Outside light replacement.

[jec911]

Morning all,

I have a query regarding the replacement of an outside light which I hope someone can point me in the right direction.

I am familiar with Part P but I deem this to be a replacement of an existing external light - which a section in the ODPM site advises you can do.

At the moment, there is a 2G light switch in our hallway, of which one of the switches has a cable which basically runs towards supplying an outside light (but it not connected to anything).

This is connected to the lighting circuit.

This has been re-directed to serve a light in the porch which was never fitted.

Consequently, the outside light currently is supplied from a mains plug in the garage.

Theoretically, I would have thought this would be a simple thing to change so that the outside light is served by the lighting circuit in the hallway which it looks like it was designed to do (this would involve pulling the cable back through to the garage from the porch and directing it back through the front of the house to supply the outside light) - and do away with having a porch light which we don't want.

However, the light instructions advise that it must be connected to a fused switched spur from the ring main. I am already running a fused non-switched spur from the only mains socket in the adjacent garage now to supply an intruder alarm, and as I understand it, it is not good practice to run another from it.

Is there any reason why I cannot connect this lamp onto the legacy (the house is 10 years old) cabling supplied from the lighting circuit (i.e. so the hallway switch can turn it on and off)?

I can only assume the reason for a fused switched spur is for safety but we have a CU with RCD on the lighting circuit...?

Many thanks,

John.

 

[jec911]

The lighting circuit is earthed btw (which is something else I thought might have been the reason).

 

[mapj1]

There are 2 issues. If the outside light is a half kilowatt floodlight, the lighting circuit may overload, so these should always have their own feed.
(Quartz halogens have a high inrush - cold current about 13 times the hot value, and if the circuit is already well loaded, nuiscecne tripping might be a serious problem.)
The second issue is if you really want the whole house plunged into darkness, if there is a problem with the fitting. Much nicer to pull out the 13 Fuse from the spur or unplug it, and carry on as before.
You don't worry too much about part P, it is far more important the job is done correctly, actually there are plenty of sparks out there working every day as if Part P did not exist - you will simply join a significant army whose paperwork is not quite right.

In any case, one of the more official lists compiled for the iee magazine 'wiring matters' with ODPM advice, suggests that lights attached to the building are not what they are worried about, and only count as notifiable if outdoor switches and sockets etc are involved.
http://www.iee.org/Publish/WireRegs..._part_p_notifications_to_building_control.pdf

 

[jec911]

The replacement light is a 13w PIR jobbie - although this is additional as the current light is on the ringmain.

However, I only have 11 bulbs downstairs and not all are 100w.

We have two floors and a lighting circuit for each - so the whole ground floor would be plunged into darkness.

I am with you on the convenience part of it though - is it ok to run more than one spur of one ringmain socket?

That document is the clearest I've seen yet. It looks like I can do what I wanted to do anyway!

Thanks for the advice mapj1