Unexpected wiring in attic for light

[PT Doc]

I went into the attic today to check on furnace. I have a switch near the hatch access point. There is a gfi near the furnace (furnace is 10' from hatch) and a very short run of Romex going to a round junction box that has a light. This light is near the furnace. From the round box there is about 8 feet of Romex that terminates in a single gang box and this is my switch near the hatch. I wanted to move the switch so I looked closer and expected 2 separate Romex runs but this is not the case. The power does not go into the box with the switch then to the light. Power goes to light then to the switch.

How does this work?

Thanks

 

[jdm5]

If I read this right, you only have a single romex running into the box with the switch, and you're expecting two.

If that's the case, they are switching the hot - there is no neutral. Pretty common,
but I don't think it's to current code...many newer smart switches require the neutral.

 

[EOC_Jason]

The switch can be anywhere in the circuit to create the break, however for safety it should be cutting the hot leg and be before any lights. I've worked on some circuits that were backwards like you describe. That's why it's always smart to throw the breaker and never rely of just a switch being off.

 

[AntonLargiader]

Basically the hot goes out to the switch and comes back on its white wire and goes on to the next load. Not unusual but you need to open the box to trace the wires.

I see no reason to suspect that anything is 'backward' as Jason suggests. It sounds like you mean the Romex goes to the light box and from there to the switch, but that doesn't mean the power is going to the light first unless a visual inspection of the actual conductors leads you to that. It just means the guy who wired it minimized the wires needed.

 

[PT Doc]

Basically the hot goes out to the switch and comes back on its white wire and goes on to the next load. Not unusual but you need to open the box to trace the wires.

I see no reason to suspect that anything is 'backward' as Jason suggests. It sounds like you mean the Romex goes to the light box and from there to the switch, but that doesn't mean the power is going to the light first unless a visual inspection of the actual conductors leads you to that. It just means the guy who wired it minimized the wires needed.

Agreed. The hot runs thru this box but is switched at the switch. The Romex comes from the gfi outlet into the light box but obviously the power is switched at the distant switch. The switch box has typical black, white and ground. I didn't open the round junction box that has the bulb since everything works fine. I am fairly certain certain that this is code at least in this county.

Could someone explain what the wiring looks like in the junction box for the bulb? I'm just curious. Would the white that returns to the bulb j box have to be taped black in this case?

This is a good use of wiring. Saved the electrician a whole 8 feet.

 

[Richard Cranium]

quite common, I have also found too many where they broke the ground.

 

[LXCam]

Real common stuff. Normally the white wire is your hot lead in and the black goes to the light. Nothing unusual.

 

[Mustang51js]

Still done today

 

[wyliesdiesels]

No mystery there.

Just a switch leg.

Permenantly recolor the white wire with a pen such as a sharpie on both ends.

BTW thats only allowed with assembled cables.

 

[PT Doc]

Thanks for the information. I might use this wiring method someplace else one day.

 

[AntonLargiader]

I use it, especially with 3-way lights. Saves some space and wire-nutting in the boxes, as well as wire.