I wanted to replace a single pole toggle switch with a smart switch. I opened the switch box to analyze the existing wiring. Typically in single pole switches there should be 3 wires going in. I live wire (typically screwed to the black screw) and one load wire and one ground wire ( green wire or just wire without the casing). But I noticed 4 wires in this switch. There was a black wire pinned to the same screw where the live wire went in. This black wire was getting constant power and it was providing power to other parts of the room. Like light switches in powder room etc.

My question is when I put in the new smart switch, can I put both the live wire and the other wire that was providing power to all other switches together with a wire nut?

Attached some photos for reference!

2 wires going in. Only one wire is live, other wire powers other parts of the room

2 Answers 2


Your analysis of the current situation is correct and quite normal. The fact that this type of switch allows two wires to be attached under the switch makes it that much easier to do, as opposed to hacks (MPO) such as one wire under the screw and one in the back-stab.

Yes, it is perfectly fine to have a pigtail to the switch and connect the three wires with a wirenut.

  • 1
    Does "MPO" mean "my personal opinion" here? Mar 21, 2021 at 18:58
  • @TannerSwett yes. I know it’s also the opinion of others here but I was speaking for myself.
    – DoxyLover
    Mar 21, 2021 at 19:06

You can do what you say. But, if the new switch provides a pair of holes like in this picture that both lead to the back of the screw down terminal, and as long as both wires are the same size, you can just connect them both there. It's easier to do and to maintain because you don't twist up the wires as much.

Hopefully the grounds are nutted together out of this picture?

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