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Why we ground electrical systems (2015)

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Re: Why we ground electrical systems (2015)

#71

Post by kmill »

mindslight wrote: post #64
kmill wrote: post #40

Earlier quoted context omitted.

When it comes to AC (even discontinuous DC), closed loops are not necessary for current flow. A basic example is a capacitor, which can permit current while it builds up an electric field between is plates. A related example is an antenna, where AC radiates energy that can vibrate electrons in a far away antenna. (Radio telescopes are proof an antenna doesn't need a ground or a closed circuit to receive.)

Closed loops ("circuits") are part of the paradigm, so yes they are necessary at the level of abstraction we generally analyze electronics in. Sure if you came from Pluto with a metal sphere teeming with excess electrons, they would disburse themselves on our planet and never return home, but that isn't circuit analysis! For example, the current into one terminal of a capacitor does equal the current out of the other…

I only brought up ground (in the Earth ground sense) because I've heard people think that antennas in general work by using the Earth as a second conductor, with EM radiation as the first. Antennas are conductors that are part of an un-closed electrical network, relying on the capacity of a conductor to hold an oscillating non-equilibrium charge (though they can be modeled as an RLC network). My previous comment was written out of a reasonably common conception of a closed circuit being a loop with constant current flow, but capacitors break such a circuit. (I don't mean to imply what bsder said was in any way wrong, just not necessarily the whole story depending on how it's interpreted.)

The realm of electrodynamics is pretty interesting, and it's where seemingly basic concepts like electric potential begin to fail -- it becomes path-dependent!

Re: Why we ground electrical systems (2015)

#72

Post by simonebrunozzi »

watersb wrote: post #66

I have been studying Grounding vs Bonding these past few weeks, great timing to see this HN discussion. Some training videos for pro electricians and US National Electric Code compliance helped me. https://youtu.be/qNZC782SzAQ Basically, bond everything together if it can carry a charge. Ground that bond at only one place in an electrical service. More than one "ground" sets up a situation where a potential differenc…

> The USA needs more people who know how to build things.

USA? The WORLD needs more people who know how to build things.

Re: Why we ground electrical systems (2015)

#73

Post by simonebrunozzi »

vvillyd wrote: post #2

I'm actually the person who wrote this Reddit post. I'd never heard of Hacker News before, but someone messaged me on Reddit telling me this 4 year old post just surfaced over here. Let me know if you have any questions about electrical theory or installation, or anything else!

Well, seems like you should do an AMA on Reddit!

Re: Why we ground electrical systems (2015)

#74

Post by [deleted] »

watersb wrote: post #66

I have been studying Grounding vs Bonding these past few weeks, great timing to see this HN discussion. Some training videos for pro electricians and US National Electric Code compliance helped me. https://youtu.be/qNZC782SzAQ Basically, bond everything together if it can carry a charge. Ground that bond at only one place in an electrical service. More than one "ground" sets up a situation where a potential differenc…

[deleted]

Re: Why we ground electrical systems (2015)

#75

Post by olouv »

Beware as this explanation does not apply to every country in the world, in France for residential systems at least, the protection (green/yellow) wire is never connected to the neutral (blue) wire, only to earth with a metal rod at the house. You would get a shock if it was somehow disconnected from the rod/earth. Neutral is also not bounded to earth inside the house. Be safe!

Re: Why we ground electrical systems (2015)

#76

Post by ThrustVectoring »

tomatotomato37 wrote: post #65
vvillyd wrote: post #2

I'm actually the person who wrote this Reddit post. I'd never heard of Hacker News before, but someone messaged me on Reddit telling me this 4 year old post just surfaced over here. Let me know if you have any questions about electrical theory or installation, or anything else!

There's one thing I don't understand between hot and neutral. How do the electric turbines upstream at the power plant only act on what becomes the hot wire? By my understanding of how motors work the magnet causes a positive current on the whole coiling/wire, meaning a positive current on one side is matched by an equally powerful negative current on the other. As both wires on the consumer end eventually join to th…

The electric generators aren't connected to your neutral wire. They deliver three phase power with three different "hot" lines, and then only one of those phases gets pulled down into your house electricity.

Re: Why we ground electrical systems (2015)

#77

Post by ThrustVectoring »

bardworx wrote: post #22

Why are there three wires in new receptacles? From my understanding, new code has you have to have a 3+ground but why is that safer? Did they just add an extra wire so you can have a hot, lead, and neutral to ground all the receptacle? (Plus the green/bare to bond the receptacle to switch/outlet) Also, for home owners, what’s the best resource to learn common sense basics of electrical work (besides reading the city/…

It's not safer, it's more useful. You run out the hot, neutral, and switched hot. That lets you use a light switch to control an overhead light/fan without killing the fan.

Re: Why we ground electrical systems (2015)

#78

Post by ars »

vvillyd wrote: post #42
bardworx wrote: post #22

Why are there three wires in new receptacles? From my understanding, new code has you have to have a 3+ground but why is that safer? Did they just add an extra wire so you can have a hot, lead, and neutral to ground all the receptacle? (Plus the green/bare to bond the receptacle to switch/outlet) Also, for home owners, what’s the best resource to learn common sense basics of electrical work (besides reading the city/…

The three wires in any typical household circuit are your Ungrounded Conductor (hot wire), Grounded Conductor (neutral wire), and Equipment Grounding Conductor (EGC/Ground Wire). The hot and neutral are what actually makes the circuit work. The EGC/ground is a safety measure that creates a ground fault current path which enables overcurrent protective devices (like breakers and fuses) to operate. As far as learning c…

> The EGC/ground is a safety measure that creates a ground fault current path which enables overcurrent protective devices (like breakers and fuses) to operate.

This is NOT TRUE!! You've said it so many times in this thread, and it's just not true.

A lot of people are tying to correct your mistakes, but you're not fixing them. Please do so, you are misleading a lot of people.

Re: Why we ground electrical systems (2015)

#79

Post by ars »

jessaustin wrote: post #55
ars wrote: post #41

Earlier quoted context omitted.

He's right and you are not. If you don't bond neutral and ground at the main, it's still bound at the transformer. > then the current will flow through the ungrounded conductor, No, it will flow through the grounded conductor. > back to the source (usually a transformer), across the windings, and eventually back to the breaker that controls the circuit The flow of power is the same via ground as it is via neutral. >…

If you don't bond neutral and ground at the main, it's still bound at the transformer. That would be a pretty good trick. The transformer is outside my house on a pole. Two wires run to it, the hot and the neutral. The "ground" doesn't leave the house. (Other wiring schemes exist, but this is standard USA residential.) [EDIT: brainfart, see helpful correction below. still no "ground" at the pole...]

> still no "ground" at the pole...

Yes there is. The neutral is bonded to ground, via an actual metal pole in the ground.

In your house is the same thing: The neutral (and the ground) and attached to a metal pole in the ground.

And the earth itself completes the circuit.

Re: Why we ground electrical systems (2015)

#80

Post by chrisdhoover »

clort wrote: post #50
amriksohata wrote: post #15

Earlier quoted context omitted.

So in the UK we have 3 wires, red, blue and green, the green is ground or earth, what purpose does this serve? Is it the same as ground as you call it in the US

In the UK we used to have red, black and green, but now we have brown, blue and green/yellow (I think this is the same as rest of EU). I presume this is because of colour blindness reasons as there are folk who can't distinguish red and black that well.

Hopefully when Brexit is complete, you can return to the true colors as god and the Queen intended.
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