Almost understanding grounding and bonding

This has had me stumped for weeks, but I am nearly there (visually if not in language).

I read that a grounding conductor leaving the main panel to connect to, say, a water pipe does not protect you from electrical shock and its main purpose is to provide some protection against a lighting strike because there is too much resistance via this path to trip the breaker if there is a ground fault and this is the only return path.

But I think this is wrong.

Surely it does provide protection in the following circumstance. If this conductor is properly bonded to the grounded conductor (i.e. the neutral) in the panel, and a hot wire generates a ground fault by touching a water pipe (assume they are all copper), then this connection will protect against electrocutian since the ground fault will trip the over-current protector (there being a path of very low resistance).

And for this reason we jumper the water meter, to provide protection if it is removed. And for this reason we bond the grounding conductor on the main panel to the grounded conductor in the main panel. Am I correct?

Secondly, the reliance on the grounded conductor for safety purposes must mean that there is very real danger if ever the main neutral connection to the house (say on the line coming to it) is cut at the same time a ground fault occurs in the home e.g. in the case of very bad weather that damages property while leaving the hot wires intact e.g. a hurricane? Is this true? In this case, while no electrical equipment would work all neutrals and ground wires (green) in the home become ineffective in tripping a breaker since the only return path will be through the water pipe or ground rod.

Almost there:

  1. The GROUNDING of a house’s electrical system, to the water pipe or grounding rod or whatever (provided the water pipe is metal, extends far enough into the ground and it has a BONDING jumper around the water meter) provides ptotection to the electrical system of the house. This is a guard against fire when the electrical service gives a surge or is struck by lightning or some such.

  2. Circuit breakers DO NOT provide protection to humans.

  3. GFCI receptacles or breakers work to protect people. So do AFCI breakers, but in a different way.

  4. BONDING (i.e. the physical, electrical connection of all metal, conducting systems of the house) provides a low resistance path for electricity to go back to the panel.

4a) Electricity DOES NOT seek out a ground. It seeks out a path to its SOURCE (i.e., the transformer).

4b) Electricity does not seek out the quickest or easiest path, it seeks out ALL paths. Low or high reistance, electricity will take them all.

4c) The lowest resistance path is the neutral conductor from the pole and transformer. The neutral conductor is GROUNDED, but is also in “the middle” of the two hot legs.

4d) In a (human involved) ground fault situation, you want the circuit to draw the most amperage, faster.

4e) A 15 amp breaker will trip, but will only trip RIGHT AWAY, it there is 4 to 5 times the rated amperage going through it. SO, we want a ground fault condition to draw as much current as possible, as quickly as possible, so as to trip the breaker BEFORE SOMEONE GETS FRIED!

  1. By BONDING all the conducting metal (conduit, if you live in Chicago :mrgreen: ) and other pipes (water and gas), the curcuit will draw mucho amps to the BONDING of the neutral conductor and the grounding electrode conductor at the service equipment (the panel).

  2. By drawing bug amps, through the connection of the neutral drop conductor to the transformer, the lowest resistance path will be kept.

  3. The breaker will trip and people will be saved.

  4. your clients will live long enough to send you referrals :mrgreen:

You see, it’s all about marketing.

Hope this helps;

Ian, in your scenario the thing that would be in most danger would be equipment but I bet the breaker trips pretty fast. Assuming your neutral opens on the line side of the service disconnect and your fault occurs on a branch circuit (tree falls, breaks the neutral on the drop and crushes a box in the attic) The voltagen on the faulted phase would drop to zero and the other phase would jump up to 240v or so. That path is through the breaker on the faulted branch circuit so it would probably trip if there was any load to speak of on the other phase. In fact I would expect to see some breakers tripped on the other side too.

As for the safety of the occupants, “bonding” is what saves you. Your whole house might see a significant shift above ground but if everything is bonded you are a bird on a wire. This is where the Ufer ground really starts to excel. With a Ufer your concrete floors and walls will also track the faulted neutral/ground so, other than the smoking appliances, you might not even notice. We are actually getting to the theory of bonding swiming pools at that point. Everything you can touch is at the same potential.

Hopefully the code will soon catch up with the definition of grounding and bonding. The only grounding conductor in the house is the one that goes from the panel to the ground electrode. Everything else is bonding or a circuit conductor.

BTW when I speak of Ufer I am thinking Florida style. Places with lesser building codes may not get all that benefit since there is not much steel in your house.

Thank you all very much. Very interesting.

Ian,

Understanding what the definition of the items in question will help in the understanding of what each is supposed to accomplish. Here are the definitions of each.

Bonding (Bonded). The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed.
Bonding Jumper. A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.
Bonding Jumper, Equipment. The connection between two or more portions of the equipment grounding conductor.
Bonding Jumper, Main. The connection between the grounded circuit conductor and the equipment grounding conductor at the service.
Bonding Jumper, System. The connection between the grounded circuit conductor and the equipment grounding conductor at a separately derived system.

Notice the similarities between the Main and System bonding jumpers.

Ground. A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.
Grounded. Connected to earth or to some conducting body that serves in place of the earth.
Grounded, Effectively. Intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons.
Grounded, Solidly. Connected to ground without inserting any resistor or impedance device.
Grounded Conductor. A system or circuit conductor that is intentionally grounded.

The Grounded Conductor is what most people mistakenly call the “neutral”. In a residential panel there is no such thing as a true neutral. What we call the neutral is a current carrying conductor therefore it is not neutral.
Look at the transformer that is supplying a dwelling unit and you can see that the grounded (neutral) is connected to a conductor that runs down the pole and into the earth. The “ED” at the end of grounded signifies that it was done in the past tense. The power company has already grounded the conductor.

The installation of the equipment grounding conductor is covered in Part VI of Article 250.
The purpose of the equipment grounding conductor is to connect all metal that is not used to carry current to earth. This connection to earth is to:
250.4(A)
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
(2) Grounding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.

Grounding plays no role what so ever in the operation of the overcurrent device nor does it protect equipment or persons from electrical shock.
Bonding is simply the connection of the equipment grounding conductors to the grounded (neutral) conductor or the continued connection of all non current carrying metal parts of a system to the grounded (neutral) at the service.
Through this bonding process we have now made a connection to the source (power company transformer) that establishes a low impedance path to facilitate the operation of the overcurrent device.
When we bond such things as water pipes or metal of a building we are establishing a path for current to flow back to the source in the event that they become energized. Through this bonding of the metal we now have a low impedance path to open the overcurrent device should the metal become energized.

This bonding is done for different reasons and using different methods than the equipotential bonding required for bodies of water as outlined in 680.26
680.26 Equipotential Bonding.
(A) Performance. The equipotential bonding required by this section shall be installed to eliminate voltage gradients in the pool area as prescribed.

FPN: The 8 AWG or larger solid copper bonding conductor shall not be required to be extended or attached to any remote panelboard, service equipment, or any electrode.

Bonding around a body of water is installed for the sole purpose to eliminate voltage gradients and is not required to be connected to the electrical system. The purpose is to have everything in the area of a body of water at the same touch potential unlike the bonding of the electrical system which facilitates the operation of the overcurrent device.
The bonding around a body of water is not done to open the overcurrent device,

Just pickin on ya Rabbi…

Go ahead Paul, you just try explaining the difference between AC impedance and DC resistance to a non-technical.

Never…just not worth the wasted brain cells…and as you can tell I waste ALOT of them in the course of a day in MY twisted mind.

Here…I will just save the brain cells and CUT AND PASTE…lol

There are a few misunderstandings about some of the more basic terms like Resistance and Impedance. They both regard the same concept: The opposition to the flow of electrical current. That is in fact the definition of Resistance. Impedance, however, is a little more complex. Impedance is the resistance of a component at a given frequency. That difference is an important one, as we will see later.

For now, we will look at resistance. Resistance is quite simple to understand. Everything in the universe has electrical resistance. It so happens, that even wood, rubber, plastic, and glass do in fact conduct electricity just like copper wires do. Their resistance, however, is so very high, that we use them to “insulate” wires, or keep them protected from other things (namely, other wires). They are called “insulators”, for obvious reasons.

There are materials, whose resistance is not high enough to be insulators, but is too high to be a conductor. These have a practical application as “resistors”, or components whose purpose it is to resist. The amount of resistance these devices have (or the resistance of anything, for that matter) is measured in a unit called “Ohm” (pronounce “O - m”), and is represented by a symbol called the Omega. Although a resistors value (in Ohms) changes slightly with temperature and with age, for practical purposes, it is the same always, no matter what the electricity is doing.

Impedance, however, is dependant on a property called reactance, and frequency. Impedance only exists where there is AC, or fluctuating DC (AC with a DC bias).
In a coil or capacitor, the reactance changes due to the way the component works with electricity. A capacitor, will increase its resistance as the frequency gets lower. A coil on the other hand, will increase it’s resistance as the frequency gets higher. They will both continue like this until their resistance is so very high, that no useable current will pass, at which point they are said to be “saturated”. In a normal resistor, at any given frequency, we can say that it’s resistance is still the same. When graphed, the value of a resistor will be a straight line across the graph. In a reactive component, however, the line will gently slope upward, or downward, with frequency.

This is reactance. Reactance is necessary for crossovers to do their job. Whenever you look inside a crossover (passive crossover, at least), you will see usually nothing more than a few coils and capacitors, and occasionally the odd sand block resistor. Remember, coils resist high frequencies, and capacitors resist low frequencies. When the two are combined, they form crossover networks. A crossover network typically uses a capacitor to keep low frequencies from going to a tweeter, and a coil to keep high frequencies from going to a woofer.

Another component that has reactance, is the speaker itself. A speaker’s voice coil behaves electrically just like a coil in a crossover network. Because of this, speaker designers face special problems when designing midranges and tweeters based on voice coil drivers. Also, due to it’s reactance, a speaker is almost never at it’s rated “Impedance” (a word often used incorrectly by speaker manufacturers). When a speaker is measured at 4 ohms, it is measured using a device that puts out DC current to do the measuring. The only other time the subwoofer will have anything near 4 ohms is when it is at resonance. The rest of the time, the voice coils impedance is very high. My 10" subwoofers reach a peak of 45 ohms, and they have a 6 ohm voice coils.

So now we’ve seen the difference and similarity of Impedance and Resistance. Resistance is in everything, Impedance only exists when you have an AC or fluctuating DC current. Impedance of a reactive component.

Hey you beat me to the punch, Paul
Got simple from about.com
resistance
In electricity, a measurement of the difficulty encountered by a power source in forcing electric current through an electrical circuit, and hence the amount of power dissipated in the circuit. Resistance is measured in ohms.
impedance

(1) The opposition to the flow of alternating current in a circuit. Represented by the letter “Z” and measured in ohms, impedance is the combination of resistance, inductance and capacitance of the circuit. See ohm. (2) The opposition that a speaker produces to the alternating current coming from an amplifier. The lower the impedance, the more power required. Most speakers have an impedance of four to eight ohms. See ohm

Mike, the FPN in 680.26 is pretty misleading since the bonding grid will be connected to the panel via the EGCs of the pump, underwater light, solar cover motor and any other electrical equipment near the pool. In my case it is even more of a connection than that since there are also 3 branch circuits, run in EMT that are connected to the screen cage.
It does say it is not “required” to extend the #8 solid but it doesn’t say this path does not exist.
In my house I exploit every ground electrode available so my pool grid is connected to the Ufer under the garage which catches the Ufer in the house and 3 rods and 20’ of buried bare copper.
I also have pretty good TVSS protection
The result is I took a direct hit on the air terminal above my weather station and all I lost was the Temp/humidity unit that connects to the wind speed sensor and the serial port on the PC. They weren’t totally dead but they were wounded. It was exciting tho. We were out in the tiki bar when it happened. Lots of stuff blinked and I had to reboot all the PCs on my network but they all survived.

Mike, the FPN in 680.26 is pretty misleading since the bonding grid will be connected to the panel via the EGCs of the pump, underwater light, solar cover motor and any other electrical equipment near the pool. In my case it is even more of a connection than that since there are also 3 branch circuits, run in EMT that are connected to the screen cage.
It does say it is not “required” to extend the #8 solid but it doesn’t say this path does not exist.
In my house I exploit every ground electrode available so my pool grid is connected to the Ufer under the garage which catches the Ufer in the house and 3 rods and 20’ of buried bare copper.
I also have pretty good TVSS protection
The result is I took a direct hit on the air terminal above my weather station and all I lost was the Temp/humidity unit that connects to the wind speed sensor and the serial port on the PC. They weren’t totally dead but they were wounded. It was exciting tho. We were out in the tiki bar when it happened. Lots of stuff blinked and I had to reboot all the PCs on my network but they all survived.

Got a pool that doesn’t have a light nor any other electrical device or equipment but a double insulated motor, Now what?

Now if there is a low voltage light supplied from a transformer located at the house or a fiber optic light with the light source located at the house or a nonmetallic niche with a nonmetallic junction box along with a double insulated motor then there is no connection between the equipment grounding conductor and the bonding grid.

As I have said so many times in the past, “it is a bad thing to connect the bonding grid to the power supply. In the event of an open neutral on the line side of the main panel you have just made your bonding grid hot.”
Why would you want to do this?

It is not now nor has it ever been the intent to connect the bonding grid of a body of water to the power source. As outlined in 680.26 the purpose of the bonding grid is to eliminate voltage gradients in the pool area not to establish a connection to the grounding electrodes of the electrical system.

680.23(B)(2) does not relieve the installer from bonding the niche to the listed light J box, even if it is low voltage. 680.23(F)(2) extends that to the panel with an insulated #12.

I suppose we can come up with a scenario where the pool is not bonded to the service but it would be rare. Usually you have several paths.

The fact remains an inground concrete pool is the best grounding electrode at a dwelling without exception. By the time you get the deck poured you might have a half mile of rebar embedded in a few thousand square feet of concrete in intimate contact with earth.
Even the Ufer in a slab built house with steel in the floor will not be this good because you are required to have a vapor barrier under the slab so you only get the footer area at the perimeter.

The whole idea of the pool being “hot” is a non sequitor. Hot in reference to what? Everything you could touch is supposed to be bonded together so you are a bird on a wire. In the case of a inground concrete pool it is a well grounded “wire”. If it is a plastic pool we have the new “bonded deck” rule to protect you 3 feet away from the water too.

It is like the people who get their panties in a wad when they talk about corner grounded delta.

Paul;

Impedence = Resistance. I.E, Low Ohms.

To "impead’ = To "resist’

2 ohms better that 1000 ohms.

Electrical school - M.S. in physics

Same thing, different term

Dang Virgnia school system :mrgreen:

OK, you ol’ hillbilly, ya got me.

Impedance is the resistance of a component at a given frequency.

New paradigm.

M.S. in Physics - Consider the Universe.

Master Sparky - Do the freakin’ job (and get paid).

I, humbly, stand corrected.

Now, Paul, give us a kiss. :wink:

(B) Wet-Niche Luminaires (Fixtures).
(1) Forming Shells. Forming shells shall be installed for the mounting of all wet-niche underwater luminaires (fixtures) and shall be equipped with provisions for conduit entries. Metal parts of the luminaire (fixture) and forming shell in contact with the pool water shall be of brass or other approved corrosion-resistant metal. All forming shells used with nonmetallic conduit systems, other than those that are part of a listed low-voltage lighting system not requiring grounding, shall include provisions for terminating an 8 AWG copper conductor.
(2) Wiring Extending Directly to the Forming Shell. Conduit shall be installed from the forming shell to a junction box or other enclosure conforming to the requirements in 680.24. Conduit shall be rigid metal, intermediate metal, liquidtight flexible nonmetallic, or rigid nonmetallic.
(a) Metal Conduit. Metal conduit shall be approved and shall be of brass or other approved corrosion-resistant metal.
(b) Nonmetallic Conduit. Where a nonmetallic conduit is used, an 8 AWG insulated solid or stranded copper bonding jumper shall be installed in this conduit unless a listed low-voltage lighting system not requiring grounding is used. The bonding jumper shall be terminated in the forming shell, junction box or transformer enclosure, or ground-fault circuit-interrupter enclosure. The termination of the 8 AWG bonding jumper in the forming shell shall be covered with, or encapsulated in, a listed potting compound to protect the connection from the possible deteriorating effect of pool water to protect the connection from the possible deteriorating effect of pool water.

Although you have pointed out one of the three different niche type of lights that can be installed in a pool, the other two being dry niche and no niche, the use of a #8 conductor between two nonmetallic components wound not be bonded to the equipment grounding conductor.

The use of fiber optic lights which is growing by leaps and bounds in my area of the nation will have no physical connection to the bonding grid. Most of the low voltage lights I have encountered over the past several years don’t have a connection to the bonding grid either.

I have seem several pool installations in the past couple of years where the bonding grid had no connection to the equipment grounding conductor at all.

Personally I see that as less safe. You are basically saying there is no real connection to the bonding grid and it may be significantly above the potential of that Bell box the 2008 has now let you put 5’ from the water and 2’ from the bonded pool deck. If you have some stray voltage that elevates the potential of the pool above the “ground” of the service, anything with an exposed bonded metal case or any wiring method will impose that difference on a person sitting on that deck.

lol…no problem William…lol…Hillbilly…lol…I love it