Electrical Outlet Wiring

[pawlowsk002]

Tim:

What do you mean, branch and lighting? Lighting circuits /are/ branch circuits. You can't have lighting on your /small appliance branches/, but this sounds like a general lighting branch, and that can have receptacles as well as light fixtures.

I def> There are two flat cables leading into the socket (which is mounted on the

P:

There are numerous things that could be in that box, and so you need to find out just what is going on before starting to wire.

-You could have one 2-wire cable feeding the box, one 2-wire cable leaving, unswitched, and one 2-wire cable hooked up as a switch loop - out to the switch and back. In this case you'd most likely have just the one cable in the switch box.

-You could have one three-wire cable feeding the box, wired to a single branch circuit, with one hot switched and one not, and two 2-wire cables leaving the box, at least one unswitched. In this case, you'd have one

2-wire feed to the switch and one 3-wire from the switch to the ceiling box. In this case, the 3-wire cable woudl have 0v from one hot to the other, 120v from either to the neutral, when the switch was on.

Be cautious, however, because with the exact same cables and connections...

-You might have one 2-wire cable feeding the box, with one unswitched

2-wire cable leaving the box, and a 3-wire cable running to the switch, acting both as a feed for unswitched outlets downstream, and as a switch loop (the switch would be connected as above, from one hot of the three- wire cable to the other).

-You might have a 3-wire Edison circuit feeding the box; two branches with a common neutral, derived from opposite buses at the panel. In this case, you'd have 120v from each hot to neutral, and 240v across both hots. Two cables leave the box to go to other loads.

-You might have a kludged version of any of these 3-wire examples, in which two 2-wire cables were used improperly instead of one 3-wire, and the extra wire was ignored or worse.

This is why it is necessary to know just what is going on in that box, what is feeding it, and where the power is going, before starting to alter things. If you don't do that, you can set yourself up for problems. For example, somebody I know once hooked up "all black to black, all white to white" in a box. Unfortunately, there was an informal switch loop involved, and he ended up with a bolted short, and all of a sudden the breaker wouldn't stay on.

He didn't hurt himself or burn anything, fortunately, but he did learn a valuable lesson. There's just no such thing as excessive understanding when it comes to working on an old electrical circuit. You just never know what to expect.

I suggest starting out with a good book. PRACTICAL ELECTRICAL WIRING is a favorite.

G P

[Terry]

Why would you bother saying that in a DYI group? This is an easy as cake project.

[Jeff Wisnia]

What you just said you did (Nailing an extension cord) is quite likely in violation of the electrical code in your area.

Now that you've told the world what you did here with a post that may be findable 'forever' I suggest you check the code and if needed change the installation to be code compliant, even if it means having to hire a licensed electrician to do it if DIY electrical work isn't permitted in your area.

I realize there's a slim chance that tacking up that cord created a serious fire hazard, but if G-d forbid there should be an electrical fire in that area of your home, maybe caused by one of the pieces of computer gear deciding to flare up, your insurer may do their best to get out of paying if they can find evidence that you did something which was not to code.

Peace, and don't take this personally,

Jeff

[Proch]

GP-

Thank you for taking the time to put that together - this is exactly what I was hoping for... I will open the box tonight or tomorrow and figure everything out before proceeding. Now... would you open the box without cutting the power? Or is this considered dangerous...

[a]

Oh, for the love of...

a

[Eric]

Um... in an earlier post you state you "were an EE in college". Did you actually *pass* the course?

First 3 words in the instructions for *any* wiring project: "TURN OFF POWER...".

was hoping for... I will open the box tonight

open the box without cutting the power? Or is

[willshak]

What if the staples are just used to hang the cord, like using cup hooks, rather than hammering them tightly to the wood, as is done with Romex.

[Proch]

I don't see how that could be true. The same kind of fasterners are used to fasten every single wire in the basement to wood.

[Proch]

Yeah, I don't see how I could make contact by simply removing the face plate.

[Eric]

Well that's true but you're probably not going to see anything useful either.

Most boxes are such a rat's nest that it's hard to see what's going on even with the switch/outlet pulled out!

Eric

actually *pass* the course?

was hoping for... I will open the box

would you open the box without cutting the

[Jeff Wisnia]

Yes, but are those stapled wires which carry line voltage what you described as "extension cords" or are they Romex or other approved permanent wiring material, and do they have plugs on their ends or do they go into traditional electrical boxes?

I couldn't hurt to check it out with your town's electrical inspector, could it?

But, do what you want, it's your house, not mine. And as I said before I think the direct risks are minimal, it's just thinking about the posible code violation which got me going.

Peace,

Jeff

[Mark Lloyd]

but different currents (or 0) will be flowing

It doesn't have to be instantaneous for the currents to be unequal. There is a difference in phase. My "problem" was in failing to know that one of the important characteristics (phase) was supposed to be ignored.

BTW, in a different class I had just been taught about phase, and the way the phase of the voltage and the phase of the current can be affected by components in the circuit (power factor). Obviously, 120V @ 0 degrees is NOT the same thing as 120V @ 120 degrees.

current on all 3.

Since ammeters don't show phase. Phase is still real, as you should know.

[Mark Lloyd]

I remember reading about that (laser printers have lower per-use cost). How good are they for photos now?

[Harry]

It certainly works better than this order:

complain, wire, scream, call insurance company

:-)

[snip]

[Mark Lloyd]

actually *pass* the course?

Then, make SURE it's off. I normally plug in a small light (could use a plug-in receptacle tester), make sure it's on, turn off the breaker, then make sure the light went out.

was hoping for... I will open the box tonight

open the box without cutting the power? Or is

[Bob]

If you take on some of the projects discussed in this newsgroup without additional instruction or knowledge, you may indeed be DYI -- Doing Yourself In.

[TimR]

Remember, code is the WORST you are allowed to build with. Not the best.

[pawlowsk002]

P:

I always start by turning the power off, then check with my neon voltage tester to make sure it actually is off. (Actually, I usually check before turning the power off, too, to make sure the switch is on. Otherwise you can get a false safe reading, and then somebody comes by and flips the switch ON...). If possible, I check before opening a box (by checking across a socket or receptacle), but in any case I always check after opening the box. Even if I have turned off the breaker or removed the fuse, I assume the wiring could be live, until I have verified that it isn't by checking it. You never know what you are going to find in an old system.

Generally, I check from hot to neutral, then from all wires to a known good ground, after turning off the power. Preferably, I check at exposed terminals. If that's not possible, I unscrew wirenuts. This needs some caution, since wires aren't always twisted together and may spring apart when the nut is removed.

After I am sure the box is dead, I see what is going on in the box. /ALWAYS leaving the wires connected/, I unwind the rat's nest and spread the connected wires apart, and then write down how everything is arranged, what is connected to what, etc. I may tag the wires with pieces of tape. Only after writing down what I start with do I start disconnecting wires.

Once everything is disconnected and safely spaced out, if I don't already know which wires are the feed, and I can't find out by visual tracing or continuity-testing the circuit, I may turn the power back on briefly to check for voltage at the various wires. Be careful when doing this, because you are checking a live circuit, and don't want to be part of it, of course. As soon as the tests are done, shut off the power again, and check to verify it's off. This is one of the few cases in which I will allow power to an opened box. If possible, I try to avoid it, but even in some cases when I think I know just what is going on, I'll double-check this way, just to be safe.

The most important thing is to know what you are doing, and I really can't guarantee that across here. I can only explain how I do it. It's up to you to be sure that the job is done safely, and if you aren't sure you can do that, you shouldn't do it. Usenet just isn't enough.

G P

[Mark Lloyd]

You also might want to be sure anyone else who's around knows what you're doing, and won't turn that breaker back on.

[Dave Martindale]

They were asking about time-averaged current of some sort, probably RMS current, while you were thinking in terms of instantaneous current.

That's sort of like being asked a question on a high school physics test about the validity of Newton's laws when you already know about relativity. *You* know that Newton's laws are not always valid, but at the same time you should be able to figure out that *in the context of the physics class*, they are.

Dave