Downlighters Earth Question

[chrisgc]

Section 524 of BS 7671 off the top of my head.

A lighting circuit may be protected by up to a 16A device (but not higher), obviously ensuring that current carrying capacity and voltage drop are acceptable.

Thanks for that kind sir.

So you think that 0.75mm flxible heat resistant cable will be sufficient for the circuit I have (12x 50w mains downlights)?

Chris

 

[BillyBoBob]

Chris Please don't use the flex for all the lights. It's concidered bad practice to wire an installation in Flex. Flex should only be used in short runs.
The last light on the end of the run will look like this................
Now at every other light you'll have two T/E on the lefthand side of the pic above.
The flex onthe right of the above pic will go to 1 single downlight and 1 downlight only.
you'll have this at all 12 of your lights.

note. the black flex in the pic is not the one I'm talking about.
And yes the pic shows the old wiring colours.

 

[flukey]

Not heard anything about that. I agree that they dont have cord grips, and I know that the choc boxes do have e'm on the lid.
If this was the case and we are still permitted to use round JB's on T/E simply because the boxes are fixed and the T/E is clipped. Would it not also be possible to use them for flex as if fitted prior to a ceiling going up couldn't they also be clipped thus solving the problem?

check out the attached link, as previously said if the jb is fixed and the cables are clipped, thats fine, as long as its accessible

if its not fixed as per downlight jb`s then they are no longer acceptable under the 17th

http://download.hager.com/hager.uk/files_download/guides/junction_box_guide.pdf

 

[chrisgc]

Chris Please don't use the flex for all the lights. It's concidered bad practice to wire an installation in Flex. Flex should only be used in short runs.
The last light on the end of the run will look like this ...................
Now at every other light you'll have two T/E on the lefthand side of the pic above.
The flex onthe right of the above pic will go to 1 single downlight and 1 downlight only.
you'll have this at all 12 of your lights.

note. the black flex in the pic is not the one I'm talking about.
And yes the pic shows the old wiring colours.

BillyBoBob,

Not using flex all through out.

All the twin and earth is in place.

BUT From the twin and earth i will be connecting this through a junction box then out of the other end of the junction box will be some flex cable (2 core preferably heat resistant) to the actual connector of the downlight (as this is double insulated).

This will of course be done seperately for each downlight.

All I am trying to find out now is if its safe to use 0.75mm 2 core flex or does it have to be say 1.0mm? The manufacturers state use 1.0mm by the way.


Also if it has to be heat resistant?

So just trying to find out what flex I can use for this part.

Also I am trying to search for 1.0mm 2 core heat resistant flex but having no luck and would be ideal if could get locally (Swindon).

So anyone know please about the flex size as some people have suggested just the 0.75mm and not heat resistant.

Chris

PS Lights are mains downlights 12x 50watts

 

[Risteard]

If manufacturers state 1mm2 then you must use it as the Regulations require you to comply with manufacturers' instructions. A cpc should also be terminated at every point.

 

[chrisgc]

If manufacturers state 1mm2 then you must use it as the Regulations require you to comply with manufacturers' instructions. A cpc should also be terminated at every point.

Thats understandable BUT anyone know where I can get heat resistant 1.00mm 2-core flex cable (by the metre preferably)?

Chris

 

[Risteard]

Thats understandable BUT anyone know where I can get heat resistant 1.00mm 2-core flex cable (by the metre preferably)?

Chris

3-core surely?

 

[chocolate]

Isn't there a section in the regs that prohibits the termination of solid core conductors and stranded core conductors into the same terminal. So the solid core of 1.5 T&E and the stranded copper of a 0.75mm2 flex ( in the same terminal of the JB ) isn't permitted.

That's why the choc bloc is preferred - two T&E's in one end and the flex out the other. Each connection within the strip connector has two screws - this allows you to do this.

It also explains why, when installing RCBOs, the functional earth wire ( white ) isn't cut to reveal the stranded copper, as this results in the same problem at the earth bar of the CCU.

 

[chrisgc]

3-core surely?

If using 3-core where am I going to put the earth as there is only two terminals in the connector on the downlighter as its double insulated - so no earth needed.

Obviously my twin and earth will be goin into junction box then two core flex coming from junction too light connector.

With 3 core there does not appear to be anywhere I could put the earth?

Any help ??????

Chris

 

[chocolate]

3-core surely?

What would you do with the cpc at the light fitting end of the cable - if the terminal enclosure is only designed to take a 2-core ?

I would have thought 2-core flex also - as long as it is reasonably short enough between fitting and JB.

 

[chrisgc]

What would you do with the cpc at the light fitting end of the cable - if the terminal enclosure is only designed to take a 2-core ?

Thats exactly what I am trying to find out lol.

So just need to know what 2-core is goinf to be acceptable?

Someone help please lol

Chris

 

[flukey]

my supplier only does 0.75 and 1.5 2 core from stock so it would be 1.5 for me.

 

[chrisgc]

my supplier only does 0.75 and 1.5 2 core from stock so it would be 1.5 for me.

hey Flukey is that Heat Resistant?

Also guessing even though manufacter of lights says to only use 1.0mm using the 1.5mm would not be a problem would it?

Chris

 

[Risteard]

See 412.2.2.3.2

 

[flukey]

sure is