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120 V or 240 V Mains - which voltage is better?

DGM said:
In the US there might not be 3 phase available in residential areas for miles. In a small shop, generating your own is often the only economically viable choice.

It cost me around $2000usd to bring it to my shop from around 1/4 mile away.
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Seems us Ozzies have the advantage there- apart from REALLY remote areas, 3 phase is only meters away and it is only the cost of having the wiring to the house and the fusebox rewired for the 3 phase meter thats an issue- and thats really only the case in older houses, anything built in the last 15 years or so pretty much has 3 phase connected as standard if you are in an area that aircon is popular
 
Dabop said:
I must say apart from 75 year old railway equipment that ran on 110v, its almost unheard of here...
industrial control in the modern world is almost exclusively 24vdc

http://w3.siemens.com/mcms/industri...terface/as-interface/pages/netzteile-24v.aspx
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Yes it's the same here - in a new factory all the control systems are 24V DC - but it's surprising how often I still run across 110V systems in old factories.

Sometimes even new panels are specified with at least some of the controls working at 110V. It's usually the case that, say, five or so major upgrades have been installed over the last fifty years at about ten-year intervals and even though none of the original fifty-year-old stuff now remains, at each of the upgrade stages the then new panels were specified as 110V to maintain compatibility with the existing ones.
 
Dabop said:
Seems us Ozzies have the advantage there- apart from REALLY remote areas, 3 phase is only meters away and it is only the cost of having the wiring to the house and the fusebox rewired for the 3 phase meter thats an issue- and thats really only the case in older houses, anything built in the last 15 years or so pretty much has 3 phase connected as standard if you are in an area that aircon is popular
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My house is on single phase only. Even though 3 phase power lines run past every house, I suspect that the electricity companies bill every customer for 3 phase power but only connect single phase if they can get away with it (after all, it's still the same amount of electricity).

When I went solar, I had the option of installing a 3 phase inverter but since my ducted air-cooling system (swampy) only has a single phase motor (no problems with it) I decided not to go with the additional expense. When battery storage technology becomes cheap enough, I may reconsider.
 
Dabop said:
Seems us Ozzies have the advantage there- apart from REALLY remote areas, 3 phase is only meters away and it is only the cost of having the wiring to the house and the fusebox rewired for the 3 phase meter thats an issue- and thats really only the case in older houses, anything built in the last 15 years or so pretty much has 3 phase connected as standard if you are in an area that aircon is popular
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It's really not need in residential applications. Single phase 220 (I'm not getting into the peeing contest what it's called) is standard and available almost everywhere.
 
agghhh the joys of product support
I know it all too well

only recently I sold my last 'new old stock' 5 1/4" floppy drive to a local store to replace their failing one
A full height 5 1/4 floppy. 360kb...

its in a original IBM XT- still in daily use as their cash register/inventory control- using a program written (by me) in BASIC- when I was in high school...

I'm looking at retiring in the next few years....
 
DGM said:
It's really not need in residential applications. Single phase 220 (I'm not getting into the peeing contest what it's called) is standard and available almost everywhere.
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Well considering that is effectively the equivalent of our 415 3 phase supply....

Again to go back to the OP of this thread- it costs you yanks a lot to stay at such low voltages- your household wiring has to be thicker to do the same amount of work- and copper is expensive...
Your street lines have to be heavier 'gauge' than ours, and you need more transformers to avoid voltage drops...

All for the dubious 'its safer' altho either 110 or 240v can kill you- and you still run 240 into almost every home for aircon, cookers etc- adding extra complexity and the chance that the circuits could intermix...
 
I'm not arguing the fact it's more costly. I think it's more of a fear with most people here that more voltage is more dangerous.

The wire is the small part of our expense. We now require "arc-fault" and GFI protection on a large portions of our house circuits.
 
Beerina said:
It's to stop you from insta-dying if you get shocked. Or at least reduce your chances.

US houses typically have 240 available for electric stoves, and general home equipment is 120.


My dad, rest his soul, as a child (this would be mid 1940s) fell in the tub, dropping a radio in with him. My grandmother had to run down into the basement and flip the main off.

I'll leave it to you as to whether the 120 volts killed my father when he was 6 or not. :)
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Easy fixed. Mandatory Earth Leakage Current Detectors.
 
I read in a museum about a weird DC system installed as an experiment in a small residential area in the early days of electric power.

It was a constant current system! There was a fixed 10-amp supply that flowed through your house (and all your neighbor's houses) and all your appliances were connected in series! You switched an appliance off by shorting it out so that the current took the easiest path through the switch rather than the higher resistance path through the appliance.

You paid for your electricity according to how many volts were dropped as the current passed through your house (the electricity meter measured volts and time rather than current and time like our modern meters). When every appliance was shorted out you only dropped a few volts through you whole house as the electricity passed through all the shorting switches so it didn't cost much.

The system obviously had tremendous drawbacks and didn't last long. If, say, one of your light bulbs blew, then until you turned it off (by shorting it out) it cut off the electricity for the whole street! And until you shorted out the blown bulb the full generator voltage would be present across it, waiting for a chance to kill you!
 
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psionl0 said:
You are conflating power lines with power cords.

In any case, you didn't read the link I provided. US power poles have 7,200 V at the lines while in the rest of the world it is 240 V.
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This is quite true. For instance, our main transmission backbone is at 220kV. This is stepped down in substations with 110kV, 66kV and 50kV lines depending on where they are headed (City, Suburb, Countryside). These are then further stepped down with local transformers, generally one or two per block, which will convert to 240V for consumers along that block. So it really depends on which lines you're dealing with. The only lines that have 240V are from the local Transformer direct to the building. It's quite common to have poles with two sets of lines, the 50kV lines on top, and the 240V ones on the bottom.
 
The question was about the biological effects of electricity not its transmission. The biological impact is mainly due to energy transmission - burning. The variability in current in domestic circuits is more important than the two-fold difference in voltage. The duration of flow is also an issue; how quickly the current cuts off. It is the energy transfer, not volts, amps or watts that is important, i.e. Volt.Amp.seconds (Joules).

Electricity can trigger a heart dysrhythmia,as a separate effect. This can be critically dependent on the path of flow through the body, and the timing in the heart cycle. Theoretically 240v might be a higher risk, but timing and the current path are more important.
 
DGM said:
I'm not arguing the fact it's more costly. I think it's more of a fear with most people here that more voltage is more dangerous.

The wire is the small part of our expense. We now require "arc-fault" and GFI protection on a large portions of our house circuits.
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Actually most of it goes back to that boomin Edison guy and his DC systems which were + and - 110v DC (one of the limiting factors was increased sparking of the commutator in the dc generators as the voltage increased) Of course DC lost the war of the currents, but not until many Edison DC plants had been installed throughout many American cities. DC had major issues with voltage drop and required powerstations within a mile or so of the end of run- meaning many many powerstations would be required, where the AC system promoted by Westinghouse and Telsla could simply step up the voltage using transformers and step down again near the end user, meaning fewer and larger plants could be built outside the city and lines run in at the higher voltages

Edison 'AC kills' demonstrations were probably the biggest fearfactor about using AC and higher voltages as he went around the country electrocuting animals and even humans (against westinghouses wishes) using Westinghouse AC generators to make the first 'old sparky'- something his own DC generators were incapable of doing due to their voltage limits

By the time many other countries were investing in electric generation, the war of the currents was over and DC had lost, meaning we werent tied to the lower voltages of the Edison systems that many US cities had already invested heavily in- some cities such as New York have only just retired still existing original DC plant (in 2008), but that 110v lower voltage all goes back to those early DC systems
So you can blame Edison for the system you guys are stuck with :p
 
Man, electricity geeks get mean... ;)

(I should know, I'm married to one)
 
Dabop said:
.....
So you can blame Edison for the system you guys are stuck with :p
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Yep, history is to blame for US voltages. (It is also the reason that the US was stuck with its crappy NTSC colour television system but that is for another thread ;)).

Of course, towns supplied with DC existed until well into the '60s. That is why if you look at sit-coms from the 1960s you will often see the robot line, "We can never be together because I am AC and you are DC". :D

Incidentally, many country towns in Australia were supplied with 250V DC during that period. As long as electricity was primarily used for lighting, AC or DC wasn't much of an issue. However, when wirelesses became popular in the 1930s the public wanted wirelesses that could be plugged into the wall (batteries were so expensive). This created a problem for towns supplied with DC because you couldn't use transformers in the wireless. It wasn't as much of an issue in the US because you could string the heaters of the valves in series so that the total voltage required was about 110V. However, it wasn't so simple in Australia with its higher voltages. The solution was to insert a light-bulb like device known as a "baretter" into the heater string. It limited the current through the heaters and sucked up over half the voltage (and power) supplied.
 
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Or you did what my grandad did and used the dc (32v in his case) to charge the radios batterys- he was doing this into the 70's, and those batterys were ancient (they actually had moss growing over them), even after the 240vac came in, that old radiogram just kept on going on its batterys and chargers
 
Dabop said:
Or you did what my grandad did and used the dc (32v in his case) to charge the radios batterys- he was doing this into the 70's, and those batterys were ancient (they actually had moss growing over them), even after the 240vac came in, that old radiogram just kept on going on its batterys and chargers
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Did he have "wet" B batteries or was it just the A batteries that could be charged that way?

Incidentally, wirelesses that ran directly off 32V (without the need for a vibrator) were also made for farms.
 
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