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  1. #1
    Join Date
    Jul 2008
    Location
    La$ Vega$, Nevada
    Posts
    49

    Default HVAC unit controls light fixture

    Saw this one last week while inspecting a 1960-built home in La$ Vega$. Previous owner built a small office in the garage and put a thru-the-wall A/C unit in. Watch the video and try to figure out what's going on here.

    YouTube - HVAC unit controls light fixture

    Ideas??? I told the 'buyer' I wanted to be there when the electrician tackled this one

    Similar Threads:
    2018 ASHI InspectionWorld
    Glenn R. Curtis CMI
    La$ Vega$, Nevada
    Inspecting Nevada since 1982

  2. #2
    Join Date
    Mar 2007
    Location
    Colorado Springs, CO
    Posts
    1,217

    Default Re: HVAC unit controls light fixture

    I would guess the circuit for the light fixture is in series with the circuit for the A/C. So whatever current goes through the A/C circuit goes through the light fixture circuit. It the circuits were in parallel they would operate independently.

    "Baseball is like church. Many attend but few understand." Leo Durocher
    Bruce Breedlove
    www.avaloninspection.com

  3. #3
    Join Date
    Mar 2007
    Location
    Plano, Texas
    Posts
    4,170

    Default Re: HVAC unit controls light fixture

    Since I never heard the a/c come on, I am thinking there is a neutral problems somewhere but I would have to think more on that one.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  4. #4
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: HVAC unit controls light fixture

    If the light were wired in series with the a/c itself, the load of the a/c would cause most of the voltage drop across the two in-series loads to be across the a/c, leaving little voltage across the light, possibly not even allowing the light to come on.

    It is possible that there is a neutral problem.

    It is also possible that whoever wired that tapped the light off the a/c switch (using the a/c as a junction box - which is a no-no) and instead of tapping the light off the hot to the switch they tapped it off the power from the switch going to the a/c itself - meaning that each speed of the fan would increase/reduce the voltage to the light as well as to the fan.

    Glenn, you also said that the a/c was on a dedicated circuit/receptacle (forgot which word you used) but, in fact, it is not as the light is also on that circuit/receptacle. Just something to be aware of when choosing your words in a video like that.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  5. #5
    Join Date
    Mar 2008
    Location
    Charlotte NC
    Posts
    2,303

    Default Re: HVAC unit controls light fixture

    Sumpin defiantly wrong! But even the most inept DIY electrician will not usually stop without the results they are after. With strange things like this the first thing I look for is 3-way switches. Notorious for being wired wrong and with the switches in the right configuration everything seems to work. FWIW


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