Hi all,

I'm rewiring part of my lounge light circuit to include six small
lights which will be switched on and off in two's by the switches on a
three-gang switch. I've never done lighting before, but here's what I
propose after a good read of Collins.

Use three junction boxes, one per pair of lights. Each box to have a
cable to the switch and two more cables, one to each light. Permanent
mains to be daisy chained through the three boxes.

Is there a limit to the number or lights that should come off one
junction box? Is it better to use one box per light? I ask as I plan
to extend the kitchen circuit to three fittings, all quite near, and it
seems that one box could do it for all three.

Antony

antgel wrote:
I'm rewiring part of my lounge light circuit to include six small
lights
Is there a limit to the number or lights that should come off one
junction box?

The limit is whether the cables will physically fit. Lighting circuits
are radials so there is not the issue of point loads that has to be
considered with rings.

2 lights per JB seems sensible and reasonable.

I ask as I plan to extend the kitchen circuit to three fittings,
all quite near, and it seems that one box could do it for all three.

Kitchens is Part P.

Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.

Owain

antgel wrote:

Is there a limit to the number or lights that should come off one
junction box? Is it better to use one box per light? I ask as I plan
to extend the kitchen circuit to three fittings, all quite near, and it
seems that one box could do it for all three.


Five cables will fit a standard 4 terminal JB without any problem. Use
1.0mm sq cable and not 1.5mm though to make it less of a squeeze

There is also nothing to stop you daisy chaining the switched live from
the first lamp holder to the second rather than running a second
dedicated wire back to the JB. That way you only have the standard four
wires per JB.


--
Cheers,

John.

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Is there a limit to the number or lights that should come off one
junction box? Is it better to use one box per light? I ask as I plan
to extend the kitchen circuit to three fittings, all quite near, and it
seems that one box could do it for all three.

If it fits in the hole and you can still get the cover back on, it's OK.

Christian.

Owain wrote:
Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.

By "point" do you mean junction box (or rose on a loop-in system)?

It is lightly loaded. I have two circuits in an 900sqft two-bed flat.
The circuit in question currently carries about 600W tops (proably
nearer 400).

Antony

John Rumm wrote:
There is also nothing to stop you daisy chaining the switched live from
the first lamp holder to the second rather than running a second
dedicated wire back to the JB. That way you only have the standard four
wires per JB.

Like it, thanks.

In message ,
Owain wrote:


Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.


I had always read that one as only applying to standard BC/ES fittings.
If the lights in question are LV then they'll be limited by the
transformer to n Watts and that's the figure I'd use. If they are
GU/GZ10 then the fitting usually has a (heat-related) limit, often 50W
(though I believe 75W GU10s are available?) so again, I'd use that
rather than 100W. Likewise R63 bulbs are very difficult to find above
60W, and the fitting may not be rated above that anyway.

Works for me anyway :-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Back up my hard disk? I cann't find the reverse switch!

In article ,
Owain writes:
Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.

It's not in the Regs. It's a recommendation in the On-Site Guide.
As with any of the diversity calculations, it's a good starting
point if you have no other information to go on. If you know the
current and future usage doesn't fit those recommendations, then
you should design appropriately.

(Some of the diversity recommendations are showing their age now;-)

--
Andrew Gabriel

Martin Angove wrote:
In message ,
Owain wrote:



Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.



I had always read that one as only applying to standard BC/ES fittings.
If the lights in question are LV then they'll be limited by the
transformer to n Watts and that's the figure I'd use. If they are
GU/GZ10 then the fitting usually has a (heat-related) limit, often 50W
(though I believe 75W GU10s are available?) so again, I'd use that
rather than 100W. Likewise R63 bulbs are very difficult to find above
60W, and the fitting may not be rated above that anyway.

They are GU10. I'm still confused by the meaning of "point" in Owain's
post.

Antony

John Rumm wrote:

Five cables will fit a standard 4 terminal JB without any problem. Use
1.0mm sq cable and not 1.5mm though to make it less of a squeeze

There is also nothing to stop you daisy chaining the switched live from
the first lamp holder to the second rather than running a second
dedicated wire back to the JB. That way you only have the standard four
wires per JB.

When you say "daisy chaining the switched live", you mean connecting
live and neutral (and earth in this case) for the second light to the
three terminals on the first light? Or are the earth and neutral of the
second light handled differently?

And another thing. For the kitchen, which is three lights off one
switch, can I use the one junction box then daisy chain the second _and
third_ lights? I assume as it's a radial that I can - it's not like
daisy-chaining spurs on a ring circuit, but I'd love a quick confirm.

Martin Angove wrote:
Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity.
I had always read that one as only applying to standard BC/ES fittings.
If the lights in question are LV then they'll be limited by the
transformer to n Watts and that's the figure I'd use.

However if the LV fitting is replaced by a standard mains one ...

In such circs I would treat the transformer as one point, as 100W min.

Owain

antgel wrote:
Owain wrote:
Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.
By "point" do you mean junction box (or rose on a loop-in system)?

I mean ordinary rose, or luminaire. A 5 x 40W electrolier would be 200W
not 500W.

It is lightly loaded. I have two circuits in an 900sqft two-bed flat.
The circuit in question currently carries about 600W tops (proably
nearer 400).

Fairy nuff. I just didn't want you (or anyone in the future reading the
archives) adding another seven lamps to an already max-loaded house
circuit.

Owain

antgel wrote:
When you say "daisy chaining the switched live", you mean connecting
live and neutral (and earth in this case) for the second light to the
three terminals on the first light? Or are the earth and neutral of the
second light handled differently?

Yes.

And another thing. For the kitchen, which is three lights off one
switch, can I use the one junction box then daisy chain the second _and
third_ lights? I assume as it's a radial that I can - it's not like
daisy-chaining spurs on a ring circuit, but I'd love a quick confirm.

Yes.

Owain