Electrical Mystery


Old 05-21-07, 01:33 PM
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Electrical Mystery

This is a thread I posted a while ago and I have some updated information. I would appreciate any help.

I recently installed a new ceiling fan in my living room which is adjacent to my garage. For power, my nearby kitchen light had a 14/2 wire with 120V across a black and white wire at the fixture so I tied these individually to a new 14/2 line, ran the new line down to a 3 speed fan switch and then a new line to the fan. It works fine.

Update - I have since learned by opening my electrical panel that the power supply that I tapped into was part of a 14/3 so called "shared neutral" line. Most of my houses is powered this way. This shared neutral line supplies my kitchen light, fan, garage light, dining light, stairway light, and several finished basement lights.

Here is the problem: The garage light is run by a motion sensor switch on the garage wall. When I switch fan speeds with the little slider tab on the fan 3-speed switch in my living room, my garage light comes on. But the garage light only comes on when the garage switch is set to the "motion detect" position. It will come on for five minutes (the preset time) and then go off. Repeating the process results in the same result. Note: changing the fan speed won't turn the garage light on or off if the garage switch is set in the "always on" or "always off" position.

The fan and garage light are on the same 14/3 so I can only guess that changing fan speeds some how temporarily interrupts the garage motion switch and toggles it into the on position. I know that I did not tap into any kind of switch loop as the garage light can be turned on when the fan is off and vice versa.

I am most concerned about safety of course. Any suggestions?

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Old 05-21-07, 01:58 PM
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I doubt that you have a safety issue. I don't know what's causing it exactly, but the speed control probably sends a signal through the electrical line which is confusing the motion sensing switch. Perhaps you'll just need to abandon the motion sensing feature, or live with the fact that your garage light will come on for five minutes occasionally when you don't need it to.
Old 05-21-07, 08:32 PM
Join Date: Sep 2003
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Learn a less on from this. You need to understand your electrical setup BEFORE making changes. Knowing that the motion sensor light was also on this circuit may not have changed anything, but at lest you would have known ahead of time.
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