ZZZZAP! Being a Home Electrician

I was exposed to electrical and electronic work very early—10th grade, in fact, as well as throughout my junior ans senior years of high school, and in my four-year apprenticeship after that. So for me, doing electrical work in the house is no big deal. Well, a big deal when the idiot before me did janky work, but otherwise no big deal.

But I’ve recently become aware that a lot of people WILL NOT TOUCH electrical stuff. Like, even a general contractor I tried to hire! Wow!

So I thought I’d lay out some of the basics, and maybe help you feel more comfortable doing, or at least thinking about, some of the easiest home electrical stuff like swapping out a light switch for a smart switch!

The Basics

OK. In the USA, we run a basic electrical system of 120 volts. You can think of volts as the “pressure” that moves electrons through the wire. The more pressure, the more electrons you can move.

That comes into play with high-load devices like, say, an electric clothes dryer. They need a lot more electrons—measure in amperes or amps—at once. 120v isn’t enough pressure to push that many at once, and so they’re often 240v devices, and they may use 30 or even 50 amps.

(On a 120v circuit, 20 amps is the most you can usually get.)

So in practice, most homes’ electrical service has two “legs,” each carrying 120v apiece. When you have a 240v appliance, it takes power from both legs at once (120+120=240).

Take a look at your home’s circuit breaker box. You’ll usually see two columns of breakers—and generally, each column is one of those 120v legs. For bigger appliances, you’ll usually see a double breaker, because it’s connected (behind the scenes) to both legs at once.

So: you’ve got three types of wire coming out of that circuit breaker box.

• Black wires carry the actual electricity. This is your “hot” line. Don’t touch it if the breaker is on!
• White wires are “neutral.” They carry used electricity back to the breaker panel. Properly wired, these don’t carry more than a stray volt or two.
• Green or bare wires are “ground.” These are generally a backup way for electricity to escape to the earth—literally, to the dirt under your home—if a hot wire accidentally comes loose and touches an appliance’s outer shell, for example.

In reality, neutral and ground are the same thing. At your breaker panel, the white and green/bare wires are literally tied together. Neutral only exists to provide a planned path for electricity to get to ground, while the ground wire is kind of an emergency path.

Measuring

Let’s talk about measuring voltage, because it’s the easiest and most interesting and useful.

You measure voltage with a multimeter, and you can pick them up on Amazon for $20 or so, as well as at any home improvement store. Turn the dial to measure AC voltage in the appropriate range (usually 0–240V).

Voltage is expressed as a difference between two things.

So if you measure between hot (black) and ground (green/bare), you should read about 120v. It might be 119, it might be 112, it might be 110… anything between 110 and 120 is fine. That measurement expresses the difference between those two states, with the ground at zero and the hot wire at 120 or whatever.

In theory, measuring ground to neutral should be zero, because they’re ultimately the same thing. In practice, it’s impossible to fully balance any circuit in a home, what with things going on and off all the time, and so it’s totally normal for ground-neutral to read a volt or two, even up to 20v sometimes. Anything more than that, or even a continual reading above a couple of volts, is cause for concern: it suggests that you have a loose neutral wire someplace, or that a neutral wire has come into contact with a hot wire—a short circuit, in other words.

And remember: Voltage is a measurement of difference. If you’re reading zero volts hot-neutral, then there’s no difference between those two wires. This is bad, because it means your neutral wire is carrying a full load of electricity. Call an electrician at once and do not use the affected circuit. Similarly, hot-ground should always read a full 120v (or whatever) difference.

More Wires

When you dig into a light switch junction box—after turning off the circuit breaker, removing the face plate, and perhaps easing the switch out of the box a bit—you’re like to see a morass of wires, especially in a multi-gang box with two or more switches.

• White: Neutral. Often, these will all be twisted up into a bundle and shoved to the back of the box. For dumb light switches, this is fine; for smart switches—which often require a neutral connection—this is a pain in the ass, because you have to somehow wedge another white wire into the mix. More on that in a moment.
• Black: Hot… and potentially load. More in a sec.
• Red: Load.
• Green/Bare: Ground.

So let’s talk about hot and load.

Hot is the wire carrying electricity from your breaker panel. This wire will go into a switch. Load is the wire carrying power from the switch to the load, like a light, or a fan, or a socket, or whatever. Good electricians will use red for the load line. Lazy ones will use black, making it harder to tell the difference. You can sometimes look and see which way the wire bundle comes into the box to tell the difference—a wire heading out the top, for example, is likely going to an overhead fixture.

A multimeter can, with the circuit energized, be the definitive answer. With the light switch off, one of its terminals will have zero voltage when measured to ground, and that’s the load wire. The other will have 120v, and that one’s the hot wire.

Tricks of the Trade

• Wire nuts.
  These are the little colored plastic nuts used to twist multiple wires together. I hate these things. First of all, you need to use the right size nut for the number of wires you’re twisting, and for the gauge (thickness) of those wires. You also do need to twist the hell out of them, because they need to form a mechanical hold as well as an electrical connection. The wires coming out of the nut should be physically twisted around each other.
• Wago connectors.
  I like these a lot better, and they’re common in newer construction. These are little plastic modules, and they come in 2-, 4-, 6-, and even 8-way versions. You just strip a little insulation from a wire and jam it into one of the Wago connector’s holes. Beats wire nuts all day long. A flat-blade jewlwer’s screwdriver can be jammed into a little release if you need to pull a wire out. Make sure you buy Wago connectors for the proper gauge of wire—homes are usually wired with 12 and/or 14 guage (AWG, a term you’ll see, is American Wire Gauge; you’ll often see it expressed as #12 AWG, for example, or just “12–14”).
• Wire strippers.
  These invaluable little tools—and get a dedicated wire stripper, don’t use one of those bulky tools that’s also a terminal crimper—usually have a little dial on one handle, which you set to the wire gauge you’re using. The dial ensures that the tool can’t bite down into the actual wire, but that it can completely cut through the insulation all ‘round the wire. Set the dial, squeeze, and pull a bit to slip the cut insulation off the end of the wire.
• Push-wired switches.
  Switches with screws on the side SUCK. Spend a little more and get switches set up to be “back wired” with whatever wire gauge you’re using (it’ll say on the switch’s box). Strip a little insulation (many switches have a molded-in groove on their back to show you exactly how much to strip) and then jam the bare wire straight into the back of the switch. Like Wago conenctors, a little recess lets you stick a flat-blade jewler’s screwdriver into the switch to release the wire (it’ll take a firm tug).
• Back-wire pressure plate switches.
  A good alternative to back-wired, these let you stick a straight wire under a little brass plate, which you then screw down tight. This is distinct from old-style “side wire” switches where you had to curve the wire underneath the screw itself—those are for the birds.

Multi-Way Switches

These can be, pardon my German, fucking confounding.

These are the kinds of switches where you have one at either end of a hallway, for example, and they both toggle the same light on and off. These are special switches, with four terminals, in addition to ground:

• Hot
• Neutral
• Load
• Carrier

The ‘carrier’ wire is what makes them special, and it runs between the switches. Essentially, the switch is toggling hot between the load and the carrier. If the electricity isn’t going to the load, then it’s going to the other switch.

If you need to rewire one of these, label the wires as you disconnect them. I’ll use bits of masking tape, and a marker to write what’s what on each. Because if you had a lazy electrician, you’ll have one white wire, one green or bare, and then like four dozen unmarked black wires. Don’t worry, Hell has a special ring for those electricians. But the old switch’s terminals are likey labeled with molded-in words or symbols on the back, indicating which wire is which. Label the wires as soon as you disconnect them, and you should be fine.

FEAR!

OK look, your’e (a) not going to hurt yourself and (b) not going to burn your house down.

• Always cut the circuit breaker before you open up a junction box or work on a circuit.
• Verify that the circuit is dead—use a voltage detector (a few bucks at the hardware store or Amazon)—before you touch it.
• Make sure that, other than a bare ground wire, you can’t see any exposed copper when you’re doing working. Wires must be fully inserted into whatever they’re inserted into. If you can see bare wire, disconnect it, trim the end off with a good pair of wire cutters, and then re-insert it.
• Always use the right size wire nuts. Tug on the wires a bit when you’re done, to make sure they’re physically secure.
• If you’ve screwed up, your circuit breaker will protect you. If you turn it on and it snaps back off, you’ve got a short circuit—meaning, a hot wire touching either neutral or ground—or your load is pulling more than the circuit breaker will allow. The latter scenario is how the breaker prevents a fire from an overheated wire that’s trying to pull too many electrons at once. Again, you’re going to be fine, because this is what the breakers are for. Just leave it off and fix the circuit.
• If you’re installing new switches, get ones with the smallest physical body that you can (not easy with smart switches, when tend to be huge). Junction boxes, especially multi-gang ones, can get crowded. The less switch you have to shove in there, the easier your life will be.

Supplies

Some suggestions, if you need them (includes affiliate codes):

• Multimeter
• Voltage detector
• Breaker finder—helps trace outlets back to their circuit breaker using sound
• Wago assortment
• Wire nut assortment
• Wire cutters
• Wire stripper — I like these way better than the bulk mechanical ones, because these fit easier into a junction box. And this kind is actually a little hard to find, but the ones I’ve had are almost 30 years old and I still love them.

And, just so you can see what one looks like, here’s a back-wire pressure plate switch, and here’s a push-wire switch.