• Posts
  • RSS
  • ◂◂RSS
  • Contact

  • Miswired Lights

    March 18th, 2015
    house, tech, wiring  [html]
    When we moved into our new house we noticed that one of the light switches would sometimes shock you, and sometimes wouldn't turn on at all. When we got someone to look at it they discovered it was badly miswired.

    There are two switches that each let you toggle a light on and off, one switch at the top of the stairs and one at the bottom. This should look like this:

    Those switches are "three-way," and toggling either switch toggles the light. The diagram above shows a completed circuit and the light would be on, the diagram below shows turning off the light by turning off the switch on the right.

    This was all working fine until one of the switches broke. The person doing the work, who apparently had no idea what they were doing, bought an ordinary "two-way" light switch and not seeing what to do with the extra wire connected it to the switch's ground terminal:

    This is very wrong, but as drawn above they would have quickly noticed the problem because it's shorting to ground and would trip the circuit breaker. But this is old conduit (BX) wiring without a separate ground conductor, so the ground connection is just through the armored cable jacket. This is an unreliable ground because a poor connection at any joint along the conduit breaks the connection, and that seems to be what happened here:

    Which explains why the light would shock people: the faceplate screws connect to the body of the switch, the body of the switch is connected to its the ground terminal, and in this setup the ground terminal has wall current.

    This is fixed now, but it does make me worry what else the previous owners did wrong.

    Comment via: google plus, facebook

    Recent posts on blogs I like:

    Streaming the Biden Infrastructure Plan

    I streamed my thoughts about the Biden infrastructure plan, and unlike previous streams, I uploaded this to YouTube. I go into more details (and more tangents) on video, but, some key points: Out of the nearly $600 billion in the current proposal that is …

    via Pedestrian Observations April 11, 2021

    Collections: Clothing, How Did They Make it? Part IVb: Cloth Money

    This is the second half of the fourth part of our four part (I, II, III, IVa) look at the production of textiles, particularly wool and linen, in the pre-modern world. Last time, we looked at commercial textile workers and the finishing processes for text…

    via A Collection of Unmitigated Pedantry April 9, 2021

    Notes from “Don’t Shoot the Dog”

    I just finished Karen Pryor’s “Don’t Shoot the Dog: the New Art of Teaching and Training.” Partly because a friend points out that it’s not on Audible and therefore she can’t possibly read it, here are the notes I took and some thoughts. It’s a quick, eas…

    via The whole sky April 2, 2021

    more     (via openring)


  • Posts
  • RSS
  • ◂◂RSS
  • Contact