Wiring garage myself?

[Charles (in GA)]

It looked like whoever made the connection did not twist the wires together before installing the wire nut and they just worked loose.

Wire nuts are described in the UL rating as a "pressure connection" type of connector. The Ideal Wing Nut, probably one of the most popular wire nuts of all time, is this type of design. You take several wire ends, perfectly straight and ends even (like a handful of pencils held tightly together) and you screw the wire nut onto them. It squeezes the wires together, you continue running the wire nut down (I use needle nose pliers to get more leverage on the nut, they do make a nut runner for Wing Nuts however), and tighten until it begins to twist the wires. Usually the wire ends (using solid wire) will have pushed all the way fully into the Wing Nut and the small end of it is expanded slightly. This is all that is needed for a real good, tight connection with a wire nut.

In the good old days, wires were thoroughly twisted together and then "diper wrapped" with electrical tape, the old cloth type. Many of those connections are still going strong.

Charles

 

[jay50]

Wire nuts are described in the UL rating as a "pressure connection" type of connector. The Ideal Wing Nut, probably one of the most popular wire nuts of all time, is this type of design. You take several wire ends, perfectly straight and ends even (like a handful of pencils held tightly together) and you screw the wire nut onto them. It squeezes the wires together, you continue running the wire nut down (I use needle nose pliers to get more leverage on the nut, they do make a nut runner for Wing Nuts however), and tighten until it begins to twist the wires. Usually the wire ends (using solid wire) will have pushed all the way fully into the Wing Nut and the small end of it is expanded slightly. This is all that is needed for a real good, tight connection with a wire nut.

In the good old days, wires were thoroughly twisted together and then "diper wrapped" with electrical tape, the old cloth type.

Many of those connections are still going strong.

Charles

I was told the wrapping of the wire nuts with electrical tape was due to electricians not trusting the wire nuts when they first came in use. IIRC, NEC does not prohibit this extra step. It is a waste of time (and $s).

 

[sajohnson]

Wire nuts are described in the UL rating as a "pressure connection" type of connector. The Ideal Wing Nut, probably one of the most popular wire nuts of all time, is this type of design. You take several wire ends, perfectly straight and ends even (like a handful of pencils held tightly together) and you screw the wire nut onto them. It squeezes the wires together, you continue running the wire nut down (I use needle nose pliers to get more leverage on the nut, they do make a nut runner for Wing Nuts however), and tighten until it begins to twist the wires. Usually the wire ends (using solid wire) will have pushed all the way fully into the Wing Nut and the small end of it is expanded slightly. This is all that is needed for a real good, tight connection with a wire nut.

In the good old days, wires were thoroughly twisted together and then "diper wrapped" with electrical tape, the old cloth type. Many of those connections are still going strong.

Charles

I've heard both -- that it's perfectly ok to just insert the straight ends into the wire nut and I've had other people tell me to give them a twist first.

I've wondered whether I'm wasting my time but it seems like a 'can't hurt' type of thing.

 

[Printer Mike]

Generally, I have had less problems leaving the wires straight together and let the wire nuts do the twisting. The most important thing seems to be that all the wires are even. Another problem that I've had with wire nuts is when they are too small for the size and/or number of wires tied together.

 

[Charles (in GA)]

I was told the wrapping of the wire nuts with electrical tape was due to electricians not trusting the wire nuts when they first came in use. IIRC, NEC does not prohibit this extra step. It is a waste of time (and $s).

I meant to have said, "In the good old days, before wire nuts, electricians twisted the wires and diaper wrapped.........

I've never heard of wrapping the wire nut with tape. Probably a long gone practice now and indeed a waste.

Charles

 

[larry4406]

With all the discussion about pigtails to outlets vs using outlet screw terminals to make the connection, please note that NEC 300.13B requires in Multi-wire circuits (those with two hots from opposing phases or poles and sharing a neutral/grounded conductor) that the neutral be connected in such a manner that the continuity of the neutral "shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity".

In other words, the neutral in multi-wire circuits must be pigtailed.

So, if I understand this, then it is against Code to daisy chain outlets together simply by using the 4 screws on the duplex outlets for common and line (white & black) while wire nutting the grounds? If so, I can tell you there are 1000's of new houses in northern VA that "slipped thru" inspection.

 

[locomike]

? I thought that is what they are there for? That can't be right.

 

[Torque1st]

So, if I understand this, then it is against Code to daisy chain outlets together simply by using the 4 screws on the duplex outlets for common and line (white & black) while wire nutting the grounds? If so, I can tell you there are 1000's of new houses in northern VA that "slipped thru" inspection.

Read it again:

...Multi-wire circuits (those with two hots from opposing phases or poles and sharing a neutral/grounded conductor) that the neutral be connected in such a manner...

As far as wire nuts go: I always twist several wires together with pliers, then cut the twisted section to length, then install the wire nut.

The last time I looked it was also permissible to pigtail a 15A duplex outlet from a 20A 12AWG circuit with a short section of 14AWG wire. I rarely do because I always have that 12AWG handy. 14AWG is easier to bend going back in the box tho.

 

[BigChevy80]

So, if I understand this, then it is against Code to daisy chain outlets together simply by using the 4 screws on the duplex outlets for common and line (white & black) while wire nutting the grounds? If so, I can tell you there are 1000's of new houses in northern VA that "slipped thru" inspection.

Like torque1st said, it is only for multi wire branch circuits (also called edison circuits). They don't want you daisy-chaining the neutrals on those circuits, because if you lose the neutral in an edison circuit it can create the potential for 240v to be running through your 120v appliances.

 

[BigChevy80]

The last time I looked it was also permissible to pigtail a 15A duplex outlet from a 20A 12AWG circuit with a short section of 14AWG wire. I rarely do because I always have that 12AWG handy. 14AWG is easier to bend going back in the box tho.

If you use 14 AWG wire anywhere in a circuit, the maximum breaker size allowable is 15 amps. Otherwise you could plug a big load into that outlet and be running more than 15 amps through the 14 AWG and the breaker wouldn't trip.

 

[locomike]

What is code for running romex for lights, overhead receptacles? Just run it along the truss's and staple?

 

[Torque1st]

If you use 14 AWG wire anywhere in a circuit, the maximum breaker size allowable is 15 amps. Otherwise you could plug a big load into that outlet and be running more than 15 amps through the 14 AWG and the breaker wouldn't trip.

Nope, short runs like pigtails (6") are allowed to use smaller gage wire. Check the code...

 

[Torque1st]

What is code for running romex for lights, overhead receptacles? Just run it along the truss's and staple?

The code gets kind of tricky on running wire. Get yourself a copy of the code and the simplified or illustrated guide to it. There are all kinds of regs on materials and how often it has to be secured and by what etc. Local code may also have tighter specifications.

 

[kvom]

What is code for running romex for lights, overhead receptacles? Just run it along the truss's and staple?

That's what we did.

 

[Aceman]

Nope, short runs like pigtails (6") are allowed to use smaller gage wire. Check the code...

You're mistaken. Pigtailing #14 to #12 wire on a 20 amp circuit is a good way to fail an inspection.

210.19(A)2

 

[Torque1st]

If you use 14 AWG wire anywhere in a circuit, the maximum breaker size allowable is 15 amps. Otherwise you could plug a big load into that outlet and be running more than 15 amps through the 14 AWG and the breaker wouldn't trip.

You're mistaken. Pigtailing #14 to #12 wire on a 20 amp circuit is a good way to fail an inspection.

210.19(A)2

The requirements for receptacles are in Table 210.24 Summary of Branch-Circuit Requirements.

14AWG Taps are allowed to feed individual receptacles on 20A 12AWG multi-outlet circuits. 20A breakers are allowed with the 14AWG taps.

The wire sizes specified in the NEC are based on voltage drops and thermal properties which makes it less than straight forward numbers in many applications. The wiring size listed is generally for long distribution runs. Smaller conductors are allowed in some panel equipment. Also notice that the ampacity of wires varies according to location, intended use, and insulation type.

Also note there are calculations for voltage drop in circuits and sometimes larger wires are required.

 

[sajohnson]

You're mistaken. Pigtailing #14 to #12 wire on a 20 amp circuit is a good way to fail an inspection.

210.19(A)2

I'm not very familiar with the NEC, but it makes sense that using short (<6") 14 gauge pigtails from 12 gauge wire to 15A outlets would be permissible since the outlets are restricted to 15A.

 

[Torque1st]

Aceman and BigChevy80 will have to look up the table themselves in the NEC. People that work with the code everyday probably know just where to find it. I spent the time to look it up rather than just guessing at this point. I could copy text but tables don't copy well. That whole 210 section of the code is good but difficult reading.

I have read probably 50% of the NEC over the years due to applicability of certain sections to many assorted projects. I don't always remember where I read certain points tho.

 

[ultgar]

If you're doing a lot of receptacles, here's another option....

Pass & Seymour plugtail outlets.... no exposed side terminals and the right angle connector allows the plugtail to fit flush with the rear of the receptacle leaving a little more room in the box....I'd still recommend using 2 1/2" or deeper boxes (especially with 12 gauge wire).

SD

 

[pmiranda]

With all the discussion about pigtails to outlets vs using outlet screw terminals to make the connection, please note that NEC 300.13B requires in Multi-wire circuits (those with two hots from opposing phases or poles and sharing a neutral/grounded conductor) that the neutral be connected in such a manner that the continuity of the neutral "shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity".

Where would you see something like this? Why? Just curious what would motivate somebody to use a multi-wire circuit.

 

[kbs2244]

I have traditionally wired garages with 2 hots from separate breakers and a common ground.
I think some one called it an “Edison circuit.”
Each box has 2 outlets.
Each outlet is fed from a different hot leg.
And each leg has its own color outlet, kept true around the shop.
IE: all the whites are on this breaker and all the browns are on this breaker.
My logic is that if you are at the far end of the shop and pop a breaker while you are in the middle of something, you can just plug into the other outlet in the box and finish up what you are doing before having to go reset the breaker.
It also makes it easy to wire up a low draw 220 outlet at any point.

 

[sajohnson]

If you're doing a lot of receptacles, here's another option....

Pass & Seymour plugtail outlets.... no exposed side terminals and the right angle connector allows the plugtail to fit flush with the rear of the receptacle leaving a little more room in the box....I'd still recommend using 2 1/2" or deeper boxes (especially with 12 gauge wire).

SD

Now there's a cool idea!

Question -- if the outlet needs to be replaced, is it difficult to use a standard outlet (if a P&S outlet isn't available)?

Unrelated question -- that's a nice photo. How did you go about posting that? My first attempt at posting photos was just ok -- I ended up with little thumbnails and even clicking on them didn't show a photo as nice as the one in your post. I was limited to <70 KB per photo, are you subject to the same limit?

 

[sajohnson]

I have traditionally wired garages with 2 hots from separate breakers and a common ground.
I think some one called it an “Edison circuit.”
Each box has 2 outlets.
Each outlet is fed from a different hot leg.
And each leg has its own color outlet, kept true around the shop.
IE: all the whites are on this breaker and all the browns are on this breaker.
My logic is that if you are at the far end of the shop and pop a breaker while you are in the middle of something, you can just plug into the other outlet in the box and finish up what you are doing before having to go reset the breaker.
It also makes it easy to wire up a low draw 220 outlet at any point.

Maybe not a concern for most of us doing relatively small projects, but it also reduces the cost of wire and possibly conduit by enabling the use of a smaller size in some cases.

I'm still not 100% clear on the concept of how two (2) circuits can share a neutral. I remember reading that instead of the currents in the two circuits combining, they actually cancel each other out. I know the current in the two circuits is 180 degrees out of phase but it seems counter-intuitive this would work.

In any case, I wish I would have wired my outlets this way.

 

[Charles (in GA)]

Where would you see something like this? Why? Just curious what would motivate somebody to use a multi-wire circuit.

I just installed Metal Halide lighting in my 60x60 metal building. Three rows of four fixtures, 400 watt lights. Each fixture draws 4.0 amps according to the data plate. I wanted three switches. Had I used a 20 amp breaker, and a 20 amp switch, both on a regular 120v circuit to supply four lights, then I would be putting 16 amps, possibly a little more, on the circuit. Code limits continuous loads (lighting is considered continuous by the NEC) to 80% of the rating of the circuit protection. Thus I would be pushing the 80% limit of the breaker. By using double pole/handle tied breakers (just like you would use for a 240v circuit) and by using double pole light switches (mine were rated 30 amps, bought on a clearance) I was able to run one additional wire over and above a normal 120v circuit (a green ground, a white neutral, and black and red hots) and create a multiwire circuit. I used a duplex receptacle, with the breakaway tab between the screw terminals on the hot side, broken out. I labeled them with a large red A and a large black B on the face plate of each receptacle. The lights are plugged in A-B-A-B in the row. Short segments (15 ft) of the neutrals carry load, but the neutral back to the panel do not carry anything, as the load is evenly distributed, two lights on the black side (8 amp) and two lights on the red side (8 amp). Only one more wire than a single 120v circuit and the potential to convert it to 240v in the future if needed for different light fixtures.

Charles

 

[sajohnson]

You pretty much answered you own question here. The two hots (for residential power anyway, not 3 phase) are 180 degrees out of phase. So, the two hots returning to the same neutral are pushing current in opposite directions at any given time. The worst case (in terms of current flowing in the neutral wire) is actually when only one hot is providing power, and the other not at all. In any other case, the neutral wire's current is actually reduced. Think of it as the neutral returning the difference in current flow between the 2 hots, not the sum.

I understand all of the above (the phase relationship, worst case being only one hot with load), but I'm still not clear on how the currents cancel each other out.

IOW, I know that with two hots and a neutral feeding a 240/120V appliance, no current will flow through the neutral if the load is purely 240V (the hots carry the current). But with two equal 120V loads, the neutral should carry current. Granted, those currents are 180 degrees out of phase with each other, but there's still current flowing through the neutral isn't there? Or do two equal 120V loads on opposite phases act as a single 240V load?

Sorry if I seem dense about this -- I have an electronics background and haven't really studied AC power, other than what I've needed to do some simple wiring around my place.

 

[tdkkart]

Lay out 2 sine waves on graph paper, exactly 180* out of phase with each other, one above the other, or one on top of the other doesn't matter.
Now, draw a vertical line across the sign waves at any point you choose.

If the point you draw the line happens to be at say +50v on one phase, because the other phase is 180* out the voltage on that line is at -50v.

Add the 2 voltages together and you come out with 0v at that point. The same is true no matter what point you draw the line, at any given point in time the voltage measured on the neutral will be 0v. No voltage equals no current.

 

[kbs2244]

I wish I understood all that.
I don't remember where I learrned it, or even if I came up with it myself.
I just know it has worked fine in lots of garages.

 

[Aceman]

The requirements for receptacles are in Table 210.24 Summary of Branch-Circuit Requirements.

14AWG Taps are allowed to feed individual receptacles on 20A 12AWG multi-outlet circuits. 20A breakers are allowed with the 14AWG taps.

Are you reading the last two sentences of 210.24? Table 210.24 lists the minimum requirements while 210.19 lists the specific requirements pertaining to these branch circuits.

Again, 210.19(A)2 says NO. Here's this same topic brought up on the Mike Holt forums:

http://forums.mikeholt.com/showthread.php?t=62344&highlight=receptacle+taps

 

[Torque1st]

Are you reading the last two sentences of 210.24? Table 210.24 lists the minimum requirements while 210.19 lists the specific requirements pertaining to these branch circuits.

Again, 210.19(A)2 says NO. Here's this same topic brought up on the Mike Holt forums:

http://forums.mikeholt.com/showthread.php?t=62344&highlight=receptacle+taps

The table lists the minimum requirements, 210.19(A)2 discusses the connecting circuit, not the device taps.

I really don't care what was discussed on other forums. The control is the code itself and your local inspector, not discussions.

 

[Torque1st]

A person can also run the numbers like the above example and find that the 6" (x2) 14AWG tap wire will drop about 0.06V and dissipate 1.2W in that foot of wire with a 20A load. A dimmer switch will get far hotter.

BTW- That plug tail outlet might be "neat" but after having experience with plug in wire devices I would pass on them. Give me the standard screw terminal type. With that said I run two layers of electrical tape around my outlets and switches to help insulate those side terminals. It is just a habit picked up from commercial wiring jobs I have been on.

Twisting wire splices, trimming, then twisting on a wire nut is also a habit picked up. It will also allow a person to actually inspect that wire twist to make sure all of the wires are securely locked together so one won't pull out later.

 

[abnorm]

Torque.....you are wrong about the 14 awg pigtails......

"""Charlie’s Rule of Technical Reading

It doesn’t say what you think it says, nor what you remember it to have said, nor what you were told that it says, and certainly not what you want it to say, and if by chance you are its author, it doesn’t say what you intended it to say. Then what does it say? It says what it says. So if you want to know what it says, stop trying to remember what it says, and don’t ask anyone else. Go back and read it, and pay attention as though you were reading it for the first time."""


http://forums.mikeholt.com/about/about_forum.htm

 

[Torque1st]

Sorry, I know what it says and why it says it. While I don't do it normally for outlets it IS allowed and for good reason. The NEC like many standards that have been "codified" into written words are tough to read and interpret. Going back to the math and the underlying engineering reasons can help a lot with interpretation.

The Mike Holt forum is a good one and I have been reading it for years. It isn't always right tho. It is just an informal discussion board. The disclaimer you referenced is correct.