 4 core cable to increase the CSA and then put in a seperate CPC?

If so, then as there are no tables for doubled up sizes eg. 5mm, 8mm squared etc, would it just be a case of doing the calcs for the single core size then dividing by 2

As long as the cores are sleeved to the correct colours, can't see a problem with that

 

[Amp David]

IM unable to answer your question and IMO others answering havent read correctly that its not PARALELLING your talking about but using 2 cores for Live n 2 cores for neutral within the one 4 core SWA ?? Thats how Iv read the question please correct me if Im wrong ??

You are correct, thats exactly what i'm thinking.

 

[Adam W]

Try 523.8 Conductors in parallel.

 

[IQ Electrical]

Ah, the myths carry on, of course you can use parallel conductors, it's common practice in large installations where CSA's of distribution circuits etc. would be physically impossible to work with in the space provided!

On the other hand, if we're talking about bootlace SWA's of say less than 95mm then I'd say it's poor design.

 

[tonys]

Do you parallel them up?

Just re read my post and was meant to say do you mean parallel them up?

Like others have said, nothing wrong with it all, normally the engineer who designs the "big boys jobs" makes these decisions.

But a part from doing it on "bigger boy cables" I must admit in front of my mate IQ, I done it for mate with a small 4 core swa for a supply to his garage and exported the Earth as well, beat that for pushing the boundaries to the extreme lol

 

[Percy]

I would not find anything wrong with this. On large cable runs for sub mains, we sometimes install parallel circuits. The cables are a lot easier and quicker to install. I usally use a cable manufactuer web site to work out a cable design. Draka or AEI cables have got a program you can do on line.

 

[Amp David]

Just re read my post and was meant to say do you mean parallel them up?

Like others have said, nothing wrong with it all, normally the engineer who designs the "big boys jobs" makes these decisions.

But a part from doing it on "bigger boy cables" I must admit in front of my mate IQ, I done it for mate with a small 4 core swa for a supply to his garage and exported the Earth as well, beat that for pushing the boundaries to the extreme lol

Naugthy boy!

 

[Amp David]

This ones a case of the cable is installed from previous and as cost is always an issue these days, so rather than supplying and installing new cable then doulbling up 1 fore core is more cost effective.

Thanks for you help people!

 

[JLD]

I would say that it's fine for cpc but for phase conductors no. If you dropped one of the connections for a cable in parallel then you'd run a very high risk of overheating.

Even if it's a distribution circuit only terminated at either end, I still wouldn't risk it, with what device would you protect the cable?

I would say it is not fine for a cpc under the same reasoning though. If you loose one of the cpcs then your Zs will raise as your R2 reading increases. This in turn would effect the fault current able to flow and so you would not achieve your disconnect times.

 

[telectrix]

as long as the conductors are well twisted and taped............

 

[i=p/u]

its fine , geeeeeeee;s

 

[IQ Electrical]

I would say it is not fine for a cpc under the same reasoning though. If you loose one of the cpcs then your Zs will raise as your R2 reading increases. This in turn would effect the fault current able to flow and so you would not achieve your disconnect times.

BS 7671:2008 makes no distinction between line conductors and cpc's on parallel cable installation.

By your logic, a standard ring final would be 'not fine'.

 

[Amp David]

How could one of the conductors become disconnected when they are both crimped into a ferrule?

 

[tonys]

How could on eof the conductor become disconnected when they are both crimped into a ferrule?

Often hear people talk about if and buts, so I can only imagine someone must go around pulling wires out of things for a laugh lol

 

[Amp David]

In this trade I think people worry to much about what could happen, rather than just getting on with it.

 

[tonys]

In this trade I think people worry to much about what could happen, rather than just getting on with it.

You know why don't yer, because of the fear the regulators instill in their brains.