Light problem.

[Joeydeacon]

I have power running to my log cabin and it is wired up to a consumer unit in the house. At the moment there are only sockets being used and I have just wired a ceiling rose up so that it can be plugged in. Is it possible to take a spur off that feed and create an independent light and switch? Just to clarify, can I use the feed to supply power the lighting and then fit a switch to turn the light and off. Many thanks.

 

[JohnW2]

I have power running to my log cabin and it is wired up to a consumer unit in the house. At the moment there are only sockets being used and I have just wired a ceiling rose up so that it can be plugged in. Is it possible to take a spur off that feed and create an independent light and switch? Just to clarify, can I use the feed to supply power the lighting and then fit a switch to turn the light and off. Many thanks.

In principle, yes. Details could depend upon what MCB you had in your house CU, but you could circumnaviagte that by spuring off to a 'switched fused connection unit', with a 3A fuse in it, and you could use its switch to control the light. Something like ..

Kind Regards, John

 

[Joeydeacon]

Hi, John. Thanks for replying. I can’t see the image but at least knowing it might be possible is good to hear. Will check out the con unit and try post again. Cheers.

 

[ericmark]

I hate the phrase "can I".
Can you wire your log cabin in law, yes, although you will likely need to register some of the work.
Can you supply lights from a socket supply, yes, however BS7671 says lights need a overload device under 16 amp, @JohnW2 has shown one method.
Have you got the skill, I have not a clue.

You need to remember new wiring has to follow current rules, so although you can still use a home with no RCD protection the new home will need it, you can get a RCD FCU

but if you already have 30 mA RCD protection there is no need to double up.

 

[JohnW2]

Hi, John. Thanks for replying. I can’t see the image but at least knowing it might be possible is good to hear. Will check out the con unit and try post again. Cheers.

You're welcome. I'm not sure why you couldn't see the image - i can Is this any better ..

Kind Regards, John

 

[JohnW2]

Can you wire your log cabin in law, yes, although you will likely need to register some of the work.

I presume that you mean 'notify', rather than 'register'. Since there is already an electricity supply to the cabin, then, in England, it's very unlikley that notification for adding a light to an existing circuit would be required. If you were to be pedantic and try to argue that connecting it via a SFCU (as I suggested) would amount to 'adding a circuit', the I suppose that you might have to tell the OP to go back to his Plan A and 'plug it in' to one of the existing sockets - but that would, in my opinion, be silly.

... however BS7671 says lights need a overload device under 16 amp, ...

You may be right (and, in any event, that would be sensible to allow a sensible sized cable to be used - hence my suggestion) - but, out of interest, what regulation do you believe imposes that requirement?

You are right that the new light requires that the circuit be RCD protected but it's quite likely that (if installed compliantly at the time) the circuit supplying the sockets (which are presumably 'likely to be used for outdoor equipment') will already be RCD protected.

Kind Regards, John

 

[ericmark]

559.6.1.6 Lighting circuits incorporating B15. B22. E14. E27 or E40 lampholders shall be protected by an overcurrent protective device of maximum rating 16A.

 

[EFLImpudence]

Now 559.5.1.204

 

[EFLImpudence]

The 16A only apparently applies to circuits with those lamp holders.

Is there a reason?


So, if not GU10, for example, what is the difference?

 

[JohnW2]

The 16A only apparently applies to circuits with those lamp holders. Is there a reason? So, if not GU10, for example, what is the difference?

Goodness only knows. As you will realise, I'd actually totally forgetten about that reg, perhaps because it makes little sense!

Kind Regards, John

 

[ericmark]

It likely came from the design of a tungsten bulb, and the way they could have ionisation of the atmosphere inside the bulb, possibly no longer required, although since a standard ceiling rose is rated 5/6 amp and many light switches were only rated 5/6 amp in real terms there was a 5 or 6 amp limit as the ceiling rose is used as a junction box.

 

[JohnD]

More often 10A, surely.

 

[JohnW2]

It likely came from the design of a tungsten bulb, and the way they could have ionisation of the atmosphere inside the bulb, possibly no longer required ...

Yes, the general sort of thinking that led someone to decide on the need for that was very probably something like that - but why 16A and, as EFLI asked in the question I responded to, why only for lamps/bulbs with certain bases?

However, this is a rare, if not unique, example of a regulation seemingly considering an OPD's role to be something beyond just 'protecting the cable'. In any other situation we would say that if a load requires over-current protection, then it should be provided within the load (which, of course, generally was the case with incandescent bulbs).

... although since a standard ceiling rose is rated 5/6 amp and many light switches were only rated 5/6 amp in real terms there was a 5 or 6 amp limit as the ceiling rose is used as a junction box.

You often say that but, as I imply above, I'm not aware aware of any other regulation which limits the circuit's OPD on the basis of the 'rating' of accessories or connected equipment (rather than the cable).

I know you have stories about bulbs getting welded into holders/sockets, but in the face of a massive current, that's likely to happen so quickly that a 5/6A OPD probably wouldn't prevent it any more than would, say, a 50A one.

Kind Regards, John

 

[ericmark]

If the ceiling rose feeds one bulb then being rated 6 amp does not really matter, same as the BA22d bulb holder being rated 2 amp, there should be a fuse built into every bulb, so 2 amp is ample.

However if the ceiling rose also feeds another ceiling rose so acts as a junction box with more than one output, then the 6 amp rating has to be considered and the whole circuit needs limiting to 6 amp.

Yes I know a ceiling rose will likely handle far more than 6 amp, so in real terms does not present a danger, however we really do not want to have some thing a jobs worth EICR inspector can pick up on.

 

[JohnW2]

.... However if the ceiling rose also feeds another ceiling rose so acts as a junction box with more than one output, then the 6 amp rating has to be considered and the whole circuit needs limiting to 6 amp.

As I said, I'm not aware of any regulation which requires a circuit's OPD to be sized on the basis of the 'rating' of accessories - whether JBs, ceiling roses or anything else. All the regs are concerned about is the CCC of the cable. ... or am I missing something?

Kind Regards, John