Wiring a 4 gang box, 4 light switches, Power at fixture.

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Old 05-12-16, 02:52 PM
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Wiring a 4 gang box, 4 light switches, Power at fixture.

I have a metal gang box with 4 separate light switches- (#1) kitchen; (#2, #3,#4) carport. Incoming cables: switch #1--two 12/3; switch 2, 3, 4.--12/2 to each switch. Switches are on the same circuit. The kitchen light was previously controlled by 3-way. Now disconnected and (1) 12/3 incoming cable taped in gang box.

Incoming Wires
Switch #1 incoming black wire connected to top left screw, incoming white wire to bottom right screw. Red wire to wire nut . Switches 2,3,4 Incoming white wires to wire nut. Switches 2,3,4 Incoming black wires connected to its switch bottom screw. (#1, 2) grounds unattached (#3,4) grounds to switch ground screw.

In box connections
A short white wire connection between Switch #1 bottom screw and switch #2 top screw. A short white wire between switch # 2 top screw to a second wire nut. Short wire from switch #3 and #4 to second wire nut. The result is 2 wires under 1 screw at switch 1 and 2. Presumably these connections are for power distribution to the individual switches.

Does NEC permit 2 wires under one screw? If not, what is the alternative?

Thanks
Ann
 
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Old 05-12-16, 03:26 PM
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Hi, Ann. Welcome to the best DIY forum on the Internet!

Does NEC permit 2 wires under one screw?
Generally not. The exception is where the screw itself tightens against a pressure plat and the two (straight) conductors enter from the back of the device. This is known as a "back-wired" device and not to be confused with a "back-stabbed" device where the wires are inserted into holes on the back of the switch or receptacle and held in place via spring pressure. The back-stabbed is often thought to be an inferior method of connection and is a common failure point.

The other exception would be if a length of wire had a small center section stripped of insulation and this stripped section was held under the screw head. Of course in this example it isn't really two wires, just a single continuous wire with multiple points of connection.

Back-wired devices are a superior product and are often referred to as "commercial" or "specification" grade and they have a higher price than standard grade devices. They are well worth the additional cost in my opinion.

The alternative is to use what are called "pigtails" where a short piece of wire runs from each device to a "wire nut" where they all join together. Pigtails are very common although the additional junction does make for a potential failure point. In certain instances the use of pigtails is mandated by code such as multi-wire branch circuits (MWBC).

A short white wire connection between Switch #1 bottom screw and switch #2 top screw. A short white wire between switch # 2 top screw to a second wire nut.
The use of white insulated wires in these connections is incorrect. There are few cases when the use of a white wire with a switch is correct and jumping power from switch to switch is not one of them. In most cases a white wire on any switch that does not also contain an indicator light or timing circuit the white is a "hot" (from the controlled fixture) and needs to be re-identified with a color other than white, grey or green.
 
 

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