Changing from / to a dimmer light switch

Navbloke · Post by **Navbloke** » Sat Feb 10, 2007 9:23 pm

I think I'm right that a new low energy lamp has come out that can be used with dimmers now. Can't remember where i saw it though.

Andrew · Post by **Andrew** » Fri Mar 30, 2007 4:24 pm

Here's a question which relates to this post: Why is it that dimmers are rated in watts (on the packaging at Homebase!) but light switches just say 10amp?

Say I had three hundred-watt bulbs running off one switch (which I don't), I take it that that 250w dimmer should not be used. What about the normal 10amp switch?

Does that question even make any sense? You can guess I'm not yet a qualified sparky.

Also, the 250w dimmer I've just got has connections for live and "switched live". Thats got to be the black cable / neutral, but why is it called a switched live and do I need to put sleeving on to indicate that? If so, would a piece of electrical tape suffice?

One more question - I've just taken the dimmer out the packet, and it makes a definite clicking noise when turning it. Is that usual, or should they be silent? The one that was already in the flat when I moved in is quiet. It doesn't sound "broken", just noisy.

Cheers dudes!

sparkydude · Post by **sparkydude** » Fri Mar 30, 2007 6:41 pm

Question 1
As the dimmer is an electronic device it has various component parts that are rated for a specific loading, and size, as if for example you wanted a 1kw dimmer the thing is huge, normally the size of a double socket , this is also because to dim a lamp the electronics need to dissipate the heat generated by lowering the voltage to the lamp. The normal switch would be fine as it is simply a set of contacts that are broken and made, and these contacts can take the higher currents hence rated for 10A

Question 2
It is called a switched live as thats what it is, a live that is switched, and not a permanent live such as you connect to the common of the dimmer/switch. Yes the black or now blue , needs to be sleeved/taped sleeving is best as it wil not fall off when the adhesive on insulation tape dries it normally falls off.

Question 3

Nothing wrong with your dimmer, some click some push , some are rotary on off, some are push on off, maafacturers vary

Nick

Andrew · Post by **Andrew** » Fri Sep 28, 2007 11:52 am

Sorry to drag up such an old thread, but I just need a little piece of clarification:

I know that metal light switches need a joining piece of earth wire from the metal box to the switch, in addition to the cable earth terminating at one of these two places. However, does it matter if you use the core from either 1mm or 1.5mm twin and earth to do this, or should I just cover myself and go with 1.5mm? (for example, what if the circuit is 1mm cable?).

Also, for both sockets and switches - if the back box is plastic (ala drywall box) but the switch / socket is metal, it's okay just to terminate the earth onto the plate and nothing more (obivous I guess, but always best to ask!).

Many thanks for your help and support.

Jaeger_S2k · Post by **Jaeger_S2k** » Fri Sep 28, 2007 12:23 pm

The 'best practice' is to earth with the same.

An earth is better than no earth!

Your guess was correct, earth to the switch.

Andrew · Post by **Andrew** » Fri Sep 28, 2007 12:31 pm

BEWARE - STUPID QUESTION APPROACHING.

How do you tell the difference between 1.5mm twin and earth and 1mm twin and earth on a lighting circuit?

Ta.

Jaeger_S2k · Post by **Jaeger_S2k** » Fri Sep 28, 2007 12:34 pm

WARNING - ANSWER TO STUPID QUESTION FOLLOWS.......

One is .5mm squared bigger than the other!

Stoday · Post by **Stoday** » Fri Sep 28, 2007 8:55 pm

WARNING - ANSWER TO A STUPID ANSWER FOLLOWS

Jaeger_S2k wrote:WARNING - ANSWER TO STUPID QUESTION FOLLOWS.......

One is .5mm squared bigger than the other!

The 1.5mm means 1.5 square mm - it's not the diameter. So one is the square root of 0.5sq mm bigger than the other.

Jaeger_S2k · Post by **Jaeger_S2k** » Fri Sep 28, 2007 10:21 pm

That's what I meant

the square root of the thingy

Jaeger_S2k · Post by **Jaeger_S2k** » Fri Sep 28, 2007 10:22 pm

Stoday wrote:WARNING - ANSWER TO A STUPID ANSWER FOLLOWS

Jaeger_S2k wrote:WARNING - ANSWER TO STUPID QUESTION FOLLOWS.......

One is .5mm squared bigger than the other!
The 1.5mm means 1.5 square mm - it's not the diameter. So one is the square root of 0.5sq mm bigger than the other.

Yeah, but which one?