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Hi, this is George with Argo, electrical services, and I am the surge protector guy. So, this is another podcast that we’re doing. And today we’d like to talk about ground and grounding. And also, you know, bonding. So, as electrician, it’s been in the industry for over 35 years, this still can be very confusing sometimes, especially to new people, new technicians or helpers, apprentices whatever you want to say. So the National Electrical Code defines ground as the Earth grounding is a conductive connection, intentional or accidental between a circuit or electrical equipment and the ground or some conductive object acting as the ground. So intentional means you know, we’re we’re putting a conductor to the ground the earth accidental is when we have a energized circuit, a live wire that goes to ground that means like you hear people talk about, oh, it’s a it’s a dead short, it’s grounded out. That means you’ve got a live wire that is not intended to go to ground or the elect grounding electrode system and and it causes the breaker to trip in an aeroplane for example, the fuse fuse fuselage acts as a ground correct grounding provides low impedance path for for ground fault current, section 250 dot 40 of the National Electrical Code. This section portrays the reasons for grounding and bonding electrical systems and equipment and it defines overall performance objectives. As an introduction for the specific rules detailed in the remainder of article 250, it includes grounded and ungrounded systems. So Section Two 50.4 section a grounded systems. System grounding is the connection to the ground Sado solidly or through impedance of current carrying conductors, the neutral point of a Wye connected transformer and the phase of a corner grounded delta connection. Okay, the purposes are to limit transient voltage or overcurrent over voltages due to lightning, land surges or accidental contacts with high voltage lines. It’s also to stabilize the voltage to Earth during regular operation, limiting the conductor length. And avoiding unnecessary bands and loops will reduce the impedance of the fault current path facilitating the operation of the overcurrent protective devices and ground detectors for impedance grounded systems. The routing of the bonding and grounding electrode conductors must not disturb the permanent path of the installation. The standard National Fire Protection Association 780 Dash 220 gives directions regarding grounding and bonding connections in lightning protection systems. equipment grounding is the connection to the ground of non current carrying conductive materials, cable trays, metallic conduits, junction boxes, transformer casings and motor frames. Bonding The purpose is to limit the conductive material voltage to ground equipment bonding is the connection between non carrying conductive materials and the supply source. The purpose is to establish an effective ground current path. To practice this practice will facilitate the operation of overcurrent protective devices and grounded to old ground attackers. The electrically conductive material and other equipment bonding connect non carry current carrying conductive materials that may become energized to this supply source. This The purpose is to establish an effective ground fault current path potential differences may harm people contacting two surfaces with different potential simultaneously bonding equalizes the potentials between the surfaces and avoiding the hazard. So this is in my words, the better your system is connected via grounding and bonding will protect humans and the components, machines electrical components in the system from serious damage and for ground or neutral wire becomes disconnected dislodge in the lab or hot wires still alive. When a technician or unknown human connects the grounded conductor back to ground, they are subject to get zapped frag stone, it has happened to me. You know back in the old days, you only had a hot wire and a neutral wire now we have a ground and this is all about having an alternative path back to ground. So we don’t get zapped when we’re changing out the outlet course it’s always best practice to turn the breaker off, unscrew the fuse whatever type system you’re working on, you know unless it is just 100% necessary to work on it. It makes absolutely positively no sense to do that. It only takes point 013 milliamps or something like that, to throw your heart into a field don’t gamble with your lie all right at the service equipment the service grounded conductor connects to the grounding electrode V me electrode conductor the bridge between the equipment grounding bus and the neutral or grounded bus via domain bonding jumper provides a ground reference to the electrical system exposed non current conductive materials and a path back of the transformer to supply source through the lat through the grounded service conductor for ground fault currents. making another connection from the grounding conductor to the utility transformer to a separate grounding electrode is typical, that is the ground wire coming down the light pole and into the ground rod beside the light pole at your home. Section two 50.4 Section A number five requires connecting the electrical equipment wiring and electrically conductive material expected to become energized forming a low impedance circuit and effective ground fault current path this circuit in the circuit enables the operation of the current devices or ground attackers, the low impedance circuit must carry the maximum ground fault current from any point where a ground fault arises to the electrical source. The NEC considers the that the Earth is not an effective ground fault current route the quantity of the quantity of current flowing to the earth back to the supply source during ground fault depends on the circuit voltage and the earth resistance. Since the earth resistance is high, and an arrangement between an arrangement using the Earth as the only path to return path to supply source will not carry enough current to clear the fall posing a dangerous voltage between metal parts and the ground. Hence, such an arrangement is not an effective ground fault current path for example 120 volt ground circuit grounded through a 25 own ground rod will produce a ground fault current of 120 volts divided by 25 ohms is 4.8 amps back to the back to the supply source. The low this low current magnitude will likely not trip the circuit breaker or melt the fuses. Once again to low current magnitude will likely not trip the circuit breaker or melt the fuses section two 50.4 B ungrounded systems equipment grounding is the connection of the non current conductive materials to the Earth The purpose is to limit the voltage to the ground and pressed by lightning or accidental contact with higher voltage lines. Equipment bonding connects the current carrying conductive materials and the supply system grounded equipment.
All right I know that’s a lot to suck in. The purpose is to establish a low impedance path to carry the maximum available ground fault current electrically conductive material and the other equipment bonding is the connection to this class system grounded equipment of the non current carrying conductive materials that may become energized. The purpose is to establish a low impedance path capable of carrying the maximum ground fault current section two 50.4 B four requires the connection of all the wiring electrical equipment and other electrically conductive material that become energized to establish a low impedance path to the power source. This practice facilitates the operation of the overcurrent protective devices in the event of a grant second ground fault in another phase, the Earth is not an effective ground fault current path. That’s the third time they’ve told us this section 250 dot 118 Five D poses conditions to use a flexible amount of conduit as an equipment grounding conductor. It prohibits using flexible metal conduit as an equipment grounding conductor, if its length exceeds more 1.8 meters, that’s about six foot This situation requires using a wire type equipment grounding conductor or a bonding jumper. This provides an effective ground fault current path. Okay, so right here, back in the day when I first started electrical work in the in the mid 80s. We I worked on commercial schools was my first job. We weren’t only schools and we would pull like circuit one, three and five from panel one a or whatever, right? So we would pull three hots one man, a black, three being a red five being a blue, we would pull one white, we would pull one ground wire, well, somewhere in that timeframe and the lady 80s, early 90s, maybe even the mid 90s That, you know, we began to we would pull a neutral for every circuit. So circuit one got its own neutral wire, circuit three got its own neutral wire circuit five got its own neutral wire, and then we would have one ground steel, I would go into industrial settings to where these guys back in the 50s and 60s, whenever they originally built some of these properties. They they were using the conduit, just like it talked about in the one point 1.8 meters of flexible metal conduit as a bonding jumper. They were using the conduit as a ground wire. It is still legal to do that. You know if everything is bonded correctly, now you’re talking about steel buildings with steel pipe and steel box is in the entire system to be connected. If you lose connection in there, we get back to that same thing where we talked about about the human conducting me in completing the circuit. So anyway, I know that was a lot to digest. A lot of this discussion bounced back into it mostly talked about commercial and industrial settings, more than residential. But I think this is important to get the concept of grounding and bonding. So we’ll be back shortly with another podcast continuing on from this point. My name is George Argo, I’m a surge protector guy. You can find me at Argo electrical.com My phone number is 770-596-1437 and I am the Gainesville Georgia electrician thanks
