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Thread: Flickering?

  1. #1
    Maintenance Mechanic RED BARN's Avatar
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    Default Flickering?

    When my A/C comes on, I get a flicker in my lights. What kind of issues should I look for? Loose wiring, incoming power problem........

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    Plumbing Designer FloridaOrange's Avatar
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    I'm sure the electrical gurus could help you more but....
    When your AC comes on the condensor startup is pretty substantial. There are devices that can make your startup "easier". I've got one on my house and it's called a soft start. Geez Frank, could've asked me or hammer at the "other" place.

    That's where I would start anyway.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default flicker

    All of the above as starters, then a failing utility main feed, or a failing transformer, etc.

  4. #4
    Maintenance Mechanic RED BARN's Avatar
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    Quote Originally Posted by FloridaOrange
    I'm sure the electrical gurus could help you more but....
    When your AC comes on the condensor startup is pretty substantial. There are devices that can make your startup "easier". I've got one on my house and it's called a soft start. Geez Frank, could've asked me or hammer at the "other" place.

    That's where I would start anyway.
    To be honest I figured it would be related to wiring or incoming feed problem from power provider. I will check into this "soft start", I've got an Uncle who does A/C work, maybe he can help obtain one.

    Thanks FO.

  5. #5
    Electrician Chris75's Avatar
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    Most dimming of the lights is normal, the cause is related to the voltage drop from the startup of the motor, Not sure how much your lights are dimming so not sure if it is a serious problem or not, but if lights are dimming from using smaller appliances then you could have a loose neutral.

    Other things to look at is the wire size and distance they used to wire the outdoor unit, other than that add a soft start kit as stated above...

  6. #6
    DIY Senior Member BrianJohn's Avatar
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    Stock response from previously answering this question.

    First you should check for possible connections issues, particularly if this problem just started.

    Light flicker (dimming and restoration of light to near preflicker level of lights from motor inrush) is a byproduct of several factors and generally is difficult to over come.

    AC motor loads (in particular compressors) but all motor loads have inrush currents. These inrush currents result in voltage drop in the branch circuit, panel bus, service laterals, utility transformer and possibility the utility HV feeders.

    Flicker is in addition user dependent; some people are more susceptible to flicker. For some reason flicker seems to bother women more that men (based upon personal experience).

    A Voltage Drop (VD) as little as 3 volts on a nominal 120 VAC system is noticeable (by me), 2.5% VD.

    We have had cases were the VD was all a byproduct of primarily single phase 120 VAC loads, in these cases we were able to put the lighting on L1 and all the motor loads on L2, the HVAC compressors were something the homeowner had to live with. This minimizes the flicker.


    To test for this VD and resulting flicker to determine the source of the inrush, use a min max amp clamp and min max multimeter at the main service watch the lights(it may take two workers) and correlate to the meters.
    Last edited by BrianJohn; 08-26-2007 at 05:33 AM.

  7. #7
    Plumber jimbo's Avatar
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    Testing for VD? Maybe refer this to Dr. 90210???

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default Vd

    Maybe a penicillin shot will help the VD.

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