Split Single Outside Light into Two

[Tom1980west]

Hi,

Hoping this is a very simple question to answer.

I currently have a single bulkhead light on the outside of my house, which is control by a switch inside the house.

I would like to replace it with two PIR lanterns, but keep the switch in place should we need it turned off.

Is this as simple as running the cable going to the existing light into a junction box to allow me to run the two new cables off of the existing circuit? If so, could let me know what type I would need, that'd be great as it needs to be outside (although it will be sheltered by the porch against the elements).

Thanks in advance

 

[stem]

You should be able to replace the existing bulkhead with a PIR lantern and then wire the second PIR lantern directly into the terminals of the first one. Saves the need for a junction box and looks much neater.

Bear in mind, that standard Twin and Earth cable without additional protection such as conduit, is not seen to be acceptable for outdoor use now, because it can be damaged by sunlight, frost, etc.,

 

[ericmark]

Yes simple split, and JB would need to be IP54 or better. There are two methods with outside boxes, one allows the odd bit of water or dust to enter but also allows it to exist again, the other simply seals very well. But to seal very well means the glands must also seal very well. So I prefer the idea of having a small hole in the bottom that water can get out again. Often that small hole is a gap in the sealing gasket which clearly needs to be at the bottom.

A box like this

is fine if all cables are cleated but if the cables could be pulled you would use stuffing glands to grip the cables. It is really all common sense.

 

[Tom1980west]

Thanks for the help, the suggested junction box is similar to what I was thinking. I need the lights on the left and right of the porch entry, so this is the simplest installation. As you can see from this image, the bulkhead is pretty well secluded from the elements behind and above the wooden beam.

One final thing, in terms of cable, there are various different widths of 3 core but I'm not sure which thickness I need - what's the driving factor for a thicker cable?

 

[Taylortwocities]

Given your layout, you need to think about where the PIR will go.

If it is located with one of the lights, then the PIR will only detect someone approaching the front door. The PIR will not see you as you leave the house.
If that is OK, then I suggest you get a separate PIR and locate it above the porch (about where the "Old Bulkhead" label is on your picture).
Then you can choose two matching lights for the sides of the porch.

For the junction, a box like Eric has suggested will be fine, that location is not going to get wet…


re

I'm not sure which thickness I need - what's the driving factor for a thicker cable?

The size of cable will depend on the size of the fuse for the circuit. Assuming it is a lighting circuit, with a 6amp fuse / MCB in the consumer unit, then 1mm² cable will be fine.

 

[ericmark]

Don't forget the drain holes, I did read this on how my lamp went wrong any air will expand and contract if you try to seal 100% likely it will fail, even the smallest of holes in the bottom stops it sucking in water. The water does not just run in it is sucked in. Shower of rain cools the box and sucks in any water around any of the joints.

 

[Taylortwocities]

Eric, the box is going to be tucked in the ceiling of the porch and protected by that overhang. It ain't going to get wet, unless someone gets up to the front door with a fire-hose

 

[stillp]

OTOH, if you have a drain hole, the spiders will get in, so better jam some Scotch-brite in the hole.