Debate Regulation 434.2.1

[Pete999]

Before anyone starts slagging me off, or calling me a Muppet that I should know better:shades_smile: I would like to start a discussion regarding Spurs off of a Ring Final Circuit. I have been in this game for a long time now, and always have, and always will spur off of a normal 32a RFC wired in 2.5mm twin with cpc, with the same sized cable, as described in the BGB Appendix 15 page 425.

Looking at the diagram on page 425 it does show that you can use 1.5mm twin with cpc provided you install a fused connection unit prior to the reduction of CSA ie 2.5 down to 1.5 correct?

Now regulation 434.2.1 states, ambiguously that providing the distance is less than 3 meters, you need not fuse down at the point of CSA reduction. I always referred to that particular Regulation with regards to industrial situations for example when you connect to a bus-bar chamber, to provide a feed to a smaller switch-fuse feeding another circuit.

I would like the forum to debate this, as some people are saying that providing the distance is less than 3 meters this ruling can be used in the domestic situation within the RFC situation, ie spur off to a new Socket using 1.5mm cable without fusing down.

As I said not something I would, or have done in the past, sorry for the ramble, but would be grateful for your opinions:clap:

 

[telectrix]

my view is that it's OK for a single socket, where the load is limited to 13A, but would not advise fitting a double without fusing down at the RFC.

 

[spark 68]

I have done it, and would do it again.

Where I have done this though was not to supply a S/O, but for a cooker hood of off the cooker supply point, and for a combi-boiler supply, both fused @ 3A, and always much less than 3m

If it was for a S/O I would have used 2.5mm.


Edit: I may do it for a dedicated single S/O.

 

[overskilled]

Wouldn't do it...all too easy for someone to swap a single for a double (convertasocket for example)

 

[spark 68]

Wouldn't do it...all too easy for someone to swap a single for a double (convertasocket for example)

I did it to a SFCU, or a single S/O for the cooker hood, if it was for a general use S/O then probably not, for the same reason you gave.

 

[Plonker 3]

Wouldn't do it...all too easy for someone to swap a single for a double (convertasocket for example)

But would you carry out a install on a circuit with a 3036 protecting it, just because someone could change the size of the fuse wire?

 

[camerabloke]

Doesn't 434.2.2 have a bearing on this. Do you not have to swap origin fuse for lowest csa?

 

[Plonker 3]

You can fuse upstream, that's how I read 434.2.2 .

Think of things like bus bar chambers.

 

[camerabloke]

You can fuse upstream, that's how I read 434.2.2 .

Think of things like bus bar chambers.

You can read it a few ways. It's unlike BGB to be vague!!!!

 

[spark 68]

Doesn't 434.2.2 have a bearing on this. Do you not have to swap origin fuse for lowest csa?

No, that reg says 'may', the forward fusing regs are an alternative method with the proviso of not being more than 3m etc., 434.2.1 gives the exception.

 

[Plonker 3]

"As long as no branches or points of connection"

Seems pretty clear, although yes sometimes you do have to sometimes read it several times to fully understand it.

 

[Guest55]

simple laws of physics superceed "traditional methods" , which are usually applied without any clear thought.

 

[Guest55]

Wouldn't do it...all too easy for someone to swap a single for a double (convertasocket for example)

thats no arguement at all is it ?
and whats stopping someone swopping your 8 kw shower for a 10kw 2 weeks later ?
as soon as an Ib has been altered after installation then all bets are off in my mind

 

[SJD]

I'm unlikely to install a <3m spur on 1.5mm cable, because I'd have 2.5mm cable with me anyway, plus the different conductor sizes where the spur is connected make it more likely the smaller size cable will come loose (unless a Wago box or similar).

 

[CrazyScozzese]

I would like the forum to debate this, as some people are saying that providing the distance is less than 3 meters this ruling can be used in the domestic situation within the RFC situation, ie spur off to a new Socket using 1.5mm cable without fusing down.

What the reg says is that you can fuse it down along the 3M max length or at the end with a FCU, but you still need to fuse it down. The fuse in the plug, if in a spurred socket, is for the cable attached to the plug not the spur cable. Alternatively you can fuse it down on the supply side, eg at CU, if you have an old radial in say 6mm2 that you have added a smaller CSA to the end off. You would need to label the CU to warn of this. That said, I have been to a seminar where the NIC man said blah blah blah ... effectively protected by the load.... blah blah blah. But any blahs mean you have to do the explaining if there is a problem.

The 3M is generally used ref adiabatic, at that length and the resultant resistance, it is less liable to generate too much heat before even an over rated MCB or fuse pops in the event that the cable is shorted out before the downstream fuse. It is for a similar reason that (short) 16mm2 tails on a 100a cut out can be deemed compliant where the max demand is met by the 16mm2 tails and they are also effectively protected downstream. I wouldn't recommend doing it, and many LABCs or even scheme inspectors would say it is not allowed... but then they could read a bit more.