Basic Electrical Safety Question

In article , snipped-for-privacy@hotmail.com says...>

Shouldn't. You have a problem.

If there are no other faults, there shouldn't be a lethal current. There will be *some* current (because there is *some* voltage).

In a typical shock situation, the persons body is in series with the hot lead. His body is the link between the hot and the neutral lines.

One can also get shocked when their body is connected via a virtual ground.

There are a couple of possibilities. These are assuming your testing in an average sized house with 120 / 240 volts AC service.

If your not familiar with electricity or house wiring, I would recommend that you call in an electrician to check things out. If you do know enough about electricity and houses wiring, try these tests out:

1. Hot and Nuetral are swapped. Measure HOT(black wire) - Ground(green or bare wire), there should be 120 volts, then measure Nuetral(white wire) - ground, you might measure a few volts, but not 120 volts. If there is more that a few volts measured on the Nuetral, Check the plug wiring if that is where your touching wires, then check other plugs and juction boxes that could be connected to the same circuit for miss wiring, check the fuse panel for Black wires, NOT WHITE, comming off the breakers.
2. If could be a bad ground (Nuetral to Ground) connection in the breaker panel, check the connections at the Nuetral connection bar. If could even be connection to the ground rod or not a long enough ground rod. Make sure all connections are tightly screwed in.
3. Check that marrettes are tightly screwed on and screws are tight.

1. There could be an appliance connected to the same circuit drawing heavy current, which puts heavy current on the Nuetral wire. Again good connections everywhere reduces the chances of a shock hazard.

There are cheap little circuit testers with three lights on them that detect miss wiring, they are easy to use (you just plug them into AC recepticals). Two of the amber lights should light up under normal conditions and not the red light. Read the instructions though in case yours is different.

Shaun

krw $BUmF;!'(B

Correct me if I have made a mistake. By nodal analysis on a simple "resistor" circuit, in case the resistor is 100Ohm, the main is 220V, I can calculate the current given the neutral line is 0V with respect to the hot wire,

220V - 0V / 100ohm = 2.2A... So I assume the neutral line is 0V... with reference to the 5V side... Thanks

Lord Garth $BUmF;!'(B

You meant there is a "charge leakage" bacause the circuit is broken? So you are in series with the hot lead? Thanks Jack

In article , snipped-for-privacy@hotmail.com says...>

Ideally, yes. In practice, not so much. In reality there is no 0V, or 0ohm.

5V?

krw $BUmF;!'(B

220V :)

krw $BUmF;!'(B

:) 220V Google ate my post.....

I should have mentioned this FIRST

ANYTIME Your working with a screw driver around electrical wiring, or even with live wires, the breaker(s) for that circuit MUST be TURNED OFF, then with a voltmeter, verify that there is no power there on any of the wires.

Same thing with checking marrettes, power must be off first before you get your hands in there.

If your checking the breaker panel, TURN OFF the Main breakers, Then verify that there is no voltage with a volt meter. Be aware that at the top of the breaker panel where the power comes in, there is live power; 240 volts and atleast 100 amps or more. Be Carfull.

IF your not sure how to do any of this, call an electrician.

Shaun $BUmF;!'(B

Hi Shaun, Thanks for your reply. Actually, I am not doing any plumbing, I just came across a book on Electrical Safety and wondering what the author is talking about... Thanks

Yes, have your house wiring checked immediately.

People who use real newsreaders don't see what you see on Google:

?hl=3Den%26answer=3D46492+remove-*-*-*-irrelevant+Usenet+*.*.*.=*.*-*-*-*-relevant.*+Terms+Home+your.reply+Summarize.what.you're.following.=up+before.the.original.*.*+*-for-your-readers At a minumum, don't delete the name of the person to whom you are responding.

...and for those who DO read via Google:

** Either he is wrong, you are wrong or you have misread what he wrote.

If the "neutral line" you alluded to in your first post is INSIDE some plug in appliance - the it must be treated as a potential shock hazard.

..... Phil

The potential on the neutral line isn't _already_ 0, it is _presumably_

0, or _supposed to be_ 0, or perhaps _often, but sometimes not_ 0.

There are a lot of faults that can put full voltage on a "neutral" wire

-- you should always treat it as hot.

I used to work in a building where there were two adjacent outlets, with a nice low-impedance 50VAC between the _ground_ pins. There were a few RS-485 boards burnt up over that, before people figured out what was going on.

--
http://www.wescottdesign.com

The 'neutral' wire is presumably bonded, at the power panel (i.e. one place in each building) to a ground wire.

Your hypothetical person can safely touch any grounded item (and you do this every time you stand on a concrete floor, touch metal door frames, water fixtures, etc.), at the same time as touching the third-prong ground, without completing a circuit and getting a shock.

The neutral wire, however, IS SEPARATED FROM the ground connection by a length of wire, with (possibly loose) connections, which carries electrical current to some appliance. You can get induced I*R voltage if there's resistance in the wiring, or L*dI/dt voltage if there's significant inductance, etcetera. The appliance current MIGHT, if you put your body in the circuit, send part of its current through you instead of through the neutral wire. So, handling a 'neutral' wire is not generally safe. That's why the third wire, the safety ground wire, is supplied: it carries no appliance current, so it is as safe to handle as a water faucet.

SNIP

The appliance current MIGHT, if you put your body in the circuit, send part of its current through you instead of through the neutral wire. So, handling a 'neutral' wire is not generally safe. That's why the third wire, the safety ground wire, is supplied: it carries no appliance current, so it is as safe to handle as a water faucet.

While it is true as stated that the equipment grounding conductor normally carries no appliance current, it can and often does carry appliance leakage current.

Even a leakage current on the order of ten amps would probably not trip a breaker and there is no simple way of knowing whether any leakage current is present short of measuring it. Placing yourself in series with a low impedance ground fault could even be fatal.

I would caution against becoming part of any household wiring circuit, no matter the color of the insulation.

Chuck

That's why ground-fault interrupters (GFI, GFCI, whatever) are required for places (bathroom, outdoors, kitchen) where people make body contact with water pipes and other grounded items. A GFI will trip on small leakage current.

The scenario of dangerous third-prong ground is unlikely, but all modern construction (in my municipality) is protected against it anyhow.

Protected against "dangerous third-prong ground" how?

whit3rd wrote: SNIP

Yes, GFCIs offer protection where they are installed. I would guess that something like 99.9% of domestic branch circuits are not protected by a GFCI in the US.

I'm not sure what exactly is meant by "dangerous third prong ground". If the equipment grounding conductor (third prong) is wired properly, it will be close to ground (earth) potential even when carrying lethal currents. Under those circumstances, touching the EGC should be safe. But inserting your body in series with the EGC when it is carrying lethal currents is quite dangerous.

Readers are left with the option of a) measuring EGC current before placing their body in series with the EGC; or b) relying on whit3rd's assertion that such a scenario is unlikely. Doubters might contact their local plumbers who sometimes find their body between two sections of metal pipe through which is passing a significant leakage current. For safety's sake, they routinely attach a bonding wire across the pipe joint before separation.

Chuck