Outlet - 4 screws

I was replacing a electrical recepticle with a new one. Few questions:

1. Why do the new outlets have four screws (two silver - two copper) and the old ones just have two (and a ground). Does it matter which are used?

2. Does it make a difference where I connect the black and white - top or bottom screws.

3. I replaced one receptacle and the light switch no longer controlled that receptacle...with a light plugged in the top or bottom...the switch would on/off the light. Anything I should be looking for there? I was carefully removing the wires seeing top or bottom. Maybe not.

4. Couple of outlet/switches have a red, what is that/why did they put that there?

Thanks.

They have four screws so that you can run power to another receptacle off the second set. It makes no difference which set you connect your wires to. For the switched outlet, you need to break the little brass tab off that runs in between the upper and lower screw sets.

Without seeing your actual wiring its difficult to say way exactly you have a red wire. Depending on how it is connected makes it work differently but you probably have something controlled by more than one switch somewhere.

Essentially, there's a screw for each contact of each outlet except for the ground. As noted, sometimes you can to do separate things with each one (one always on, one switched, or separate circuits for each), so there's a breakoff tab connecting the two sets. Often they are on the same cable, so you can leave the neutral tab (jumper), but there could be situations where you would need to separate the neutrals as well.

coopns said:

2. Does it make a difference where I connect the black and white - top or bottom screws.

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Black or red [not both] to short slot, white to long slot, unless your colors are mixed up, and this does happen.

Red often is used to indicate a switched hot, but not always...you need to check.

iminaquagmire said:

They have four screws so that you can run power to another receptacle off the second set. It makes no difference which set you connect your wires to. For the switched outlet, you need to break the little brass tab off that runs in between the upper and lower screw sets.

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Actually the only intention of having two sets of screws is to separate the top and bottom outlets, not to allow for easier in and out wiring. A good electrician wouldn't use both sets of screws if wiring in and out. He would splice the hot and neutral through the box, with pigtails from those splices going to one set of the outlet screws.

nickdel said:

Actually the only intention of having two sets of screws is to separate the top and bottom outlets, not to allow for easier in and out wiring. A good electrician wouldn't use both sets of screws if wiring in and out. He would splice the hot and neutral through the box, with pigtails from those splices going to one set of the outlet screws.

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I have never seen it done that way without unless there were more than two lines coming into the box. That's just extra work and more wires in the box.

nickdel said:

Actually the only intention of having two sets of screws is to separate the top and bottom outlets, not to allow for easier in and out wiring. A good electrician wouldn't use both sets of screws if wiring in and out. He would splice the hot and neutral through the box, with pigtails from those splices going to one set of the outlet screws.

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Huh? Where do you get that from? I've seen and done a lot of installs and no one does that except in some rare commercial/hospital applications and in those instances you usually have a 4x4 box with a mud ring to work with. Residential outlet boxes aren't exactly roomy and I'm all for not adding anything that doesn't absolutely have to be in one. I can just imagine having to do that on every GFCI outlet.

-rick

Well, I said good electrician, but what I meant was someone who knows that, when you piggyback the outlets like that, losing one means you lose the whole line. So when you put eight outlets on a circuit, and one connection goes bad, all the other outlets on the remainder of the line drop out. So instead of the customer having one bad outlet, now they could have whole rooms out, and the guy they call in for the repair has to go into every box and spend possibly hours (depending on the layout of the circuit and the house) searching for the trouble, costing the customer possibly hundreds of dollars. If the wires were properly spliced through the boxes, then only one outlet would have died, and the repairman would be in and out.

And it's not extra work, it's the proper way to wire a string of outlets, and it's the method electricians who care about their tradecraft use, not guys who just want to get the job done as fast as possible and get out of there so they can rob someone else. And I say "rob" because I've worked for guys who only care about volume. They don't give a damn about how the jobs are done, and that shit pisses me off. The only time I wouldn't splice the wires through is if I go into an existing box and, not only is it tight, but there are other things obstructing the wires and the device, like those old metal new-work boxes that have nails going through the top and bottom of the box.

And GFCI outlets are different because they have a load side. And if the remainder of the circuit isn't on the load side, then when you plan the job you put in a deep box. When the job is planned right, there won't be any worry about the depth of the boxes.

And it's the same with a multiwire branch circuit. Unless it's absolutely necessary, someone who knows what he's doing won't use one, even though the code allows them.

Well, I said good electrician, but what I meant was someone who knows that, when you piggyback the outlets like that, losing one means you lose the whole line. So when you put eight outlets on a circuit, and one connection goes bad, all the other outlets on the remainder of the line drop out. So instead of the customer having one bad outlet, now they could have whole rooms out, and the guy they call in for the repair has to go into every box and spend possibly hours (depending on the layout of the circuit and the house) searching for the trouble, costing the customer possibly hundreds of dollars. If the wires were properly spliced through the boxes, then only one outlet would have died, and the repairman would be in and out.

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On the one hand, I agree. It's a good reason why we splice all the ground wires (e.g. in a metal box) and only attach one to the receptacle. Lose the ground connection to the receptacle and all the other grounds remain uninterrupted (including the one to the metal box).

But on the other hand, we are making the heroic assumption that a splice and wirenut are more reliable than a connection to a receptacle. If the splice or wirenut fails, then we have all the same problems you are so depserately trying to avoid.

On balance, I probably trust my connections to receptacles better than my bad splicing and cheap nuts.

Last week it was nipples and this week it's nuts. I have been playing with my big ol' green nuts each night, and every day of this week. I don't wrap my nuts in tape like I used to though. Intstead I like to twist my nuts hard.

Are you sure?

quote; Well, I said good electrician, but what I meant was someone who knows that, when you piggyback the outlets like that, losing one means you lose the whole line. So when you put eight outlets on a circuit, and one connection goes bad, all the other outlets on the remainder of the line drop out. So instead of the customer having one bad outlet, now they could have whole rooms out,

The ONLY way you could lose ANY other outlets would be if the brass jumper between the two terminals melted, and for that to happen you would have needed a MASSIVE short circuit. The "piggyback" does NOT go THROUGH the outlet, it goes between the two terminals. Essentially, the entire outlet could melt down, but as long as the jumper is intact power will continue to flow through the system. SO, if one outlet does go bad and the rest fail, just look for the one that became a blob of melted plastic.

The incoming hot could come detached from the receptacle also.

It comes down to workmanship...how many people use a torque screwdriver when attaching wires and properly shape the loop to put under it? Probably nobody except maybe people putting things together for use in spacecraft.

A properly made wire nut splice is probably more reliable than a wire underneath a screw. Heating and cooling probably won't loosen a splice, but it could on a screw if it isn't torqued properly. Plus, trying to fold back 2 insulated wires and the ground is easier than the five wires if you use the thing as a terminal strip.

Ian Gills said:

Last week it was nipples and this week it's nuts. I have been playing with my big ol' green nuts each night, and every day of this week. I don't wrap my nuts in tape like I used to though. Intstead I like to twist my nuts hard.

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Is this a metaphor/parable/allegory?

I will say a screw terminal would seem to offer more contact force, which means lower contact impedance. How it holds up over time is another issue.
There was a wire nut that was losing a half a volt with 10A though it. When I took it apart one of the three wires wasn't scored or twisted, yet the nut felt tight.

Ian Gills said:

we are making the heroic assumption that a splice and wirenut are more reliable than a connection to a receptacle. If the splice or wirenut fails, then we have all the same problems you are so depserately trying to avoid.

On balance, I probably trust my connections to receptacles better than my bad splicing and cheap nuts.

Last week it was nipples and this week it's nuts. I have been playing with my big ol' green nuts each night, and every day of this week. I don't wrap my nuts in tape like I used to though. Intstead I like to twist my nuts hard.

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Yeah, I trust my splices more than copper under a screw. And you shouldn't use tape on a splice, or on the terminals of a device. You're just putting more shit in the box that can burn.

hj said:

The ONLY way you could lose ANY other outlets would be if the brass jumper between the two terminals melted, and for that to happen you would have needed a MASSIVE short circuit. The "piggyback" does NOT go THROUGH the outlet, it goes between the two terminals. Essentially, the entire outlet could melt down, but as long as the jumper is intact power will continue to flow through the system. SO, if one outlet does go bad and the rest fail, just look for the one that became a blob of melted plastic.

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That's not true. Over time, with people yanking on cords, and heat at the terminal, screw connections come loose all the time. And if one wire - hot or neutral - comes loose, all the outlets down the line will lose power.

jadnashua said:

It comes down to workmanship...how many people use a torque screwdriver when attaching wires and properly shape the loop to put under it? Probably nobody except maybe people putting things together for use in spacecraft.

A properly made wire nut splice is probably more reliable than a wire underneath a screw. Heating and cooling probably won't loosen a splice, but it could on a screw if it isn't torqued properly. Plus, trying to fold back 2 insulated wires and the ground is easier than the five wires if you use the thing as a terminal strip.

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Ok, well I admit I don't use a torque wrench. But I do properly shape the loop, and I don't ring the wire with my lineman's pliers to strip it. I use a knife or a stripper. You can get used to anything, and get fast with enough practice. Isn't it better to make a habit of good practices, rather than bad, like ringing wires and not making a loop at all and not making proper splices and using back stabs?

Lockwashers work by springloading a connection.

If properly done wirenuts
springload a connection more than a screw head does,
then the wirenut connection should, in principle, be better able to resist loosening.

Thatguy said:

Is this a metaphor/parable/allegory?

I will say a screw terminal would seem to offer more contact force, which means lower contact impedance. How it holds up over time is another issue.
There was a wire nut that was losing a half a volt with 10A though it. When I took it apart one of the three wires wasn't scored or twisted, yet the nut felt tight.

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When you take the screw out of a device you'll notice that it only screws into about two or three threads, and you can in fact overtighten and strip those threads, rendering that terminal useless. You can only apply so much force before it fails. And if a wire is loose in a splice, regardless of wirenut security, the splice wasn't made correctly, and the person making the splice didn't check it. The wirenut should not be used to hold the wires together. The splice should be strong enough to keep the wires together. The only reason you put a wirenut on the splice is to prevent it from shorting out. If a wirenut falls off a splice, the splice should not come undone. The only time when a wirenut should be used to hold wires together is when splicing stranded wire to solid wire.

nickdel said:

The only reason you put a wirenut on the splice is to prevent it from shorting out.

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It provides contact force to reduce contact impedance, for the same reason that car battery terminals have tightening bolts. I guess that's why the wirenuts have tapered springs inside.
At small currents and high voltages, contact impedance is not so important.