6A Roses

[EFLImpudence]

What does the 6A mean? Is it only the obvious or is there something else?

Apart from the obvious and it is often stated this is the reason for the use of 5 or 6A OPDs on lighting circuits, is it really true that the terminals can only have a CCC of 6A?

The only occurrences of 6A flowing through a terminal block would be between the loop conductors in the live and neutral blocks on a fully loaded circuit at the first accessory on the circuit.
Fault current would be considerable more, of course, and presumably the block can handle this.
If 1mm² conductors are adequate for any fault current expected then presumably the terminal blocks must be as good or better than the cable.



As is apparent

the terminal material between the conductors is considerably larger than a 1mm² conductor which has a CCC of 16A.
Were we to put the loop conductors in the same terminal hole? would this remove the 6A limit?


What is going to be damaged should the circuit have, say a 10A OPD?

 

[securespark]

Witness the thousands of lighting circuits that were installed when 1 x 60W lamp in each room was considered the norm, but since then the circuit has expanded massively along with the circuit breaker. Most of these piecemeal circuits (and I'm thinking about a Wylex Standard CU here) have been "upgraded" with a 10A breaker. A fair few I have seen have had a 16A breaker fitted.

They seem to be running OK.

 

[AndyPRK]

While I don't see an issue with the op.

It's a stretch to say most have 10A breakers. !!!!

 

[ericmark]

I agree the ceiling rose design seems to be ample to take 16A even if it is only rated at 6A. However I had a problem using a 16A supply for an outside lamp, I used a 8W Ikea bulb which went faulty clearly without any internal fuse which should be included with a BA22d cap which resulted in the bulb being welded onto the holder when it went faulty. With a 6A MCB this is less likely to happen. This diagram

shows how even with LED lights a resistor is used as a fuse even with cheap Poundland types. However it seems Ikea are not as good as Poundland and we have really no control as to where people buy their bulbs from.

The bulb holder is only rated at 2A and other than a fault that is not a problem. As to circuit sizes yes there was a peak where lighting circuits were overloaded with silly MR16 lamps, it resulted in the lighting circuits being divided into two with upper and lower floor, but in 2008 the change in the rules for use of RCD protection highlighted many errors with the splitting of the lighting into two circuits where it had resulted in borrowed neutrals one cure was to re-combine the two circuits, but this also coincided with the introduction of low energy bulbs so combining circuits was not really a problem as today lighting circuit load has very much reduced.

We have to accept both DIY and Electricians have in the past ignored some of the rules and have overloaded circuits using the lighting circuit to both light and heat the room using MR16 light fittings, which resulted in swapping MCB's to 10A and splitting circuits with borrowed neutrals and even when the 2008 rules came in instead of removing the borrowed neutral have put the two MCB's on the same RCD there is really no excuse for this, they know they have a borrowed neutral at least before the RCD the electrician could claim he did not realise the two way switching on the stairs was causing a borrowed neutral but when it trips the RCD they must be aware of what has happened and know very well moving the two MCB's to same RCD is not a permitted cure.

So faced with either borrowed neutral or 10A MCB to my mind the 10A MCB is the lesser of the two deviations from regulations, and from what I am lead to believe with amendment 3 there is some relaxation on the following manufacturers recommendations?

So personally I would not chance a 6A MCB to a 10A MCB for lighting, however if a 10A MCB was already fitted I would not worry about it, as 16A that is to my mind stretching it a bit too far even if it is the regulation limit for lighting circuits. I believe we have to use some common sense, if the installation has gone daft with ceiling fans, extractor fans, shaver sockets, and use of MR16 lights to heat and well as light the room then it's time to say enough is enough and some division of the circuit is required. However if only just on the limit and it trips every so often with a 6A MCB then moving to a 10A is not really any problem even if it does not comply strictly with manufacturers recommendations.

 

[securespark]

While I don't see an issue with the op.

It's a stretch to say most have 10A breakers. !!!!

Fair point. Maybe it would have been more accurate to say that of those lighting circuits which have had their CPD "upgraded", most are 10A, with a few 16A.

Perhaps I just visited all the DIY-ravaged houses!!

 

[Iggifer]

Nope, last Wylex board I took out had a 10A retrofit on the lights.

I don't see an issue personally, the surface area is clearly bigger than that of the cable, but I guess we don't know what %age of copper there is in the brass terminals.

2-Plate all the way!