Wiring downlights question

[Ribol]

Need some advice from someone who knows regarding fitting some downlights.

My house has 1.0mm wiring lighting cable into the loft which currently connects to the single ceiling rose for a pendant type light.

I would like to do away with that and fit 6 x downlights and I am thinking GU10 bulb downlights.

Without upgrading to 1.50mm wiring, so sticking with the original 1.00mm wiring, what type/wattage GU10 bulbs(6) can I run safely?

Many thanks for shedding any light on this

[cjs]

You need to make sure the wiring will accommodate the maximum load that is possible, in this case it is 6 x 50w lamps, even if you don't put in 50w lamps, someone else might! This is not an issue however, your lighting circuit will take up to 6 amps which is a total of 1380 watts at 230v. You will be loading it with 300w. I doubt the rest of the lighting on the circuit will be anywhere near the balance.

[Ribol]

cjs said:

You need to make sure the wiring will accommodate the maximum load that is possible, in this case it is 6 x 50w lamps, even if you don't put in 50w lamps, someone else might! This is not an issue however, your lighting circuit will take up to 6 amps which is a total of 1380 watts at 230v. You will be loading it with 300w. I doubt the rest of the lighting on the circuit will be anywhere near the balance.

Thanks for that.

As you correctly say, the whole of the lighting on this circuit/fuse is nowhere near your 1380 watts figure.

The reason for the question is that I asked a similar question in an electrical factors where I went to enquire about lights. The comments from both the salesman and an electrician shopping there was that I was pushing my luck load wise. Were they talking the electrical equivalent of bo locks then?

[Marcellus]

I'm not technical but Mrs M is (Electro/mechanical Engineer) and about 8years ago we rewired our flat with downlighters and because of the theoretic max load I know in our bedroom where we had about 12 downlighters we had to break it into 3 circuits with each circuit back to the main fuse board.

It was something to do with the start up peak not the running peak iirc.

When our flat was subsequently inspected the inspector commented that it was good to see such diligence in circuit loadings as these days too many electricians push their luck.....

OK that was before all the current legislation on testing etc etc but I can only imagine that it's got tighter.

[Raverbaby]

You'll be fine OP. Your not going to have ALL your lights on at one time, even if you do you'll probably be nowhere near 6Amps (unless its downlight city).
Your 6A fuse will protect the circuit from overload.
Remember to move any insulation well away from any wiring, and also the lights themselves ensuring there is adequate space above and around fitting as these run very hot.
The manufacturers will tell you how much clearance you require above your lights, its normally 100mm/4".

[Ribol]

Raverbaby said:

You'll be fine OP. Your not going to have ALL your lights on at one time, even if you do you'll probably be nowhere near 6Amps (unless its downlight city).
Your 6A fuse will protect the circuit from overload.
Remember to move any insulation well away from any wiring, and also the lights themselves ensuring there is adequate space above and around fitting as these run very hot.
The manufacturers will tell you how much clearance you require above your lights, its normally 100mm/4".

Thanks for that.

I still have an old style "fuse box" and this circuit is on a 5A fuse, so in theory a capacity of 1150w? Forgetting this room, the rest of the lights on this circuit add up to only 380w, so making 680w total with these new ones.

Only thing above downlights is the roof(loft), the holes are smack in the middle of the joists, no loft insulation near them. All wiring on top of joists so not covered/enclosed.

Not too sure what they were on about in the shop then(see above), I thought I must have been missing something - it would seem not from what you say.

[Raverbaby]

Your lights should be away from joists, having them close becomes a bit of a fire hazard. I wouldn't recommend cutting joists to suit your lights, you may have to reconfigure the lights to suit, hopefully its not too late!!
I always take what the "salesmen" say with a pinch of salt, many of them probably haven't wired a plug.
Your calculations are right, A 5Amp fuse will take 1150watt(230v) although it will need to be more over a period of time before it actually "pops".
With this in mind I can only imagine that theres been a mix up when you were chattin to the 2 chaps.
If your in england i'm sure you need permission from building control to carry out this work, although i'm not 100% sure. Part P is what you will need to google!

Edited by Raverbaby on Thursday 17th June 23:43

[Ribol]

Raverbaby said:

Your lights should be away from joists, having them close becomes a bit of a fire hazard. I wouldn't recommend cutting joists to suit your lights, you may have to reconfigure the lights to suit, hopefully its not too late!!

I didn't explain that very well, the holes for the lights are the same distance from the joist either side of them ("smack in the middle")

[Smiler.]

Ribol said:

Raverbaby said:

You'll be fine OP. Your not going to have ALL your lights on at one time, even if you do you'll probably be nowhere near 6Amps (unless its downlight city).
Your 6A fuse will protect the circuit from overload.
Remember to move any insulation well away from any wiring, and also the lights themselves ensuring there is adequate space above and around fitting as these run very hot.
The manufacturers will tell you how much clearance you require above your lights, its normally 100mm/4".

Thanks for that.

I still have an old style "fuse box" and this circuit is on a 5A fuse, so in theory a capacity of 1150w? Forgetting this room, the rest of the lights on this circuit add up to only 380w, so making 680w total with these new ones.

Only thing above downlights is the roof(loft), the holes are smack in the middle of the joists, no loft insulation near them. All wiring on top of joists so not covered/enclosed.

Not too sure what they were on about in the shop then(see above), I thought I must have been missing something - it would seem not from what you say.

Is the wiring in contact with thermal insulation?

If it is, then the cable rating is significantly lower than for other installation conditions.

1.0mm² is always a bit iffy because of this.

Furthermore, having a re-wireable fuse is the worst kind of protection, due to the fusing factor.