US system is not as inefficient as I once thought



BTU/hr is still referred to in much of Europe at least (maybe all, but I don't claim to know it all). However, I don't think it is ever quoted without also quoting the equivalent kW rating. In my experience in last 5 years in UK, it's normally worked out in kW now, but you do get the odd appliance (typically a US computer system) which only gives you its requirements in BTU/hr and you have to convert.
--
Andrew Gabriel

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On 6 Oct 2003 13:34:51 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Then to really add to confusion, the British Government's Board of Trade many years ago established the Board of Trade unit (sometimes erroneously called BTU!) meaning 1 kWh, hence the term 'units' of electricity is quite common.
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Robert Calvert wrote:

Maybe the BTU's are going the way of the Horsepower. Now, you can get a 7-1/2 HP compressor that runs on a 15 amp 120 volt circuit. (Note to John - that's SINGLE phase) A knowledgeable salesman at Sears explained it to me, "Them are Madison Avenue Horsepower."
I've also noticed that 12 ounce steaks at the restaurants are getting smaller as well.
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However an insulation sufficient to block 5000 volts would be substancial. And God help you if your dog chews through a lamp cord.
Tim

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| However an insulation sufficient to block 5000 volts would be substancial. | And God help you if your dog chews through a lamp cord.
You'd definitely need help scraping the mess off the walls :-)
There are definitely some cases where lower voltage is better. Consider a light bulb suitable for ever higher voltages. A 100 watt filament for 5000v would be thinner and/or longer than a 4 watt filament for 120v.
I do think a higher voltage is more suited to larger appliances in a home. Incandescent lighting and some smaller devices would be better at a lower voltage. I have posted before about the system design I would have made if I had the opportunity to do so without legacy economic impact (e.g. if I could go back via a time machine and make the early system design decision). The system I would have would be a dual-voltage system in the home. Larger loads would always be connected line-to-line at 288 volts. That would be 144 volts relative to ground on single phase supplies, or 166 volts relative to ground on three phase supplies. This might even be made higher such as 360 volts (180 or 208 volts to ground). The lower voltage would always be single phase with 12 volts relative to ground (but might be set up as dual phased with 12-0-12 for 24 volts line-to-line). This would primarily be used for incandescent lights up to 60 watts, electric shavers, small tools, and small appliance wall-warts. Larger appliances would use the 288 volt system. The service drop would be 288 volts, and the 12 or 12/24 system would be derived from it.
So with the above system, would you find 288 volts, or maybe even 360 volts, acceptable?
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Yes, I agree Phil. I was trying ti imagine an entire residential system at elevated voltages. And boy, I could sure put good use to that time machine if you ever find it! Make wine today, push a button and instant aged! drink it, then go back. Wat-a-plan!
Tim Gard


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at
machine
Unless you have a super energy hog of a home (e.g.: resistance heating or electrically powered demand water heater) a 200 amp service is "Plenty". The reality is that most familys would not see any difference to their life styles had they only a 100 amp service.
I definitely would like to see more 240 volt appliances to include dish washing machines and "super" microwave ovens. But 120/240 is "pretty good."

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| Unless you have a super energy hog of a home (e.g.: resistance heating or | electrically powered demand water heater) a 200 amp service is "Plenty". | The reality is that most familys would not see any difference to their life | styles had they only a 100 amp service. | | I definitely would like to see more 240 volt appliances to include dish | washing machines and "super" microwave ovens. But 120/240 is "pretty | good."
I have seen microwave ovens that use 240 volt. But they were big ones, probably with a lot of power. I'd like to see more appliances available in 240 volt (6-15P or more as the case may need to be) versions. One thing that will need to be changed for that is removal of NEC 210.6(A)(2).
My big beef is against anything that needs a 3-wire supply (dual voltage). But, I do read from computer power supply specs that most of them are more efficient on a 220-240 volt power source (though not enough so to justify using a step-up transformer to get it).
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What, pray, does it say?

Exactly.
"Standard" US electric clothes dryers have 240 heaters but 120 volt motors and timers/electronics. Electric stoves have 240 heaters but 120 volt timers/electronics. That might have something to do with the fact that in a significant part of the market (condos, in particular) you don't get 240 volts but only 208. Running a 240 volt motor on 208 is asking for trouble. Running a 240 heater at 208 doesn't make much difference and in any case it isn't a "big deal" to substitute a 208 volt heater.
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| | |> |> I have seen microwave ovens that use 240 volt. But they were big ones, |> probably with a lot of power. I'd like to see more appliances available |> in 240 volt (6-15P or more as the case may need to be) versions. One |> thing that will need to be changed for that is removal of NEC 210.6(A)(2). | | What, pray, does it say?
You couldn't look it up?
Basically it says that circuits cannot be wired to supply voltage in excess of 120 volts between conductors for loads less than 1440 VA. That means for smaller appliances, we're stuck with 120V only, unless we try to get clever and insist that our 2000W 240V 6-15P welder is portable enough to use in every room of the house :-)
|> My big beef is against anything that needs a 3-wire supply (dual voltage). | | Exactly. | | "Standard" US electric clothes dryers have 240 heaters but 120 volt motors | and timers/electronics. Electric stoves have 240 heaters but 120 volt | timers/electronics. That might have something to do with the fact that in | a significant part of the market (condos, in particular) you don't get 240 | volts but only 208. Running a 240 volt motor on 208 is asking for trouble. | Running a 240 heater at 208 doesn't make much difference and in any case it | isn't a "big deal" to substitute a 208 volt heater.
OTOH, if all of the load is well balanced over the 2 line conductors, that should be more efficient even for the same load.
Europe has proof that the electronics can run on 240 volts. So can motors (but 208 volt versions would be needed). So can light bulbs safely if they are of the bi-pin type (though at the small wattages, a low voltage from a tiny transformer might be better).
A true two-wire applicance could still be shipped with a 14-XXP cord, but you could substitute a 6-XXP for it (I would).
Ever seen a 14-15R receptacle. Try plugging a 6-15P into it. It fits!
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On 14 Mar 2007 20:10:34 GMT, snipped-for-privacy@ipal.net wrote:

Australia has been 240VAC only for domestic use since before I was born. I'm really glad we don't have to screw around with multiple voltages in homes.
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W "Some people are alive only because it is illegal to kill them."
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Well, what all books say, is, that the voltage is stepped up from the alternator at the power plant (usually ~21 kV for ~300 MW units)to several hundreds of kV (usually 150 kV,220 kV and 400 kV)to make transmission of large amounts of power more efficient then stepped down at 15kV for primary distribution, then stepped down at 400/230 volt for secondary distribution (at least on this side of the pond).This is, I think, as efficient it can be, from the very start.(Each stage has efficiency close to 99%).The final domestic voltage (low voltage,LV)is selected for safety mostly...Here, in EU, you can have in your home 3-phase to drive large A/Cs or whatever, and the same type of distribution is used for industrial areas...Large hotels/industries or whatever are supplied directly from 15kV and do their own transforming, and even larger (half a dozen for all of Greece)are supplied from 150 kV.Of course, the hotel load of, say, a brown coal power station, consists of ~two dozen 1MW 6.6kV (6600 volt motors).Even at that voltage the motors draw like, 150 A each phase.That voltage of course, is extremely dangerous, and when someone is working on such a motor, they take the whole circuit breaker out of its bus bars, on a trolley like a supermarket (trolley), so that no one turns the motor on.Even if you don't touch the contacts and the motor is energized, imagine being pulled by a shaft of a 1500 HP motor...
-- Tzortzakakis Dimitrios major in electrical engineering mechanized infantry reservist dimtzort AT otenet DOT gr
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I don't know.. but I would love to go there for a few years or so to find out!
Anyone from down under wanna pay for a grant for a Yank to come and watch the electrons flow?
Pretty sure I could watch them from the beach most of the time! :o)
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I read in sci.engr.electrical.compliance that Robert Calvert
about 'US system is not as inefficient as I once thought', on Tue, 30 Sep 2003:

The extra copper involved is your neutral. Your 'two hot wires' correspond to the European live and neutral.

The European distribution system is quite different from that in US. Power is distributed *extensively* as 3-phase 230/400 V. There may be 500 customers on one MV/LV or HV/LV transformer. In US, power is distributed extensively at MV (several kV) and small transformers feed 1 to maybe 4 customers.
Converting a European distribution network to effectively a six-phase system would be vastly expensive, and there are serious safety issues with 460 V supplies in the home. One advantage of the 120 V supply is that a shock from it is not so likely to be fatal.
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Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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you
Hang on a sec.. Excuse my ignorance, but are you saying that there is no neutral in the US 120/240V system?
What's the return path? Ground??
Thanks, Cameron:-)
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I read in sci.engr.electrical.compliance that Cameron Dorrough
ect.com.au>) about 'US system is not as inefficient as I once thought', on Tue, 30 Sep 2003:

Of course there is. It is the neutral which is the extra conductor needed in the US system compared with the European single-phase system.

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Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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That would give you 230v to earth, which is a larger danger than 120V.
My home laboratory is wired with balanced 60v out of phase legs to hot and neutral. This greatly reduces electrical noise.
--
Guy Macon, Electronics Engineer & Project Manager. Remember Doc Brown
from the 'Back to the Future' movies? Do you have an "impossible"
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"Guy Macon" <http://www.guymacon.com/ wrote in message says...

and
120.
Europeans already have this.
Robert

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This supply type was used for some farms in the UK in the case where only a single phase HV supply was available to the final stepdown transformer. It would not be installed today, and it was never the preferred option AFAIK. Farm machinary was often available in 480V versions specifically for this supply type.
--
Andrew Gabriel

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European has not though of this for the reason that three phase power feeding is here very typical way to distribute power. A typical electrical distirbution panel get in three phase power: three phase conductors and one neutral/ground.
There is 230V from one live to neutral. And 400V between two live wires.
In ideal three phase power where all single phase loads are similar the neutral current is zero. In case of not so evenly loaded loads, the neutral current is from zero to one phase current maximum.
Normal household loads are single phase. Large loads use three phase power.
This is well working and efficient way to distribute power.
--
Tomi Engdahl (http://www.iki.fi/then /)
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