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I will be redoing my room lights for 24 VDC LEDs, with multiway switches.

I'm located in Poland.

Should I put the switches on the 24V side or the 230V side of the circuit? What are the points to consider?

230V will be done by a qualified electrician, but 24V I'll do myself.

Having the PSU always on doesn't bother me as it's no-load draw is only 0.5w.

Is there anything else I should take into account?

Data dump:

  • one of the switches will be placed on my bed's headboard
  • cable length will be about the same
  • the no-load power draw on those is only 0.5W
  • this will be dumb white LEDs, no dimmer either
  • going by the spec the current draw is 1.8A (3 meters of a 14.4W/m strip, 24V)
  • power supply used is FTPC50V24
  • the only common point with the existing lighting will be the location of one of the switches - old lighting is not multiway and the fixture is in a completely different place
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  • Where in the world are you? Codes and available equiptment vary by location, so we need to know your jurisdiction to give a good answer. For example, here in the US pretty much all of our light switches are rated for at least 15A, so finding a 2A capable one isn't a challenge. What kind of switches are you thinking of using, that don't support 2A?
    – Nate S.
    Commented Jan 28, 2021 at 16:31
  • @NateS. Poland, edited into the question. I've just assumed that since 400W is a lot for lighting switches would rated way lower, I have no idea about the actual ratings. I work with low-voltage electronics, where 24V is maximum of what I might encounter.
    – jaskij
    Commented Jan 28, 2021 at 16:35
  • @NateS. A quick search later, two top results were 4A and 10A, I'll edit the question once I'm back at the PC
    – jaskij
    Commented Jan 28, 2021 at 16:44
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    Mkay I don't know too much about the electical system in Poland so I'll let someone else write up a proper answer. A little quick searching (though I can't read Polish) seems to find that most light switches sold for use in Poland are rated for at least 10A. 400W is actually not that much for lighting, if you consider that the codes were written with incandescent lighting in mind -- that's just 4 100W bulbs, which large rooms often need.
    – Nate S.
    Commented Jan 28, 2021 at 16:44
  • @NateS. True, I didn't think of that. Come to think, my living room had eight bulbs but I don't remember if that chandelier was rated for 100W bulbs.
    – jaskij
    Commented Jan 28, 2021 at 16:46

1 Answer 1

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All things being equal (meaning, any wire and switches are rated for the voltage and current they will be carrying) you'll typically experience fewer losses and longer component life if the control is done at the line voltage side, instead of the lower voltage side.

Power loss due to resistance in a wire is proportional to the current squared (Ohm's law, P = I^2 * R), and raising the voltage lowers the current for the same power draw. Switching the line voltage also means less arcing on the switch contacts due to the lower current. Additionally, even though the power consumption of the power supply is low, leaving it on means using up more of its rated lifetime for no reason.

Granted, this may not make a significant difference in your specific application, but it's worth taking into consideration. If the code in Poland doesn't require one way or the other and the cost is similar for both, I would wire the switches on the line voltage side.

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