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Found Odd Light Fixture Wiring...Question

Found Odd Light Fixture Wiring...Question


   
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Old 01-28-14, 08:53 AM
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Found Odd Light Fixture Wiring...Question
Hello.

I am replacing an old two bulb ceiling light fixture. Upon removal of the old light I have found wiring that is unusual to me (a regular homeowner). I have described the wiring below:

LIGHT FIXTURE: there are two bulbs with white and black wires coming from each. The two whites are connected and the two blacks are connected.

JUNCTION BOX: there are two wires coming into the junction box, each with black, white and ground. One wire runs off somewhere and the other goes to a switch. Inside the box, the two white wires are connected, the two grounds are connected and the two black wires are loose.

CONNECTION: one of the black wires in the box went to the combined black wires for the two light bulbs and the other black wire in the box went to the combined white wires.

See pic below.

Name: Light Wiring.jpg Views: 2916 Size: 19.5 KB


My question is whether this is correct. Why not white to white, black to black all around?

Thanks for your help.

Monomoy
 
Last edited by Monomoy; 01-28-14 at 09:13 AM. Reason: upload pic
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Old 01-28-14, 09:49 AM
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there are two wires coming into the junction box, each with black, white and ground.
Those would be two cables. Wires are individual conductors.
the other black wire in the box went to the combined white wires.
Assuming: the other black wire in the box went to the combined white wires was a typo and was really one white to black of power in that is a switch loop. A very common way of wiring lights. The switch loop caries power to the switch on the white and returns it on the black. Though often ignored the white of the switch loop cable should have by code been redesignated as an ungrounded conductor ("hot) using red or black or any color but gray or green bands of tape or colored with felt tip marker. Marking must be done on both ends.
 
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Old 01-28-14, 11:20 AM
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My question is whether this is correct.
No. If you've described it correctly, there are two problems with it. One is the power to the switch isn't being fed on the white wire, redesignated as a hot wire. The other is that the switch is on the neutral after the fixture. That means that turning the switch off does not kill power to the fixture.

To correct this, the white wire going to the switch needs to be marked with electrical tape or permanent marker as Ray suggested and spliced to the black wire in the other cable. That will leave you with one black wire and one white wire, plus grounds, for connecting your fixture.

Why not white to white, black to black all around?
Because that isn't how a switch loop works. Doing that creates a dead short when the switch is closed (switched on).
 
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Old 01-28-14, 12:52 PM
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Light
Yes, I have described it correctly. I just pulled another light in an adjoining room and it is done the same way, except that there are three cables entering that box. See pic below.

Name: light wiring pic.jpg Views: 26931 Size: 28.6 KB


But, everything works through the switch?

NashKat1, you say that to correct this, "the white wire going to the switch needs to be marked with electrical tape or permanent marker as Ray suggested and spliced to the black wire in the other cable. That will leave you with one black wire and one white wire, plus grounds, for connecting your fixture."

So to restate this, the white wire from the switch should be spliced to the black wire from the other cable coming into the box. The white wire from the other cable is then no longer spliced to the other white wire and available to connect to the white wire on the fixture. I think I have this right. Yes?

The other light pictured above has 3 cables in the box and I would not know which of the other two cables to connect to from the switch....any ideas?

Thanks a lot.
 
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Old 01-28-14, 01:58 PM
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Based on that picture it looks like you have several miswired switch loops along with the white appearing to be the hot.
 
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Old 01-28-14, 02:12 PM
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So to restate this, the white wire from the switch should be spliced to the black wire from the other cable coming into the box.
Yes, if it is power in for the light.

Name: Sw_Loopb-1_zpse1170390.jpg Views: 1133 Size: 15.7 KB
 
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Old 01-28-14, 02:33 PM
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The other light pictured above has 3 cables in the box and I would not know which of the other two cables to connect to from the switch....any ideas?
I'm starting to lean toward what PCboss stated and Ray implied:
Originally Posted by pcboss
Based on that picture it looks like you have... the white appearing to be the hot.
You need to disconnect and separate all of the house wires in each of the ceiling boxes, then restore the power and use a multimeter - preferably an analog one - to test for 120V hot-to-neutral and hot-to-ground.

With the power off, you also need to pull the switch associated with the ceiling box with 3 cables in it and test for continuity to determine which of those cables is connected to the switch.
 
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Old 01-28-14, 02:42 PM
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This is an example where you have more then two cables at the light. The load cables go to other fixtures and are not controlled by the switch.

Name: Sw_Loopb-1_zps62792cf4.jpg Views: 4973 Size: 26.2 KB
 
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Old 01-28-14, 05:04 PM
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the switch is on the neutral after the fixture. That means that turning the switch off does not kill power to the fixture.
That is exactly what the OP's drawing shows, a switched neutral. The switch will control the light, but there will always be 120 volts on the light bulbs. It's wrong.
 
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Old 01-29-14, 05:34 AM
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Be sure to label each wire before you disconnect things so you can put it back exactly the way it was (even though the finished result will not be what it was originally).

You will need to disconnect some wires in order to find out which cable supplies the power, which you need to find out.
 
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Old 01-29-14, 06:39 AM
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Thanks
Thanks - I see the issue now. Question for Ray2047 - in your picture, should the bottom wire in the switch loop say "ReColored Black"?....it is a white wire with black colored on the ends...yes? The other wire from the switch to the light is black.

Now, for the real novice questions:

how does one test wires for lead/power, continuity etc......sorry? Is there a sticky that covers this? I have a "Hi - Vis Voltage Tester" with red and black wires that power a small light. I also have a multimeter but never really figured out how to use it. I'm sure an internet search will yield lots but if there is a cut and paste or sticky thread that would be great. I'm new to this site. Thanks
 
Last edited by Monomoy; 01-29-14 at 08:33 AM. Reason: typo
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Old 01-29-14, 09:30 AM
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should the bottom wire in the switch loop say "ReColored Black"?
A matter of semantics. I shortened the sentence "white wire recolored" and did not specify a color because black is not the only color that can be used. You seem to be reading it as "white wire recolored black" but my intent was to indicate a white wire that has been recolored any color but gray or green.
 
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Old 01-29-14, 09:49 AM
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Ray2047 - OK understood. Thanks a lot.
 
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