Help wiring a dimmer switch please.

[JohnB]

Hi

I am reasonably competent with basic eleccy DIY - fit socket extensions,
wired up my shed & garage etc - but i've never fitted a dimmer switch !

Anyway the one we have in the house has gone pear shaped and the missus
wants to keep it and got a new one from B&Q. Instructions are useless.

The old one has 2 connections one marked "Com" which has the thick red wire
and one of the thin red wires connected; and one marked "L" with the other
thin red wire connected, - usual earth to face plate.

The new one has 3 connectors L1, L2 & then another with a strange symbol on
it - as far as I can glean from the instructions it is for a transformer (?)
- low voltage supply ?

Have we got the "wrong" dimmer switch ? If not how should I wire it up.

Thanks for any tips.

 

[BigWallop]

Hi

I am reasonably competent with basic eleccy DIY - fit socket extensions,
wired up my shed & garage etc - but i've never fitted a dimmer switch !

Anyway the one we have in the house has gone pear shaped and the missus
wants to keep it and got a new one from B&Q. Instructions are useless.

The old one has 2 connections one marked "Com" which has the thick red wire
and one of the thin red wires connected; and one marked "L" with the other
thin red wire connected, - usual earth to face plate.

The new one has 3 connectors L1, L2 & then another with a strange symbol on
it - as far as I can glean from the instructions it is for a transformer (?)
- low voltage supply ?

Have we got the "wrong" dimmer switch ? If not how should I wire it up.

Thanks for any tips.

Can you describe the funny symbol please.

 

[John B]

Can you describe the funny symbol please.

It looks like the "approximately" symbol (~) or an "s" on its side with
a forward slash through it a bit like this - but "curvy"

____ /
/ \/
/\____/

Cheers

John

 

[Dave Plowman]

Anyway the one we have in the house has gone pear shaped and the missus
wants to keep it and got a new one from B&Q. Instructions are useless.

The old one has 2 connections one marked "Com" which has the thick red
wire and one of the thin red wires connected; and one marked "L" with
the other thin red wire connected, - usual earth to face plate.

Is there another switch close by? The second wire connected to 'com'
probably goes to this.

The new one has 3 connectors L1, L2 & then another with a strange symbol
on it - as far as I can glean from the instructions it is for a
transformer (?) - low voltage supply ?

L1, L2 and common are the standard three terminals of a two way switch,
and many dimmers do actually have a two way switch fitted. I'd just treat
the one with the strange symbol as 'com' - and even although it's designed
for low voltage lighting it will be ok with normal. No 'low voltage'
dimmer actually works on the low voltage side - they are simply of
different (more expensive) design to cope with the inductive load, but
will work ok with a normal one.

 

[MarkM]

It looks like the "approximately" symbol (~) or an "s" on its side with
a forward slash through it a bit like this - but "curvy"

____ /
/ \/
/\____/

Cheers

John

IIRC, this indicates the switched AC output, so would be the live
output going to the load. Check the connections on the dimmer
(*unconnected to anything*) with a continuity tester (with multimeters
from Maplin so cheap these days, there's no excuse not to have one!) -
you may find that L1 and L2 are actually commoned to allow further
switches to be daisychained.

 

[Dave Plowman]

you may find that L1 and L2 are actually commoned to allow further
switches to be daisychained.

L1 and L2 terminals always indicate a two way switch. Are you saying some
ignore this convention? I wouldn't have thought it complied with the
relevant BS if they did.

 

[The Natural Philosopher]

Hi

I am reasonably competent with basic eleccy DIY - fit socket extensions,
wired up my shed & garage etc - but i've never fitted a dimmer switch !

Anyway the one we have in the house has gone pear shaped and the missus
wants to keep it and got a new one from B&Q. Instructions are useless.

The old one has 2 connections one marked "Com" which has the thick red wire
and one of the thin red wires connected; and one marked "L" with the other
thin red wire connected, - usual earth to face plate.

The new one has 3 connectors L1, L2 & then another with a strange symbol on
it - as far as I can glean from the instructions it is for a transformer (?)
- low voltage supply ?

Have we got the "wrong" dimmer switch ? If not how should I wire it up.

Thanks for any tips.

Dimm,ers just go in series with the live supply, with the neutral
carried straight through.

Your new one has a chanegover switch - thats all - bet its a push on
push off switch rather than a rortary click ...thes can be used with
anothetr changeover swicth for two way control...

Try the 'odd' terminal and eiher of the other two. In fact the only way
to wire it wrong is to use L1 and L2, in which case it simply wont work.

Polarity is not important, since its simly AC passthrough.