4.8A @ 240V vs. 11.6A @ 120V - voltage efficiency

I was looking at a power supply on a big server box the other day and noted just how much power it seems to be wasting (presumably as heat as opposed
to some other means like microwave radiation or flashing lights). It had a listing with two voltage ranges, 100V-127V at 11.6A and 200V-240V at 4.8A.
I've seen several other power supplies, mostly from online tech specs, that either show some level of increased efficiency at the higher voltage(s), or at least no difference. Or is this really efficiency? Perhaps could it be the case that it simply can provide a little more current on the DC side when operated from the higher voltage? Any possibility that it's really a frequency issue (e.g. more efficient at 50 Hz for some reason)?
I really think this is increased efficiency at higher voltage due to higher currents at the lower voltage causing more heating. The few samples I have seen don't really give me a good sense of how widespread this is, and how much is lost over all power supplies on average. Anyone else have any real figures for this?
The National Electrical Code used in the USA has a restriction 210.6(A)(2) that limits the voltage between conductors to 120V for circuits supplying cord-and-plug connected loads using 1440V or less, in dwelling units. This a restriction I would like to see removed, or at least made substantially lower, so that people in the USA can have circuits to power computers that can run at a higher voltage for more efficiency, if they choose to do so. Otherwise people wanting to do this would have to either violate the rule, or be clever and try to get around it by claiming the circuit is, or could be, for some appliance that exceeds 1440 VA (where that "appliance" may be a UPS that subsequently supplies the computer(s)).
Finding proper surge protectors might be an issue. In theory I could use German standard equipment because I think surge protection does not care (much) about the frequency (e.g. 50 Hz vs. 60 Hz). Certainly it would care about the voltage, and this would be quite different between Germany and the US when looking at voltages relative to ground (where surges would presumably be shunted), making such protection substantially less effective.
A side question: Given that grounded plugs are reversible in Germany, do surge protection devices protect both power conductors with redundant parts or are the devices designed to require that the plug only be inserted one way (I've heard some UPSes require this and won't start if the plug is in the opposite way).
There's virtually no market for 240V wiring in the USA. Special circuits have to be installed to get that voltage and it won't be commonplace to get them already in place unless many appliances use it. But the appliances won't be made because almost no one can use them due to lack of circuits. That much is a common problem in deploying something new. The NEC rule is also in the way, and that probably needs to be changed before any of this can be possible.
Under the concept of energy efficiency, many jurisdictions in the USA are now pushing toward more energy efficient lighting like fluorescent lights. Unlike incandescent, these lights actually work better on higher voltages. There is also the NEC rule 210.6(A)(1) that blocks this. That one I think should be rephrased to apply to incandescent only. Inductive ballasts do come in multi voltage (separate wires per voltage). I presume electronic ballasts can be autoranging and handle anything up to 277 volts easily.
Probably the biggest issue in enabling more use of higher voltage in the USA is the variation. Some homes have 240 volts while a few (typically apartments and condos in large buildings) only have 208 volts. But at least this can still be handled by the few types of loads being considered for this (e.g. fluorescent lights with autoranging ballasts and computers with dual voltage or autoranging power supplies). The costs of switches for the fluorescent lights would be higher due to the need to switch both current carrying conductors, but once in mass production, they should be less of a cost increase than the up front costs of changing incandescent to fluorescent.
One side benefit of this is that more common availability of US style 240 volt circuits would reduce the need for special circuits under Article 647 of the NEC (these are the balanced power circuits with 60 volts between hot and ground and 120 volts between both hots). A lot of audio equipment now comes capable of international voltages these days.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You're making a very large number of extrapolations here on insufficient evidence:
noted

4.8A.
a
Nothing to do with 50 Hz vs. 60 Hz. I suspect the lower current rating at 240 V input is due to the rectifier input stage. You're looking at current input, not power input, which would be a better way to judge efficiency. The waveshape changes when you're trying to make a +300 V intermediate source from a voltage doubler driven by 120 V than by a full-wave rectifier driven by 240 V.

higher
have
how
real
You haven't got any indication of more efficiency at the higher voltage, though.

210.6(A)(2)
supplying
This
substantially
that
so
Why? No desktop and precious few servers draw more than 1440 VA; and if you need more power (aka Tim Taylor), you can always put a 240 volt outlet; electric dryers, ranges, air conditioners, etc. run off these quite happily with 30 Amp plug-in cord sets available at every lumberyard and home improvement store. That gives you 7200 VA, roughly - you haven't needed 7200 VA in a single computer cabinet since they got rid of the tubes.

use
care
Germany
would
effective.
Equipment approved for sale in Europe will not have UL (or CSA) stickers for sale in the United States (or Canada). Probably perfectly adqueate technically, but good luck getting fire insurance if you have a lot of non-approved gear in the house.

circuits
to get

Just about every household has 240 V available for the range, A/C, etc. - this is not unusual. Why do you need a kilowatt to run a computer anyway? That's not very energy-efficient in the first place - you're trying to find a solution to the wrong problem.
But the appliances

circuits.
rule is

this
The NEC (and CSA) are barely restraining the waves of stuff that manufacturers would otherwise produce; we certainly have no shortage of electrical gadgets now.

240
647
between
equipment
??? I'm baffled....these are installed for noise reduction, not general power outlets...for every kVA in a "balanced" circuit I bet there's at least an MVA in single-ended circuits.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
|> The National Electrical Code used in the USA has a restriction | 210.6(A)(2) |> that limits the voltage between conductors to 120V for circuits | supplying |> cord-and-plug connected loads using 1440V or less, in dwelling units. | This |> a restriction I would like to see removed, or at least made | substantially |> lower, so that people in the USA can have circuits to power computers | that |> can run at a higher voltage for more efficiency, if they choose to do | so | | Why? No desktop and precious few servers draw more than 1440 VA; and if | you need more power (aka Tim Taylor), you can always put a 240 volt | outlet; electric dryers, ranges, air conditioners, etc. run off these | quite happily with 30 Amp plug-in cord sets available at every | lumberyard and home improvement store. That gives you 7200 VA, roughly - | you haven't needed 7200 VA in a single computer cabinet since they got | rid of the tubes.
Why I want the rule changed or removed is _because_ "No desktop and precious few servers draw more than 1440 VA". But I don't want to put in the extra wiring and monster size outlet for 30 amps. I'll take a 20 or 15 amp outlet instead, wired on AWG #12.
|> Finding proper surge protectors might be an issue. In theory I could | use |> German standard equipment because I think surge protection does not | care |> (much) about the frequency (e.g. 50 Hz vs. 60 Hz). Certainly it would |> care about the voltage, and this would be quite different between | Germany |> and the US when looking at voltages relative to ground (where surges | would |> presumably be shunted), making such protection substantially less | effective. | | Equipment approved for sale in Europe will not have UL (or CSA) stickers | for sale in the United States (or Canada). Probably perfectly adqueate | technically, but good luck getting fire insurance if you have a lot of | non-approved gear in the house.
More and more stuff is on the market now days without any such stickers, anyway. And in many cases those that do are fraudulent. Better to have a genuine TUV than a false or absent UL.
|> There's virtually no market for 240V wiring in the USA. Special | circuits |> have to be installed to get that voltage and it won't be commonplace | to get |> them already in place unless many appliances use it. | | Just about every household has 240 V available for the range, A/C, | etc. - this is not unusual. Why do you need a kilowatt to run a | computer anyway? That's not very energy-efficient in the first place - | you're trying to find a solution to the wrong problem.
Who said I need a kilowatt to run a computer? If the circuits were allowed to be common (e.g. remove the NEC rule against them), then at least the market would get to decide. OK, I have multiple computers so I may well be exceeding the 1440 VA in total. Individually, no one computer comes close.
| But the appliances |> won't be made because almost no one can use them due to lack of | circuits. |> That much is a common problem in deploying something new. The NEC | rule is |> also in the way, and that probably needs to be changed before any of | this |> can be possible. | | The NEC (and CSA) are barely restraining the waves of stuff that | manufacturers would otherwise produce; we certainly have no shortage of | electrical gadgets now.
Many of which are far more dangerous than having an outlet that has TWO opposing poles of 120 volts relative to ground.
|> One side benefit of this is that more common availability of US style | 240 |> volt circuits would reduce the need for special circuits under Article | 647 |> of the NEC (these are the balanced power circuits with 60 volts | between |> hot and ground and 120 volts between both hots). A lot of audio | equipment |> now comes capable of international voltages these days. | | ??? I'm baffled....these are installed for noise reduction, not general | power outlets...for every kVA in a "balanced" circuit I bet there's at | least an MVA in single-ended circuits.
The point is, the 240 volt circuits wired to USA style is basically the same with respect to being balanced such that you will get the same kind of noise reduction. So if 240 volts are allowed to be used in the USA for loads under 1440 VA, then audio equipment could gain an advantage as well.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 6 Apr 2007 21:36:39 GMT, snipped-for-privacy@ipal.net wrote:

As a a practical matter how can anyone stop you from plugging in a PC to a NEMA 6-15 ? PC cords with 6-15 plugcaps are certainly available. We used them in computer rooms all the time where they did not want L/N loads on the same panels as the mainframes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 06 Apr 2007 20:04:20 -0400 snipped-for-privacy@aol.com wrote:
| As a a practical matter how can anyone stop you from plugging in a PC | to a NEMA 6-15 ? PC cords with 6-15 plugcaps are certainly available. | We used them in computer rooms all the time where they did not want | L/N loads on the same panels as the mainframes.
This is my plan. But I'd still rather get the rule dropped so it can be more widespread, at least to the extent the market is willing to do it.
What might the inspector say with 6-15R's installed in several places? I guess I'll find something that is over 1440 VA to claim it will be used at times. But once the circuit and outlet are in place, I'll plug computers in. Maybe I can find an appropriate UPS that is over 1440 VA and point to that.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

units.
computers
do
if
these
roughly -

got
What sort of computing machinery needs more than 1440 VA on a single cord set? The cost of a new plug is trivial - move over the range or the clothes dryer and you've got a 30 A 240 V outlet ready to use. The cost of 240 V outlets and wiring doesn't hold up the spread of 240 V through-wall A/C units.

effective.
stickers
adqueate
of
stickers,
have
Except when it comes to getting fire insurance...a genuine TUV sticker does nothing in North American jurisdictions.

commonplace
place -

YOU said it, just a few lines above!
If the circuits were

computers
But there IS no restriction - you can run 240 V outlets anywhere you like in a residence, since you already have a 120/240 system.

Because no-one needs them? Does anyone need a 5 kW hair dryer?

of
Looks to me that 240 V is perfectly feasible within the present wiring rules, and in fact already exists in most homes anyway....you're campaigning to remove a restriction that doesn't exist. Finding 240 V light bulbs might mean a trip to the downtown industrial supplier instead of stocking up at the supermarket, though.

of
TWO
You've lost me here...how is 240 V pole to pole, 120 V to ground more dangerous than 240 V pole to ground? I was told at an arc flash seminar that circuits around 100 V to ground rarely develop sustained arcs...200+ V to ground would seem to increase that risk.

style
Article
general
at
the
kind
as
What exactly is the problem you're trying to solve here? No-one is clamouring for balanced circuits in residential construction.

Your advocacy of the necessity for 240 V to ground in residential applications would be more understandable if I had some idea of what problem you're trying to solve, that can't already be solved within the exisiting code framework.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
|> Why I want the rule changed or removed is _because_ "No desktop and |> precious few servers draw more than 1440 VA". But I don't want to put |> in the extra wiring and monster size outlet for 30 amps. I'll take a |> 20 or 15 amp outlet instead, wired on AWG #12. |> | What sort of computing machinery needs more than 1440 VA on a single | cord set? The cost of a new plug is trivial - move over the range or | the clothes dryer and you've got a 30 A 240 V outlet ready to use. The | cost of 240 V outlets and wiring doesn't hold up the spread of 240 V | through-wall A/C units.
I think you still don't get it. You seem to think I am saying that my computer draws more than 1440 VA. But it does not. It's the NEC rule that prohibits the 240 outlets for loads that use less than 1440. Since the computers use less, the computers cannot be used to justify putting in a 240 volt outlet.
If I am going to put in dedicated ciruits for computers, I'd rather put in 20 amp circuits instead of higher amperage. But with 240 volt I only have to put in half as many (e.g. 1 instead of 2). And that means only 1 circuit dissipating some power because of the current flow instead of 2 doing that.
|> More and more stuff is on the market now days without any such | stickers, |> anyway. And in many cases those that do are fraudulent. Better to | have |> a genuine TUV than a false or absent UL. |> | | Except when it comes to getting fire insurance...a genuine TUV sticker | does nothing in North American jurisdictions.
Again, a very good reason to push for the rule removal as a first step in correcting these issues. It could open a market for the equipment based on 240 volts and get UL approval for them instead of having to import stuff that insurance companies are too ignorant to understand (and yes, it is ignorance by being too narrow to understand the meaning of other safety labels).
|> |> There's virtually no market for 240V wiring in the USA. Special |> | circuits |> |> have to be installed to get that voltage and it won't be | commonplace |> | to get |> |> them already in place unless many appliances use it. |> | |> | Just about every household has 240 V available for the range, A/C, |> | etc. - this is not unusual. Why do you need a kilowatt to run a |> | computer anyway? That's not very energy-efficient in the first | place - |> | you're trying to find a solution to the wrong problem. |> |> Who said I need a kilowatt to run a computer? | YOU said it, just a few lines above!
No I did not.
The NEC rule requires loads be more than 1440 VA for 240 loads in homes. I want to remove the rule so people can install circuits for loads that are smaller than 1440 VA, even as small as 144 VA (around what a computer might be).
| If the circuits were |> allowed to be common (e.g. remove the NEC rule against them), then |> at least the market would get to decide. OK, I have multiple | computers |> so I may well be exceeding the 1440 VA in total. Individually, no one |> computer comes close. |> | But there IS no restriction - you can run 240 V outlets anywhere you | like in a residence, since you already have a 120/240 system.
Try installing a 240 volt 15 amp dedicated circuit in your home, and indicate it is for a a few computers that each draw no more than 144 watts, and see what the AHJ inspector says about that with respect to NEC 210.6(A)(2). If he follows the rule to the letter, you get a red tag.
|> | But the appliances |> |> won't be made because almost no one can use them due to lack of |> | circuits. | | Because no-one needs them? Does anyone need a 5 kW hair dryer?
Again, you still misunderstand. I am not saying computers need lots of watts (aside from some very larger super servers like the one at work that draws 11.6 amps at 120 volts when it's power supply is presumably maxxed out).
| Looks to me that 240 V is perfectly feasible within the present wiring | rules, and in fact already exists in most homes anyway....you're | campaigning to remove a restriction that doesn't exist. Finding 240 V | light bulbs might mean a trip to the downtown industrial supplier | instead of stocking up at the supermarket, though.
The rule exists. It is NEC 210.6(A)(2). I suggest you read it.
|> | The NEC (and CSA) are barely restraining the waves of stuff that |> | manufacturers would otherwise produce; we certainly have no shortage | of |> | electrical gadgets now. |> |> Many of which are far more dangerous than having an outlet that has | TWO |> opposing poles of 120 volts relative to ground. |> | You've lost me here...how is 240 V pole to pole, 120 V to ground more | dangerous than 240 V pole to ground? I was told at an arc flash | seminar that circuits around 100 V to ground rarely develop sustained | arcs...200+ V to ground would seem to increase that risk.
Most shorts are from a wire to some kind of ground source, whether via wire or via people. Line to line shorts are more rare. And an arc at 240 volts still requires a rather close gap to sustain. Worry more about the 480 volt circuits.
| What exactly is the problem you're trying to solve here? No-one is | clamouring for balanced circuits in residential construction.
That is because most people don't know. And it does no good to promote them because existing rules prohibit both kinds in homes. What I am proposing is to remove one of those rules.
| Your advocacy of the necessity for 240 V to ground in residential | applications would be more understandable if I had some idea of what | problem you're trying to solve, that can't already be solved within the | exisiting code framework.
Wow, you got 2 things wrong in one sentence:
1. I've never said it is a necessity. I've said it is an advantage. 2. I never advocated 240 V to ground. I advocate 240 V line to line.
I advocate the removal of the rule 210.6(A)(2) so that homeowners have the option to use a 240 volt (line to line) circuit if they so choose for loads that are smaller than 1440 VA, including computers and audio equipment under 100 VA.
The problem is that there is very little equipment such as protectors and UPS devices for a 240 volt line to line system available. If the rule is removed, people _may_ choose (I never advocate forcing them to use it) a line to line 240 volt circuit to power more things. The existing code framework simply prohibits it, and so no market can very easily get established. And one of the advantages of doing this, to save on wasted power, is lost.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This clarifies things a little bit, although I still don't understand the need for 240 V desktops.

Since
putting
No, I didn't get it, my office's copy of the NEC has disappeared and I can't find a similar prohibition in the C22.1, which is the code I'm much more familiar with.

put
only
only
of
Lost me again - are you running a server farm or something? In a residence?

sticker
meaning
But you still haven't shown (to me, anyway) that there's any advantage to 240 V for hand-held or small appliances.

A/C,
homes.
that
computer
Wish I could find our NEC book - but I can't find a similar prohibition in CSA C22.1-06 anywhere in 26-710 and following rules.

Again, this is an NEC only rule - but I don't think it has a counterpart in Canadian code, at least after 5 minutes of searching my copy. Don't small window A/Cs in the 'States sometimes run on 240 V? But those would be over 1440 VA.

of
But what residential appliances, aside from server farms, would need 240 V? Looking around me I see table radios, stereos, table lamps, wall warts, and of course a laptop computer and printer. None of these machines particularly need 240 V to operate - I speculate wall warts are much better off at 120 V than at 240. I just looked at the electric kettle and it's claiming 1500 watts - now, in the UK they can have electric kettles running on 240 V but they fuse their cord sets at 6 Amps, so it works out to the same number of watts.
I really don't think proliferating residential outlet types is a good idea - you're going to wind up with the same weirdness that existed in the UK for years, when appliances were sold without plugs. With tens of millions of D-I-Y'ers in the US, I speculated you'd have thousands of accidents every year if there were two different voltage outlets in a large number of homes. Which is almost certainly why the NEC has the rule in the first place!

wiring
240 V

Yes, I've been combing the office for our NEC and no-one knows where it is.

more
sustained
So since line to ground shorts are more common than line-to-line, reducing the line-to-ground voltage would be a Good Thing, right? We already have a 120 V line-to-ground system - are you also advocating changing to 240 V line-to-ground?
480 V is not an issue since that's not found in residential occupancies - again, when I find our NEC, I will see what the scope of NEC 210 is.

promote
the
Clear enough. But there's no advantage to removing the rule, and as I mentioned above, K.I.S.S. is a very good rule especially for residential wiring. Nothing under 1440 VA works better at 240 V than at 120 V.

But there's NO wasted power! Your entire argument appears to be built on reading a sticker on a power supply and assuming higher efficiency at 240 V.
NEC is based on concensus, write in a proposal and see how far it goes....
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, I don't think you can buy an electric kettle in the UK less than 2000W, but 2400W and 3000W are the most common ratings. When I last looked around at worktop kitchen appliances in the US, the higher powered products used in Europe were simply not to be found in the US, probably because of the 1440W limit. For example, my quite standard (for the UK) Sharp microwave/grill/ fan oven didn't exist in the US, probably because it's over 2000W. Seemingly identical vacuum cleaners were lower power in the US too, although that may be slightly more related to the thickness/weight of flex which would otherwise be required.

Well, that in itself would cause the fault to take longer to clear, but it has to be tied together with earth fault loop impedance and characteristics of the protective device.
Actually, most of the serious electrical incidents are caused by overheating of connections. That problem is 4 times worse at half the voltage and double the current.

With the exception of filament lamps, the converse is equally true, or most of the world would not use 220-250V.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
|> But what residential appliances, aside from server farms, would need 240 |> V? Looking around me I see table radios, stereos, table lamps, wall |> warts, and of course a laptop computer and printer. None of these |> machines particularly need 240 V to operate - I speculate wall warts are |> much better off at 120 V than at 240. I just looked at the electric |> kettle and it's claiming 1500 watts - now, in the UK they can have |> electric kettles running on 240 V but they fuse their cord sets at 6 |> Amps, so it works out to the same number of watts. | | No, I don't think you can buy an electric kettle in the UK less | than 2000W, but 2400W and 3000W are the most common ratings. | When I last looked around at worktop kitchen appliances in the | US, the higher powered products used in Europe were simply not | to be found in the US, probably because of the 1440W limit. For
If you have a 20A circuit, it would be a 1920W limit. But lots of circuits are 15A, and something using even 1000W stands a chance of overloading a circuit and eventually tripping a breaker (we hope not any more than that). Many homes have a dedicated circuit for a heavy duty microwave oven.
|> So since line to ground shorts are more common than line-to-line, |> reducing the line-to-ground voltage would be a Good Thing, right? We | | Well, that in itself would cause the fault to take longer to clear, | but it has to be tied together with earth fault loop impedance and | characteristics of the protective device. | | Actually, most of the serious electrical incidents are caused by | overheating of connections. That problem is 4 times worse at half | the voltage and double the current.
Theoretically, that would argue for raising the voltage for everything. But then you might be trading off fire hazard for shock hazard. Such a thing would never really happen due to economics.
|> already have a 120 V line-to-ground system - are you also advocating |> changing to 240 V line-to-ground? | |> Clear enough. But there's no advantage to removing the rule, and as I |> mentioned above, K.I.S.S. is a very good rule especially for residential |> wiring. Nothing under 1440 VA works better at 240 V than at 120 V. | | With the exception of filament lamps, the converse is equally true, | or most of the world would not use 220-250V.
And those filament lamps tend to work even better at voltages down low like 12 volts or so. One just needs to minimize the amount of wiring between the drop-down transformer at the load.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
     snipped-for-privacy@ipal.net writes:

If risk of electrocution was significantly linked to mains voltage, then the US would have a much lower rate of electrocutions per capita than UK and other 220-250V countries. US actually has a higher rate of electrocution per capita than the UK (and probably most other EU countries). That's not to say US deaths wouldn't increase any further if US changed to 240V, but mains voltage is not the most significant factor in this.

The optimum design voltage for a 100W filament lamp is around 50V. However, redesigning power distribution systems for a 100 year old technology in its twilight years is probably rather silly.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It would be *very* interesting to find a tabulation of electrocutions per terawatthour per year, especially categorized by voltage. Analysis would be good, too - I understand the UK now has some extremely fascist rules on who's allowed to do household wiring.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Those are new, and no one takes any notice of them (most people don't even know of them). Actually, anyone can do wiring, but the local council has to pay to have it inspected unless the electrician payed his trade body membership fee, so as you can imagine, the councils have no interest in enforcing, and never wanted the rules in the first place.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's difficult enough finding any comparable measures between countries. I did a quick compare UK total accidental electrocution deaths per caipta against just US residential deaths per capita as that's all I could quickly find, but the US was still higher.

Those are new, and few take any notice of them (most people don't even know of them). Actually, anyone can do wiring, but the local council has to pay to have it inspected unless the electrician payed his trade body membership fee, so as you can imagine, many councils have no interest in enforcing, and never wanted the rules in the first place. We only have one year's statistics since the introduction of the new rules (Part P) and it shows an increase in deaths, verses a steady decline beforehand. This is exactly as predicted by those who analysed the UK government's faulty justification for Part P beforehand (including myself).
If you look back at the amount of domestic wiring done in the UK, the minority is done by electrical tradesmen, and the largest part of that is in newbuilds. There are nowhere near enough electricians to account for the majority of wiring as measured by volume of wiring accessories sold -- the majority of wiring for last 25 years has been DIY, with a further significant proportion attributable to non-electrican tradesmen.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
| snipped-for-privacy@ipal.net writes:
wrote: |>| Actually, most of the serious electrical incidents are caused by |>| overheating of connections. That problem is 4 times worse at half |>| the voltage and double the current. |> |> Theoretically, that would argue for raising the voltage for everything. |> But then you might be trading off fire hazard for shock hazard. | | If risk of electrocution was significantly linked to | mains voltage, then the US would have a much lower | rate of electrocutions per capita than UK and other | 220-250V countries. US actually has a higher rate of | electrocution per capita than the UK (and probably | most other EU countries). That's not to say US deaths | wouldn't increase any further if US changed to 240V, | but mains voltage is not the most significant factor | in this.
I think a factor there is that in UK and EU, much more concern exists over the electrocution risk, and better steps are taken to address it.
|>| With the exception of filament lamps, the converse is equally true, |>| or most of the world would not use 220-250V. |> |> And those filament lamps tend to work even better at voltages down low |> like 12 volts or so. One just needs to minimize the amount of wiring |> between the drop-down transformer at the load. | | The optimum design voltage for a 100W filament lamp is | around 50V. However, redesigning power distribution | systems for a 100 year old technology in its twilight | years is probably rather silly.
I have suggested that the optimum design was for a _current_ of 2 to 4 amps.
I'll still go with low voltage (12 volts) halogen.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8 Apr, 22:28, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

They are about the only application I can think of where 120V is better than 240V, and since they are rapidly becoming a thing of the past even in domestic use, and are getting close to extinct in industrial and commercial use except for specialised applications, e.g. stage lighting, this hardly seems to be a good reason for selecting 120V as a mains Voltage. I can certainly think of something drawing only a few hundred Watts, though it is somewhat off topic, as they are not widely used in domestic installations. I am talking about many types of dischage lamps, which we in the UK can run on simple inductive ballasts, but which need autotransformer type ballasts to operate on 120V. Of course, many installations of this type in the US operate on 277V anyway, and with the use of electronic high-frequency ballasts gradually spreading to large lamps this advantage may one day be a thing of the past.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
|> I think you still don't get it. You seem to think I am saying that my |> computer draws more than 1440 VA. But it does not. It's the NEC rule |> that prohibits the 240 outlets for loads that use less than 1440. | Since |> the computers use less, the computers cannot be used to justify | putting |> in a 240 volt outlet. |> | | No, I didn't get it, my office's copy of the NEC has disappeared and I | can't find a similar prohibition in the C22.1, which is the code I'm | much more familiar with.
Well, maybe there is no prohibition in that code.
|> If I am going to put in dedicated ciruits for computers, I'd rather | put |> in 20 amp circuits instead of higher amperage. But with 240 volt I | only |> have to put in half as many (e.g. 1 instead of 2). And that means | only |> 1 circuit dissipating some power because of the current flow instead | of |> 2 doing that. |> | | Lost me again - are you running a server farm or something? In a | residence?
Maybe I will be. But I want the option even if it's just 1 computer.
|> | |> | Except when it comes to getting fire insurance...a genuine TUV | sticker |> | does nothing in North American jurisdictions. |> |> Again, a very good reason to push for the rule removal as a first step |> in correcting these issues. It could open a market for the equipment |> based on 240 volts and get UL approval for them instead of having to |> import stuff that insurance companies are too ignorant to understand |> (and yes, it is ignorance by being too narrow to understand the | meaning |> of other safety labels). | | But you still haven't shown (to me, anyway) that there's any advantage | to 240 V for hand-held or small appliances.
For many appliances, I'm sure there is little (doesn't justify any change) or no advantage. But for some others there could be. Less current means less heat loss in wiring. Not much per circuit, but it all adds up.
|> | But there IS no restriction - you can run 240 V outlets anywhere you |> | like in a residence, since you already have a 120/240 system. |> |> Try installing a 240 volt 15 amp dedicated circuit in your home, and |> indicate it is for a a few computers that each draw no more than 144 |> watts, and see what the AHJ inspector says about that with respect to |> NEC 210.6(A)(2). If he follows the rule to the letter, you get a red |> tag. |> | Again, this is an NEC only rule - but I don't think it has a counterpart | in Canadian code, at least after 5 minutes of searching my copy. Don't | small window A/Cs in the 'States sometimes run on 240 V? But those | would be over 1440 VA.
Smaller A/C units work on 120 volts. Larger ones use 240 volts. In the 1960's my parents had 3 window A/C units in the house. The 2 smaller ones used 120 volts, but we had to put in dedicated circuits anyway to prevent occaisional blown fuses. The big one in the dining/living room used a 240 volt circuit.
IMHO, the option should exist, if the market chooses to do so, to use 240 volts for smaller units.
|> |> | But the appliances |> |> |> won't be made because almost no one can use them due to lack of |> |> | circuits. |> | |> | Because no-one needs them? Does anyone need a 5 kW hair dryer? |> |> Again, you still misunderstand. I am not saying computers need lots | of |> watts (aside from some very larger super servers like the one at work |> that draws 11.6 amps at 120 volts when it's power supply is presumably |> maxxed out). |> | But what residential appliances, aside from server farms, would need 240 | V? Looking around me I see table radios, stereos, table lamps, wall | warts, and of course a laptop computer and printer. None of these | machines particularly need 240 V to operate - I speculate wall warts are | much better off at 120 V than at 240. I just looked at the electric | kettle and it's claiming 1500 watts - now, in the UK they can have | electric kettles running on 240 V but they fuse their cord sets at 6 | Amps, so it works out to the same number of watts.
Why would wall warts be better off at 120 instead of 240, especially if they are the autoranging international models?
| I really don't think proliferating residential outlet types is a good | idea - you're going to wind up with the same weirdness that existed in | the UK for years, when appliances were sold without plugs. With tens | of millions of D-I-Y'ers in the US, I speculated you'd have thousands of | accidents every year if there were two different voltage outlets in a | large number of homes. Which is almost certainly why the NEC has the | rule in the first place!
UK changed the type of plug for a given voltage/amperage load combination. I don't recommend such a change. We do already have a lot of different plug configurations. I'm just suggesting the building wiring rules not be the factor in deciding which voltage is used, up to some reasonable level. In UK it is have 240 relative to ground. In the USA and Canada the 240 is two live wires at opposite phase angles 120 relative to ground that are 240 volts between them. As I understand it, the UK outdoor work tool voltage is like that, but 55 volts relative to ground for a total of 110 volts line to line, reducing the ground fault shock hazard a lot. Our 240 volt system doesn't raise that shock hazard over what we already have with 120 volts.
|> | You've lost me here...how is 240 V pole to pole, 120 V to ground | more |> | dangerous than 240 V pole to ground? I was told at an arc flash |> | seminar that circuits around 100 V to ground rarely develop | sustained |> | arcs...200+ V to ground would seem to increase that risk. |> |> Most shorts are from a wire to some kind of ground source, whether |> via wire or via people. Line to line shorts are more rare. And an |> arc at 240 volts still requires a rather close gap to sustain. |> Worry more about the 480 volt circuits. |> | So since line to ground shorts are more common than line-to-line, | reducing the line-to-ground voltage would be a Good Thing, right? We | already have a 120 V line-to-ground system - are you also advocating | changing to 240 V line-to-ground?
No. I advocate staying with the existing system in the USA and having 240 volts with 2 opposite phase angles that are only 120 volts relative to ground each.
| Clear enough. But there's no advantage to removing the rule, and as I | mentioned above, K.I.S.S. is a very good rule especially for residential | wiring. Nothing under 1440 VA works better at 240 V than at 120 V.
I disagree. Many switchable or autoranging power supplies to work better at 240 volts. I also believe whether we have or don't have 240 volt devices should be a market forces decision. If no one wants anything running from 240 volts, then no one will make anything that way. But I suspect it will come to exist somewhat slowly. Computer power supplies and many other appliances will work correctly when given 240 volts either by the UK system (240 L-N) or the USA system (240 L-L). And many work better at that voltage. The big show stopper would be people putting in such wiring. But I think over time many will as they import appliances from places like UK, India, and China, that run on 240 volts.
|> The problem is that there is very little equipment such as protectors |> and UPS devices for a 240 volt line to line system available. If the |> rule is removed, people _may_ choose (I never advocate forcing them |> to use it) a line to line 240 volt circuit to power more things. The |> existing code framework simply prohibits it, and so no market can very |> easily get established. And one of the advantages of doing this, to |> save on wasted power, is lost. | | But there's NO wasted power! Your entire argument appears to be built | on reading a sticker on a power supply and assuming higher efficiency at | 240 V.
For the same DC power provided, it is very plausible for the power supply to produce more heat when running at a voltage that requires more current through the internal transformer wiring. I've already seen specific figures of efficiency as a percentage for power supplies from web site specifications, which in a great many cases lists a higher efficiency when operated at a higher voltage. This tends to be for the autoranging units as opposed to those with the "115/230" switch.
| NEC is based on concensus, write in a proposal and see how far it | goes....
Perhaps. Right now I'm discussing it here to see what other issues might exist. One certainly seems to be a lot of lack of understanding. But what I might do is propose it in another venue ... that of lawmaking when some new energy saving law is being proposed. There is now talk of prohibiting certain wattage ranges for incandescent lights nationwide (they already are deploying such a law in California). I suspect fluorescent lights may work better on 240 volts, although it may be harder to get people to use that voltage in the US due to the need for double-pole switches since two lines are hot. Again, I just want the option to exist in the marketplace.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
noted

a
maximum input current ratings don't translate well to power supply efficiency to a fixed load. you would need to measure input power and output power under both 120 and 240 volt conditions to determine if a difference in the power supply efficiency exists.

that
or
Or is this really efficiency? Perhaps could it be

the curent on the DC side is determined by the load (mostly) assuming a voltage regulated supply. at a higher input voltage to a pass element (regulater transistor) i would expect to see lower EFF do to increased heating in the element. many supplies switch taps to a primary of a transformer to provide the same voltage to the secondary when selected for the different voltage range.
'universal' switching supplies are becoming very common in newer equipment. these operate 110 to 240 with no switching or rewiring necessary.
Any possibility that it's really a

higher
have
real
Phil, as far as power supply efficiency is concerned the design is more relevant then the input voltage. for example switching supplies are more efficient than linier (usually).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
| Phil, as far as power supply efficiency is concerned the design is more | relevant then the input voltage. for example switching supplies are more | efficient than linier (usually).
And so I would not propose a linear P/S design for a computer or most other DC loads. But I still do believe that there is a bit more efficiency to be gained with the higher supply voltage being used.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Perhaps just a higher current crest factor due to the design of the supply when operated on 120v. John


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.