Gang Box - One hot, two switches


Old 10-23-05, 07:50 AM
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Question Gang Box - One hot, two switches

I've changed a single box to a double gang box. I have the original hot wire coming in, the original wire out to ceiling light and I've brought a new wire in which is connected to ceiling spot lights. I was ready to start the pigtailing process to make all my connections and it dawned on me that once pigtailed together either switch would complete the circuit for both lights. My Harry Homeowner electric book only covers single box scenarios. Am I right in this logic? Do I need to bring a second hot wire into the box to make the switches work independent of each other? Please advise. Thanks!
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Old 10-23-05, 08:28 AM
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Location: Oregon
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You pigtail the _supply_ to both switches, but you keep the load side separate. Switch 'A' will selectively connect wire A to the supply, but not affect wire B. Switch B will selectively connect wire B to the supply, but not affect wire A.

Old 10-23-05, 09:15 AM
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1. Add your new white wire to the other white wires in the box.
2. Connect your new black wire to one of the screws on your new switch.
3. Take one of the black wires off the existing switch and connect two pigtails to it.
4. Put one pigtail on each switch.
If the first switch needs to be on for the new light to work you picked the wrong black from the first switch in step 3.
Old 10-23-05, 09:52 AM
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If all you have is a single cable in the box with a white and a black wire (and a ground), then you cannot add your new switch here without running a wire to replace the previously existing wire.
Old 10-24-05, 02:52 PM
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Thanks guys- that makes perfect sense!
Old 10-24-05, 08:04 PM
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Looking to understand

I have nothing to add to the above statements, but I am confused with the answers...maybe I am not reading them correctly...

I have 2 areas in my house with the same situation, one wire coming into the box, and 2 wires leaving...example...My bathroom has a light, and a fan, both fed from the same hot wire coming in, but each controled by its own switch. Here is a picture of the switch:
Now, if I read correctly, this isnt possible...although its working in my house
Old 10-24-05, 08:16 PM
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The devil is in the details, and we have few details here. Bob stated an "if" which was neither confirmed nor denied. So we really don't know what the situation is here. All we know is that at least something "makes perfect sense" to at least one person.

Stevetra, you stated that you have "the same situation", but I'm not sure we can verify that. I don't even know if a "wire" refers to a single conductor, or to a cable assembly of multiple conductors. Furthermore, we can't meaningfully discuss the wiring of the switch without also discussing the wiring at the fixtures. We have no idea how your setup is wired, and the fact that you have "one wire coming into the box, and 2 wires leaving" tells us very little.

Everything is possible with enough wire.
Old 10-25-05, 05:30 AM
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Ahh yes, those details.

Ok, I will describe as best as I can, one area where this switch is being used.

In my Kitchen, to the right of my sink I have a switch like the link in my earlier post beside a window. The top toggle of the switches a 24" florescent light over the sink, the bottom toggle switches the garbage disposal on and off.

The switch is wired as follows.

Wires in the box:
a 12-2 conductor brings power to the box. (black, white, ground)
a 12-2 wire to the Disposal
a 12-2 wire to the light

Connections in the box:
All white wires connected together
All grounds connected together and pigtailed to the ground screw on the switch
all blacks to the switch

Switch connections:
Incoming black wire to left side top screw WITH tab intact, thereby delivering power to both upper and lower toggles on the switch.

Right side of switch has TAB REMOVED with the black wire from the light connected to the top screw, and the disposal connected to the bottom screw.
Both units switch independently
Old 10-25-05, 06:43 AM
Join Date: Sep 2003
Location: Central New York State
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You are describing a valid hookup. It can be argued that you shouldn't have a light sharing the circuit with a disposal, but that's a different discussion.

This post is talking about a different setup. The original poster has not stated whether or not he has power coming into the box. If the original poster only has a switch loop (a single 12-2 or 14-2 cable) then he cannot add a second switch to run to the spot lights unless he gets power first to the spot lights (unless he changes the existing cable to be 12-3 or 14-3).
Old 10-25-05, 07:10 AM
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Ahh, ok that makes sense now....

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