Seperated Lighting and Plug Circuits

**statjunk** · 10-19-2007, 05:28 AM

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

**jadnashua** · 10-19-2007, 07:28 AM

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.

**jwelectric** · 10-19-2007, 08:25 AM

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.

**statjunk** · 10-19-2007, 12:18 PM

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

**BrianJohn** · 10-19-2007, 01:31 PM

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.

**Speedy Petey** · 10-19-2007, 03:06 PM

Originally Posted by statjunk

My interpertation of lights dimming is cheap and bad installation. Regardless if this is true or not that is my interpertation.

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.

**jwelectric** · 10-19-2007, 03:18 PM

Originally Posted by statjunk

Every house I've wired has the lights and plugs seperately. I've never had lights dimming. Not once. Tom

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.

**BrianJohn** · 10-19-2007, 03:47 PM

Every house I've wired has the lights and plugs separately. I've never had lights dimming. Not once. Tom

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.