It seems that a lot of people are wondering what the difference is between Power over Ethernet and class 4 (the new class proposed by the NEC). Basically the difference is power; PoE is 90 W MAX, and class 4 systems are up to 450 Volts, unlimited wattage. Even though class 4 is more powerful, it still only requires the same safety precautions as poe because typically a computer monitors for fault in the wire (including human touch), and power is shut off if a fault occurs. This is what makes it intelligent. It's also a DC power system (not AC). DC works better with our digital devices, as well as LED lighting, and is more energy efficient for many reasons. If you have any questions, I'm happy to answer them. I write tech articles about this kind of thing all the time, and work with lots of engineers who love to answer questions from curious people
abandoning the general use of 120 vac wiring throughout residences
- Thread starter wyreman
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You might like DC but the supply to your residences is AC thus you have to convert it if you want DC. And that means an energy loss.
petersonra
Senior Member
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- Northern illinois
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- engineer
if i understand the way class 4 wiring works it is basically pulsed DC that has to be converted to straight DC at the end of the line. So you have to convert from AC to pulsed DC. Then it goes out on wires to whatever is receiving it where it is converted to straight DC.
There appear to be two advantages. One is that whatever protection features are needed for protection of life and property are built in, and it does not need electricians to run the cabling since it can be run pretty much as you please like class 2 wiring.
There appear to be two advantages. One is that whatever protection features are needed for protection of life and property are built in, and it does not need electricians to run the cabling since it can be run pretty much as you please like class 2 wiring.
- Location
- Illinois
- Occupation
- retired electrician
I thought it could be converted back to AC also.
As far as not needing electricians, that will vary a lot based on jurisdiction. In many areas, if it is in the code book it will require an licensed electrician of some sort to install those circuits. It may be a "low voltage" license or places like the small town I am in, will require the standard electrical license as we do not have a low voltage or other limited application license.
Let’s get this straight. Power is interrupted AFTER the system detects touch contact. Current is unlimited. So this is safer? Yes you won’t die from fibrillation. It will just break your limbs from the force of contracting muscles never mind the burning tissue! So much safer.
DC has two fundamental flaws.
Originally Edison started power distribution with DC generators he called dynamos. As stated it worked great with electric lighting. But distribution was limited to a couple hundred feet.
Tesla introduced the AC generator, AC motors, and proved that Edison’s lights worked just as well on AC. In addition it could be distributed over neatly unlimited distance with a transformer. This seems like the end of the story.
Much later Tesla raised the idea that HVDC was superior to AC but conversion was an issue. Today AEP runs a huge multistate HVDC transmission system. One problem solved.
Still LED lights and some electronics hardly compares to HVAC, water heaters, clothes washers and dryers, refrigerators and freezers, and various kitchen appliances all of which run on AC and consume the majority of power. At a minimum we know that AC to DC and DC to AC power losses are 5-6% (VFDs do this). Imagine if we saved 3% on lighting and electronics by going to DC but lose 5-6% on the majority of large loads in the residence. Excuse me if I fail to see how this makes sense.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
I suspect there is a sweet spot for class 4 wiring. I don't think it will replace all wiring, but it has the potential to replace a substantial part of the wiring of most homes, and maybe in commercial establishments..
My suspicion now is that between the unions and the contractors and all the other people that make money off of permits and inspections, it'll probably never be really economically feasible
My suspicion now is that between the unions and the contractors and all the other people that make money off of permits and inspections, it'll probably never be really economically feasible
brantmacga
Señor Member
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- Georgia
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- Former Child
I looked for it recently and couldn’t find it.
Someone asked me to rewire their 150/yr old 2-story home without cutting the walls or floors open. I passed on it.
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Yes I'm completely aware of that. Power lines distribute AC to buildings, and our individual loads that require DC have to convert the AC they get into the DC they need. Usually these conversions at the individual electrical load level are very inefficient, you're right. That's why there are systems, like the class 4 systems and PoE, that distribute DC power to devices that need it. This way loads don't have to convert the power they get (because they're already receiving DC). In many of these systems, there's just one conversion at the electrical panel level, bringing down the many conversions needed down to one. Hopefully that helps you better understand!
Hey Paul, many HVAC systems are run are DC motors. In fact HVAC systems with DC motors at 50% more efficient, so there's definitely an incentive for people to make the switch. In buildings (specially commercial buildings) that have HVAC systems with DC motors, as well as EV charging stations (which are becoming more common) about 74% of our building's loads are actually DC. And these systems all have to make inefficient conversions from AC to DC at the load level (wasting about 15 - 20% in consumed energy). So yes, distributing DC power does make a big difference in commercial buildings. Maybe not as much in homes, but reducing the carbon footprint of commercial buildings would make a big difference for our environment.
I see where you're coming from with the Class 4 thing, and I'm attaching an article for you that will help you understand how they work better:
class-4-power-and-differences-between-circuit-classes
New Class 4 power is different from Class 1, 2 and 3 circuits. Find out more about this new format of electricity.
www.belden.com
I'll give a quick summary: there's always a computer monitoring to make sure safety features are operating correctly. On top of that, the safety features involve sensors and monitoring tech etc. to monitor for faults like human touch. Power is stopped almost immediately in class 4 power systems if one of these faults is detected, so the person doesn't have much time to get burned, your limbs will not break, and your muscles probably wouldn't contract much either. Class 4 can be compared to saw stop (https://www.sawstop.com/), but for power. Maybe it seems too good to be true, but the truth is, we have the technology. The NEC wouldn't just approve something if it was BS.
I also want to mention that DC power is more safe to come in contact with than AC power because its electromagnetic field doesn't pulsate, collapse or change directions. These movements are forces that induce a current through an insulator like our skin. Since the electromagnetic field of DC power doesn't pulsate, it's more difficult for a current to be induced into our skin. Induction of an electrical current through our skin can react with our nervous system, and this is what makes an electrical shock happen and what makes it painful. Obviously it's not completely safe to touch an electrical current of any kind, but if you look of ElectricBOOMs videos on Youtube, I believe he even demonstrates this by touching a DC power line with his experimental equipment.
Here's his video on the subject:
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
as I understand it, the way these circuits work is that there is pulsed DC out to the receiver. So if it detects some kind of issue the person would only be connected to the DC voltage for one pulse which is on the order of milliseconds in duration.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
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- EC
You must have just crawled out from under a rock! With slick marketing and a lot of BS the NEC will write anything into the code just like they did with AFCIs. So, the fact that you finagled the NEC is no affirmation that your technology viable. In my opinion this whole "digital electricity" thing is a solution looking for a problem. Just a lot of "floobie dust" that some people think will make them rich.
-Hal
I never even said I was a proponent of digital electricity. That's just one class 4 system out there. I actually prefer Argentum Electronics's solution. But yeah, I am still learning from the engineers on my team, so I didn't realize there was so little faith in the NEC? I would imagine not everyone feels as pessimistic about it as you do, though.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
I think you will find a lot of skeptics here regarding the course the NEC has taken the last few decades. I am one of them.
Unfortunately, it is a mostly "volunteer" effort. So, to get any actual representation in the process basically means whomever the employer is basically has to pay for someone to be the volunteer. No employer does that without expecting to get something in return.
If you look at the makeup of the code making panels, it is entirely made up of people employed by entities that have a very serious financial interest at stake. There are hundreds, maybe thousands of people on these panels. As far as I know, not a single one of them is not employed by an entity that does not have an interest in making this stuff more expensive. I don't believe there is a single representative of the people actually paying for all of this "safety".
Helps me understand?
That's a little bit arrogant If I may say so. I spent over 50 years in the electrical industry mostly power electronics and all over the world. And you want me to understand your marketing expertise? Oh, wait a minute........I did a marketing degree as well as..........
Behave yourself..........................................
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I used a confusing double negative there. So, I corrected it.
Perhaps when I initially explained my point, I should've been more clear so you knew that I knew AC is delivered to buildings. The way you responded made it seem like you didn't understand that distributing DC power throughout a building would eliminate individual conversions at the load level, so yeah, I corrected you. Sorry if I hurt your ego.Helps me understand?
That's a little bit arrogant If I may say so. I spent over 50 years in the electrical industry mostly power electronics and all over the world. And you want me to understand your marketing expertise? Oh, wait a minute........I did a marketing degree as well as..........
Behave yourself..........................................
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
The thing is that except for a relative few loads, there is no real need or benefit to distributing DC power instead of AC power inside a building UNLESS there are cost effective utilization devices available and none exist yet. And I have no doubt whatsoever that the unions and contractors and inspectors will fight the use of class 4 circuits to the bitter end, or at least conspire to make it so expensive as to not be cost competitive.
It wasn't my ego that was the problem. And you still have the conversion energy to deal with whether it is several DC units or a single unit.
Yes, it's peanuts. Take a washing machine, a dishwasher, coffee machine, electric kettle............etc. None of which requires DC.
Abandoning AC power in residences is not an option.
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