Need help with adding a light fixture to an existing circuit

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Old 12-20-17, 07:46 AM
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Need help with adding a light fixture to an existing circuit

I'm a very beginner (but learning) with this stuff and I would like some help. So far I have added a GFCI circuit and did some basic repairs here and there but thats my experience level.

What I would like to do is to add a new light fixture to an existing circuit. In this circuit there are multiple light fixtures, possible outlet (I can only see a wire exiting one of the light fixtures and going upstairs), and a light switch.

For the reasons of simplicity and the layout of my basement ceiling (and this is all happening in the basement), I cannot add a new wire to one of the existing light fixtures but I rather need to go from the light switch. This is where I m confused.

Right now the setup is like this:

Main box ------> Light fixture 1 (There are 2 wires coming out of this one, one going to the next light fixture, and another one goes upstairs) -----> Light fixture 2 -----> Light switch

So I want to go from that light switch to a new light fixture. But every example I saw online involves adding a light fixture to an existing light fixture.

What I had in mind is, adding 2 pig tails in the existing light fixture for its on/off positions. What I dont know is the order of which wire goes where.

A) The incoming hot (black wire) pigtails with the switch's hot and the hot of the new light fixture. The neutral (white) does the same.

OR

B) The incoming hot wire connects to the hot wire of the new light fixture, and the returning neutral of the new light fixture connects to the hot of the light switch and the neutral of the light switch connects to the neutral of the main incoming (existing) wire.

Not sure which is the right way.
 
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Old 12-20-17, 05:21 PM
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FYI.... we call those cables. Wires are what are inside the cables.

What I had in mind is, adding 2 pig tails in the existing light fixture for its on/off positions
Wouldn't that be connecting your new fixture to an existing one ?

If your power enters the circuit at the light and you have a two wire cable to the switch with white and black on the switch..... you cannot connected anything to that switch. That is called a switch loop. Always hot is sent down to the switch on white and returns switched on black. There is no neutral there and you need a neutral.

For that kind of setup.... you must tap directly off a light that works with that switch.

This is what you have there.....
Name:  switchloop+.jpg
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Old 12-20-17, 05:47 PM
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Understood. But why cant I tap on the black leaving the light switch?

So the hot coming to the light switch leaves the switch when switch is on. So why not connect to the leaving wire? That way when the switch is on, the leaving current will go to the new added light, and then come back and continue as normal.

so in your diagram, I would disconnect the black wire from the switch. Add a pigtail there. Pigtail then connects to the NEW white wire that goes to the new light. Then it comes back on the black wire to the box where light switch is. And then I connect that new black wire and the other existing black wire

The issue is the other light fixtures are so far away (and to be honest, closest one has 3 wires going in/out of it, so i m not sure being the 4th one is a good idea) that the entire exercise becomes counter intuitive.

so the only way to add a light fixture to an existing loop is to run a wire from the existing light fixture. Does it matter WHICH light fixture you run the new wire to?
 
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Old 12-20-17, 07:09 PM
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Connect where..... at the light ?
Not at the switch. You need hot and neutral to run a light.
There is NO neutral at the switch or in that cable.

You can connect at any light that the switch controls.
 
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Old 12-21-17, 04:33 AM
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Here is a diagram of what I had in mind. I numbered each wire with 1 being the incoming hot to the switch and 4 is the original leaving wire which I was planning on splitting and adding a "detour". Why won't this work?
 
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Old 12-21-17, 04:55 PM
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In your diagram.....
1 is hot from the light box to the switch.
4 is switched hot back to the light.
There is no neutral in this equation.
You need a switched hot and a neutral.

If you interrupt the switched hot with your new light..... you will end up with two lights in series that will operate at half brightness.
 
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Old 12-21-17, 06:48 PM
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I understand now sorry. I realize I sounded very stupid . My confusion was that I thought the light fixtures also didnt need neutral like the switches.

Anyways, I found a light fixture that I can connect to the question is, is this the right way.

this light fixture is between the light switch and another light fixture (there are two light fixtures and a switch in this loop). This is a different loop than the one I posted before. In this loop the light switch has 2 cables going in.

In this loop, power comes in from the box into one light. From this light 2 wires leave. One goes to the switch, the other goes to the other light (the one I want to connect to). Then from this light, it goes to the switch. So essentially the switch has 2 cables, one from each light and the lights connect to each other

i opened up the light I want to connect to and I see 2 pigtails on the light and those connect to other wires all together. So basically there are 3 white wires and 3 black wires on wire nuts. My plan is to add a 4th wire set to these and run it to the new light.

will that work?
 
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Old 12-21-17, 06:54 PM
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Sounds like a plan.

The red flag in any wiring where you want to connect to a switch is when you see a white wire on the switch. That usually signifies a switch loop.
 
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Old 12-21-17, 07:33 PM
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Actually I dont know what I said will work here.

I was going to bundle all 4 white wires together and all 4 black wires together in that light fixture box, but does that make sense?

power comes in via the hot wire, how would it work if I just connect all wires together? It would almost be like having a T where the power is SPLIT across two lights.

Right now in that box I see a white pigtail connected to TWO white wires and subsequently a black pigtail is connected to TWO black wires (one goes to the other light and one goes to switch). I thought when you wire lights you had to connect blacks together and the whites are separately connected in series, what I m doing isnt series, its splitting a series.

Why is this so confusing?
 
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Old 12-21-17, 08:59 PM
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So basically there are 3 white wires and 3 black wires on wire nuts. My plan is to add a 4th wire set to these and run it to the new light.

will that work?
Yes... that will work.

Some people don't like to make large splices so they split them in half. It makes for extra wiring and wire nuts.
Seeing 4 wires in one wirenut is common. Power and then three lights equals four wires.

As long as you connect your new light's white and black wiring to the same place the existing light is you should be ok.
 
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Old 12-22-17, 02:30 PM
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I just wanted to post and update. It worked as expected I also want to say thanks, I probably would have burned the house down without you thank you so much!

Now I have 5 outlets I want to install. I have bunch of open ground terribly wired outlets from 1980s that I decided to convert to GFCI, TR, and WR. I spent about $300 on everything. A lot I know, but I want to do it right. Anyways, hopefully i wont burn the house down
 
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Old 12-22-17, 03:00 PM
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You only need one GFCI at the first receptacle if one circuit or a GFCI breaker.

Fixing the ground though is best because the GFCI does not provide a ground. Under latest code you can run a new wire from the nearest device with a ground. Under older code the new ground wire must be connected to the main ground within five feet of the panel.
 
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Old 12-23-17, 06:27 PM
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I started at 7:15am today and besides the 1.5 hour errand run, I didnt stop till 8pm. This thing took all day. Added 5 double receptacle (one regular one GFCI each box) of these 3 were existing I had to convert.

one thing I noticed in some of the old boxes was the ground wire from the incoming wire into the box was on purposedly cut. So imagine black and white wires are both 6-7 long and ground wire is just cut off/snapped.

anyways i cleaned up everything, reintroduced the ground wire from the source, grounded the box as well as each receptacle.

i m aware about the gfci protecting the entire circuit but it so happens that every one of these boxes were in different circuits with the exception of only one and for that one I said screw it I ll just add GFCI to match

now onto my next project which is to wire a 240 volt 40amp 5hp compressor. That one requires its own thread though because even after watching several youtube videos about 240v and how there is no neutral and you connect both 20amp breakers, a colleague of mine at work confused the heck out of me by saying I may or maynot have dual phase and i shouldnt assume etc etc and I dont know what that stuff means.
 
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Old 12-23-17, 07:48 PM
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Dual phase. I think it's your colleague that is confused.

You have a single phase 120/240v service. That service has two legs. Each one measured to ground is 120v. There is 240v between them.

Your 240v 5hp compressor will require a 20A 240v circuit. That will be a two pole 20A breaker. Your wiring will be #12 from the panel to the compressor.
 
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Old 12-26-17, 11:15 AM
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I may or maynot have dual phase and i shouldnt assume etc etc and I dont know what that stuff means.
Number of phases can be confused because although residential service is single phase, each leg is 180 degrees out of "phase", which is where the confusion stems from. IOW, when someone hears one leg is out of phase with the other, they assume it is a two phase electrical service.
 
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