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wiring downlights



 
 
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  #1  
Old September 19th 06, 01:58 PM posted to uk.d-i-y
bob
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Posts: 35
Default wiring downlights

Hi all,

I am in the process of replacing a pendant light with some downlights.
I believe I have a lighting circuit similar to 'Method 1' on this page
http://www.ultimatehandyman.co.uk/lighting_circuits.htm.

This is based on the folllowing observations:
(a) I have a single 3 core cable entering the rose, so I don't think it
is 'Method 2 - loop in wiring' a

(b) I can see no visible junction boxes in the ceiling void so I don't
think it 'Method 3 - junction box wiring'.

I have 3 diy books (Collins, B&Q, DK) and none of them seem to describe
this circuit. Does anyone know what it is called?

Basically what I need to know is if I replace the rose with a 20A
junction box, do I connect similar colour cores from the downlights to
the circuit cable from the switch in a star topology i.e.

1 red/2 browns at 1 terminal (1 red back to the switch, 1 brown to
each downlight)
1 black/2 blues at 1 terminal (1 black back to the switch, 1 blue to
each downlight)
3 earths at 1 terminal (1 earth back to the switch, 1 earth to each
downlight)

I am replacing two pendants with four downlights, hence why I am only
connecting two downlights to each junction box above.

Any advice, greatly appreciated.

Ads
  #2  
Old September 19th 06, 02:17 PM posted to uk.d-i-y
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Posts: 819
Default wiring downlights

I am in the process of replacing a pendant light with some downlights.

Don't. It is environmentally irresponsible.

This is based on the folllowing observations:
(a) I have a single 3 core cable entering the rose, so I don't think it
is 'Method 2 - loop in wiring' a


By "3 core" cable, do you mean two proper cores and an earth, or three
proper cores and an earth?

I am replacing two pendants with four downlights, hence why I am only
connecting two downlights to each junction box above.


You will need a lot more than 2 downlights to replace a pendant fitting,
which is why downlighters are so irresponsible.

Christian.


  #3  
Old September 19th 06, 02:25 PM posted to uk.d-i-y
external usenet poster
 
Posts: 6
Default wiring downlights

bob wrote:

I am in the process of replacing a pendant light with some downlights.
I believe I have a lighting circuit similar to 'Method 1' on this page
http://www.ultimatehandyman.co.uk/lighting_circuits.htm.


(b) I can see no visible junction boxes in the ceiling void so I don't
think it 'Method 3 - junction box wiring'.


The junction box could be quite a distance from the fitting, so it's
probably this method.

I have 3 diy books (Collins, B&Q, DK) and none of them seem to describe
this circuit. Does anyone know what it is called?


Don't worry about the method name. Different books use different names
anyway. :-)

Basically what I need to know is if I replace the rose with a 20A
junction box, do I connect similar colour cores from the downlights to
the circuit cable from the switch in a star topology i.e.

1 red/2 browns at 1 terminal (1 red back to the switch, 1 brown to
each downlight)
1 black/2 blues at 1 terminal (1 black back to the switch, 1 blue to
each downlight)
3 earths at 1 terminal (1 earth back to the switch, 1 earth to each
downlight)


Yes that's correct.

To be pedantic the existing red wire is your "switched live", the
black is the "supply neutral" and the earth is the "supply cpc" -
according to one book anyway. :-)

John
--
John White,
Electrical Contractor
  #4  
Old September 19th 06, 02:56 PM posted to uk.d-i-y
bob
external usenet poster
 
Posts: 35
Default wiring downlights

Sorry, yes 2 core and 1 earth.

John just to confirm, I take it doesn't matter if the red/black/earth
earth wires are running back to a switch (Method 1) or a junction box
(Method 3) as this is the supply regardless, correct?

I've had a look in the double switch, there are 3 cables entering it,
2 of which run to a pendant and the other I presume is the circuit
cable?

  #5  
Old September 19th 06, 03:06 PM posted to uk.d-i-y
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Posts: 819
Default wiring downlights

John just to confirm, I take it doesn't matter if the red/black/earth
earth wires are running back to a switch (Method 1) or a junction box
(Method 3) as this is the supply regardless, correct?


Yes, it is of no relevance. You have the switched live and neutral for the
existing light. This is all you need for the replacement, too.

Christian.


  #6  
Old September 19th 06, 03:13 PM posted to uk.d-i-y
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Posts: 6
Default wiring downlights

bob wrote:

Sorry, yes 2 core and 1 earth.

John just to confirm, I take it doesn't matter if the red/black/earth
earth wires are running back to a switch (Method 1) or a junction box
(Method 3) as this is the supply regardless, correct?


That's right. As the new lights are using the same switches, all you
are effectively doing is replacing one light fitting with another.

I've had a look in the double switch, there are 3 cables entering it,
2 of which run to a pendant and the other I presume is the circuit
cable?


It depends how it is wired.

If you have:

- all the neutral (black) wires are joined together
- all the earth wires are joined together
- the three live (red) wires going to switch terminals
- a wire linking the two the switches

then the cable that is joined to the link wire is the supply, and the
other two cables go directly to the light fittings.

John
--
John White,
Electrical Contractor
  #7  
Old September 19th 06, 03:57 PM posted to uk.d-i-y
bob
external usenet poster
 
Posts: 35
Default wiring downlights

If you have:

- all the neutral (black) wires are joined together
- all the earth wires are joined together
- the three live (red) wires going to switch terminals
- a wire linking the two the switches


Yes, that's exactly how it looks :-).

Also, there are some main circuit cables (looks like 3 core and earth)
running above the downlights through the joists. They are not
touching the lamp but are close enough to concern me, what termperature
is this PVC outer sheeth of this cable typically rated to?

I notive the wires which go to the lampholder have a fabric like
sheeth, is this rated to higher temperature than PVC outer sheeth of
2/3 core and earth cable.


And finally, is it ok to use green/yellow electrical tape to cover the
"supply cpc" or must I use sleeving complying with BS 2848 to meet Reg.
543-03-02, as indicated by this post http://tinyurl.com/zuu8y.

Thanks again for you help on this.

  #8  
Old September 19th 06, 04:14 PM posted to uk.d-i-y
external usenet poster
 
Posts: 6
Default wiring downlights

bob wrote:

there are some main circuit cables (looks like 3 core and earth)
running above the downlights through the joists. They are not
touching the lamp but are close enough to concern me, what termperature
is this PVC outer sheeth of this cable typically rated to?


The current carrying capacity of PVC cable is usually specified at 70
Degrees C.

Push the other wires as far away from the downlighters as possible.
You can usually find enough slack to do this.

Make sure that the downlighters are far enough away from the joists
too. This is typically 75 mm but check the installation instructions.

You should really have checked for other wires before you cut the
holes, and repositioned the downlighter accordingly. But of course you
realise this now. :-(

I notive the wires which go to the lampholder have a fabric like
sheeth, is this rated to higher temperature than PVC outer sheeth of
2/3 core and earth cable.


Yes - much higher.

And finally, is it ok to use green/yellow electrical tape to cover the
"supply cpc" or must I use sleeving complying with BS 2848 to meet Reg.
543-03-02, as indicated by this post http://tinyurl.com/zuu8y.


You need to use sleeving, as tape can fall off after a while.

John
--
John White,
Electrical Contractor
  #9  
Old September 19th 06, 04:25 PM posted to uk.d-i-y
bob
external usenet poster
 
Posts: 35
Default wiring downlights

Thanks John.

  #10  
Old September 19th 06, 08:05 PM posted to uk.d-i-y
external usenet poster
 
Posts: 8,674
Default wiring downlights

bob wrote:

Hi all,

I am in the process of replacing a pendant light with some downlights.
I believe I have a lighting circuit similar to 'Method 1' on this page
http://www.ultimatehandyman.co.uk/lighting_circuits.htm.

This is based on the folllowing observations:
(a) I have a single 3 core cable entering the rose, so I don't think it
is 'Method 2 - loop in wiring' a

(b) I can see no visible junction boxes in the ceiling void so I don't
think it 'Method 3 - junction box wiring'.

I have 3 diy books (Collins, B&Q, DK) and none of them seem to describe
this circuit. Does anyone know what it is called?

Basically what I need to know is if I replace the rose with a 20A
junction box, do I connect similar colour cores from the downlights to
the circuit cable from the switch in a star topology i.e.

1 red/2 browns at 1 terminal (1 red back to the switch, 1 brown to
each downlight)
1 black/2 blues at 1 terminal (1 black back to the switch, 1 blue to
each downlight)
3 earths at 1 terminal (1 earth back to the switch, 1 earth to each
downlight)

I am replacing two pendants with four downlights, hence why I am only
connecting two downlights to each junction box above.

Any advice, greatly appreciated.



the ceiling rose _is_ a junction box. Hence replacing it is a job that
doesnt need doing. Nor do you need to understand the wiring, just
connect to the same connections the present light is connected to.

As for downlighters, if you mean halogens I'd recommend doing the cost
calculations first. With eg 6 downlighters you'll be replacing bulbs 6x
as often, and downlighting costs thousands in extra run cost over its
life. It also heats up the place in summer... it really is a classic
example of style over function. And environmentally it wont mark you
out as smart or caring. And they have other problems, but I wont bore
us all.


NT

 




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