Basic wiring of a receptacle...

[Electrical Student]

Basic wiring of a receptacle? I was taught to wire a basic duplex in the order of ground, neutral, ungrounded. But another instructor informed me if you have to do it live, to terminate the ground last to reduce the possibility of shock by accidentally contacting the yolk with the ungrounded conductor. Makes sense but now you lost your o.c.p. What do you guys think?

 

[iwire]

Basic wiring of a receptacle? I was taught to wire a basic duplex in the order of ground, neutral, ungrounded. But another instructor informed me if you have to do it live, to terminate the ground last to reduce the possibility of shock by accidentally contacting the yolk with the ungrounded conductor. Makes sense but now you lost your o.c.p. What do you guys think?

You should not be working it live

1910.333(a)(1)

"Deenergized parts." Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Live parts that operate at less than 50 volts to ground need not be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.

Note 1: Examples of increased or additional hazards include interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.

Note 2: Examples of work that may be performed on or near energized circuit parts because of infeasibility due to equipment design or operational limitations include testing of electric circuits that can only be performed with the circuit energized and work on circuits that form an integral part of a continuous industrial process in a chemical plant that would otherwise need to be completely shut down in order to permit work on one circuit or piece of equipment.

Note 3: Work on or near deenergized parts is covered by paragraph (b) of this section

 

[charlie b]

Bob is right: you should not do live work.

That said, as a purely academic exercise, I will say that your instructor is wrong. If the ungrounded conductor then touches the yoke, you are going to get shocked, no matter what other wires may or may not also be connected. However, if the ground wire is attached first, and if the ungrounded conductor touches the yoke, it will complete a circuit, forcing a high amount of fault current to flow, thus tripping the breaker. So the shock you receive will be very short in duration, and will not likely cause any harm. That, indeed, is the purpose of the ground wire in the first place.

On the other hand, if the ungrounded wire touches the yoke while you are holding the receptacle by the yoke, and if the ground wire is not attached, then current will flow through your body. It will be a high enough current to be able to kill you (see Bob?s answer), but not enough to cause the breaker to trip.

 

[iwire]

I will say that your instructor is wrong. If the ungrounded conductor then touches the yoke, you are going to get shocked, no matter what other wires may or may not also be connected.

My experience from the dark ages when live work was expected it would be neutral, hot, and last the ground as his instructor said.

Much less chance of getting a shock or causing sparks.

If the yoke is grounded first it is very difficult to keep your body 'ungrounded' to work with the hot. With the yoke grounded first landing the hot becomes much like the game 'Operation' very difficult to get the hot conductor on the screw without hitting the yoke and getting spark shower. Keep in mind this was typically done barehanded and there is almost no way to hold the device without touching the yoke and grounding your body.

Of course now I know better than to work it hot, my safety is worth more than others inconvenience.

 

[charlie b]

I have heard a few ?dark ages? stories, mostly from Chief Petty Officers in my early Navy days. In the light of today?s safety conscious world, it is hard to understand the former way of thinking. But I still contend that the instructor is wrong, in terms of which would be safer, assuming the unfortunate event of touching the hot wire to the yoke.

If your body were otherwise ?ungrounded,? such as you might be by standing on a rubber mat, then there is still no difference between the amount of shock you would get by touching the hot wire to the yoke while the yoke is in your hand. Your body cannot be a path for current to flow, except to the extent that there is a capacitive coupling between yourself and nearby metal. The difference between having the yoke connected to the EGC or having not yet connected that wire is the amount of time the shock will continue. With the EGC connected, the shock lasts well under one second (i.e., breaker trip time). With it unconnected, the shock lasts until you manage to let go of the yoke.

 

[iwire]

But I still contend that the instructor is wrong, in terms of which would be safer, assuming the unfortunate event of touching the hot wire to the yoke.

Charlie, you will have to trust me on this or try it yourself.

If I connect the EGC first, and then hold the device by the yoke I will get blasted as soon as I touch the hot which I may have to while striping or shaping it.

OTH if I do not ground the yoke first it is isolated so I can hold the yoke and touch a hot without feeling it ...... assuming I am not standing in a puddle.

At 120 volts my boots if dry or rugs, or wood floors etc keep me 'ungrounded'

None of this has anything to do with tripping a breaker, the intention is to do it without tripping the breaker.

Of course this is all just a thought exercise and I never used to work like this, or drill live service bus with a corded drill by eliminating the tools EGC, or tap 480 volt service conductors or ...

 

[LarryFine]

If I had to land live conductors on a device, I'd hold the yoke with my Kleins and land the hot first. That way, it's under control and it's *relatively* safe to hold by the yoke and finish terminating.

 

[Electrical Student]

Thanks guys.

"OTH if I do not ground the yoke first it is isolated so I can hold the yoke and touch a hot without feeling it ...... assuming I am not standing in a puddle."

This has been my experience as well. I am also very aware of Osha's 1910.333(a)(1) and realize working hot can almost always be avoided.

 

[PetrosA]

Ground last.

 

[jim dungar]

I learned: hot on last and off first. That way only one operation involves energized conductors.

Stripping and trimming out a wire does not involve me holding the receptacle with one hand.

But what do i know, the last time I earned a living as an electrician was more than 30 years ago. Now i am just a DIYer.

 

[Electrical Student]

With that said. I was taught to do service taps in the same order. Neutral first. However, I don't think that's the safest option either. From what i can gather from it, it is a wiring method that my poco created to protect their equipment but it doesn't protect the gentlemen hooking it up.

 

[LarryFine]

I learned: hot on last and off first. That way only one operation involves energized conductors.

Normally, yes, but in this case, when the hot is terminated first, the only thing with a voltage on it relative to the rest of the world is the hot terminal(s). When the hot is made last, there's a voltage between it and everything around it that's already been terminated.

It's similar to a car battery. If the ground terminal is connected when you connect/disconnect the hot, there's voltage between the wrench on the + terminal and everything else around it. With the ground disconnected, there's no voltage between the wrench and ground.