Electrical Surges/Light dimming

Discussion in 'Electrical Forum discussion & Blog' started by mds, Jan 22, 2009.

  1. mds

    mds New Member

    Messages:
    9
    Is is normal to have electrical dips/surges in a house? I remodeled the entire house 3 years ago. I upgraded the electrical service to 200Amps, put in a new HVAC system, etc. When the A/C and heating (and maybe the washer/dryer, can't quite remember) kick in, there is a dimming of the lights in the house. This seems to happen more when the condensers for the A/C kick in. Is this normal? Is there a fix to this? Is this impacted by power usage in my neighborhood?
    Thanks,
    MDS
  2. Rowdy

    Rowdy New Member

    Messages:
    8
    Location:
    Tennessee
    MDS, I usually just lurk, I am a retired electrician and spend most of my time these days on genealogy and such, but seeing that no one is jumping in on this I will give my two cents$

    It could be normal, electricity is a funny animal. Voltage is pressure just like hydraulics or water in a hose, if you shut it down or turn it on fast it will surge or draw down. You can have it checked by an electrician to make sure the amperage draw is within the proper limits of the appliances that are causing the symptoms you describe.

    There are too many variables to give a definite answer, but if you feel uncomfortable, call an electrician and they can determine for you if it is normal or if there is a problem. Myself, I wouldn't worry unless you feel your electric bill is extremely high, or if the dimming is lasting more than a couple of seconds or accompanied by a growl when the condenser kicks in.

    I almost forgot, do your lights flicker? If so there may be loose connections, call an electrician and have them check it out. See why I spend most of my time on genealogy, I forget things;-)
    Last edited: Jan 22, 2009
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina

    Why do you have the AC and the heat coming on at the same time?
  4. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    When you switch off one of these heavy 240v loads you should see less than a 0.1% voltage rise measured at the panel.

    If your meter can't resolve this small of a change, for a few bucks you can make a circuit with 2 ea. 1N4006 diodes and 2 capacitors that will let you measure very small changes in the incoming AC.

    On the other hand, for a voltage change from 120v to 115v incandescent brightness changes 100x[1-{(115/120)^3.5}]=-14%, so you may not be looking for a small voltage change.

    More neighborhood power usage = less voltage change.
    Last edited: Jan 23, 2009
  5. mds

    mds New Member

    Messages:
    9
    I am new to this so I have a few questions. If I can "measure very small changes in the incoming AC" then will that allow my electrical system to avoid the dimming of the lights when the A/C condensers kick in?
    Thanks,
    MDS
  6. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    No, it's to diagnose the problem.
    A default fix is to torque down your panel connections, but for some I think you should use a torque wrench and I can't imagine how to get the specs. on how much torque. And there is some level 2 arc-flash danger with resi. wiring inside the panel.
    I prefer troubleshooting to cut-and-try, but if it's easy and cheap then try it.
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