On Mon, 26 Apr 2004 22:49:31 -0400 KR Williams wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Sun, 25 Apr 2004 20:17:53 -0400 KR Williams wrote: |> | In article , phil-news- |> | snipped-for-privacy@ipal.net says... |> |> On Sat, 24 Apr 2004 22:59:49 -0400 KR Williams wrote: |> |> |> |> | IIRC 600V wiring is required for all residential circuits. I |> |> | thought this was true for appliances too, but I could be wrong. |> |> | I'm not a power expert, as you've noted. |> |> |> |> I've seen wiring rated only 300 volts at the local big box store. |> | |> | Really? I thought all wiring hat to be rated for 600V. If |> | you're right, this isn't goodness. Again, if I'm wrong, I |> | appreciate you pointing out my errors! |> |> All I know is I have seen the wire with that rating available for sale. |> Whether it is allowed or not, I cannot say. I'd expect to have problems |> using it for 480 volts. | | Irrelevant. I believe all wire used in the US for even 120V | circuits must be rated at 600V. Show me otherwise.
Irrelevant. I've never claimed that any such wire is, or is not allowed or prohibited. I've only said that I have seen it on sale. If you want to see it, go to the Lowe's store.
|> If you would be comfortable with wire rated for 600 volts when using it |> on 480 volts, why not be comfortable with wire rated for 300 volts when |> using it on 240 volts? | | You're talking nonsense. Wire used for 120V (and as you noted | that 240 is simply two - 120V circuits) must be rated for 600V. | Perhaps an electrician can answer here.
So you have a 240/120 volt circuit. Nothing less that 600 volts is acceptable to you? (I'm _not_ asking if it is legal ... I'm asking if _you_ would be comfortable with that ... answer as if there was no law in place one way or the other). What if it's a 480/240 volt circuit? Would you insist on the voltage rating being 1200 volts?
| Certainly 765kV insulation would be a tad stronger stuff than | 600V. Please don't insult the readers here!
That's silly. 765 kilovolt insulation would be a whole lot stronger.
Certainly 300 volt insulation would be a tad weaker stuff than
600 volt insulation. But 240 volts is also a tad weaker than 480.
|> Having split windings and extra leads and a bigger wiring box might add |> $1.50 to the manufacture of the motor. I'm sure someone decided that |> cutting out that $1.50 on a few million units would save a lot of money |> or increase the profits if the savings is not passed on. | | Perhaps, but if Sears ships dual-voltage motors on its *cheapest* | power tools this seems unlikely. A packaged motor doesn't need | to be user-alterable. You may be right, but it seems strange.
Different markets. Buyers of dryers readily include a wide cross section of the population. Buyers of power tools tend to be men who are a bit more knowledgeable about what they are using it for.
|> |> |> The major room that won't have them is the bathroom (even though hair |> |> |> driers pull a power level that really should use 240 volts). |> |> | |> |> | I don't agree at all. Who needs more than a kW for a hair- |> |> | drier?! I'd rather *not* have 240V anywhere close to water. I |> |> | had 240V to my pool pump for the obvious reasons, but poolside |> |> | appliances ran off 120V. The 240V GFCI breakers were nutso too. |> |> |> |> It's only 120 volts to ground, same as a 120 volt circuit. |> | |> | Of course. Tell me something I don't know. That is indeed the |> | beauty of the system. One can split off the low-power circuits |> | from the high-power circuits and they all play nice. |> |> I still think you are confusing power and voltage. Everything that is |> low power can be made to run on higher voltage. 7 watt night light bulbs |> can be made in 240 volt versions. You can find them in Europe. | | Good grief! I'm an engineer with 30 years experience, though in | electronics and lately in microprocessor development (no power | experience; that was my dad and brother's business ;-).
Then maybe youa re saying "power" where you meant "voltage"?
| I do, however, know well the difference between power and | voltage. I also understand that one doesn't need high voltage | (and its risks) to distribute trivial power. Thus my contention | that the current "Edison" connection is a marvel of trade-offs. | In other words exceptional engineering, and continues to be after | *many* years. You've not convinced me that you're smarter then | Edison, even after some years.
Edison chose a center-neutral system for 2 reasons which are related to each other (one requirement necessitated the other). He wanted the voltage exposure to be kept low (apparently he thought 110 volts would low enough). He also wanted to reduce the cost of wire.
Simply compare the two systems:
- 240/120, center tap connected to ground and neutral.
There's 4 wires, 3 of which must have full current carrying rating.
- 240, center tap connected to ground.
There's 3 wires, 2 of which must have full current carrying rating.
The predominant shock hazard is ground fault. Both systems present the same voltage risk.
System number 2 reduces costs by eliminating a current carrying conductor. A neutral only carries current when the loads are not balanced. Attaching loads to both hot wires ensures balance.
System number 2 eliminates the still frequent hazard of "open neutral". If a current carrying wire becomes open, equipment abruptly stops functioning. System number 1 allows equipment to continue to function when there is an "open neutral" condition, when the loads are in balance. But once the loads are out of balance, a voltage imbalance exists, leading to damage or destruction of equipment, and in one case I have personally witnessed, a fire.
System number 2 presents a single voltage adequate for a full range of residential, and small commercial, loads. The advantage of having a single voltage, as opposed to the dual voltage of system number 1, is that it allows the use of three phase power in a compatible way by using a transformer in wye/star secondary configuration, with the center point grounded, and 3 hot wires with the same voltage (the voltage to ground will now be 15.47% higher).
Three phase is useful because it provides 15.47% more power with the same wiring capacity. Compare 2 three phase systems with 100 amp wires vs. 3 single phase systems with 100 amp wires. That's 72 kW vs. 83.1389 kW.
System number 2 reduces the effect of non-linear harmonic loads, which may balance poorly on single phase when loads are mismatched, and will balance badly or not at all in the three phase version. System number 2 makes three phase more viable as an alternative due to compatible voltages. With neutral-base systems, three phase does not give you both 240 and 120 volts (as you'd get in single phase) without using an awkward and limited capacity 240/120 delta system with a center tap on the A-to-C winding (high B leg).
If you have power from a 240Y/138.5 volt system, you could use 240 volt appliances that do not have a neutral on that. But you could not use 120 volt appliances safely at 138.5 volts. Likewise, if you have power from a 208Y/120 volt system, you get your 120 volt loads powered, by will be undervoltage on equipment probably designed for 240 volts. I've personally seen motors burn out due to this.
Of course most residences do not need three phase power. But the larger ones could use it if the voltage compatibility issues did not exist.
|> |> It won't |> |> make any difference near water. What do you think is wrong with 240 |> |> volt (2-pole) GFCI breakers? |> | |> | Nothing, except the expense. 2-pole GFCI breakers are |> | *expensive*. 120V GFCI outlets are dirt cheap. ...and work just |> | as well for small loads. |> |> Much of the expense would disappear with economy of scale if everything |> ran on 240 volts. And you could run things on half as many circuits. | | SO, what's your point? You're smarter than Edison? I thought | you were all for split-phase 120, which would put the conductors | at 60V? Of course that wouldn't be in any way compatible with | split-phase 240, so...
I believe that if Edison were to finally accept AC, and lived to this day, and understood why we added the grounding wire, he would realize the neutral wire was now moot. I don't claim to be smarter than Edison. I claim to live in an age when we know more about electricity, and have learned well how to deal with it.
Splitting 120 into 120/60 is partly and example, and partly a means to get certain advantages to a center grounded neutral-less system with devices that currently expect 120 volts (assuming they do not expect a particular wire to be neutral).
| I don't think you've thought your position through very well.
I've thought it through for quite some time. It even took me a while to be convinced after the idea had been suggested to be about three times by others. But as I worked through the math, and understood that we do in fact have some things doing this now (air conditioners, microwave opens, and other low end 240 volt appliances), it eventually became quite clear that the only reason we need a neutral today is because we have equipment that expects it. If we didn't have that, the neutral would be moot (and gone in my house).
|> |> Microwave ovens can be had for 240 volt, and that |> |> is my plan to get. |> | |> | I think mine could be wired for 240V, but that wasn't of interest |> | since the house is already standing. I wasn't about to re-wire |> | the place. |> |> No need to change things once they are in place. | | If you're going to change the "standard", as you've proposed | things *will* change.
I acknowledge that I am stuck with the neutral wire because it is not economically practical to change everything to not depend on it. But that doesn't mean I can't try to make at least small incremental improvements.
| |> |> And no, I don't want 240 volt in the bathroom, but |> |> the reason is because I don't think there ever will be any bathroom |> |> appliances for 240 volt (at least not in the USA). But otherwise I |> |> would have no objection to 240 volts there, as long as it is center |> |> tap grounded so the ground potential is only 120 volts. |> | |> | Absolutely. I see no reason for 240V anywhere that massive loads |> | aren't. AC units, sure. Hair driers, please. |> |> I'd go with 240 volts, if products are available wired safely for it. | | People aren't wired safely for it. Of course I'll now get the | usual euorpeon suggesting that 240V is somehow safer than half | that...
That people do not understand the system I propose, is part of the problem.
I consider the European system less safe than what I propose. That is mostly because of the 220-240 volts to ground.
|> Those designed for Europe may not be due to the grounded wire issue. |> Things designed for 240 volts specifically in the USA will be wired |> for it the way it is. | | Whatever that means. Of course things are designed to operate in | their native language!
To the extend that plugs are polarized in Europe, equipment may be designed to expect a certain wire to be the grounded one. That is a common case in the USA from years gone by. That's why one of the two slots in a 1-15R, 5-15R, or 5-20R, is longer than the other.
If such an appliance designed for 240 volts and a specific wire is grounded were plugged in to a system where both wires are hot, it could expose the user to 120 volts on the chassis or such, or even fault it directly to ground itself.
|> |> I'd almost consider having no outlets at all in the bathroom. But there |> |> are still people around with hair. |> | |> | I have a beard too. Gotta plug that Wahl-wart in somewhere! ;-) |> |> And those can be done on 240 volts, too. | | Sure, but the risk of electrocution is higher with the voltage. | Perhaps not significantly, but it cannot be less.
That risk exists only when contact with both hot wires is made over distant portions of the body subjecting the heart to the milliamps that can stop it. Such risks predominantly happen in the form of a ground fault, where someone touches a live chassis and a ground, such as water or a wet concrete floor, at the same time. As you know, it is situations like this that GFCI protection is now required. That would remain in neutral-less systems since that hazard is the same.
|> |> |> Sure, many things available that use 240 volts can also use 120 volts. |> |> |> But I prefer to use them at 240 volts regardless. The only things that |> |> |> I would be using at 120 volts are those that do not have any 240 volt |> |> |> versions (which is most things). |> |> | |> |> | I don't (prefer). I'd rather leave things at the lowest voltage |> |> | possible. 120V is just peachy for 90% of my uses. Dedicated |> |> | outlets (240V) work for the rest. |> |> |> |> Then why not run everything on 12 volts? |> | |> | Absurd. The occasional vacuum cleaner would object. |> |> Because of the amps. | | Of course. You admit your absurd position then?
I believe you were referring to a vacuum cleaner objecting to being designed for 12 volts, because it would draw 10 times the amps it would had it been designed for 120 volts.
Imagine a world where all power had been configured for 12 volts instead of 120 or 240. How heavy would the wires now have to be in order to handle that much current? It would be well more than 10 times the cross sectional areas because of I^2*R. If you only increase the wire by 10 times, you still have 10 times the disspation because of the I^2 part.
|> Stuff that is at the upper end of 15 amps on 120 volts is going to be |> on the upper end of 150 amps on 12 volts. That will be a whopper of a |> plug. OTOH, there are some nice IEC standards for pin and sleeve plugs |> up to 690 amps. I'm sure they are quite expensive, too. | | Expensive is not the idea. Safe is the idea. Safe enough, is | engineering.
How safe is a subjective judgement.
I do believe that the few small risks of a 240 volt no-neutral system are outweigh by both the economic (one less wire) and other safety (no more open-neutral risk) issues.
| I know exactly what you're proposing. I'm simply stating that it | is *nuts*. No benefit + major expense == poor engineering.
You should have already read all the benefits listed further above.
|> What I would have designed for the US or any other place, had I had the |> opportunity to make that decision back in the 1880's, would be a system |> which is center-grounded, no neutral, 2 or 3 hot wires at the same voltage, |> and that voltage would probably be picked at somewhere from 240 to 300. | | You stated that you'd have done a center-grounded 60V service. | In any case Edison did quite well. We have the same hot-ground | potential you advocate, and a cheap way of doubling the power | (and a lot more) to that which needs it, without more risk.
I threw it out as an example. I had been looking at it as a means to gain the noise reduction capabilities of it for 120 volt equipment. But I've found workarounds. One is to use 240 volts.
|> One problem is that when you have dual voltage systems, the ratio of the |> voltages is different between single phase and three phase. | | Who cares?! Transformers take care of all that trivia. | Residential circuits don't see such things, so what's your point?
Some residential circuits could gain advantanges of three phase. And comemrcial offices could also have the same voltage as homes.
|> What my idea |> would do is eliminate that difference so that you get the standard voltage |> whether you get single phase or three phase (unless you have industrial |> needs that require a step up in voltage). | | Good grief! Only commercial/industrial customers care about | anything different and many of them have different requirements.
Put your 240 volt stove on that 208 volt circuit at the office. Yuck ... only 75% of the power.
|> If I were to pick 260 as the |> standard, then single phase would be 130 volts to ground, and three phase |> would be 150 volts to ground. | | Who cares what you you have pulled out of your ass. It's still | not "equal" as you proposed above.
It would be the same line-to-line voltage everywhere. My proposal does not depend on any particular voltage choice as long as that choice is adequate for the big loads.
|> |> Instead of having a 240 volt transformer center tapped to give you |> |> two sides of 120, why not go with 120 volts center tapped at 60? |> |> Wouldn't that be even less of a shock hazard? |> | |> | Because perhaps it would make a mess of 240, when it's needed? |> |> But we could use 60 volts for small stuff. | | Ho you do that, he asked? Are you proposing to split the split? | If so, you'd better look at the neutrals!
I'm not actually proposing a 120/60 system. The 120/60 system is the strawman for those who claim 240 volts is dangerous, to see if they will stick with their fear. If you were to suggest that we would be better off with a 120/60 system, then I'd have to believe that you believe that a 240/120 is more dangerous enough to worry about.
But I believe you do not believe 240 is dangerous, but instead are just tossing that out as a bone.
|> I'd rather run really big stuff like the stove or water heater on 480. |> Actually I've found water heaters available for 480. | | You're nuts. Split-phase 240 is plenty for residential | installations. If you need more than this you're | commercial/industrial and soul be using something other then | electricity, in any case!
And three-phase 240 is plenty for larger residential (5000 sq ft and up) and office commercial (where lots of residential stuff still gets used).
Industrial is where a higher voltage would be needed.
|> |> |> BTW, shared neutral wiring effectively gets you the same benefit of less |> |> |> current for a given total (and balanced) load. Two 60 watt lights with |> |> |> one on each pole of a shared neutral 3-wire circuit will draw a total of |> |> |> 0.5 amps, the same as a 120 watt 240 volt light would. |> |> | |> |> | Obviously, but now I need both 120V and 240V lamps. No thanks. |> |> | Leave the trivial loads at 120V. |> |> |> |> That isn't a 240 volt lamp. That could be 2 120 volt lamps on each side |> |> of a shared neutral circuit. |> | |> | Now you're demanding that I need four-wire 240V to every outlet |> | in my house? I don't think so! |> |> 240 volts would be 2 wires plus ground, unless some part of the load needs |> 120 volts and has no integrated transformer to get it with. | | Why bother? Transformers are expensive and waste electricity. | ...likely more than the appliance (reading lamp, radio, or cell- | phone charger) plugged in!
If the electrical system were as I proposed, circuits would not be designed for getting 120 volts. Where they do need to have a lower voltage, and usually this is DC anyway, they already have to have a transformer. It would be trivial to make it have a 240 volt secondary.
And BTW, I have in fact seen 240 volt wall warts with 6-15P's.
|> | I think you're wandering around this whole issue, so perhaps |> | you'd better define what exactly your "perfect" house would look |> | like. |> |> Given today's appliance availability, it would be just more 240 volt |> circuits around than what would be considered normal, and I would use |> 240 volts on more things, where available. | | I'd put a 240 next to every window, if the house didn't have | central air. Otherwise there are very few places I'd bother with | 240. Perhaps an odd-ball under the kitchen sink (no clue for | what) and some in the basement for tools (easily added later). | Other than that I don't see any use for "two-forty-everywhere". | Me thinks you haven't thought this through as well as you | thought!
Under the kitchen sink is an unsafe place for any receptacle for which there is no equivalent within 24 inches on the countertop.
|> Were I to redesign the standard system, I'd go with the single standard |> voltage idea, probably 300/150 and 300Y/173. | | You keep saying such, but you certainly aren't convincing in your | arguments.
It's never easy to convince 100% of the people of anything. There are always a few holdouts.
|> I'm only comparing to show equivalency. I wouldn't want the shared neutral |> system. I'm just stating that the shock hazard is the same. | | | You keep shifting your proposal. I don't think you know what the | hell you're talking about, much less have thought it through.
Perhaps you are mixing examples with the proposal.
|> That wasn't what it was designed for. Edison designed it to save on wire. | | An admirable goal. Copper isn't free.
And now I can save even more.
|> He wanted everything to be on 110 volts, period. His idea was to have the |> neutral wire serve for what we use the grounding wire for today. | | Umm, the "Edison connection" is split-phase 220/240/whatever. | Are you telling me that Tesla invented it? ;-)
No. But a compatible AC system was used the same way. It worked as well as the DC system (plus the advantages of AC).
Too bad Edison didn't come up with the DC transformer.
|> My point |> is that given the grounding wire we have today, the neutral wire is not |> needed any more for anything but getting 1/2 or 1/1.732 voltage. Edison |> didn't want three phase power and didn't even want AC at all. If you want |> to really follow Edison, then wire up for 110 volts DC. | | Oh, that's why split-phase AC is called the "Edison connection". | Perhaps the dude one-upped Tesla?
Edison gets the credit for the split part, but not the phase part nor the AC part. Tesla merely pushed for AC. George Westinghouse bought into it and replaced Edison's DC system with a compatible AC system (same voltage and same split ... but now derived from lots of smaller transformers, and with a reduced fault current). AC also makes arc interruption easier.