Cable for External PIR Light

claret73 · Oct 5, 2010

Have a few External PIR Lights to fit and currently the customer has them plugged into a socket in the loft...
Have discussed breaking into the lighting circuit & feeding into Spurs, but am wondering if I need to be using Arctic Flex on the load side to feed outside? Can I use a lesser cable that would be suitable for fitting externally? 1x fitting has a drop of around 4Meters, clipped direct & to the fitting & the others no more than a metre.
Cheers

telectrix · Oct 5, 2010

you can use normal pvc flex outside. you don't say whether they are 500w floods or lower power fittings. for 500w floods, i would come off a ring main with fused spur/s @ 5A.

Amp David · Oct 5, 2010

Got hold of a drum of pond flex and have used that recently. Its good because its UV resistant

malcolmsanford · Oct 5, 2010

How many are you talking about here .................? and is spuring into the exisiitng lighting circuit the best option. Perhaps if you have 1 or 2 outside lights then yes. If you have more than that then perhaps a spur of a ring or a new circuit would be better.

If you are going to use flex that tells me that your coming off the "lights" circuit to a box somewhere and then running flex to each individual light from that box. Might not a better way to go is from that box run some PVC conduit to each light into a through box then gland the cover plate and flex connect inside the box.

Amp David · Oct 5, 2010

malcolmsanford said:
How many are you talking about here .................? and is spuring into the exisiitng lighting circuit the best option. Perhaps if you have 1 or 2 outside lights then yes. If you have more than that then perhaps a spur of a ring or a new circuit would be better.

If you are going to use flex that tells me that your coming off the "lights" circuit to a box somewhere and then running flex to each individual light from that box. Might not a better way to go is from that box run some PVC conduit to each light into a through box then gland the cover plate and flex connect inside the box.

This is exactly what I did Malc, but instead of coming of any existing circuits, (as house electrics arn't the newest in the world and not getting stuck there testing and opening a can of worms), I stuck in a 2 way CU from split tails, 1.5mm T+E in conduit then drop to each light in flex. Nice looking job and took no time at all.

andekoch · Oct 5, 2010

I use NYJJ (high tuff equivalent) for outside/ UV exposed cable. Have been considering pond flex recently though sinc eit is cheaper and easier to work with than NYYJ which is pretty stiff and a bugger to get into the fittings.

claret73 · Oct 6, 2010

Hi
Thanks for the replies...
The PIR's are totalling 3 fittings. 1 at front, 1 at back & 1 at side of house above flat garage roof. 2 are at the height of the Loft Space & 1 is below roof line of kitchen extension, so height of 1st floor window.

So, my thoughts were to break into the upstairs lights in the loft & feed a Fused spur for each fitting & out of that take flex out accross the loft to each fitting. The back one has the drop to the Kitchen window height. TBH, Conduit would be more obtrusive than clipping in a neat straight line (this runs about 1m, then is clipped to soffit around to fitting).

I need to do the diversity calc on the lighting circuits as they would be 500w each. Upstairs inc 3x 500w PIR's total 2kw thereabouts but can come off the ring circuit I think, as an unknown spurred 2.5mm (need to trace this) is in the loft which these fittings were plugged into originally.
If I've missed anything, please comment...
Cheers again
Andy

malcolmsanford · Oct 6, 2010

Don't come off the lighting with that load claret it's far too much. I know that as they are PIR the chances are they will only be on for a few minutes but if for some reason they all activate you will have 6.5amps plus if the lights are on in the house, it's exceeding the 6amp breaker and if it's a 5amp you will have bigger problems. The chances are you making a situation where the protection device can nuscence trip, and quite a lot of calls for you!!

If you can't get a seperate supply from the CU then find the ring upstairs and fit a FCU 13amp it. Then run round the loft in 2.5mm to each light and terminate into a box. The 2 at loft level flex into the boxes. The lower one well your call but again I would conduit down to it I think it looks neater than clipped flex, but that is just me

claret73 · Oct 6, 2010

Malc
Excellent advice! Many Thanks. After doing the calcs, I saw it was too big for the lighting. It's a 3036 5A. Fortunately I have the 2.5 Spur into the loftspace, so can use that for the FCU. I did say it was a client (actually it's my Dad's House) & the ring is supplied for both up & down...

I'll do a ZS & calc the Fault current & will go with your suggestion of looping round boxes. I think I'll ask him what he prefers with Conduit or clipped. It's just in an obvious drop on the back wall down to the kitchen roof, so no hiding anything really.
Thanks for all your Input on this Malc!!! Very appreciated...If you've seen me pop up occasionally on here, you'll know I'm fresh out of L3 Guilds, so now having a few little friends & family jobs to do, it's always good to find ways of doing something that hadn't occurred to me.
Cheers
Andy