Light switch

[Sickboy]

I am installing a light and taking the supply from the ring main since there is no lighting circuit available. I was planning to run 2.5mm T&E from the existing socket (which is on the ring) to a switched FCU and then 1mm T&E from the FCU to the light fitting.

However, a switched FCU looks a bit ugly as a light switch so I was hoping to be able to run from the socket to an unswitched FCU (at socket height) and then through a normal light switch, and on to the fitting. I bought a 1-way light switch but it only has connections marked 'L' on either side of the switch. There is nowhere to connect the Neutral or Earth.

Can I use this switch? Is it possible to use a normal light switch and an unswitched FCU? If so, should I connect both sides of the Earth using the connection on the mounting box of the light switch? Do I connect the Neutral using a connector block or is this dangerous?

 

[ban-all-sheds]

A bit of chock-block is OK, it's what you have to use with 3-way switching anyway.

I'd also use it for the earth, and take a separate connection from it to the box, rather than use the box as a connector.

Or you could use a DP switch like this http://www.tlc-direct.co.uk/Products/BG930.html - it looks just like a lightswitch.

 

[Sickboy]

Thanks

I'm not familiar with DP switches. What do they do? Do I still need the FCU or does the DP switch have a fuse in it? Would I need to change the fuse for a 5A fuse for the lighting circuit.

Why do you not recommend using the mounting box as a connector for the Earth? What is the difference between that and the chock-block?

 

[ban-all-sheds]

I'm not familiar with DP switches. What do they do?

DP - Double Pole. They switch two terminals, i.e. live and neutral, so you wouldn't need to use choc-block on the neutral. Of course there's always Plan C, which is to not actually cut the cable at the switch, just carefully remove a few inches of sheath, cut the live to go in the switch, cut the earth to sleeve and choc-block it, but leave the neutral intact...

Or Plan D, which is to use a 2-module grid plate with a switch module and a fuse module in it, e.g.

but that's probably not a lot more attractive than using a switched FCU...

Do I still need the FCU or does the DP switch have a fuse in it?

Yes and no.

Would I need to change the fuse for a 5A fuse for the lighting circuit.

3A better. Which you'd need in the FCU anyway.

Why do you not recommend using the mounting box as a connector for the Earth? What is the difference between that and the chock-block?

They're just not as robust, and don't do such a good contact, IMO. Also, they aren't all fixed very well to the box, and can be pulled out if they're subjected to the mechanical stresses from two T/E cables being pushed and pulled about, although this is unlikely.

 

[Sickboy]

Thanks

I think I will go with plan C and just remove the sheath for a couple of inches. Saves an extra connection for the Neutral and stops the box being so cluttered.

 

[securespark]

If you use a DP switch and flush-mount it, it will require a min. 25mm box not 16mm plaster-depth box that light switches commonly use.

 

[AdamW]

stops the box being so cluttered.

You could always use a deeper box! Even drylining boxes come in up to 45mm depth. And if it is a stud wall you are fitting to, a deeper box takes no more work to fix. In fact after using a few recently I have decided that I now love dryline boxes, they are my second favourite type of box.

I am not a spark, but to me trying to leave one conductor of T&E intact whilst cutting the others just seems less-than ideal to me. It would be easier and less fiddly to use the choc-block idea I reckon.

 

[securespark]

snip carefully down the outer pvc with side cutters, and you should be ok.

Practice on some off cuts first if you're worried.

 

[plugwash]

head for the midlle (where the eaerth runs) with a sharp knife

you won't go through copper with it unless you press insanely hard and there is no plastic on the earth to worry about

do that on both sides then carefully prise sheath away from inner cores

easy