Electricians, Step Inside, Please. Polarity Question.

[The10mmKid]

The recommended practice for achieving a 3-prong is to replace the 2-prong with a GFCI receptacle. Easy fix and super safe.
Do not jumper the green (ground) terminal to the neutral. It's never the solution as was previously mentioned.

Da' Kid

[felix]

NEVER connect ground to neutral. They are NOT the same. Neutral BELONGS to the circuit, and ground does NOT. ... felix

Ground is the neutral for extraneous inputs, such as static, lightning, etc., completing its own circuit external to ours. ... felix

[Whiterabbit]

Also agree with swheeler,
With AC polarity only exists in the book.
And only matters to the "book people".

Maybe somewhere it makes a difference but with household 120V AC it just doesn't.
Pleas don't flame us too hard for this.

I will flame indeed. Do you really believe this?

Old cast iron equipment (like power drills and fans, for example) run neutral to the case. Any failure of a hot line, rather than zapping you, would short out to the case and trip the breaker.

Saving you.

Reverse polarity? the drill would work fine like you suggest, and you'd never know. As long as you were wearing gloves. bare skinned, you'd be singing a different tune!

[Whiterabbit]

NEVER connect ground to neutral. They are NOT the same. Neutral BELONGS to the circuit, and ground does NOT. ... felix

And this one scares me. When I read way back up that some people cheat and wire ground to neutral on the plugs..... That's just scary!

[Sonnypie]

What I want to know is to be an electrician do you have to be bi-polar.......?

No... but it helps.
I'm still musing about your toilets spinning backwards down there on the bottom of the world, Jeff.

Cat nailed exactly what I would have pointed out.
Also, you can go to most home improvement stores and take a packaged device (Switch, receptacle) and often the bottom (back) of the box has example diagrams on it.

But ultimately, fixing things found in the home inspection are the responsibility of the seller to fix.
Not the buyer.
And that is why a home inspector is hired. So you don't buy a pig-in-a-poke.

[Lloyd Smale]

yes and no. If you go beyond your house your transformer is grounded and the neutral bushing on the transformer secondary is usually grounded to the case and the case is grounded to the pole ground. Your primary voltage neutral is also grounded at least every 5 poles so in fact no matter what you do your ground and neutral are tied together in the ground unless your utility uses ground isolators and I dont know of a single one that does anymore. The only places i can think of are where there was trouble with livestock. We used them when we had the navy ELF underground submarine antena in the area but after they decided it was not needed anymore and decomissioned it we took all the isolators back out. they helped with static feedback into homes but werent near as good when it came to lightning protection. .

NEVER connect ground to neutral. They are NOT the same. Neutral BELONGS to the circuit, and ground does NOT. ... felix

Ground is the neutral for extraneous inputs, such as static, lightning, etc., completing its own circuit external to ours. ... felix

[C.F.Plinker]

The neutral bus is grounded at the service. For most houses that is the panel next to the meter. From there on the neutral and ground are separate. If you put in a sub-panel (say to power all of the tools in your garage) you run a feeder from the service panel to the sub-panel. This feeder would have the phase wires, neutral, and ground. The neutral would connect to the neutral bus in the sub-panel and the ground would connect to the ground bus in the sub=panel. The neutral bus and the ground bus would NOT be tied together in the sub-panel.

[C.F.Plinker]

Well I thought about doing that but I feel better finding the exact problem and I also want to double check the polarity myself.

Please let us know what you find. We have been assuming that "polarity reversed" means that the phase wire and the neutral wire have been reversed. The tester will tell you this as well as if any of the three wires are open or the phase and ground are reversed.

[Dale in Louisiana]

What about those heavily hung individuals on the Discovery Channel, who go up in helicopters and work on the high voltage lines without turning them off? Are they old or bold? Doesn't seem like a young man's game to me...

Not that **I** would do it myself, but those guys are part of the energized circuit. there is no path from the conductor to ground. That's the idea of doing it from a helicopter. The metallic suit is to move the corona discharge from body parts, where it'd hurt, to the suit. Above about 10 kV, the electricity will actually start streaming from energized parts into the atmosphere, because that is ONE path to ground. It's a small amount, unless it's coming off YOUR ears.

I have done the same thing at 13,800 volts from an insulated bucket on a utility bucket truck. Once you get past the 'there's one God-awful amount of electricity in my hand' it's just mechanical work.

In a properly assembled and operating electrical system there are only KNOWN voltage sources and paths to ground. On a jury-rigged, bubba'd, hacked up, thrown together system, you're on your own, so be VERY careful.

I used to tell my technicians that it wasn't the large refinery power systems that would get them, it was driving back into the woods to some peckerwood sawmill, where you couldn't depend on ANYONE doing things right.

I'm still here, and I never lost a technician, so something must be working in my favor.

dale in Louisiana

[375RUGER]

Why are neutral and ground common inside the distribution/breaker box?

[oneokie]

Why are neutral and ground common inside the distribution/breaker box?

Wondering the same thing myself. Would like to hear the explanation for same.

[felix]

Look outside on YOUR utility transformer. If it is a four wire system going into it, then there should be a four wire system going into your house. If not, the power system is delivering power through a three wire system, such that the neutral wire is at zero voltage to ground, i.e, common. More and more time there exists more and more sensitive electronics within your household. Sooner or later you will get unexplained computer, TV, etc. failures seemingly appearing from nowhere. Any time neutral is set to ground there exists a circuit that can obtain all kinds of electrical noise, such as radio waves included. These noises, over time, will destroy home equipment power supplies within your hi-tech electronic gadgets. ... felix

In addition, if you have a three phase motor in your house that has its speed controlled with frequency generation via a computer/controller/whatever, that frequency will be reflected back throughout your house with a three wire system. That is BIG TIME noise and will destroy electronics in no time unless high powered filters are placed after the whatever and before the motor being controlled. ... felix

[Jammer Six]

Dad used to check if current was on by grabbing the hot lead and then touching the (back in that day, metal) box. He showed me how to do it when I was about ten, and I watched him do it, then I tried it, and about blew a hole in my panties.

[odfairfaxsub]

Why are neutral and ground common inside the distribution/breaker box?


in the utility world and principle in wiring situations, you have hot legs (single phase 2 wires or 3 phase 3 wires) then you have neutral (return or voltage ballence relationship which returns to the substation) and a ground (grounds metal cases and surfaces you will touch in case they get in contact with a short) the difference between the ground and neutral in my opinion is

1. which one has a better ground shedding mechanical relief? the substation ground mat or your 2 ground rods in your house?

or

2. yeah how come their common in the pannel but the moment you touch the two together in a box ahead of a gfi they trip, the reason is i recon is it protects the circuit ahead of it not behind it.

in utility work we try to common our service neutral in the field to ground rods on every pole at a desirable ohm value. the transformer may appear to have a ground connected to them is for case ground protection to help shed some ground/case/phase short. the rest that cannot shed will go back into our ground mat in the substation.

[odfairfaxsub]

From there on the neutral and ground are separate.

if your talking about in the pannel they are common because even if you seperate them in the box they are still common due to the different mechanical connectors being screwed into the metal pannel box. thats coninuety at its best

[375RUGER]

So, if polarity reverses 60 times each second then why does it matter if the polarity is reversed at a particular outlet?

And why does old time metal case drill motors have a plug that can be plugged in either way and you don't get zapped? Then and now.

[Catshooter]

Jeff,

I was an industrial/commercial electrician. As such, I worked with three phase most of the time.

Let me tell you, trying to fit my bi-polarness into three phase . . . well, it ani't easy.


Cat

[C.F.Plinker]

And why does old time metal case drill motors have a plug that can be plugged in either way and you don't get zapped? Then and now.

You didn't get zapped because the electrical insulation within the drill motor protected you. Now let's assume that the insulation at the switch broke down and there was a short circuit to the case. With the plug in the outlet one way the switch would be at neutral (ground) potential, the case would be at the same potential, and your body wouldn't see any voltage to ground. But when the plug was turned around the case would be energized at 120 volts. When you touch the case you are also energized at that voltage. If you are insulated from ground -- heavy rubber soled boots-- no current can flow and, like the bird on the transmission line or the lineman with rubber gloves, you don't get hurt. But if you reach out and touch a grounded object with your other hand or kneel down on the ground you have completed a circuit to ground through your body. Hopefully the fault current is high enough to blow the fuse or trip the breaker very quickly. If the current is above .005 or .006 amps your heart can stop beating. This is ventricular fibrillation. How many times have you heard of someone getting hold of a faulty tool that he or she could not let go of and getting a severe electrical shock. This is what is happening.

Back in the early 60s they started adding the equipment grounding conductor (green or bare wire) to the tool cords. This wire was connected directly to the case and when the switch short circuited to the case would conduct the fault current back to the panel. Since there was an ohm or less the resulting current was enough to trip the breaker quickly. After this they came out with double insulated tools. These had a plastic case which wouldn't conduct electricity and thereby prevented shocks. The double insulated tools had the two prong plugs on them. Later they came out with ground fault current interrupters which open the circuit if there is more than a 5-6 mA difference between the current in the hot wire and the current in the neutral wire.

Since then the codes and standards have been improved and 3 wire grounding outlets are required in new buildings, and ground fault current interrupters and arc fault interrupters are now required in a lot more locations than they used to be.

This is being done to keep you and me and our kids and grandkids from getting hurt.

[Dale in Louisiana]

Guys-

The neutral conductor, in electrical parlance, is the grounDED conductor. It is made to carry current during normal operation. The ground wire is the grounDING conductor. It is ONLY supposed to carry current as a safety function.

The neutral doesn't HAVE to be grounded from a strictly theoretical sense, but keeping it at ground potential insures that the highest voltage to ground in a 120/240 (most houses) system will be 120 volts. Assuming you make contact with ONE energized conductor, you are a lot more likely to live from 120 volts than you are from 240.

Note taht I am talking ONLY about 120/240 systems. As the other electrical folk here know, then you start dealing with 3-phase, a whole other set of headaches comes into play. some real electricians know this. Some don't.

I used to teach this stuff to budding electricians in years past. It's fun stuff to me.

dale in Louisiana

[C.F.Plinker]

So, if polarity reverses 60 times each second then why does it matter if the polarity is reversed at a particular outlet?

We're using the term "polarity" in two different ways. One way is, as you used it first above to mean that the instantaneous voltage is above or below some reverence voltage. Here we say that the polarity varies 170 volts above or below neutral 60 times a second. The other use is when we say that the energized conductor has a different voltage than the neutral conductor. In this case we are talking about an rms (root mean square) voltage which has a constant value even though the instantaneous voltage is changing. When we say the polarity of the wires is reversed we are talking about the latter.

When things work as they should we may not care if the hot and neutral are interchanged. After all the motor in your drill motor turns the same direction regardless of which way the plug is inserted in the outlet. Good practice (not to mention the National Electric Code) requires that the hot leg is the one that is switched. Now let's assume that your drill motor now has a grounded case and you left it plugged in. If the winding shorts out to the case and the switch is in the hot leg nothing will happen because there is no voltage on the winding. However, if the switch is in the neutral because the outlet was wired backwards there is voltage on the winding and the motor will start. And because it is just lying on the bench it will try to get into as much trouble as it can.