0.75mm Flex into 6A MCB

[uksparks]

Hi,

As per title, how would you feel about connecting a few garage lights onto some 0.75mm flex straight into the 6A MCB, ignore switching, just that its 0.75mm.

I have to say I normally go via a FCU but in this occasion I don't feel I need to as its in the garage with a 6A MCB I can come off.

referring to table 4F3A on page 378 it states 0.75 can take 6A.

id say I'm good to go, I k ow I'm probably stating the obvious but it's not something I usually do, hooking such a small co doctor up to an MCB.

reason for it being small is due to the fact I'm using 3 core and earth flex so I can use the switched output on the lights so they Interconnect on PIR.

 

[uksparks]

It's under 521.9

 

[uksparks]

It points you to BSEN 50565-1, for grades of cable, then to 422.3.201 and 521.9.1

 

[Andy78]

So with reference to my post #8, Am I wrong in my interpretation of table 52.3 ?

I understand that 521.9 applies which is what Davesparks is referring to, and I would never personally consider flex for fixed wiring, or less than 1mm live conductors for any fixed circuit, but the table does seem to support the OP's ideas.

 

[uksparks]

Well it's not "heavy duty" as its not good for 450v i wouldn't think...

 

[uksparks]

It's a confusing grey area I say, I suppose, the bottom line to this is if the cable is suitably protected or not, I will reevaluate my usage of 0.75mm cable and use 1mm from now on.

as said, this is only to feed an outside light, I am not a silly billy wiring an entire light circuit up with it.

 

[hotfingers]

I'll just go and get the book...

521.9.1

 

[uksparks]

It's a strange one actually, Reg 422.3.201 says suitably protected against mechanical damage, but it's strange how it doesn't say a word about suitable protection if it's twin and earth which is just a different shape...

why should flex need any more protection than any other cable irrespective of the CSA of the conductors.

 

[Andy78]

It's a strange one actually, Reg 422.3.201 says suitably protected against mechanical damage, but it's strange how it doesn't say a word about suitable protection if it's twin and earth which is just a different shape...

And different conductor construction, and insulation construction, and sheath construction.......

 

[davesparks]

It's a strange one actually, Reg 422.3.201 says suitably protected against mechanical damage, but it's strange how it doesn't say a word about suitable protection if it's twin and earth which is just a different shape...

It's a fairly recent change in the regs which allowed flex to be installed at all, it was previously limited to 2 metres max length for appliance tails.
Every cable has to be suitably selected with regards to protection suitable for the environment it is in, regardless of what type it is.

 

[uksparks]

Andy, you have a point.

Dave, well I shod think myself lucky that I live in such a modern world with updated regs!

 

[davesparks]

Have you considered the max conductor operating temperature of the flex? A lot of it is rated to only 60degrees when fixed wiring and accessories are all rated for 70degrees. Will this make any difference? I don't know, but you need to consider it

 

[uksparks]

This is quite an interesting thread which I don't recall being touched upon before!

 

[davesparks]

This is quite an interesting thread which I don't recall being touched upon before!

It certainly beats a thread about stiff cutters!

 

[Andy78]

Any takers about my post #8 and the regs stating a minimum csa of 0.75mm for the use of flex ?

 

[davesparks]

Here's a bit of relevant history
14th edition

13th edition