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Thread: Electrical Surges/Light dimming

  1. #1

    Default Electrical Surges/Light dimming

    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. #2
    DIY Junior Member Rowdy's Avatar
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    Default Electrical Surges/Light dimming

    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 by Rowdy; 01-22-2009 at 10:38 PM.

  3. #3
    Electrical Contractor/Instructor jwelectric's Avatar
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    Default

    Quote Originally Posted by mds View Post
    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.
    Thanks,
    MDS

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

  4. #4
    Homeowner Thatguy's Avatar
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    Default

    Quote Originally Posted by mds View Post
    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?
    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 by Thatguy; 01-23-2009 at 09:36 AM.

  5. #5

    Default

    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. #6
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by mds View Post
    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
    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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