Seperated Lighting and Plug Circuits

Discussion in 'Electrical Forum discussion & Blog' started by statjunk, Oct 19, 2007.

  1. statjunk

    statjunk DIY Senior Member

    Messages:
    542
    Hey guys,

    So I read the posts about not needing to seperate the light and plug circuits and I'm a bit confused. When I'm in someone's house and they plug in a device and the lights dim. Isn't that due to the lights and plugs being on the same circuit?

    I've always seperated my lights and plugs because of this. Is there another reason the lights are dimming?

    Tom
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    21,802
    Location:
    New England
    Old, undersized, or less than perfect connections, or underpowered main could do it too. At the cost of copper, I can see the reluctance of avoiding separate lines for the hard-wired lighting, but personally, I still prefer it. In a room without hard-wired lighting, it doesn't make a difference, since you'd likely be using plug-in lamps.
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    To install lights and receptacles (plugs) on separate circuits is a design issue and will have little or no effect on the dimming of the lights when a large draw appliance comes on.

    It takes 6.25 times 10 carried to the 18th power of valance electrons to equal one coulomb. One coulomb for one second equals one amp.
    If I have an appliance that draws 10 amps come on then it is going to need a whole bunch of these electrons when it starts and will jerk some of them from other things that is already on.

    This draw of electrons away from a light bulb is noticeable to the eye therefore some people think that something bad has happened and get scared.

    What scares me is driving down the road in the mornings. Just this morning I was in a 45 MPH speed zone behind a school bus when here comes a pick-up with a ladder rack stacked four ladders deep on both sides and a sign on the doors that read, “We Fix Anything INC†running around 65 MPH.
    Now it wasn’t the speed that scared me so bad but the fact that the unshaven man driving the squatted in the back pick-up was holding a cup of coffee in one hand and talking on a cell phone with the other. I suppose he could fix everything except himself.

    Now I am sure that you are going to get all kinds of answers as to why the lights dim ranging from the type of wire nut used all the way to the name of you power company.
    The truth of the matter is that there is a voltage drop across the entire system any time a high draw appliance is started especially if it is a motor or inductance draw.

    There is more danger in getting into you car and driving to the store than there is in the dimming of the lights.

    Now it is your money that is being spent so I suppose it would be up to you to install the circuits the way you desire.
    The one thing I can say with 40 years of experience is all this talk about being in the dark if a breaker trips and the dimming of lights is nothing more that talk.
  4. statjunk

    statjunk DIY Senior Member

    Messages:
    542
    I've never considered it a safetly hazard. Just an annoyance. My interpertation of lights dimming is cheap and bad installation. Regardless if this is true or not that is my interpertation.

    Every house I've wired has the lights and plugs seperately. I've never had lights dimming. Not once. However my friends (2) that have houses built within the last 8 years or so that have wiring that connects lights and plugs. They have dimming issues.

    Like I said just appears to be a poor set up to me when the lights dim regardless of what causes it.

    I'm willing to admit that maybe it isn't the lights and plugs on the same circuit but I'd like to hear some other opinions.

    Tom
  5. BrianJohn

    BrianJohn DIY Senior Member

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    151
    Location:
    VA
    Flicker is a byproduct (as stated) of loads coming on line, as little as 3 Volts drop can result in noticeable flicker, In my experience some people (MAINLY WOMEN) are more likely to notice flicker or maybe not tolerate flicker.

    3 volts drop (VD) is nothing when a compressor is starting, utilities typically use smaller conductors than contractors are required to utilize, for a variety of factors, that coupled with minimally sized transformers (transformers that are sized to carry maximum load are more efficient) and the VD can reach or exceed 3 Volts easily in the best of homes.
  6. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    This is absolutely NOT true!

    I have seen this in new, old, lighting and receptacles separated or not.
    It has more to do with what's outside the home than how it is wired inside.
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    So you have wired a total of one house and they haven't turned on the power yet.

    Yes I can see why you are thinking the way you are.
  8. BrianJohn

    BrianJohn DIY Senior Member

    Messages:
    151
    Location:
    VA
    I do not wire houses I work as a testing and power quality/grounding expert. My rates are fairly steep, so home owners rarely hire me....BUT, I have done quite a few residential FLICKER studies (mostly large big buck homes) wire a house with number 8 AWG, separate the circuits lighting and outlets (which I did in my house) and flicker can still be an issue. There is more too it than just the branch circuit wiring.

    And that's the way it is.
  9. statjunk

    statjunk DIY Senior Member

    Messages:
    542
    Why would you say something like this?

    Grow up.

    Tom
  10. statjunk

    statjunk DIY Senior Member

    Messages:
    542
    That's kind of what I was looking for. Thanks for the info.

    Since I wire my plugs in 12 and lights in 14 I'll continue to keep them seperated but it's good to know.

    Thanks

    Tom
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    Because you made this statement and expected the rest of us to believe that you have mastered electron flow from some kind of silly wife’s tale of keeping the receptacles and lighting circuits separate.

    Now if that statement was not enough to bring forth some type of remark we can add the opening question that you asked into the discussion;
    First you ask why the lights dim and then come back and let everyone know that you have the solution to the problem.
    How can you have the solution if you don’t know the cause?
  12. statjunk

    statjunk DIY Senior Member

    Messages:
    542
    I never claimed to have a solution. Re-read my posts. Secondly, none of the houses I've wired have had lights that dim. That is a statement of fact.

    Your stating in a condesending way that I've only wired one house, is your mindless running off at the mouth.

    Your obviously very knowledgeable in electrics. I'd stick to that. In the meantime work on your communication skills.

    This thread was started as a discussion topic. I wanted to see others experience with this in testing these theories and what not. That is all. BrianJohn provided exactly what I was looking for.

    Tom
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    Well I must be misunderstanding you original question then. You said in the original post;

    No I just put two and two together and came to a conclusion.
    In order for this to be true it would mean that you have only wired one house and the power has not yet been turned on.

    Thank you for the complement. I do need some help in communication as I have a problem speaking some of the different languages of the students in my classes.

    Brian didn’t say anything different than any of the other had to say. He even shot down your belief in separate circuits cures the problem.
    Unless you can control the power from the point of generation to the point of use there is no way to control the dimming of lights when a high draw appliance or even a switch from one power grid to another occurs.

    Having worked in the field for almost 40 years and standing in a classroom for the last 7 years the one thing I do know, incandescent lights will flicker when there is the slightest difference in voltage drop no matter how they are wired. They can be on separate panels and they will still flicker.

    If you want to get real technical incandescent lights turn on and off at least 60 times a second as the sine wave changes from positive to negative.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Well, if you really want to get technical, the filaments don't stop glowing as the a/c transits zero, they take too long to cool off. They do dim, or oscillate their level. Now, a florescent does generally turn off.
  15. sure sure ,, if you really want a really annony flickering on indscent lamps why not run this on the 25 HZ supply then you will get the idea why

    but if you want almost complety flicker free run either in DC or go with 400 HZ or higher with good power supply unit.

    Merci, Marc
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    One of the worst headache inducers (at least to me) is to have a computer monitor set to 60Hz refresh rate with florescent lamps...I REALLY hate that, and can't understand how people can live with it.
  17. BrianJohn

    BrianJohn DIY Senior Member

    Messages:
    151
    Location:
    VA
    Jim in the days of CRT monitors (OR SO LONG AGO) "Screen Shake" was an issue related to EMF either from location near a distribution transformer or from a EMF that was a result of a neutral grounding issue. I investigated and resolved 100's of these monitor problems. It would amaze me when customers would tell me "Oh this has been going on for 2 or 3 years." Ten minutes of looking at that monitor drove me BONKERS and gave me a headache.
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Absolutely, a nearby transformer or nearly anything of sufficient size to generate a magnetic field can disrupt the display of a crt, but my point of having it set to a 60Hz refresh when florescent lamps are the main illumination has the thing slighly out of sync can be a real pain. With LCD displays becoming the norm, that isn't a factor much anymore. But, if you have one, almost any crt these days can support much higher refresh rates, and will look better and give your eyes less grief if you raise it in the setup to a minimum of 72Hz (which is the minimum EU standard, I think).
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