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Old 04-28-2008, 01:54 PM   #1
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It works, but what the heck did they do... daily puzzle?


since I bought this house the light fixture in the spare bedroom has just been a simple ceramic plate with a socket on it. Bought a fan to put in there finally so I take the plate off and find:

3 sets of red/black wires come into the box. (wiring is pre-grounds)
2 blacks and a red twisted and taped together, shoved back in the box.
2 red twisted together and on one screw of the light.
1 black on the other screw.

When light switch is off, red-to-red on the screw carry current.
When light switch is on, one red to the black conducts (obviously that's when the light would turn on).

There are no 3-way's and the light is the only fixture on the switch (no sockets, other lights, etc). The wiring appears to be original from when the house was built 60ish years ago so I'm not too worried about it being a monkey job by the last owner.

Any thoughts? I can't get my head around why one red runs hot and the other red neutral, as if there was a crossover or something after the light; and why 2 blacks are taped to a red?

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Old 04-28-2008, 02:36 PM   #2
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It works, but what the heck did they do... daily puzzle?


What are you using to measure for voltage? You could be measuring a phantom voltage if you are using a digital meter.
Where are you located? Colours sound like you might be UK or at least Europe.
You measure voltage not current.

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Old 04-28-2008, 02:48 PM   #3
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It works, but what the heck did they do... daily puzzle?


Detroit.... remember, wiring is 60+ years old so its red and black.

voltage is 120 via simple two prong tester, not digital. This is what I have:
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Old 04-28-2008, 05:53 PM   #4
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It works, but what the heck did they do... daily puzzle?


Quote:
Originally Posted by moneymgmt View Post
since I bought this house the light fixture in the spare bedroom has just been a simple ceramic plate with a socket on it. Bought a fan to put in there finally so I take the plate off and find:

3 sets of red/black wires come into the box. (wiring is pre-grounds)
And obviously, pre- white is neutral as well...

Quote:
2 blacks and a red twisted and taped together, shoved back in the box.
The blacks are a hot in, a hot feed out to another light or outlet somewhere - just the circuit continuing merrily along...

Quote:
2 red twisted together and on one screw of the light.
Neutrals.

Quote:
1 black on the other screw.
This is the switchleg returning from the wall switch.

Quote:
When light switch is off, red-to-red on the screw carry current.
When light switch is on, one red to the black conducts (obviously that's when the light would turn on).

There are no 3-way's and the light is the only fixture on the switch (no sockets, other lights, etc). The wiring appears to be original from when the house was built 60ish years ago so I'm not too worried about it being a monkey job by the last owner.

Any thoughts? I can't get my head around why one red runs hot and the other red neutral, as if there was a crossover or something after the light; and why 2 blacks are taped to a red?
[/quote]

You are misinterpreting the readings from the tester. the 2-wire switchleg red is not neutral, it is hot always. The return from the switch is black, hot when switch is on. Also, if you have an illuminated switch all bets are off...
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Old 04-28-2008, 06:57 PM   #5
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It works, but what the heck did they do... daily puzzle?


Red has never been used for neutral. Someone did some creative wiring when they wired this house.
Did the wires have voltage on them or did they indicate a short with the red light? You have know how to interpret what your meter is telling you.
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Old 04-28-2008, 10:53 PM   #6
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It works, but what the heck did they do... daily puzzle?


Quote:
Originally Posted by joed View Post
Red has never been used for neutral.
Never, say Never when it comes to old wiring. Just because it's not supposed to be used doesn't mean some yahoo didn't use it.

If I had a nickel for every 'never' in my house I could afford to pay a pro to re-do all my wiring.
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Old 04-29-2008, 02:28 AM   #7
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It works, but what the heck did they do... daily puzzle?


a really good investigation of why , what , works wouuld include some tagging and temp disconnecting leads to see what goes down..but that doesnt seem the mission

as for NEVER USED FOR THAT . .on a job I narrowed down the short to an underground run between house and barn . . .pulled the old wiring out OF THE OLD METAL PIPE and sat there laughing me butt off . . . .the . ."installer" . . .pieced together different strands of wire with tiny little "U"-bolts . . . .I kid you not

U-Bolts . . . .match that for never . .the man had to be Scottish
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Old 04-29-2008, 08:10 AM   #8
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It works, but what the heck did they do... daily puzzle?


Thanks Leah and Kingsmurf, I won't reiterate what you said.

LawnGuy: I'm picking up on what you're saying so let me see if I'm getting this right: The 3 twisted wires are black hot in, black hot to another room, red hot to the light switch. The 2 reds on the light are neutral in, and neutral out to the next room. That leaves the lone black as the hot from the light switch. yes/no???

The one thing I'm not grasping is the 120v between the 2 red neutrals when the light is off?

Thanks!
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Old 04-29-2008, 08:35 AM   #9
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It works, but what the heck did they do... daily puzzle?


Quote:
Originally Posted by Leah Frances View Post
Never, say Never when it comes to old wiring. Just because it's not supposed to be used doesn't mean some yahoo didn't use it.

If I had a nickel for every 'never' in my house I could afford to pay a pro to re-do all my wiring.
I should have said "red has never been code to be used as neutral". Who knows what someone did.
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Old 04-29-2008, 02:03 PM   #10
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It works, but what the heck did they do... daily puzzle?


Quote:
Originally Posted by moneymgmt View Post
Thanks Leah and Kingsmurf, I won't reiterate what you said.

LawnGuy: I'm picking up on what you're saying so let me see if I'm getting this right: The 3 twisted wires are black hot in, black hot to another room, red hot to the light switch. The 2 reds on the light are neutral in, and neutral out to the next room. That leaves the lone black as the hot from the light switch. yes/no???

The one thing I'm not grasping is the 120v between the 2 red neutrals when the light is off?

Thanks!
If you pulled the 2 red neutrals apart, and their is a LOAD downstream (into the next room / outlet and beyond) you're taking a reading in series with the load.

A neutral with a load on it, when broken, will read 120v from the loaded side to the grounded side, until you make the connection. (Could just be a night light at the end) This is why it's important that DIYers (and electricians) understand that sometimes what you see is misinterpreted.

BTW, in an older home, as well as newer homes (but not as much I'd imagine) it is perfectly normal for a ceiling box to contain a circuit homerun, one or more feed-outs, and a switchleg. Sometimes, no switchleg because there was no wall switch, just a pull chain.

Reason being, many homes had lights first before any wall outlets were added.

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