Wiring for 3 gang 1 way dimmer switch

[amlj]

Hi.
I'm looking to put in a 3 gang dimmer switch in place of the current 3 gang switch. I thought it would be simple, as I would just replicate the wiring. However, the current one is wired a bit confusingly. There are clearly 3 red wires leading to the lights from the "one way" connections. A black goes to the COM at the base. I don't understand why a red joins the top left one way to the 2nd on top row COM. Then that COM bridges to bottom right which makes sense. The new dimmer has 3 separate boxes on the rear with L1, L2 and COM. I was planning to take the 3 reds from the 3 L1s and to put the black in one COM and join that to the 2 other COMs with bridge wires. I'm doubtful now though, as I don't get why the top left bridge wire exists at present.
I'd be grateful for any advice. Thanks v much.

 

[robinbanks]

In terms of the behaviour of the room lights, does one switch act as a master off for the other (2) lights?

In this diagram below, a switch operates a light, but also activates switches that may operate other lights, thus one switch can act to turn on or off all lights..

Why someone would do this with only lights, I'm not sure, as it'd be more flexible to just have 3 lights, 3 switches and independent 1 way switching of each light.. but I do have a similar circuit with a PIR where one switch can be "PIR off, or PIR on and controlling the lights" and the other switch is "lights are controlled by PIR, or lights are on all the time overriding PIR"


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If the lights function in a "each switch does one light" then you might be incorrect about "the 3 red wires go to the 3 lights" - the top left red is perhaps the live supply to the switch and the black goes to one light, the other two reds go to the other lights. It doesn't matter whether a supply wire goes into the COM or L1 in a 1 way switching, i.e. you may have this:

 

[amlj]

Thanks. I see what you mean. That certainly makes sense. I've just had another look at the reds and none of them have any other markings on. Seems a bit odd but I guess any proper electrician looking at it would be able to tell. There are 3 cables exiting the wall. The 2 lateral ones are single reds. The central one has a red and a black and it is that red which is top left. I guess that goes along with what you are saying. I should therefore use that red and bridge it to all the COM ports and use the black and the 2 single reds to the L1s. That makes good sense. Thanks v much.