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Dimmer 2 Momentary Switch Voltage Current


slocombematthew
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Hi, 

 

I am currently rewirering my house and installing dimmer 2's and rgbw's. I bought a load or MK grid switches so I could have momentary on/off's at the top, rocking switches in the middle and scenes below. The scenes and rockers will be connected to my raspberry pi's. My electrician has pointed out that there needs to be physical segregation between data cables and 240v within the back box. He says its to do with the possibility that one of the 240v cables could make one of the data cables live if someone where to do something wrong. I understand the risks of electromagnetic interference, but this is separate to that issue. So If I install the system using momentary switches from the dimmer 2's will there be any 240v in the switch. To make my question clear what voltage and current is the S1 and Sx circuit when the dimmer is used in momentary mode?

 

If they are low voltage I could fit them outside the grid back box.

 

I know the RGBW's are elv so they shouldn't be a problem.

 

Many thanks for reading 

Edited by slocombematthew
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  • Inquirer
  • Hi Robin, 

    I dont have them yet, we are just 1st fixing so only running in the cables. I dont want them here until after plastering. Does anyone else know?

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    I am not suggesting you are going to do anything dangerous or illegal, but I have read this topic a few times and I think someone might draw false conclusions which *are* dangerous...

    • I bet, in the UK and the rest of the world, all connections on that dimmer are to be treated as "belonging to the mains voltage domain".
    • I do not think regulations take an excuse like "yes, but the S1and S2 pins can only source a few tens of microamps so it is safe".
    • In large parts of the world this means all wires have to be at least 0.5 mm2 and rated for mains voltage, and under NO circumstances any part of the dimmer is to be connected to circuits below 50 V AC (like, a doorbell, a gate opener, ...). It is a mains device, to be connected to mains circuits only.
    • Besides, SX is at L potential... So your switch is referenced to "live" and not "neutral". Not that being referenced to neutral would make it any better. And swapping L and N is not making it OK either...
    • Because it is "live", your switches have to be rated for mains voltage. Not because of the current, but because of the separation needed to avoid getting mains voltage shuttled to your finger tip...
    • If you feel the urge to connect this dimmer to 5V/12V/24V circuits, then please consider the RGBW instead. This is the opposite: 12 or 24 V only, no mains connections.
    • Add coupler relays (relays rated for mains with large separation between coil and contacts) to make really safe connections between S1-S2-Sx and circuits that do not run on mains. This is allowed and recommended.

    Does this help? Or did I just cause more confusion?

    Edited by petergebruers
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    Thanks Peter!

     

    Peter is correct about L and Sx being at the same potential.  To answer the earlier question about Sx to neutral, it's 120VAC.  I'm in the US.

     

    I'm trying to use these Dimmer 2s with a Forbes and Lomax push-button momentary switch.  Which btw, seem to work fine together in my testing, but you're saying this is dangerous, right?

     

    This is what Forbes and Lomax support told me: " Yes, we have had clients use our “momentary” switches with both Fibaro and Aeotec nano and micro switches and dimmers and we have had positive feedback about them"

     

    I've also been told that these Forbes and Lomax momentary switches are "UL Listed for 32V AC/DC"

     

    So my conclusion is that this combination, contrary to Forbes and Lomax advice, is in fact not acceptable and dangerous.  And a solution would be to insert a coupler relay.  Although it's unlikely I could fit all of this into the switch box, so might be out of luck.

     

    Could anyone recommend the smallest possible coupler relay that might have a chance of fitting in the switch box along with the Dimmer 2?

     

    Thanks for your help!

     

     

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  • I'm using an MK 12 grid switch box, with 240v push to make (momentary) switches. In the bottom section I have ELV which needs to have a physical barrier from the LV. I have an earthed steel plate between the top 4 switches and the other 8. I originally asked when researching the relevant safety legislation.  I then thought about the fact there was no physical barrier between the cables going into the Fibaro unit, so I treated it as 240v. The ELV send messages to my Pi which operates relays in a segregated central location.

     

    Sorry George, cant help.

    Edited by slocombematthew
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    28 minutes ago, George Basco said:

    Because I measured it, I'll add that the current that flows between S1 and Sx is 30 micro amps.

     

    Thanks for sharing. And that is one of the reasons these modules do not work if there is in the order of 10 uA of leakage. This can happen with some electronic switches ("touch") or if your switch has some sort if indicator (LED or neon). The current is not the same on all Fibaro modules, but it certainly is very low...

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    To follow up on my comments about the  Forbes and Lomax push-button momentary switch.  Turns out that these switches are rated to 250 VAC (

    Please login or register to see this link.

    ).  So at this point there's no reason to think this combination isn't safe, and as I stated above, has been working just fine for me.

     

    Thanks Peter for raising the issue..

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