Can circuits be hard wired in flexible cable?

[tombrooker84]

Hello guys, Going to open a big can of worms here, but here goes. I'm having an argument with another electrician on site, and he is of the opinion that the is no regulation against the use of flex in domestic premises, for all circuits? I was always of the opinion that there was a regulation against the use of flex but I cannot seem to find one, in fact the opposite, when we looked and I cannot quote the exact reg now, but it says "as long as its suitable then its ok". I wondered if its something a simple a british standard marking, or is it literally due to the fact that twin and earth is a lot cheaper, nearly double the price for heat resistant flex, but surely you would recoup that in a couple of hours less work, due to the fact it would be easier to install. I also mentioned terminating it a the cutting of strands thus reducing surface area, but i suppose the reply to that would be "right tool for the right job" and your fine. Also perhaps T&E distinguishes a professional job from a DIY job... but hey ho. Tom

 

[VoltzElectrical]

the point i was making was that the CPC on a flex may not intercept the fault at all......yes ok..this can happen with T&E ....but less likely due to the structure of this type of cable....

How would that work??

There is nothing wrong with using flex to wire a whole house, other than the prohibitive costs. As for the reg being quoted re. fixed wiring.... what does that mean? Just follow the normal routes. All that need s to be considered as far as the regs go, are current carrying capacity, heat resistance, and disconnection times with due accord to heating under fault conditions (adiabatic equation). Other than that, it id down to cost/ convenience factors. bootlace ferrules? over-egging the omelette IMHO.

 

[trev]

one question that needs to be asked is,
Why would you?

 

[GLENNSPARK]

How would that work??

There is nothing wrong with using flex to wire a whole house, other than the prohibitive costs. As for the reg being quoted re. fixed wiring.... what does that mean? Just follow the normal routes. All that need s to be considered as far as the regs go, are current carrying capacity, heat resistance, and disconnection times with due accord to heating under fault conditions (adiabatic equation). Other than that, it id down to cost/ convenience factors. bootlace ferrules? over-egging the omelette IMHO.

and when did i say there were owt wrong with eh voltz??and "how would that work" as in how would the CPC not intercept a fault in flex.........when did i say it wouldn`t eh?....look at threads before posting because what i said was that the CPC of the flex MAY NOT intercept the fault....not WOULD NOT!!!!.....or maybe its you who is "over egging" the omelette...eh??.......and yes Trev....why would you???

 

[VoltzElectrical]

eh. eh. eh. Calm down. eh.

 

[GLENNSPARK]

Eh...eheheheheheheh??????...eheheheh

 

[GLENNSPARK]

eh. eh. eh. Calm down. eh.

no probs volts......i wasn`t in the best of moods anyway yesterday....not your fault mate......

 

[CrazyScozzese]

You make a good point tho' Glenn, In flex the CPC is not between the other two conductors as they are in triangular positions, so if they overheat due to an overload and burn through the insulation, they are far more likely to touch each other. To touch the CPC would require them to burn through a second layer.

T&E requires them only to burn through their own insulation to touch the CPC, and as it is between them, the chances of touching each other before the CPC are minimal.

Would this not be safer in this instance as the overload was not disconnecting before the cables broke down, so if an RCD was employed it would then interrupt the supply?

 

[GLENNSPARK]

thats what i mean crazy......if you look at 3 core flex end on....its like "trefoil" configuration......so the chances of a live-live fault are greater....so if the earthing arrangement was TT and as such was relying on an RCD for sole fault protection could be a chance that the protective device may not opperate at all....as i se it its much better to have an uninsulated CPC running the full length of the cable......to intercept any breakdown in insulation that may occur on the live conductor/s..........

 

[Adam W]

thats what i mean crazy......if you look at 3 core flex end on....its like "trefoil" configuration......so the chances of a live-live fault are greater....so if the earthing arrangement was TT and as such was relying on an RCD for sole fault protection could be a chance that the protective device may not opperate at all....as i se it its much better to have an uninsulated CPC running the full length of the cable......to intercept any breakdown in insulation that may occur on the live conductor/s..........

So would you not use singles in conduit on a TT system?

 

[CrazyScozzese]

Not where I was considering flex to make things easier to wire???

 

[GLENNSPARK]

So would you not use singles in conduit on a TT system?

well this is it Adam...and had thought about this....but lets say that the conduit was metal...and earthed ...so there would be an earth path through whatever had gone through the conduit...a drill perhaps.....

 

[Adam W]

well this is it Adam...and had thought about this....but lets say that the conduit was metal...and earthed ...so there would be an earth path through whatever had gone through the conduit...a drill perhaps.....

... But it wouldn't if it were plastic - it would effectively be similar to flex.
Singles in pvc conduit is an accepted installation method so why not flex, which is basically 'pre-wired conduit'?

 

[Engineer54]

... But it wouldn't if it were plastic - it would effectively be similar to flex.
Singles in pvc conduit is an accepted installation method so why not flex, which is basically 'pre-wired conduit'?

I'm not getting involved in this discussion, as i'm sure everyone is aware of my opinion of using flexible cord as a buildings hard wiring medium...

However you can't compare a multi core cable with a conduit system wired in singles, they are completely different and with different characteristics... Multi core cables are not pre wire conduits. ...lol!!