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

[psionl0]

They will run 3-phase regardless, it’s just a matter of when/where/how they produce the split phase power that comes into the house. If you don’t have split phase coming into your house, I’d suspect that’s more a case of how your house is wired than what the electrical company has available.

You are clearly conflating how power is supplied in the US and how it is supplied in the rest of the world.

The power poles passing every every residence in Australia all have 4 wires on them - 3 live wires and one neutral wire. The live wires all carry AC at 120 degrees out of phase with each other. If a household is to be supplied with three phase then it needs to tap all 4 wires and have that tapping run to the meter box. It it is to only have single phase power then it only needs two wires running to the meter box - one tapped to the neutral and one tapped to one of the live wires at the power pole.

My understanding is that at least some residential split phase systems are not generated using center tapped transformers, rather they are 2 lines and the neutral from a 4 wire wye 3-phase system. If it’s center tapped, you will have nominal voltages of 120V/240V if it’s directly from a 3-phase distribution system you will have nominal voltages of 120V/210V. 210V is common in commercial settings even if it’s 240V for residential, and most equipment is happy with either

While commercial premises may indeed have 3 phase power supplied directly, I have seen no information that suggests that residential premises are supplied the way that you describe. Until you can provide some links, I will prefer to trust the link that I posted in the OP. (http://science.howstuffworks.com/environmental/energy/power7.htm)

WRT current draw, while 240V/210V produces a lower current draw for the same power output it’s typically used specifically because you have a need for higher power draws. As a result, it’s typically going to be wired for higher current draws than 120V.

That's the first bit of theory you have made up that makes sense. Of course, this was pointed out several times on page 1 of this thread.

 

[Dabop]

PsionIO is correct for most urban areas in Oz, however it is still quite common in rural areas to have only a single phase (2 wire) system available, or in some areas they actually still use a single wire, earth return system where the poles have only a single wire running along the top!
Center tapping is very very rare, AFAIK it was only some very rural parts of Tasmania and Victoria that had a centertapped 240/480v system and none installed recently (ie after 1970's), certainly I have never seen one in person in NSW or Qld

The center tap 110/240 US system is very definitely the odd man out in the electrical world (along with NTSC mentioned before- I always remember the initals by using the memory aid 'Never The Same Colour') and is really only found in the USA or places they had a strong military presence in for extended periods of time

 

[lomiller]

You are clearly conflating how power is supplied in the US and how it is supplied in the rest of the world.

No, I’m not. 3-pahse is part of every power distribution system in the world because it’s a more efficient way to deliver power. The only differences are how and where it’s converted into the single phase or split phase power that comes into your house.

The power poles passing every every residence in Australia all have 4 wires on them - 3 live wires and one neutral wire.

3-phase systems can have either 3 or 4 wires depending on whether they are wye or delta. You can also have a separate ground with either, since neutral isn’t necessarily ground. If the loads on each phase are not balanced there can be current in the neutral in a wye configuration, which is why you may want a separate ground.

While commercial premises may indeed have 3 phase power supplied directly, I have seen no information that suggests that residential premises are supplied the way that you describe..

Then why are common household products like cloth dryers designed to work with either 208V and 240V?
http://www.google.ca/url?sa=t&rct=j...EN.pdf&usg=AFQjCNFNG4JXqfgxw7b0HFuYeGD2bEzETw

Until you can provide some links, I will prefer to trust the link that I posted in the OP. (http://science.howstuffworks.com/environmental/energy/power7.htm)

Are you sure you understand what you are linking?
One of the advantages of a 3 phase system is that you can get different single phase voltages by virtue of how you wire it. IOW you can get singe phase 208V or single phase 120V out of a 3-phase system

 

[slyjoe]

...snip

Then why are common household products like cloth dryers designed to work with either 208V and 240V?
http://www.google.ca/url?sa=t&rct=j...EN.pdf&usg=AFQjCNFNG4JXqfgxw7b0HFuYeGD2bEzETw

...snip

Read the specs in your link - single phase.

 

[lomiller]

Read the specs in your link - single phase.

Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.

 

[slyjoe]

Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.

I know how wye and delta connections work. I thought you had implied because the clothes dryer could work with 208 or 240 that 3 phase power was supplied to residential homes.

I apologize if i misunderstood your previous post.

 

[CORed]

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

Since the primary use of electricity in the early days was lighting, I suspect that one factor in keeping 110v (or 120v) was that it was compatible with the 110v light bulbs. Incandescent bulbs work equally well on AC or DC, but trying to run a 110v bulb on 220-240v will burn it out immediately (unless you put two of them in series).

 

[CORed]

Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.

Clothes dryers are used in both residential and commercial settings. I suspect the reason for making them compatible with either 240v or 208v is to allow them to be used for either.

Most commercial power in the US is 440v three phase, but many businesses have a transformer that steps it down to 208/120v three phase.

 

[lomiller]

Clothes dryers are used in both residential and commercial settings. I suspect the reason for making them compatible with either 240v or 208v is to allow them to be used for either.

Most commercial power in the US is 440v three phase, but many businesses have a transformer that steps it down to 208/120v three phase.

More like it’s an artificial distinction. If you live in a large apparent it’s fairly likely your residential power available for an in suit dryer is 208V not 240V. Since only the heating element is actually using they higher voltage you’d never know the difference between center tapped 240V and Delta connected 3-phase unless you took a meter to it.

 

[psionl0]

No, I’m not. 3-pahse is part of every power distribution system in the world because it’s a more efficient way to deliver power. The only differences are how and where it’s converted into the single phase or split phase power that comes into your house.

Yes you are. "Conversion" to single phase doesn't happen (you just use one of the phases) and "split-phase" power is uniquely North American. So are pole top transformers that supply power directly to the house.

Are you sure you understand what you are linking?
One of the advantages of a 3 phase system is that you can get different single phase voltages by virtue of how you wire it. IOW you can get singe phase 208V or single phase 120V out of a 3-phase system

It is clear that you don't understand what I am linking. For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.

However, you have not shown that this is the practice anywhere. In fact, many areas may not have 3 phase power running past homes to begin with. The current practice is to feed a single phase voltage into the primary of the power top transformer and run tapped 240 volts from the secondary to the house.

Until you can show that it is otherwise for domestic premises, your theories are worthless.

 

[lomiller]

Yes you are. "Conversion" to single phase doesn't happen.

If you want to split hairs and just call it connecting a load, that’s fine too, it doesn’t make any difference you are still connecting to a 3-phase power distribution system. Conversion is accurate as well because this is part of a wye-delta conversion.

It is clear that you don't understand what I am linking. For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.

It’s possible even without the transformers. A transformer is only required if you also want to step down the voltage or produce a center tap.

However, you have not shown that this is the practice anywhere. In fact, many areas may not have 3 phase power running past homes to begin with. The current practice is to feed a single phase voltage into the primary of the power top transformer and run tapped 240 volts from the secondary to the house.

They all have 3-phase either running past you house or relatively close to it. If you only have a single phase directly in front of your house it is 1 of 3 phases coming off a nearby transformer. Except possibly in rural areas where the distance between houses can be very long, electric companies don’t move electricity any significant distance using single phase.

 

[psionl0]

It’s possible even without the transformers. A transformer is only required if you also want to step down the voltage or produce a center tap.

It's a good thing that you are not an electrician. Connecting 7,200 volts directly to your house is the quickest way to the graveyard that I can think of.

 

[Dabop]

It's a good thing that you are not an electrician. Connecting 7,200 volts directly to your house is the quickest way to the graveyard that I can think of.

I've seen the results after a cyclone where this is exactly what happened, a sheet of corro blown off a roof or fence hit the powerlines, shorting the 11Kv (I think thats what they use in Qld- not my area, I'm down in the 100's of volts lol) to the 240/415 3 phases immediately below

Much sparking, smoking etc ensued, and several houses in that street basically had to replace every single item in the house that was plugged in, some had to basically be rewired, others passed a megameter test, but quite frankly I'd rather a full rewire after something like that, the mains wiring in a house was never designed to handle 10000v plus...

 

[lomiller]

Connecting 7,200 volts directly to your house .

As usual, you are spouting nonsense. Your statement had nothing to do with the voltage on the power line, and I addressed it regardless.

A transformer is only required if you also want to step down the voltage or produce a center tap.

What you actually said:

For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.

AGAIN. YOU DO NOT NEED A TRANSFORMER TO GET SINGLE PHASE OUT OF A 3 PHASE LINE.

 

[Dabop]

As usual, you are spouting nonsense. Your statement had nothing to do with the voltage on the power line, and I addressed it regardless.



What you actually said:

AGAIN. YOU DO NOT NEED A TRANSFORMER TO GET SINGLE PHASE OUT OF A 3 PHASE LINE.

He is referring back to the OP which clearly stated that the (unusual) US system HAS a transformer at every house (apparently) as per http://science.howstuffworks.com/environmental/energy/power7.htm and apparently they dont (like the oz system I and heare referring to) actually run 3 phase past each property, apparently they can be quite some distance away

Can I suggest READING the thread and perhaps you mightnt SHOUT so much...

 

[lomiller]

He is referring back to the OP which clearly stated that the (unusual) US system HAS a transformer at every house (apparently) as per http://science.howstuffworks.com/environmental/energy/power7.htm and apparently they dont (like the oz system I and heare referring to)

Which is completely irrelevant to our exchange because transformers have exactly nothing to do with single phase vs 3 phase.

Can I suggest READING the thread and perhaps you mightnt SHOUT so much...

Perhaps if people would pay attention the fist time (or even the second, third, forth...)

 

[Mikemcc]

It's really called: NFPA 70: National Electrical Code (NEC) (2017).



It changes constantly and is not cheap to keep up with.

http://www.nfpa.org/nec

We have the same silliness in the UK with the IEE wiring regulations, presently 17th edition but due change next year. Just to confuse things the IEE no longer exists as such, there was a merger with two other institutions a few years back to form the IET (Institution of Engineering and Technology)

Alec,

Never mind worrying about wire gauge, my pet peeve when working in the US is twist-on-wire terminals. Absolutely shocking that anyone would use these in metal disconnect boxes. I've even seen them used on the protective earth connection! Where possible I always strip them out and replace them with DIN rail terminals and decent ferrule crimps.

 

[Hellbound]

He is referring back to the OP which clearly stated that the (unusual) US system HAS a transformer at every house (apparently) as per http://science.howstuffworks.com/environmental/energy/power7.htm and apparently they dont (like the oz system I and heare referring to) actually run 3 phase past each property, apparently they can be quite some distance away

Can I suggest READING the thread and perhaps you mightnt SHOUT so much...

That's not true, though. There aren't transformers at every house, except in rural areas where houses are far enough apart that it's cost effective. Transformers typically server several houses in an area, usually a block or so (depending on the density of dwellings and the type of building, an apartment or large office building might be served by its own transformer, for example).

 

[GlennB]

With zero knowledge of these matters I can only sit in wonder, jaw-dropped, at the astonishingly savage level of disagreement between people who certainly appear to have considerable knowledge of the subject

Here in Greece we have 230v three-phase domestic supply, and I was told that was a good thing It certainly means (I was told) that I don't have to worry about live/neutral wiring of plugs the way I used to back in the UK.

 

[psionl0]

As usual, you are spouting nonsense. Your statement had nothing to do with the voltage on the power line, and I addressed it regardless.

A transformer is only required if you also want to step down the voltage or produce a center tap.

What do you mean by "IF"? Under your pet theory, what voltage is on the American lines?

What you actually said:

For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.

AGAIN. YOU DO NOT NEED A TRANSFORMER TO GET SINGLE PHASE OUT OF A 3 PHASE LINE.

2 phase = single phase?

Worst strawman ever.