I’ve been teaching electricity and controls to the employees of one of the best heating contractors. For weeks now I’ve been hearing from the owner, installation supervisor and the employees: “Ya gotta do something about John. John’s scared of electricity.”
John agrees: “I’ve always been afraid of electricity. I’ll always be scared of electricity. No one can get me over this. I even bought an electricity book at Home Depot, but I haven’t read it yet.”
During the class when we were wiring low-voltage circuits, one of the wires popped off John’s board. I watched as he grabbed the loose wire and was about to put it back on the terminal.
“Whoa, John!” I cautioned. “Un-power the circuit first.”
John looked up at me, puzzled. “Huh?”
“Turn the electricity off to that circuit,” I repeated, “before you put that wire back on.”
“Like I said before - because you can get hurt.”
Maybe this is why John’s afraid of electricity.
After that, the supervisor asked me to work with John alone.
John and I agreed to meet at 6:45 Thursday morning. We sat down and I was thinking, “I can’t just start with, ‘So, I hear you’re afraid of electricity.’” I don’t think a person can just say that to a guy and expect very good results.
So I fell back on an old standard beginning - an open-ended question. “So what’s bothering you about electricity?” I was afraid I’d get silence. What then? But John jumped right in.
“I’m always going to be afraid of electricity. Nothing anyone can do about that. I just hate the feeling of that stuff going through my fingers and arms.”
“Me, too,” I added, but I don’t think he heard me.
John continued. “I don’t have any problem with the low-voltage stuff. Can’t get hurt with that. Here’s where I have a problem: Lots of times they want me to mount a switch and an outlet on the outside of the boiler or furnace. And then they want me to wire it up to electricity.
“Now, there’s a black wire and there’s a white wire. I get it that the black wire is hot. Here’s what I don’t get: Sometimes they tell me to wire in a black wire and a white wire. But other times they tell me to wire in two black wires and run the white wire around it. Why is it sometimes one way and sometimes another?”
“Ah,” I replied. “I can see why you’re confused. The switch, of course, is a switch. The outlet is a load. Switches and loads aren’t wired the same as each other. Even though they’re about the same size and shape when you look at them, electrically they’re very different.
“But let’s start back at the difference between the black wire and the white wire. If the wiring has been done correctly - and you can’t count on that without checking with your meter - the black wire brings ‘hot’ electricity into the circuit. ‘Hot’ means that the electricity is full of energy ready to become another kind energy - heat, light, motion, sound or magnetism.
“A load changes electricity into one of those other kinds of energy. So a load might be a light bulb, a motor, a speaker or a magnetic coil. The rule is that the wire bringing the hot electricity to the load is black.
“After the load, the electricity is empty of energy. But it still has to get back to where it came from. It’s like a train - after it delivers its load, the empty cars still have to return to where them came from.
“To return the empty electricity from the load, we use a white wire. It symbolizes that the electricity is ‘neutral,’ and no longer hot.
“So for an outlet, since it’s a load, you’d use a black wire to bring in the hot electricity and a white wire to take out the neutral electricity.”
John asked, “How do you know which wire to put where?”
“There are two ways. Notice that the slots on the outlet are two different sizes. The black wire goes on the screw terminal near the shorter slot. That screw terminal is usually brass so that’s your second clue. The white wire goes on the side with the longer slot. That screw terminal is usually silver.”
“Wow, that’s pretty easy,” he said. “But what about this? There are two screws on each side. Do I have to put a wire on both of them?”
“Nope. Notice that on each side there’s a piece of metal connecting the two screws. That piece of metal is called a ‘jumper.’ It takes electricity from the screw terminal where you put the wire to the terminal that the jumper is connected to.”
“Why two terminals on each side then?” he asked.
“There are two reasons. The second set of screws of the same color makes it easy to add other things onto the circuit, such as another outlet. We can talk more about that later.
“The other reason is that sometimes the top and bottom outlets need to be wired separately. An example is when one of the outlets is controlled by a wall switch. In that case, you’d remove the jumper between the two terminals and wire each of the two outlets separately – one in a circuit with a wall switch and the other wired so it’s powered all the time. Then you’d have two different black wires coming to the two terminals on one side and two different white wires coming out of the two terminals on the other side.”
“OK.” John said. “I got it about the outlet. I wire it like a load because it’s where loads plug into a circuit. Light bulbs and motors are loads. They change electrical energy into some other kind of energy. But what about the switch?”
“A switch does not use electricity. If the switch is closed ('turned on'), it let's electricity pass as if the switch weren't even there. If the switch is open ('turned off'), it stops the electricity. So we want to put the switch in the electricity’s ‘roadway’ so it can stop it or let it through.
“If you had your choice, would you want to stop the electricity in the black wire or the electricity in the white wire?”
“That’s easy,” John smiled. “You gotta stop the hot electricity before it gets to the load so the switch goes in the black wire.”
“That’s right. That’s how it’s supposed to be done. But you can’t count on it and you have to check with your meter to be sure. (See my column, “The Human Electrical Circuit,” in the May 2005 issue of PM. Click on “Archives” along the left-hand side of www.pmmag.com. Free registration is required to view archived editorial.) But if you do the wiring yourself, you put the switch in the black or ‘hot’ wire.
“OK, I got that,” John said. “But they said I should put a black wire on each of the two terminals on the switch. Where do I get two black wires when there’s only one?”
For a moment I didn’t understand. Then I got it. “Oh! I see. You’ll be inserting the switch into the black wire. That means you - after making sure there’s no power to the black wire - cut the black wire. Then you have two ends of the black wire. One goes on one switch screw terminal and the other end goes on the other terminal. It doesn’t matter which one goes where.”
“What happens to the white wire?”
“Nothing. You don’t do anything with the white wire. It just goes around the switch.”
“OK. I think I got this. I have a black wire and it’s going to be connected to hot electricity out of the electrical panel. But it’s not connected yet, because I don’t want to get hurt. And I have a white wire that’s going to be connected to neutral at the panel. Both of these are going to the furnace or boiler. But instead of me going right to the unit, the boss wants a switch and an outlet on the outside.
“So I mount the switch and the outlet. Then I bring in the black wire to the switch. I check one more time to be sure it’s not connected at the box. I cut the black wire and put each end of the cut on one of the screw terminals on the switch. I bring the white wire around the switch, but I don’t connect it to anything.
“Now I wire in the outlet. I bring the black wire from the switch to the brass terminal screw of the outlet and I wire it in there. That’s the side with the shorter slot of the outlet, which means it’s hot.
“Next I bring the white wire to the other - neutral -side of the outlet. That’s the side with the silver terminal screw and the longer slot.”
“That’s it, John.”
“OK, now I have another question while we’re at it. They keep wanting me to wire in an attic fan.”
“Well, in theory, adding an attic fan is a lot like adding another outlet. We can talk about that next time.”