Dimmer extension Connections

[RSinn]

Hi, can someone tell me why the dimmer extension has the additional connections per dimmer channel? fig1 below is as per loxone docs, but surely there must be either the L or N bridged in the box with the dimming/switching just happening on one leg which means you don't need all 4 connections and can wire as per fig.2....or does this not work like a standard dimmer? what am i missing? thanks.

seems like a lot of excessive wiring in the panel. i understand i could loop the L and N between each channel, but still seems not required.

[Chris Pitman]

Each channel is completely sperate ie 4 wires assume say up and down stairs lights on different rcbos but you could use some channels for both up and down stairs circuits, I have done something similar don't put a whole rooms lights on one dimmer mix across a couple that way if one fails you still have some lights.

So yes if all off same rcbo then loop all the inputs  

[RSinn]

thanks chris. I understand the 4 outputs are separate and these can either be wired to the same or separate RCBOs, what I'm questioning is why each channel needs 4 wires. To my mind each lighting circuit needs 2 wires (excluding earth), the left most L & N on each channel seem redundant if wired as per fig.2. Why are these additional wires required?

[Chris Pitman]

From left to right L - in from fuse (normal 230v) N - in N - out AQ/L - out (the dimmer voltage pwm output)

Can't remember if the N are tied internal seem to remember under certain wiring setups could cause issues hence why loxone left sperate option

[Jonathan Dixon]

Yes good spot: If different channels are fed from different RCBOs the neutrals need to be kept independent across channels to avoid constant tripping the RCBOs (that said I'd feel weird mixing one dimmer bank on multiple circuits..).

I've not got one but based on every other mains dimmer I've used I'd imagine the two neutrals per channel are wired together internally, so the "forth" terminal (load N) is just a convenience; the load N could be wired directly back to the supply RCBO.

But To the OP question a dimmer can't work if it *only* has visibility of the L line as unlike a simple rely, it needs to measure the voltage between L and N in order to sense when the zero crossing occurs , as this is when it cuts the waveform to implement leading or trailing edge dimming. So it has to have 3 terminals minimum (supply L, dimmed L, and system N) even if the load current is only passing through the L portion of it. 

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[Rob]

Each dimmer channel is electrically seperated from the others internally.

The only internal connections are between the Neutral In and Neutral Out on EACH channel, not across channels.

As has been said, this avoids tripping of RCBO's on unbalanced circuits.

[RSinn]

That's great guys. I'm not planning splitting circuits over separate RCBOs I was just showing 1 connection. The bit I was missing is " it needs to measure the voltage between L and N in order to sense when the zero crossing occurs , as this is when it cuts the waveform to implement leading or trailing edge dimming." and why its different to a relay. Thanks @Joth.

As always I knew you guys would know! thank you.