I am replacing a bunch of switches and receptacles in my house.
While I understand the basics, this is pretty much my first electrical project, and I figure there must be some hidden "gotchas" or surprises that people run in to when doing this.
Any advice on what to watch out for?
Best Answer
Yes, aside from checking with a tester to make sure the circuit is actually off... there are several subtle issues that frequently catch novices.
Don't remove screws all the way - they are captive. After some distance they will start getting stiff. Stop there, don't force them.
There's your tab. This $1 outlet was ruined, by soldering (!) and removing the screws.
Receptacles - Tabs
Most common North American style receptacles 2 sockets and 2 attachment screws. Between the screws is a "tab" of metal that can be flexed back and forth and snapped off.
Check the tabs. If your old receptacle has any tab(s) broken off, you must break them off on the new receptacle.
If you break one off by accident, and the receptacle is valuable, that's fixable.
On receptacles, brass screws are for hot and silver wires are for neutral.
Broken tabs and GFCIs, USB or other specialty outlets
Replacing a tab-broken outlet with anything else is a specialty task that calls for more research. Don't just cram the wires on anyway! The answer might be "but you lose functionality if you do".
GFCI receptacles otherwise
Take care to distinguish LINE from LOAD.
If you are replacing a plain outlet with GFCI, leave the warning tape on, and hook up only the LINE terminals (cap off spare wires). Power up the circuit and test the GFCI. After it works, shut off the breaker and consider adding wires to LOAD if you want to use this GFCI to protect that downstream part of the circuit, which is a cost-saver if you know what you're doing. Otherwise, add those wires to LINE. Most GFCIs support screw-to-clamp for 2 wires per screw.
Switches - 3-way (UK: 2-way)
Anytime you see 3 or more screws (besides ground), watch out. 3-way switches are tricky, because screw position and wire colors are meaningless, and that's usually what novices go for. Screw colors matter (or labeling).
I'm a big fan of buying a 5-pack of colored tape, and marking both travelers with yellow tape. (alternately: blue tape). This makes it a lot easier to tell what's going on in a busy box. There is no need to distinguish them from each other, so use the same color. Two same-colored wires in the same cable suggests travelers.
Marking is helpful because the native wire colors of travelers mean nothing. I've seen 3-way circuits in a how-to guide where 3 different pairs of colors were used in the same 3-way loop!
4-way (UK: 3-way)
These switches have 2 brass and 2 black screws. Two pairs of travelers attach. One pair of travelers attach to the brass screws. The other pair of travelers attach to black. In most cases, it's easy to group them in pairs - any pair of travelers is always in the same cable or conduit. Just make sure that is so.
For marking, I typically mark all 4 travelers yellow, since you can easily see the grouping by looking at the cables.