13A socket on a lighting circuit - theoretical question.

[rsgaz]

Because threads on this topic usually descend into a long winded unhelpful argument, I've not really paid much attention to them, I usually just skim through them, but...

Assuming the circuit is 1.5mm² and assuming you have "reference method 100" or better, can't you just stick a B16 in the consumer unit and then have your single socket in the loft, without fear of anything bad happening at all, even when you for 'some reason' decide to take a kettle up in the loft?!?! (not that I agree with that stance/reasoning anyway)

Am I missing something obvious/prohibitive here?

The reason I fear I am missing something obvious, is, how come this doesn't seem to get suggested in those threads, if this is, indeed, perfectly fine to do?

 

[ericmark]

Yes you have missed something.
1) In the main some where on a lighting circuit you have some thing rated 6 amp so in the main you can't lift to 16 even though 16 amp is the BS7671 limit for lighting circuits.
2) "Every installation shall be divided into circuits, as necessary, to:" and six reasons are given, biggest is "(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit." now that can be got around, in my old house we had an emergency light at top of stairs so failure of lighting circuit would not cause a danger. But also in loft I have lights but loft is boarded so even there loss of light would not cause too much danger, but if the loft is not boarded and you have lights in loft then again could be considered to be causing a danger.

However as I have said before, LAP do grid sockets, so you can fit a double socket box with a single socket, switch and fuse, using a 1A fuse then it is unlikely should the TV pre-amp be unplugged and a kettle plugged in instead that the B6 MCB would trip before the fuse blows. In fact fluorescent light fittings use to come with a 3A fuse inside, so a fault in one fitting would not take out all, I suspect a 3A fuse would work with a 5A fuse in the consumer unit, but with 6A MCB it likely would not which is why I say 1A.

 

[JohnD]

Yes you have missed something.
1) In the main some where on a lighting circuit you have some thing rated 6 amp so in the main you can't lift to 16 even though 16 amp is the BS7671 limit for lighting circuits.

In my house, all the light switches and fittings are rated at 10A

if the loft is not boarded and you have lights in loft then again could be considered to be causing a danger.

good point

 

[ericmark]

In my house, all the light switches and fittings are rated at 10A

All my ceiling roses are rated 6A, I have not a clue why, I am sure they could carry 30A, but since the ceiling rose is a junction box that feeds next lamp, it means limited to 6A MCB, a BA22d bulb holder is often rated 2A, however in theory there should be a fuse in every bulb, and it only feeds one bulb, so that is OK.

 

[EFLImpudence]

All my ceiling roses are rated 6A, I have not a clue why, I am sure they could carry 30A, but since the ceiling rose is a junction box that feeds next lamp, it means limited to 6A MCB,

Why? Does the same not apply to a 13A socket on a 32A radial?

a BA22d bulb holder is often rated 2A, however in theory there should be a fuse in every bulb, and it only feeds one bulb, so that is OK.

How many Amps will the lamp draw? I.e. pass through the holder.

Assuming the circuit is 1.5mm² and assuming you have "reference method 100" or better, can't you just stick a B16 in the consumer unit and then have your single socket in the loft, without fear of anything bad happening at all, even when you for 'some reason' decide to take a kettle up in the loft?!?! (not that I agree with that stance/reasoning anyway)

You could.
You can design a circuit to supply whatever you want.

Am I missing something obvious/prohibitive here?

Yes, the fact that the British like to do what they have always done because that's what they always do so that's what they do.
Also the calling them "lighting circuits" confuses a lot of people who fit fans, boilers, shavers, amplifiers and other things on the circuit yet still call it a lighting circuit.

The reason I fear I am missing something obvious, is, how come this doesn't seem to get suggested in those threads, if this is, indeed, perfectly fine to do?

I think it has been suggested but tradition is a strange powerful thing.

 

[ericmark]

Why? Does the same not apply to a 13A socket on a 32A radial?

Because we know the 13A rating refers to how much can be drawn from the socket, not how much it can handle as a junction box, however if you were to use a 45A supply to a 4 mm² ring final then one would have to ask if the socket could handle that supply.

How many Amps will the lamp draw? I.e. pass through the holder.

We I know my Gran plugged the iron into the lights, as to watts of iron don't know, however likely more than 500W, but it was against the law to use a lighting circuit for power, I assume when the power and lighting supplies were combined that law was repealed?

 

[JohnW2]

.... Assuming the circuit is 1.5mm² and assuming you have "reference method 100" or better, can't you just stick a B16 in the consumer unit and then have your single socket in the loft, without fear of anything bad happening at all, even when you for 'some reason' decide to take a kettle up in the loft?!?! (not that I agree with that stance/reasoning anyway) .... Am I missing something obvious/prohibitive here?

You could do that, but you have seen some of the arguments 'against' it - e.g. that some copmponents on a lighting certain might not be adequately protected by a 16A OPD, and that having sockets and lighting on the same circuit might not satisfyt some people as regards ';separation of circuits'. I am not necessarily impressed by either of those arguments.

In passing, despite your having emboldened it, it would not necessarily have to be one 'single' socket - you could have as many 13A sockets as you liked on a 16A (or 20A) radial, provided only that the CCC of the cable was no less than the rating of the OPD - so 50 sockets on Method C 1.5mm² protected by a B16 would be acceptable!

Kind Regards, John

 

[EFLImpudence]

Because we know the 13A rating refers to how much can be drawn from the socket, not how much it can handle as a junction box,

Why, then does the same not apply to a ceiling rose?
Is it your opinion that the terminal blocks in a rose are considerably smaller than those in a 16A J501 junction box?

however if you were to use a 45A supply to a 4 mm² ring final then one would have to ask if the socket could handle that supply.

Same argument.

We I know my Gran plugged the iron into the lights, as to watts of iron don't know,

Did it hurt the rose?

however likely more than 500W, but it was against the law to use a lighting circuit for power, I assume when the power and lighting supplies were combined that law was repealed?

Against the law? Did enforcers visit to check?

 

[securespark]

There is no issue having 2, 5, 6 or 10A accessories on a 16A circuit, unless each accessory is loaded beyond its rating.

 

[JohnW2]

There is no issue having 2, 5, 6 or 10A accessories on a 16A circuit, unless each accessory is loaded beyond its rating.

Agreed - but (as with 20A switches on 32A circuits), some people try arguing on the basis of what I would call an inappropriate conception of 'loaded'.

Kind Regards, John

 

[JohnW2]

... but if the loft is not boarded and you have lights in loft then again could be considered to be causing a danger.

I suppose so - but, if the loft is not boarded, then having no lights at all would be an even greater danger (or, at least, a much more frequently encountered danger) - but there is no regulation of any type which demands lights in lofts.

Kind Regards, John

 

[EFLImpudence]

My light switches are 10A on 16A circuit, but -

as I have queried before the actual contacts (same with socket switches in UK) are very small 'pimples' that come together.
The csa of the current path at the point of contact must be extremely small.

 

[JohnW2]

My light switches are 10A on 16A circuit, but - as I have queried before the actual contacts (same with socket switches in UK) are very small 'pimples' that come together. The csa of the current path at the point of contact must be extremely small.

Indeed - but, as you know, with the exception of fault currents (which is a different matter) no single load on a lighting circuit is ever going to result in anything approaching 10A flowing through the switch contacts.

Even winston has not suggested that anyone would feed a vacuum cleaner through a light switch! Even if 16A were flowing through the cables connected to the supply side of the light switch were carrying 16A (e.g. to supply winston's super-high-powered vacuum cleaner!), that would not flow through the switch contacts.

Kind Regards, John

 

[EFLImpudence]

Indeed - but, as you know, with the exception of fault currents (which is a different matter) no single load on a lighting circuit is ever going to result in anything approaching 10A flowing through the switch contacts.

I think I have made that point in reference to the 2A lamp holder.

Even winston has not suggested that anyone would feed a vacuum cleaner through a light switch! Even if 16A were flowing through the cables connected to the supply side of the light switch were carrying 16A (e.g. to supply winston's super-high-powered vacuum cleaner!), that would not flow through the switch contacts.

Agreed (obviously to me) but Eric is saying that is not the case.

My switches must surely be capable of switching 10A through those very small 'pimples' (what's the right word?).

I mentioned the pimples to emphasise how big the terminals are in a rose.

 

[JohnW2]

Agreed (obviously to me) but Eric is saying that is not the case.

He always does.

My switches must surely be capable of switching 10A through those very small 'pimples' (what's the right word?).

I somehow doubt that it is the 'correct technical terminology', so maybe you should rap yourself on the knuckles (or, at least, 'correct/educate yourself!) - but I do understand what you mean

... but. yes, one assumes that if a switch (of any sort) has just a single stated 'current rating', that that 'rating' relates to the current it can safely break (and not the current that can flow between two conductors in one of its terminals).

Kind Regards, John