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Post by Peegoo 🏁 on Nov 26, 2022 10:33:46 GMT -5
This guy does a fantastic job of demonstrating how the neutral line of a residential AC mains circuit functions when properly and improperly implemented.
Even if you're not into this stuff, it's pretty fascinating to visualize with the model he uses.
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Post by Peegoo 🏁 on Nov 26, 2022 11:25:42 GMT -5
Here's another cool demo. If electronics components like capacitors and transistors boggle your brain, this makes it really easy to understand precisely how they function at their basic level.
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tmc
Wholenote
Posts: 993
Formerly Known As: tmc
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Post by tmc on Nov 26, 2022 20:26:41 GMT -5
I'm fascinated by this stuff!
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Post by roly on Nov 26, 2022 20:58:59 GMT -5
Thanks Mr. Goo.
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Post by markfromhawaii on Nov 28, 2022 11:09:25 GMT -5
Ah yes, the open neutral: The bane of utility trouble calls. Is it coming from the utility transformer tap to the meter, or is it on the customer side. Especially troublesome when it’s intermittent. Very dangerous in unbalanced load situations to a cooktop. When I worked at our utility, we noticed a several instances of corroded neutral lugs at the customer’s meter socket that caused the loose neutral condition. Retirement is good. 😉
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Post by slacker 🐨 on Nov 28, 2022 14:09:04 GMT -5
I was a bit confused by this. The outlets in every house I've lived in are wired one hot and one neutral. I'm assuming that the neutral's for the outlets are wired to a common neutral bus in the box. If you disconnected that none of my outlets would work, right? Same for the lights? If they continued to work, what's the circuit path for that?
Maybe I have a simplistic understanding, but I thought you had two hot lines, that are 180 degrees out of phase. From either one to neutral is 120V, from one hot to the other is 240V. So the 120v circuits would be dead if you disconnected the neutral bus, right? If they had a path through the other opposite phase hot you'd have 240v potential, right?
Was this not meant to represent house wiring or do I just not understand how it really works?
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Post by LeftyMeister on Nov 28, 2022 16:54:19 GMT -5
That was really good. I teach basic electricity and can just show this video in the beginning while I drink my coffee. lol! He mentioned that a lightbulb is a resistive load. He appears to be using incandescent bulbs. Technically, an incandescent bulb is a coil, so it's an inductive load. But the resistance is much higher than the reactance, so it is commonly called a resistive load. This terminally often confuses newbies.
Slacker, you're correct. He's actually showing a 4-wire system (L1, L2, N, & G). In a 120V system, the neutral and ground should be bonded, so you'll see three wires at the outlet or switch (ie, L1 or L2, N, & G), in which case lifting the neutral is akin to breaking the circuit, so the outlets would not work.
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Post by LeftyMeister on Nov 28, 2022 17:01:31 GMT -5
Regarding the second video, there are several analogies between water and electricity that make it effective for teaching:
1. They both like to find the path of least resistance.
2. They both like to find their way back to ground, or equilibrium.
3. The both respond to pressure (voltage), flow (amps), and resistance.
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Post by LeftyMeister on Nov 28, 2022 18:22:27 GMT -5
When I worked at our utility... Mark, with your background, I have a question that maybe you (or anyone else) can answer. My girlfriend's home is a 1890's farmhouse that has a heatpump and baseboard heaters to supplement when it gets really cold. A couple of the baseboards are hardwired for 240V and are rated at 6.25A at 1500W. She also has a couple of portable plug-in heaters @ 120V. They're also 1500W and double the current @ 12.5V. I understand ohm's law and why the current doubles at half the voltage. My question is does the doubled current cost twice as much on her electric bill? My understanding is the utility company charges based on kW per hour, so would both heaters cost the same to run? |
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Post by K4 on Nov 29, 2022 0:19:48 GMT -5
It is a watt meter or a power meter. So 1500 watts is 1500 watts, even if it is 1 volt and 1500 amps, or 1500 volts and 1 amp.
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Post by Peegoo 🏁 on Nov 29, 2022 1:54:31 GMT -5
I'm assuming that the neutral's for the outlets are wired to a common neutral bus in the box. If you disconnected that none of my outlets would work, right? Same for the lights? If they continued to work, what's the circuit path for that? They continue to work if they are connected in series (L1 to L2) as in the demo above. Note that the demo is DC power, so phasing is not a factor. Most homes these days are supplied with two live (hot) lines and one neutral line; ground comes from a ground rod in the earth at the foundation. The two hot lines are 180 degrees out of phase. If each live line is 120vAC, they can be combined to provide 240vAC for a clothes dryer or oven branch.  |
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Post by markfromhawaii on Nov 29, 2022 5:31:34 GMT -5
When I worked at our utility... Mark, with your background, I have a question that maybe you (or anyone else) can answer. My girlfriend's home is a 1890's farmhouse that has a heatpump and baseboard heaters to supplement when it gets really cold. A couple of the baseboards are hardwired for 240V and are rated at 6.25A at 1500W. She also has a couple of portable plug-in heaters @ 120V. They're also 1500W and double the current @ 12.5V. I understand ohm's law and why the current doubles at half the voltage. My question is does the doubled current cost twice as much on her electric bill? My understanding is the utility company charges based on kW per hour, so would both heaters cost the same to run? Lefty, there may be other surcharges that the utility imposes so it may not exactly be double. Also, some utilities charge more or less based upon certain kwh levels for residential rates. Here’s Hawaiian Electric’s Effective Rate Summary for October. Your utility probably publishes something similar. www.hawaiianelectric.com/documents/billing_and_payment/rates/effective_rate_summary/efs_2022_10.pdf |
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