2 wires going into 1 terminal in dimmer switch?

mxo

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I replaced a 1-gang 2-way dimmer switch. The existing switch had 2 wires going into L1 and two into L2. Picture attached - note there are 4 red wires, 2 in each terminal.

I wired it in the same way for the new dimmer switch, and it does work.

But I’m wondering why there are two wires going into each terminal and whether this is actually safe?
 

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Thanks, makes sense. It was fiddly to screw the two wires into a single terminal so I was wondering about whether this configuration is safe, but seems to be expected given it’s a two-way circuit (downstairs and upstairs switches for lighting on a corridor landing).

The ground wire was connected to the old metal switch and I’ve done the same with this new switch (also metal faceplate). But in other rooms where I swapped out plastic switches for metal switches, ground was connected to the metal back box rather than the switch and I’ve left it like that. Is this safe as long as the two screws connecting to the back box remain in place?
 
Thanks, makes sense. It was fiddly to screw the two wires into a single terminal so I was wondering about whether this configuration is safe, but seems to be expected given it’s a two-way circuit (downstairs and upstairs switches for lighting on a corridor landing).

The ground wire was connected to the old metal switch and I’ve done the same with this new switch (also metal faceplate). But in other rooms where I swapped out plastic switches for metal switches, ground was connected to the metal back box rather than the switch and I’ve left it like that. Is this safe as long as the two screws connecting to the back box remain in place?
No.
Add a link wire between back box and faceplate.

Does this mean that if the light is dimmed to almost off you are unable to switch it on from the other end?
 
No.
Add a link wire between back box and faceplate.

Does this literally just involve cutting a piece of wire and connecting the ground terminal in the back box with the ground terminal on the switch?


Does this mean that if the light is dimmed to almost off you are unable to switch it on from the other end?

It can do but the minimum brightness on the switch is programmable so I’ve increased it.
 
Any issue with just connecting the earth wire to the faceplate instead of the back box?
 
Not really but it's a belt & braces if you do both. Don't forget to slip a bit of green/yellow sleeving over the link wire.
 

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