Ceiling fan/light wiring question


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Old 09-13-14, 01:02 PM
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Ceiling fan/light wiring question

Hello. Just joined and this is my first post here.

I'm trying to install a ceiling light (NO fan) in a bedroom and want to make sure I do the wiring correctly. My house was prewired for ceiling fans in the bedroom so I'm just using the existing wiring and switches. House was built in 2000.

The bedroom has a switch box by the door with 3 switches. Switch 1 controls an electrical outlet. Switches 2 and 3 are for the ceiling fan/light. There is currently no ceiling fan or light installed.

I bought a Fluke voltage detector so I can be sure the wires are not live. So I checked the wires at the switches and at the ceiling and found something curious which I don't really understand.

Switch A has a Black and a Red wire, plus Ground. Black is live.
Switch B has 2 Black wires plus Ground. One of the Blacks is live.

Ceiling has one each Red, Black, White, Ground.

Checking for live wires at ceiling with all combinations of the 2 switches:

A off, B off: No live wires at ceiling.
A on, B off: Red and Black live only
A on, B on: Red and Black live only
A off, B on: Black live only

So it looks like switch A provides power to both red and black. And switch B provides power to Black only.

So now my questions:

1. Is the above described operation of the switches for ceiling fans normal/standard/common? Or is it an indication of a wiring problem?
2. If the wiring described is OK, which switch and wires should I use for the light (remember, no fan)? I know I need to use the white (neutral) and the ground. But should I use the black or the red?
3. Can someone point me to a schematic diagram which explains the switch behavior I am seeing?
 
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Old 09-13-14, 01:50 PM
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Welcome to the forums! Your proximity tester is giving you false readings. Nonetheless, One of your switches will energize the red wire and the other will energize the black wire. Leave the switch wiring alone. Cap off the red wire in the ceiling box and connect your light to the black and white plus ground in the ceiling box. Only one switch will work, and it will be the one with the two black wires on it.
 
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Old 09-13-14, 02:32 PM
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Thank you for your response chandler.

I have separated the wires coming out of the ceiling fairly wide. So when I place the tester against one wire, it is at least 3 or 4 inches from any of the other wires. I would hope that's wide enough for this proximity tester.

When only switch A is on I think I should only see the red wire at the ceiling live. If what you're saying is correct, I am, for some reason, getting false positives on the black wire. I do notice that in this situation the tester only seems to beep on certain spots along the black wire. And a few times it gave me intermittent beeps at a regular interval, about once a second. Can you explain this behavior?

The tester is the Fluke 1AC-A II. Just bought it.
 
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Old 09-13-14, 02:44 PM
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On your particular model, tip will glow when voltage is present.
So turn on switch 1 (only), check red and black at ceiling. Only either red or black should have voltage.

Do the same with switch 2. Only red or black should be hot.

Choose the switch you want to use, probably #1, and wire accordingly. Post back if your test fails.
 
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Old 09-13-14, 02:46 PM
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It is not an accurate tool, even if it carries the Fluke name. It only tells you there is a presence of electricity in the proximity. The best measurements will come from an analog meter. Electrical induction will give false positives with the detectors.
 
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Old 09-13-14, 03:39 PM
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Success

Done. I used the black wire for power. Only one of the two switches turns on the light, as desired.

I guess I was reading an induction current with the tester. So now the question is whether I should keep the tester or return it. I still have 2 more lights to install. I only bought the tester for these installs. I was planning on keeping it. But if it's not reliable is it worth keeping?

Thanks again.
 
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Old 09-13-14, 03:42 PM
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The tester is the Fluke 1AC-A II. Just bought it.
Then helpfully you can return it and get something that works well enough to reliably work as a useful test instrument. All the the non contact test does is give you a warning that there may be voltage present. Good as a quick safety test but not as a confirmation there is voltage. Far more useful is a $8-$15 analog multimeter. Do not get a digital multimeter. Except for a couple of expensive ones with special circuits they can be fooled by induced voltages.

Some of us here have spent many posts trying to help a poster who said they had power at a cable only to find out the poster used a non contact tester and the real problem was the cable was dead or not the correct cable.
 
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Old 09-13-14, 03:45 PM
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It is reliable for detecting the presence of electricity. For that end, it is useful. But as you found out pinpointing the voltage can only be done accurately with an analog meter. Even digital meters can detect Phantom voltage and unless you are accustomed to it, it will mislead you.
 
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Old 09-13-14, 03:53 PM
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I do have an old, small analog multimeter. Maybe I'll try that for the next one.
 
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Old 09-13-14, 05:15 PM
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Hmmm,
Chandler predicted success is post 2 by using black wire. Uncanny? No.
Sometimes it helps just to know where cables likely go and eliminate other possibilities.

I use a non-contact tester quite a bit. But I would never start wiring a device without checking with a meter.
 
 

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