Two switch loops in Single gang Box

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Old 06-15-20, 10:23 AM
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Two switch loops in Single gang Box

I have a single gang box with a dual switch fed by 2 switch loops. One switch loop goes to sconce lights, the other goes to a ceiling fan. (Long story how it got this way.) The 2 switch loops come from 2 different circuits--each on a different breaker. My question is whether this is any sort of problem? (There is nothing else in this switch box.) Thanks!


 
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Old 06-15-20, 11:52 AM
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It is a problem the way you have drawn it. The tab between the hots(should be the white wires) should be cut to keep the two switches independent.
 
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Old 06-15-20, 02:30 PM
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Nitpicking:

"... should be the white wires ..."

The wire bringing the switched hot back to the light fixture gold screw or black lead must not be white even if tagged with black tape.
 
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Old 06-15-20, 05:23 PM
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This is what you need to do.
 
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Old 06-15-20, 08:56 PM
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OK so seems the wire color is not completely perfect but more a minor thing. As far as cutting the joining tab on the switch, I should have been clearer, there is none. This is actually a dual control rather than a dual switch. The dual control varies a ceiling fan speed and dims light.

This dual control has a single flying lead, the common, where I joined both incoming hots of the 2 switch legs. (Then has a 2nd lead out to the fan, and a 3rd out to the lights.)

This lies the heart of my question if joining 2 incoming hots a single common is an issue? So far the dimmer works on the installed lights. The fan box has on/off voltage, but admittedly I have not installed the fan as yet. Thanks!
 
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Old 06-15-20, 09:26 PM
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Hots from two different circuits must not be joined.
 
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Old 06-16-20, 05:52 AM
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OK thanks! Sounds like I have to change this: Either get them both on the same circuit, or put in a 2 gang box and put each switch loop on a separate control.

I'm curious what the worst is can happen? Can I wind up with 220V on the joined hots?
 
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Old 06-16-20, 10:38 AM
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Well if the feeds are on different legs in the panel you would have a dead short, and the breakers should trip.
Geo
 
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Old 06-16-20, 12:45 PM
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You really should remove that switch and buy another switch unit where the two switch toggles do not share a common hot terminal screw.

There are a variety of circumstances where someone in the future redoes the wiring or rearranges the breakers in the panel and then funky things happen (like in the previous reply) where the previous day it worked okay.

You have two cables each bringing raw hot into the box. Except for the bare ground wires, no wire in one cable may be interconnected with any wire in the other cable. (They can still share the same box.)
 
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Old 06-17-20, 07:04 AM
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Switch is disconnected now and one switch loop will be moved. Thanks for all the help with replies.

I have one more curiosity...so my understanding is that, with some exceptions, and because of no neutral present, new switch loops are against code.

I heard something about running a 14-3 with the white connected to a bonafide neutral on one end and then other end capped off in the switch loop box? How about this?
 
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Old 06-17-20, 10:26 AM
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14/3 is the way to get a neutral at a switch box.
 
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Old 06-17-20, 11:02 AM
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Yup, the switch loops aren't really the issue in newer code editions, it's that people want to use a smart switch, or extend the circuit to an always-on receptacle. In both cases (and probably others), you'll need a neutral, and some people might bootleg a neutral or do something not-right.

So a 14/3 will provide a standard switch loop with red/black, and a future neutral capped off if needed.
 
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Old 06-17-20, 12:18 PM
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It all depended on train of thought. Many electricians would run the feed thru every ceiling light and then just drop down a switch loop. I've always taken the feed thru the switch boxes.
 
 

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