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Smart Home Forum by FIBARO Team

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Wiring of S1 control input to alternate switched live



I am wondering it if it safe to wire the S1 control input of an FGS211 to a switched live that might be live when the  L input was disconnected.


The situation is that the Fibaro unit will be located on the other side of an isolator in an installation where the switched live comes from a different circuit. This means that if the isolator is off, and the switched live was left active (unlikely but conceivable) the L pin would be floating (or pulled towards neutral by other loads) whilst the S1 input was at 240V.

It's a bit unusual but arises because the switched live comes down an armoured cable from the house into the garage, and there is a separate isolator and RCD  there.  I can't put the FGS211 next to the switch in the house because there is no neutral there, but equally there is no unswitched live from the house lighting circuit available in the garage.

From an electronics perspective, if the S1 input is relatively high impedance it shouldn't matter as very little current would flow but that depends on the internal design of the FGS211.

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  • By the time we get to the light (a streetlamp) there are only two wires so there's no way to a pass a live, a switched live and a neutral to that location.  In any case, the live and switch live would still be from different circuits so the question might still stand.

    If what I'm asking/proposing isn't safe I'll probably abandon the physical switch control entirely and have the streetlamp controlled by Z-wave only.


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    Maybe i don't understand it fully (sorry not native english)

    the light itself has a neutral and a phase (else it will not lid)

    make the switched phase a normal phase, and put the switch2 overthere and use a fibaro or differant branche switch to control it



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    OK, certainly I can control the FGS211 remotely via the gateway or even an association with another z-wave device. However I wanted to use the signal from the existing switched live, simply because it's already there and the family are used to controlling the street lamp with the switch. As I've said I can't put another module in with the light switch because there is no neutral there.

    So the diagram you end up with looks like this:

    Please login or register to see this attachment.


    The existing installation connects the switch live to the lamp directly (in the garage) which is definitely dangerous since it means that the garage neutral can become live if the street lamp switch is on and the isolator is off. However if we know that S1->L  on the FGS211  is high impedance then it's a much better setup. A related question is whether it would work if one placed, say, a 10k resistor in the connection between the mechanical switch and the S1 connector (orange wire on the diagram). This would limit any current flow throw S1->L to 25mA max

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