Circuit Question

[ldworks]

I have a client whos sockets have been wired in 6mm in some places but wired in 2.5mm between somepoints. As far as i can see this is not a serious problem as 2.5mm cable is requirement any way.Always knew u could have a bigger cable than u need but never smaller than circuits needs?!!?!?!?

 

[telectrix]

thou shalt not reduce the size of the conductors in a circuit ( forgot the exact reg,) but if it;s 6mm to start, it must remain 6mm throughout.

 

[ldworks]

I realise that as the smaller cable acts as almost a fuse and can caused problems by heating up (so ive been told). Gonna tell the customer to take out the few links of 6mm and put in 2.5mm which is mostly in the circuit in conservatory. y they did it in 6mm i will never know as its not like a volt drop could happen from upstairs to downstairs(not to uprate cable to 6mm!!!) and only runs normal domestic appliances. Wonder if this was a DIY job or something!!Does this make sense to anyone?

 

[olly w]

thou shalt not reduce the size of the conductors in a circuit ( forgot the exact reg,) but if it;s 6mm to start, it must remain 6mm throughout.

I don't recall ever coming across that.

When i was at college we were taught how to reduce the size of cable on a street lighting circuit to reduce the cost while allowing for volt drop at the furthest point.

 

[telectrix]

maybe street lighting is diff. but on a domestic, a 6mm cct ( radial ) would perhaps be fused at 40A. then it is reduced to 2.5mm capable of carrying say, 25A. PROBLEM.

 

[olly w]

What if it starts with 6mm drops to 2.5mm but is protected by 20amp mcb? no problem.

 

[SirKit Breaker]

I bet getting 2 6mm's into the socket terminals is a right laugh. Surely this must be a no no, as far as i am aware the maximum CSA cable that should go into a standard socket terminal is 10mm! so 2 x 6 = 12, this must mechanically overload the terminal and its screws.

 

[olly w]

I've wired ring circuits with the two legs from the mcb in 6mm then the rest in 2.5mm (the 6mm to allow for volt drop)

By the way i didn't design it i just installed it and thought it was crap myself, but it sort of made sense.

 

[R&M]

I believe you should give us a little more information, like what is protective device? Is the circuit ring or radial? How long is that first leg? Then maybe answers could be more accurate and more useful for you.

 

[andekoch]

Check that the 6mm legs (sound like extensions off the original 2.5mm ring) are not 6mm due to the installation method. Alternatively it may just be that the installer has a lot of 6mm he needed to get rid of. As far as I know you can always go up in size, above the design size, if you wish for whatever reason but cant go down. I am pretty sure there is no reg that states all the wiring needs to be the same size.