Comments by "GH1618" (@GH-oi2jf) on "The Engineering Mindset" channel.

  1. If you had combination breakers on all the circuits, you would be covered and would not need the GFCI receptacles.
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  2. It’s the Amperes you have to worry about, not the Volts.
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  3. The neutral conductor is always at or near ground potential if there are no faults.
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  4. Everything with batteries is irrelevant in a discussion of AC wiring. In automobiles, the negative terminal of the battery is connected to chassis ground, but this is just a convention. There were some positive ground automobiles long ago.
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  5. It is more accurate to say the free electrons drift. They are moving all over the place, but there will be a net drift of electrons in an active circuit. They don’t move very far in an AC circuit.
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  6. You had better not.
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  7. Electronics is a different field with its own conventions. There are two symbols, one for chassis ground and one for Earth ground.
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  8. There has to be a circuit through the secondary of the transformer. The electricity takes all paths which complete the circuit in inverse proportion to their resistance. All paths which are nonconductive (infinite resistance at ordinary voltages) can be disregarded.
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  9. I think you are mistaken, however the NEC is an industry model code. Local codes may vary. The circuit shown is known as a Multiwire Branch Circuit. It is allowable, provided that the circuits use both phases and have a single disconnect.
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  10. It will probably blow the filament in the lamp.
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  11. An accurate physical model is beyond the scope of the subject, in my opinion. Practical electricity does not require an understanding of the physics. I agree that a bad model should not be presented. What is the point in that?
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  12. The GFCI compares the hot and neutral lines of its circuit and opens if there is a significant difference. A difference is an indication of a ground fault. I don’t know what you mean by “residual.”
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  13. The transformer secondary is the source of electromotive force. The neutral is grounded at the pole supporting the transformer and also at the customer’s service panel. Current normally flows in the neutral to complete a circuit with one of the supply lines, but if you touch a “hot” line you will make a circuit through the ground.
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  14. The neutral is a current-carrying conductor in normal operation. The ground wires should only carry fault current.
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  15. Don’t worry about color. The ground wire should be green (or bare copper, as here), but picture at 5:09 is otherwise good. The connections are what matter.
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  16. Ohm’s Law: E = IR. E is voltage; I is amperage; R is resistance in Ohms.
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  17. A current will flow wherever there is a potential difference. As he said, the path through ground is high resistance, so current will be low compared to through the neutral.
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  18. It is North American. Canada uses the same electrical system as the USA. I’m not sure about Mexico.
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  19. He is only concerned here with the customer side of the transformer, so has not explained the utility (primary) side fully. In the North American system, one side of the primary is connected to one phase of a 3-phase “WYE” distribution network. The other side is connected to the neutral of the 3-phase distribution network. The neutral of the secondary is connected to the 3-phase neutral, and to ground, so the neutral is connected from the substation to the customer’s wiring. You will often see only a single insulated bushing on the top of a pole-mounted transformer because the enclosure of the transformer is tied to neutral. The neutral wire is generally placed on the poles below the transformer, where it will be connected to the neutral terminal on the transformer.
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  20. Of what?
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  21. You can think of it either as single-phase with a center tap, or two-phase with a phase angle of 180°. The two conceptualizations are equivalent. The primary is fed by one phase of the 3-phase distribution network, so it is essentially a single phase transformer. We call the center-tapped secondary a “split phase.”
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  22. The code does not specify the orientation. Most people, including electricians, install them with the ground pin at the bottom.
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  23. wrong. There is a distinction. The neutral is a grounded current carrier.
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  24. It is called “neutral” because it is held at ground potential.
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  25.  @delanamanuel1451  — No, when you add lamps in parallel, the resistance drops and the current increases.
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  26. No, Earth is not hollow. Consult a book on geology.
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  27. If you are standing on the ground and touch an ungrounded conductor which is “hot,” you will have made a path for a current from the hot wire through your body to ground. “Hot” means that there is a potential difference from ground.
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  28. Electrons are charged particles. Like charges repel, so when the power company pushes electrons into the wires, the electrons already in the wires (the ones least tightly bound, that is) move along. Electrons don’t know anything about the source, they are just trying to equalize the forces on them caused by the charge imbalance. As it happens, the path of least resistance leads to another wire back to the transformer, so they move toward the source.
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  29. They are in series on a 240v circuit. For 120v circuits, only one is part of the circuit.
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  30. It is up to the power company to decide how to get the power to your house. It will be three wires from the final transformer. The 3-wire service cable can’t be run 2100 feet through the air. Are they putting in more poles or running it underground?
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  31. Ronald Schild — I think the “ground up” orientation is a convention observed by hospitals and preferred by some people. In a recent project, my electrician installed them ground down and the inspector didn’t have anything to say on the subject. I prefer ground down.
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  32. Time for an upgrade.
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  33. Mike Rosoft — From the point of view of the distribution system, it is 2-phase if they deliver two phases and the neutral. But when you connect the two lines to a 208V motor, that looks like a single phase to the motor. If you had a motor that took the two lines plus the neutral and had two 120V windings exploiting the phase shift between the lines, that would be a 2-phase motor. It is all a matter of perspective.
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  34. I call it “line.” We have free speech. Call it what you please.
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  35. Tubmaster 5000 — Ok, but was the neutral tied to ground at the service panel?
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  36. In the main breaker panel, the neutral bar is grounded by bonding it to the case. It doesn’t matter in that case, but it still seems wrong to me. You must not do that in a subpanel.
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  37. correct. He also misstated Coulomb.
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  38. You are correct.
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  39. Voltage is a potential difference between two points. The neutral is held at ground potential, so neutral to ground should be zero. Neutral to either hot wire is 120V.
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  40. No. If you have 3-phase service, you have three hot wires. Some places might have only single-phase service. The US had single-phase AC before we developed the split-phase system.
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  41. Look at the videos on the 240V/120V split phase system to see how neutrals work. The basic idea is that you want part of the circuit to be connected to earth so there is a known voltage on a “hot” wire relative to earth.
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  42. AC power at 60 Hz changes direction 120 times per second.
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  43. Wrong. This has been explained before. The neutral wire is the grounded conductor. It is always neutral. The “hot” wires have a significant potential difference from ground and the neutral conductor. They are always “hot.”
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  44. ⁠ @sulkel — Almost right. A Coulomb is 6.24 x 10^18 units of electric charge. An Ampere is a net charge movement of one Coulomb per second.
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  45. erik edwards — You don’t have a circuit without two wires. Whether Ac or DC, there is current in both wires. All “neutral” means is that the wire is held to ground potential.
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  46. It isn’t completely different, though. Just take away one hot wire, change the phase angle to 180° and lower the voltage and you have the North American split-phase configuration.
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  47. Do a little study and get your permit and inspections.
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  48. TheBaconBoss — The terminals are not “positive” and “negative” in AC. His demonstration using a battery could be done with it connected either way. It was just an illustration.
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  49. No need. Three-phase delta gives you efficient power transmission with only three wires. More phases would just use more wire with no real benefit.
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  50. The easiest way is to ask for an electronic energy meter from your power company, if you do not have one already. They can display instantaneous power.
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