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Need to interrupt a low voltage lighting loop circuit

  1. Nov 30, 2011 #1
    Need to interrupt a low voltage lighting "loop" circuit

    I configure a lot of low voltage lighting for a living. Although it's not a deal-breaker for the project I'm working on, I'm having a disagreement with a colleague as to whether the following configuration should work:

    Shapeable, low-voltage track lighting (monorail we call it) is made of two pieces of exposed conductive material attached to either side of an insulating material between them. The bulb-holding fixtures then attach to the rail with connectors that touch conductive material on either side of the insulated material and there you go.

    Typically these systems are installed so that the rail is a straight line, or a "S" or "C" curve or something...but they can also be formed into complete squares or circles.

    Question is, if you form the rail into a square or a circle, do you need to interrupt the rail loop with an isolating connector (these are available) or will it matter to let them connect back to themselves?

    My position is that, even if the rail is in a continuous circle, the top or bottom half is being energized all at once opposite the other side and the fact that each conductive side of the rail runs in an uninterrupted loop shouldn't matter. My colleague thinks this will interfere with the circuit somehow and add load to the transformer.

    In my mind, this isn't any different to taking the low voltage leads from a transformer, running these wires out 20 feet, then attaching each to itself near the transformer again...would that really stress a transformer?

    If it matters, these are AC transformers, 12 volt systems typically no more than 300 watt total draw. System would be about a 20 foot circle.

    Thanks for any insight...
  2. jcsd
  3. Nov 30, 2011 #2


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    Staff: Mentor

    Re: Need to interrupt a low voltage lighting "loop" circuit

    Welcome to the PF.

    Your position is correct. As long as it is the same conductor that joins back up with itself in the closed figure, everything is fine.
  4. Nov 30, 2011 #3


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    Science Advisor
    Homework Helper

    Re: Need to interrupt a low voltage lighting "loop" circuit

    What you are describing is exactly the same as "ring main" wiring for mains power sockets (at least that's what it is called in the UK). For higher currents it has the advantage that there are two wires in parallel supplying the current to the load (i.e. the two halves of the "ring") so you can safely use thinner gauge wiring, though that probably isn't relevant for your application.

    Your colleague might be thinking about a single "shorted turn" of wire around the transformer core (which is a very bad idea!) but that's a different situation from what you have.
  5. Nov 30, 2011 #4
    Re: Need to interrupt a low voltage lighting "loop" circuit

    Thanks to you both guys for taking the time to answer my question.

    It's always good to hear you're not going crazy.
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