Dimmer switches can be switched out with single poles. I'm really confused by that group of twisted black wires. Did it just have a wire nut on it?

Three way switches have an extra wire.

The dimmer switch had 2 black single wire leads coming from it, one was wired to the single black wire, and the other was wired to the pair of black wires twisted together. The house is a modular built and wired in Canada, if that makes a difference.

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Yea you'll need to get a little piece of 14 ga wire to pigtail off the twisted black wires. Final product should look like this.

Worked like a charm. Thanks, internet stranger!

Could be another branch that feeds off of this box.

Thank you for asking this question, it didn't even occur to me! I bought a new light fixture and replaced mine with the intent of using smart lights, but they say not to use dimmers on them, so I also bought a regular paddle switch to replace the dimmer, just haven't gotten around to it yet. Now I have the answer to a question I was probably going to run into.

The single black was most likely the light and the twisted pair was likely the branch line. The switch sits in the middle to be a switch/interrupt of the power.

Call an electrician. Please don’t be learning on your home around when it comes to electrical.

There's no switched outlet in the room, so it's not that. Beyond that, I have no clue.

Is that doubled up wire on the line, or load side of the switch?

It's wired to the new switch on the line side, and working fine.

It likely provides unswitched power to lighting in the house.

Yes you can do that, just wire it back up the same way. Put the single black on the top screw, and add a pigtail to the two twisted wires (add a wire and marette to the two) then put the pigtail to the other screw. Easy peasy!

Right. Learn on somebody else's home. /s

That's constant power feeding another switch or plug the single wire the output to the light

Like that in layout, not like that in colours.

If you wire the switch like that it will go bang

This is not for a 3-way switch.

IF (BIG IF) this was previously wired exactly right, the bare wire (ground) is properly wired. The two blacks SHOULD be power into the switch and power on to another device. The single black wire should be hot to the light's hot lead.

I'm concerned that maybe the previous person made this work but got the colors wrong, creating a shock hazard.

The dimmer switch that was here came wired from the original modular home builder, a little more than 20 years ago. There were 2 black unmarked wires coming from the back of the sealed dimmer switch, one wired to the single black wire in the box, and the other wired to the pair of black wires. There was no place to screw the ground wire, but it was inserted through a hole in a metal tab, and twisted to itself.

Looks like a shittily wired box. Either there's a line and neutral with no load (in which case, you would wire a receptacle there, not a switch), or it's an old school no-neutral lights-only loop and they used white for load. Both are wrong, but given they're wiring a switch one would have to assume it's the latter and would still work even with the colors being wrong.

Switching line and neutral would be pretty stupid.

Sounds pretty normal. For a single pole switch, line and load are interchangeable. Without a neutral in the box (actually I lied - there is a neutral in the box, but you can just ignore it; tuck it deep in the back of the box), there's nothing to confuse or do wrong. Ground to ground. One of the black lines to one of the gold-colored posts, the other black line to the other post (you'll want a pigtail for the line that is two twisted-together black wires). Differentiating line vs load only matters if you're using a smart switch or 3-way switch (two switches control one light).

The wiring is line in/line out which is the two twisted lives (black) as well as a switched live out (black alone).

The whites are the neutrals.

Wiring a switch to bridge between live and neutral (as it would be if they copied the pictures) is a problem

I was referring to the linked article, not OP's picture. As I assumed you were doing, too, when you said, "Not those colors".

Yerp. Sometimes still done today. It's not up to code as we need a neutral in the switch box.(Now) Black feed white switch loop. Neutral already existing at the light connected to another point in the same circuit (hopefully).

Edit: You can't always go off color of wires. I wire 3 and 4 way switches using white wire.(14-3 with ground) I identify with tape. Some electricians don't.

This works but decora switches usually have both screw terminals and push-in terminals.

If you wanted to get rid of the pigtail you could put 1 of the doubled up wires on the line screw terminal, and the other into the line push-in terminal. Then connect the single load wire to either of the load terminals.

Worst case scenario, voltage detectors (or your fingers) don't lie. Turn on the power, check the wires, see what's energized when the switch is off.

Meter, fingers, apprentice, metal grounded box whatever is closest. If it's early AM fingers is the best for a wakeup.

Backstab terminals are awful. Do not recommend.

Why?

This is not good advice; back-stabbed connections fail at a much higher rate. If you don't want to pigtail, the plate connector on decora switches can take two wires. You just have to straighten them and make sure the right amount is stripped.

They make poor connections, are difficult or impossible to release the wires, and can cause unsafe connections that could short.

Yes

So you guys use solid wires? They have not been used where I live for decades... Only very old cables are still solid, the kind wrapped in cloth

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That’s the standard in the US.

The amount of times I have stabbed myself with a screwdriver trying to release the wire is way too high. I just cut the wires off anymore when replacing an old switch.

Same. If I see them, I replace them with new receptacles and bend the wires like a normal human being.

In canada, all wire are solid wires afaik

Sure! Is it a good idea? I have no fucking clue.

pretty much, All in-wall electrical wires are solid, and extension cables are stranded, as the commenter above said!

I replied to the wrong guy, my bad :)

Higher currant capacity, 120v system so we pull more amps more frequently.

Where the heck is that? Solid is much safer for mains wiring.

And all stranded wires require 1 gauge larger wire by code for the same level of power delivery! :)

If you are curious, turn off the circuit breaker, separate the black wires, and see what doesn't work.

I'd guess it's a nearby outlet (non switched)

Sigh. In Europe, the colour coding would help - switched wires have a different colour.

It seems like the 2 blacks are basically the live wire passing thru that .. wall box?

In California at least, stranded is used only inside conduit for most gauges of wire, so it's seen more in non-residential. In residential, you use solid for most wiring. Stranded would only be used when you're doing things like a run that goes underground to a secondary building on the property (stranded of whatever size is needed to feed the sub panel) since you'd be running underground conduit, incoming lines, or really low gauge wires like alarms or speakers.

220v European and the regulations here are solid wire in all domestic and industrial installations. After the plug you can use stranded

YOU shouldn't. Pay an electrician. Burning your house down is not a good risk to save a few bucks.

In many countries solid wire is used. Generally multi strand is only used if wires are pulled through conduits.

In domestic builds conduits are used less frequently.

>currant

How many grapes per hour?

*current.

Underground conduit is rare. Armoured cable is far more common.

They are learning by asking questions and getting sensible answers.

You can tell how it’s wired by the fact the original dimmer was between two blacks.

I’m not saying to assume that white is neutral for the purpose of fitting a smart switch here, I’m saying assume white is neutral so you don’t wire a switch to short it to live. The new switch needs to be wired like the old dimmer, not like the picture in the link at the start of this sub thread.

Second this. Yes OP can do that.

What do you use if not conduits? We use them here

I live in Argentina. What makes them safer?

Direct bury armoured cable.

Underground conduits tend to fill up with water.

Ah, ok, you mean underground ones. We use conduits in the wall, either metal tubes, or plastic corrugated conduit, I thought you meant those.

Looks like it was a 3 way switch maybe

Solid core, while less flexible, has a lower surface area. Firstly, this makes them more resistant to corrosion. Second, they have a lower "dissipation", or voltage drop for a given length, as the skin effect in multiple strands increases impedance. Overall, this makes solid core less likely to fail and cause fires in static applications like home wiring.

ok, say you guys give him good advice, doesn’t mean he’s going to do it correctly. I just left a customer’s house, the guy wired up his outlets himself, says he’s done it hundreds of times but for some reason half the room isn’t working. I went to the first outlet, he hadn’t tightened a screw correctly and the wire was just sitting there and heating up because of the bad connection. He was risking a house fire because he didn’t do a “simple” outlet correctly.

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In the US, we pretty much only use solid wire (Romex) in residential

skin depth is a function of frequency, not cross sectional area.

the reason stranded conductors have higher impedance at the same guage is because they have a smaller cross sectional area.

to illustrate: a pile of smaller circles can never completely fill a circle.

hahaha

Yeah, and I encountered work by qualified electricians where somebody forgot to tighten a screw too.

Yeah, that's more or less what I was trying to say. Not that the skin depth is different, but the way it's distributed in space is different in stranded, especially at higher frequency. E.g. http://www.bdloops.com/solid_vs_stranded_loop_wire.html

Skin effect utterly meaningless at low voltages in domestic and industrial systems. It is only significant in very high voltage long distance reticulation.

In most construction, wiring now goes in the cavity in walls.

In some places like the UK, wiring can be direclty rendered in the wall.

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A half bushel per league on a good day. Auto correct favors juice over juice apparently.

We make houses out of solid brick, or brick that, while hollow, you can't pass wires through. The wall is built, then a channel for the plastic conduit is carved into it.

This is standard: https://i.imgur.com/rZdWBD9.png

In residential it's rare. On utility sites it's used quite commonly for power and comms between settings and buildings. We only use stranded for that because there may be lots of bends in the conduit from point A to B. Specifically where it has to be in conduit and in Class 1 Div II areas.

By the way, you don't need a pigtail for the twisted wires - you can untwist them and put them both under the screw on the lightswitch (one on each side of the screw). Note this only works on this style of screw with the brass "clamp" that the wires go under.

Yeah, it wasn't one of those clamping styles, or I would have done. It would have been much easier to get everything stuffed back in the box!

Ok, don’t call an electrician, do everything yourself. Then call us when you can’t figure out the situation you got yourself in and we’ll be sure to charge the “homeowner tried to do it themself” price. Cause when we have to figure out your three way switch you messed up, that’s another $250 diagnosis charge.

Been doing my own wiring for about 50 years.

Education. Read the appropriate wiring standards. Be compliant. Take care. Check your work. Test.

Have never had to pay an electrician to diagnose anything.

Good for you