grounding and bonding for dummies

As this series progresses, you'll see these terms many times. If the impedance were to increase to 5 ohms, the current would be reduced to 24 amp, which could flow indefinitely on a 30-amp circuit. Ham gear usually has a ground terminal just for this purpose. Other more complex arrangements are sometimes required. The NEC is concerned only with the safety aspects of a ground system, and not the effect on operation of computers or other equipment. 0000003043 00000 n Why Analog Devices components are sooo expensive? It is important to understand the distinction between the grounded conductor and the equipment grounding conductor. Grounding Versus Bonding: Part 1 Q&A – Jade Learning. trailer Understanding the differences between bonding/grounding and earthing is best illustrated with an example. This layering of shells results in “surface voltage gradients.”. Hope you will join us for those as well! Very good way to explain the difference to the newer or upcoming electricians. 250.6 (Objectionable Currents): “An increase in the use of electronic controls and computer equipment, which are sensitive to stray currents, has caused installation designers to look for ways to isolate electronic equipment from the effects of such stray circulating currents. Therefore, a ground rod doesn't lower touch voltage to a safe value for metal parts that aren't bonded to an effective ground-fault current path. Bonding Vs. Grounding. 250 — Grounding and Bonding. Correct wiring and grounding errors on the power system serving the sensitive machine. Ground loops, which are introduced by communication wiring between sensitive machines fed from different power sources, may require more elaborate correction schemes, such as optical isolation. Bonding and Grounding can be a very confusing subject full of conflicting information, magic, and myths. All Code references are based on the 2005 National Electrical Code. The permanent joining of metallic parts together to form an electrically conductive path. Bonding, Grounding and Earthing One of the most misunderstood and confused concept is difference between Bonding, Grounding and Earthing. I then recall that my employer had specifically told me to bond all 4-square metal junction boxes together in this building. Issues crop up when equipment bonding/grounding and earthing are confused. For example, one very popular piece of test equipment is a receptacle tester consisting of three neon lights in a plug-in housing. • Grounding and bonding means that conductive parts are connected together and to the earth. Grounding can get really confusing. The requirements for grounding within a facility are covered by Article 250 of the NEC . The best guide for signal-reference grounding is IEEE Standard 1100-2006, “Recommended Practice for Powering and Grounding Electronic Equipment.”. Ground fault. The next step was to eliminate the wiring errors and install a ground wire from the source to the CNC machine (Fig. Notice in Fig. I am an Electrical Engineer and teach electrical classes occasionally,that is such an accurate and understandable explanation,I will use it in my classes,great job; Larry Strunk e.e. There is a bare, solid copper No. Search Products And Discover New Innovations In Your Industry. Art. The electronic equipment is then grounded to an earth ground isolated from the common power system ground. The grounded service conductor, grounded conductor(s), and equipment grounding conductor(s) are all bonded together at the service equipment enclosure; and are also connected to a grounding electrode. 0000006612 00000 n Bonding jumpers ensure a solid electrical connection between conductive parts. Instead, the basic concepts behind them will be examined, since once these are mastered, it becomes much easier to understand and apply the Code requirements. A standard multimeter cannot be used to measure this, since it does not give accurate resistance readings below 1 ohm, and is severely affected by the resistance of the test leads. 250. 250 easily claims that. Grounding diagram for a typical electrical system shows NEC-defined terminology. Electrical engineers and contractors can help customers avoid situations like this by providing proactive counsel in this area. Bonding (bonded). 250, 250.4(A)(2) and (3), 250.110, 404.9(A), 406.6, 404.9(A), 314.29, The Shocking Truth About Grounding Electrode Conductors. Other standards agree: ANSI/IEEE Standard 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems (Green Book) and Soares Book on Grounding use the same physics and electrical theory as Art. A major dilemma […], Electrical Continuing Education. It would be impossible to even begin to cover all of the detailed Code requirements relating to grounding and bonding. Manufacturing index hits highest point in two years, Top 5 Plant Engineering articles October 26 to November 1, 2020, How to match drives (VFDs, VSDs) to the motor, Six ways to improve cybersecurity: Barriers vs. resiliency, Project uses AI to strengthen global supply chains, How augmented, virtual reality can reduce manufacturing skills gap, Predictive model reveals function of energy harvester device. – The potential difference across insulation materials is limited. While conduit or metallic tubing can be used as the grounding conductor, it produces a higher impedance circuit and is less reliable than wires, due to poorer conductivity and threaded connections. 0000003620 00000 n 0000004844 00000 n The Table lists the percentage of total resistance and the touch voltage for the light pole in Fig. All Code references are based on the 2005 National Electrical Code. 2). If someone were to investigate which NEC Article suffers from the most misapplications, violations, and misinterpretations, they'd find that Art. Knowing that the NEC Code-Making-Panel was considering replacing this term with the word “earthing” gives us a good indication of just what the term is trying to relay to us: to wit, “grounding” means to provide a conductive path between electrical equipment and the earth. Manufacturers of sensitive machines have discovered that isolated ground rods can decrease the number of nuisance problems, such as rebooting, data errors, and intermittent shutdowns. For this scenario to make sense, you need to understand three concepts: touch voltage, hazardous level, and surface voltage gradients. An old adage says, “Words cannot hurt you,” but when it comes to grounding and bonding, not understanding certain words can hurt everyone. While the ideal arrangement for a sensitive computer might be an isolated ground wire to a separate earth electrode, this approach clearly violates the Code since the fault path would be through the earth. Obviously, if the ground circuit opens up when a fault occurs, then it is not able to perform its intended function. Coming posts will address this in more detail! Search Products And Discover New Innovations In Your Industry!! He can be reached at larry.ray@us.schneider-electric.com. 250 to ensure electrical conductivity between metal parts of the electrical installation. <<9D1918B5A5F9CB4E85A09FC06094FA44>]>> startxref great info but is bonding the enclosures ( J boxes ) better than using grounding bushings? Waterer is an Engineering Fellow for Schneider Electric's Square D Engineering Services, Norcross, Ga. The importance of bonding and grounding in commercial, industrial, and institutional buildings cannot be overstated. Where the NEC uses the term “grounding” to mean “connecting to the earth,” “earthing” will follow in parentheses. This refers to the means by which power source voltage relationships are established. I also have a piece on the difference between Arc fault and Ground Fault protection- how the Solid-State components work- the oscilloscope effect, and general theory. Understanding the difference between bonding/grounding and earthing requires implicit understanding of several important concepts and terms, including those outlined below. Grounding (earthing) electrode. Many times when the NEC says “grounding,” it's referring to bonding. All rights reserved. What is bonding? Grounding and bonding as electrical installation protocols overlap to a certain extent, but they are not identical. Knowing when to ground a generator is critical for operator safety. A variation of this convention will be used for “ground” and “grounded.”.

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