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

[[email protected]]

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.

 

[TimPerry]

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.

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.

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?

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

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?

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).

 

[JohnR66]

Perhaps just a higher current crest factor due to the design of the supply
when operated on 120v.
John

 

[[email protected]]

|> 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.

 

[[email protected]]

| 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.

 

[[email protected]]

On Fri, 06 Apr 2007 20:04:20 -0400 [email protected] 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.

 

[[email protected]]

|> 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.

 

[Andrew Gabriel]

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
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.

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.

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.

 

[[email protected]]

|> 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.

 

[[email protected]]

| In article <[email protected]>,
|> 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.

 

[Andrew Gabriel]

| 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.

| 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.

 

[Andrew Gabriel]

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.

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]

It would be *very* interesting to find a tabulation of electrocutions
per terawatthour per year, especially categorized by voltage.

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.

Analysis
would be good, too - I understand the UK now has some extremely fascist
rules on who's allowed to do household wiring.

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.

 

[[email protected]]

| In article <[email protected]>,
| [email protected] writes:
|>| 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.