I want to wire this regular switch&outlet receptacle so that the outlet has constant power. This receptacle will replace the switch in the picture.
The current receptacle (where the switch is connected) only has two wires: hot and neutral.
My question: how can I install the switch/outlet combo so that the outlet has constant electricity?
This is a picture of the current receptacle. The switch/outlet combo will replace this switch:
Many people find it annoying only because it is different from what they're used to / most of the youtube videos, but it's actually a marvelous system that does a lot of cool stuff for you.
At the very least, you never need to handle a ground wire. The metal conduit and boxes does it for you. Use "self-grounding" receptacles, those and any switch pick up ground via the mounting screws. Done and dusted!
You use THHN individual wires, which are cheaper and easier to work with than cable. One rule in conduit is "no remarking wires", so you can't re-mark white wires to be hot (and the opposite is never allowed). You need to use native white or gray wires for neutral.
That means only 2 wires come down from the light. If you read the below (my original answer), you know that being a switch, those 2 wires must be always-hot and switched-hot.
You need neutral. So in conduit fashion, you will need to "follow the pipe" to see where it goes (expect: the light junction box), and you will need to "pull" a white neutral wire into the pipe. Just one white THHN wire, same size as those already in the pipe. Expect 20 cents a foot, by the foot.
Then you either need a fishing tape, or lots of fidgeting and a little bit of luck, to walk that neutral wire down the pipe.
My own technique for shoving wires (to avoid driving to the other building to get the fishing tape) is to optimize the slack in the existing wires so they can move back and forth 6-12 inches easily. Then push the new wire in until it binds (don't kink it). Then hold the new wire, while pulling the existing wires back for that 6-12" of free play. Then shove all the wires back in that 6-12", and the new wire will now move with the others. Rinse wash repeat, the new wire will slowly ratchet in.
Needless to say, you do all this with the circuit and preferably the building shut off.
"Receptacle always on" is how most people want to wire it, and it's built for that. Let's think about what receptacles and switches need.
Besides ground, receptacles need:
Besides ground, switches need:
Notice how always-hot is common - both switch and receptacle need it? Then the switch has a unique terminal (switched-hot).
As for the neutral, that uses silver screws. There is one. It is directly opposite the taller neutral pin on the receptacle. Not a wild guess that's for neutral, so we can check off neutral.
What is left?
You have one brass screw near the switch, and the switch still has a unique terminal unaccounted for. What's unique up there? Switched-hot. Cross that off.
Now what's unaccounted for now? Two terminals that both want "always-hot". And what's left on the device? Golly, 2 terminals bridged together. That's convenient!
That's not the purpose of that tab. You only break that tab if you have two separate isolated circuits on that device. For example, if you had a light you wanted to control on circuit 1 and the receptacle you wanted to put on circuit 3. If you didn't break the tab you'd have a 240v bolted short and the tab would probably likely melt off for you. If the source of the receptacle and the light you are controlling are the same circuit, you wouldn't break that tab as the incoming hot wire for that box would attach to that terminal, the neutral to the silver terminal, and the switch leg to the light on the brass terminal on the other side.
Did I explain that right?
Here's a diagram of how the device is internally connected:
