Electricians, Step Inside, Please. Polarity Question.

[Jammer Six]

[Jammer waves his hands excitedly over his head and dances around]

Tell him about that bloody hose and the water and the water pressure!

[cbrick]

Very interesting thread. I too am in the process of buying a home, I too had the home inspection say that two outlets and a wall switch are reversed polarity. My initial thought was, no biggie I'll just get an electrician to check it out and fix it. I'll also have ground fault outlets installed in the bathroon & kitchen where there aren't any. I also need a water tight junction box installed at well pump.

Then I found this thread and read through all of it and came to the conclusion that my initial thought was correct, bite the bullet and hire an electrician and do it right.

Rick

[odfairfaxsub]

polarity realy serves dc electricity better. polarity as in one wire is positive and the other negative but works a/c as well i guess just never called it that. its either a hot, a phase, a hot leg, phase leg, power leg, or neutral or ground.

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

this was probably the best explained this way. jolly good!!!

[gray wolf]

This place is a wonderland of information.
I like the way things are explained, and questions answered.
Thanks men.

sam

[Catshooter]

Actually 2muchstuff is incorrect. Don't do that Beau.

Here's the problem. When you look at the new light bulb that you're about to screw into the light fixture, look at the base. See the shiny aluminum male threaded portion? And on the very bottom the little brass colored dot about 3/8" or so?

Well the shiny aluminum part needs to connect to the neutral. Just imagine if that part was connecting to the hot. It's very easy to touch that part as your screwing the bulb in. When it connects to the neutral it's very difficult for it to hurt you.

But if the polarity is reversed, that aluminum shell becomes hot. So when you plug in a lamp to a reversed polarity circuit, uh oh.

Now if you don't track down the source of the reversed polarity? Well, who's to say that the problem isn't in a light switch box somewhere? So when you're in your bathroom with one hand bracing you on the sink faucet, one foot on the toilet and straining to screw in that light bulb and your finger touches that bulb's shell . . . you could be late for work.

For you electricians who say there is no such thing as polarity in alternating current, that is, in a rather esoteric way true. But in a house the practical truth is touch a neutral, what happens? Touch a hot, what happens?

Hope that helps you Beau and answers Springfield's question too.


Cat

[Longwood]

So I need to change a simple wall plug in the bedroom of my new house.
No biggie.
Do I hunt for the lost flashlight, move my truck and the stacks of boxes so I can get at the breaker panel in the freezing garage, or since I know as long as I don't touch the black wire I am OK and change the plug on a hot circuit?
No biggie.
I have done it a few times befo,,,,,,,
ZAP!
Then the cussin and name calling, starts

[Catshooter]

375RUGER & oneokie,

The ground conductor is conected to the neutral in your breaker (or fuse) panel very deliberatley and as a safety.

Let's say you've holding your sawzall in one hand and with the other you plug it in. Now, unknown to you some little pixie has gone inside it and not only broken one of the hot wires off, but the little bugger has pushed that shiny copper wire hard against the metal case of the tool that you're holding in your sweaty little paw.

Since the sawzall has a three prong cord and your home grounding system is in wonderful shape the hot AC voltage, which usually shows a preference for using the path of least resistence will jump down that grounding wire and run all the way back to your electrical panel. Now the power has a safe place to go, and you probably didn't feel much of it, we hope.

Now usually the hot flows into the electric motor of the sawzall and the motor's resistance puts a damper on just how many amps the hot is allowed to draw from your panel. But in this new pathway there is waaaaaaaaaaay less resistence and it limit of amps is way, way higher. It will start drawing more and more amps since there is much less resistence to restrain it.

Soner or later the amount of amps the circuit is drawing has exceeded the 15 or 20 amp breaker/fuse that you're plugged into and pop goes either the fuse or the breaker.

This all takes place fairly quickly of course. Exactly how fast depends on lots of factors but it usually, in a home takes a quarter of a second or so.

That is why the grounding conductors all tie into the neutral.

The way a Ground Fault Interupter works is that it's circuitry is always watching how many amps are on the hot. It is at the same time always comparing that number to the amount of amps that the neutral has on it. When they are different by much more than .005 of one amp it shuts off the power.

Simple stuff really.


Cat

[oneokie]

375RUGER & oneokie,

The ground conductor is conected to the neutral in your breaker (or fuse) panel very deliberatley and as a safety.

That is why the grounding conductors all tie into the neutral.

Simple stuff really.


Cat

Exactly.

By having the neutral buss and the ground buss connected, stray voltage does not back feed all the circuits in that box. Also, to MY thinking, it eliminates the need for a 4 wire service from the meter to the service panel, and/or the need for ground rods connected to the service panel neutral buss.

Many of the new breaker box service panels do not have the neutral and ground buss bonded (connected).

[Catshooter]

The only requirement for a four wire service (that isn't three phase) has been for a mobile home. Or for a sub-panel. At least as far as I know. All though you never know. I've seen and worked with a five wire service. Four hot conductors and a ground. No neutral. That was weird.

Connecting the neutral & ground in the service panel doesn't eliiminate the need for ground rod(s). Ground rods are where shorting electricity goes, so they are very much needed.

In my 34 years I have never seen a new-in-the-box panel have the ground tied to the neutral bus. That's because the manufactuer doesn't know if the panel is going to be for a service or a sub-panel. All panel come with the parts needed to make that connection.


Cat

[floodgate]

One problem that has not been discussed is that of an outbuilding (barn, shop, trailer or "man-cave") fed from the house breaker-box. Codes differ as to whether you should carry the ground (not the neutral) from your house meter box in a 4-wire setup, or whether you should ground to a new ground-rod at the outbuilding, with a three-wire link. You can develop quite a bit of potential between buildings, even in the ground, and a long run of neutral can get pretty "hot" versus the ground via current times line resistance. Is a separate ground rod at the sub-panel in the shop - and no ground link to the house - the best way to go? I've heard it argued both ways. This is a setup many of us use; I have a three-wire, 110 vac (150 ft. of #10 stranded) cable to my shop from the house, and no local ground rod, but am not real comfortable with it. My IBEW "wireman" buddy says, "it depends". On what?

floodgate

[C.F.Plinker]

My IBEW "wireman" buddy says, "it depends". On what?

floodgate

It largely depends on what you are serving in the building and how many branch circuits are in the building. Get with your IBEW buddy and a copy of the National Electric Code section 250-32 and see which exceptions to the requirement for an ground rod at each building, if any, apply to your building(s).

[Catshooter]

In the National Electrical Code, it's not both ways if you have a panel in the out building. It's three wire (for 120 volt set up) or four wire (for 240 volts), with a ground rod at the sub panel.

But Floodgate if you're not having problems do you need to fix it? You can always add a ground rod if it would make you feel better. It can't hurt. Do you have a sub panel there? 240 volts? You definatley want a gounding conductor to the house.

In my experience most electricians don't really understand the whole grounding/bonding thing.


Cat

[floodgate]

Catshooter:

Thanks! I'm not having problems. No panel in the shop (3-wire 120 v.), just a powerstrip with overload cutoff, and no ground rod. I do have a 3-wire (#10 solid, 175 ft., center neutral, no ground lead) 220v. line to the the pump controller at the barn, and there I do have a ground rod. So I'm trying it both ways, and no problems over 10+ years.

floodgate

[odfairfaxsub]

Now if you don't track down the source of the reversed polarity? Well, who's to say that the problem isn't in a light switch box somewhere? So when you're in your bathroom with one hand bracing you on the sink faucet, one foot on the toilet and straining to screw in that light bulb and your finger touches that bulb's shell . . . you could be late for work.

good point catshooter, that would prob be my most found problem with bulbs that shoot out too much, outdoor lights with reversed neutral and hot, bugs tracking the circuit out to ground. good call

[Catshooter]

Then I wouldn't worry Floodgate. Electrical problems usually, not always, but usually let you know with little warnings. Most people pay them no mind and that can be bad.

Thanks odfairfaxsub. I've let the smoke out of many, many electrical components over the years and have even learned from some of them!


Cat

[2muchstuf]

OK guys ,
I stand corrected.
Excellent example catshooter.
I now see the light.

I guess it's just my old school thinking coming out.
For right around 100 years it didn't matter witch way you put the plug in.

A much more informed 2

[jblee10]

Floodgate. I would be worried about voltage drop with that length of #10. Of course I have no idea what size or amperage pump you are running. But running equipment at low voltage can be hard on it.

[Lloyd Smale]

your best bet is to contact your local electrical inspector. Many of the codes are up for interpatation. You need to please him not a book to get your inspection past. In our area if you have an outbuilding with a pannel it would need seperate ground rods and it would need two of them to be exact and i believe they would have to be 12 feet apart. Bottom line is it never hurts to have to many ground rods. Ive got two on my house, two on the garage, two on the pole barn and two on my emergency geneator circuit thats tied into the rest of the system.

One problem that has not been discussed is that of an outbuilding (barn, shop, trailer or "man-cave") fed from the house breaker-box. Codes differ as to whether you should carry the ground (not the neutral) from your house meter box in a 4-wire setup, or whether you should ground to a new ground-rod at the outbuilding, with a three-wire link. You can develop quite a bit of potential between buildings, even in the ground, and a long run of neutral can get pretty "hot" versus the ground via current times line resistance. Is a separate ground rod at the sub-panel in the shop - and no ground link to the house - the best way to go? I've heard it argued both ways. This is a setup many of us use; I have a three-wire, 110 vac (150 ft. of #10 stranded) cable to my shop from the house, and no local ground rod, but am not real comfortable with it. My IBEW "wireman" buddy says, "it depends". On what?

floodgate

[Beau Cassidy]

Well everything is a moot point now as the seller didnt want to hold up his end of the agreement on a few points. It was an awsome house (5 bedroom 4 1/2 bath) but things happen for a reason.

[Catshooter]

Lloyd,

I would avoid calling an inspector unless I needed him (there is an electrical permit involved).

Many inspectors won't come out until there's a permit purchased.

Mostly it's sorta like calling the ATF for help. You really don't want them around unless you have too. "I'm from the government and I'm here to help" ? It can happen, I've had good inspectors, lots of them. But that's a really risky door to open. Once it's open you can't close it. He does.


Cat