Replacing existing light switch - what the...?

Question

Located in the US, I have done some basic rewiring of fixtures and have replaced a few switches in this house. But I am stumped as to what is going on in this box. No idea how to proceed and difficult to find search info that is relevant. Apologies if this is a totally stupid question.

Tried to make clear what connects where in photo using colors they are all black wires - it's hard to see where they go, and how many there are.

Purple - wires coming from the box

White - the first wire from the switch

Red - second wire from switch

Currently in the box - 3 single pole dimmer switches

Switch 1 - single recessed can

Switch 2 - 4 recessed cans

Switch 3 - two exterior lights

Switch #3 is the one I need to swap out, it is broken - I am replacing it with a single pole NON-dimmer (really porch lights are either on or off - no need for dimmer)

Each switch has one black wire individually connected to one in the box with a wire nut (as the others I have swapped out have been)

Except switch #3 connects to two wires from the box (one for each outdoor fixture, I guess?)

One black wire from each switch are (total of 3 wires from switches) bundled together with a single wire nut with two black wires from the box.

All of the ground wires are connected together with a single wire nut, to a single bare copper wire, the rest of the bare wires are neatly bundled together in the back of the box.

There are also five white wires from the box all bundled/connected together with a single wire nut (none go to any of the switches)

Problem -

All of the other switches I've replaced had a single wire from the box connected to a single wire from the switch with a wire nut. 1 wire to 1 wire - unless it was a single/3way optional switch, where one wire needed to be capped for single pole use.

I had no problem figuring out how to replace a switch with the same type.

My only guess is it's some sort of trick to save room in the box by using fewer wire nuts. Wiring in series? I would like to understand - should anyone have patience to explain or point me in the right direction.

Questions -

Is this box wired properly? I remember some of these switches being extra buzzy, but not sure it has anything to do with the wiring in the box or is just normal.

Should I just put the new switch in and leave things the way they are?

If yes, what about joining 2 wires to one screw on the new switch? Or add another wire to the wire nut to run a single wire to screw? Errr....that's probably a stupid question. I can figure that out later.

I would be happy to provide more info if needed. Many thanks in advance, even if the answer is you are obviously over your head,call an electrician....! Hopefully not too painful to read.

Answer 1

Almost nothing in house power is ever in series, except a switch is in series with the thing it switches.

Your three switches take power, "always Hot", in parallel from the bundle of 5 - one in, one out to elsewhere, 3 for the 3 switches. Simple. We don't need to care at this time which one is power in or power out, or where they come from or go to.

Your switches control various lights, which they are connected to by the other wires "switched hots" connected to them. In the case of switch 3, that's one out joined to two by the evidence of "that's the way it was."

The neutrals are not involved with "dumb" dimmers or switches.

Fortunately, you didn't pull the trick we've seen too often of disconnecting everything and only then, when it's too late asking how to wire it.

Answer 2

Yes, the "all black" motif is maddening, but that's how standard cables come. I own 10 colors of THHN wire for use in conduit, and if I were doing this circuit, I would use the following (generally preferred) colors:

• (per law) Safety ground = Green, yellow w/green stripe or bare
• (per law) Neutral = white or gray
• Always-hot - black
• Switched-hot switch 1: Red (i.e. hot when you want that light to be on)
• Switched-hot switch 2: Blue
• Switched-hot switch 3: Yellow

And you can actually buy 5-packs of colored electrical tape ($4-6), spiral the tape onto the wires, and mark them accordingly. Then, you can remove devices at will without having to worry about mixing up wires.

Now it looks like all switches take "always-hot" power from the same fat wire nut with your red, white, white respectively, and other wires too which are no concern of ours.

And each switch has 1 wire (switched-hot) that only goes to 1 other wire. (or 2 in the understandable case of the dual lamps).

So let me fire up the mighty Photoshop, and....

I slightly purpled the black, so it would stand out in the sea of black.