Wrong usage of overloads.

Discussion in 'Automation & Control' started by MaxHeadRoom, Sep 6, 2019.

  1. MaxHeadRoom

    Thread Starter Expert

    Jul 18, 2013
    18,638
    5,765
    You can still find control examples posted regarding the use of contactor control wiring implementing the O/L in the wrong part of the circuit.
    For many decades the O/L in ladder circuitry has been inserted on the common or Neutral side of the coil.
    This has been a no-no for some time now, but the practice still seems to exist.
    It is considered a dangerous practice, especially where the common side is a ground-referenced conductor.
    The diagrams shown, the O/L should be on the Left of the coil.
    Max.
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    Last edited: Sep 8, 2019
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  2. SamR

    Active Member

    Mar 19, 2019
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    Yeah but some of the starters we had probably dated back to maybe the 40s and certainly the 50s and the overloads were part of the internal starter wiring weren't they? The electrical supply houses used to give away a pretty good Square D booklet on ladder logic diagrams and control wiring for starters. ~30-50 pages I probably still have one around here somewhere. We had to build into and around a lot of "grandfathered" electrical equipment designs. It was always a pleasure to raze and build from scratch with new gear. I was told to salvage some motor control centers from an abandoned area of the plant and had to tell the Project Manager the gear was not up to code and we could either buy new or surplus code compliant but could not use the scrap gear. If it was in place it could be grandfathered, but not to relocate to reuse for new construction. Plant was 75 years old 25 years ago and still some of it in operation today.
     
  3. MaxHeadRoom

    Thread Starter Expert

    Jul 18, 2013
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    I have the Groupe Schneider/Square D in PDF if needed, and yes, even they have made the error if showing it on the wrong side still.
    I had heard that it was originally did to save a little time and wire on motor P.B. stations.
    On most it is easy to correct it.
     
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