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

[Dabop]

They were all wet lead acids- rubber cases, tar sealed with external busbars between the cells
This is purely from my early memories ie before my teens, it had a 3v?? circuit that was quite thirsty on power and a 90v plus circuit that used very little power
the 90v plus was a string of 6v? car batts, charged up with a 24v home made charger in groups, and the 3v? one was off a pair of cells and was swapped from cell group to cell group as they ran flat, then when the entire battery was flat it was charged up again
All batts were under the edge of the house, with many wires running through holes drilled in the floor under the radiogram... (antenna, earth, various leads to various batterys)

 

[bobdroege7]

Speaking of the 240V/120V three-wire, single-phase, mid-point neutral system used in the US ....

Shortly after I came home from work one afternoon, half the electricity went out in my house. It was very bizarre. Some kitchen appliances were working. Others weren't. There didn't seem to be any logic to what was working and what wasn't.

Even though I have (or should have had) enough knowledge of electrical systems to understand what was happening, with my house seemingly dying around me, my brain wasn't working right.

I called the power company thinking they could, at least, tell me who could fix the problem. One of the selections in the phone menu was "If only one half of your power is out in your home, press ...." Oh ... That's when I realized what must have happened.

In less than an hour, the power company had a service truck at our house. The technician installed some device that attached to our electrical meter sort of like the face-sucking creature in the Alien movie. It restored power to my house until, a few days later, a connection in the box by the curb was repaired.

A similar thing happened to me.

A squirrel decided to meet his maker by chewing through one of the power lines to my house, so I lost half of the power to my house.

Because in the US most residential service is 2 out of the 3 phases. 220 volt appliances will be wired to both, and 120 will be one to ground.

Not an electrician, but I have been trained and issued low voltage gloves and most of my electrical experience is changing ballasts on fluorescent lights where the voltage was 277, which is one phase of a 480 volt 3 phase system.

 

[jadebox]

Because in the US most residential service is 2 out of the 3 phases. 220 volt appliances will be wired to both, and 120 will be one to ground.

I knew how it works, but in the moment I wasn't thinking. I felt like I was in a scene from Apollo 13 with systems failing one at a time.

After calling the power company, I shut off breakers for lines going to 220V appliances. Some were making really odd noises.

 

[jsfisher]

Because in the US most residential service is 2 out of the 3 phases. 220 volt appliances will be wired to both, and 120 will be one to ground.

[pedant] To neutral. [/pedant]

 

[CORed]

As we dont work with these 'gauge' wires, I would have to consult google to find out what size they actually are, but I can state with 100% accuracy, and I'll support with links, that if you want the same load (stated in watts) then it will 100% guaranteed halve the current every time you double the voltage

(what is the NEC- I assume from your comment it is some kind of regulatory body in the US???)- The only NEC I have come across here makes cash registers and the like, and altho the power companies certainly have no qualms about taking my cash, I doubt they have much to do with the wiring codes...)

;-)

NEC, is the National Electric Code.

ETA: "Guage" refers to American Wire Guage

 

[CORed]

Are they literally the same set of wires (ie on the same fuse) as the 120V outlets or do the 240V parts of the system run on a different set of wires that have their own fuse at the meter box?

Usually different set of wires on a dedicated two pole breaker (I'm not an electrician but I'm pretty sure that doing it any other way would not be up to code). 120 volt circuits use single pole breakers mounted on one of the two hot busses, 240 volt circuits use a double pole breaker mounted on both hot busses. Usually a 240 volt appliance (stoves and clothes dryers being the most common) will have a dedicated breaker and 240v outlet. There will usually be 4 wires (Two hot, a neutral and an equipment ground). Stoves often have lights, clocks, sometimes an outlet that use 120 (one of the hots to the neutral), while burners and oven run off 240 (one hot to the other). Thinks like electric furnaces, central air conditioners or electric water heaters will be 240v hard-wired, again usually with a dedicated two pole breaker for each appliance.

 

[aleCcowaN]

And further down again, the poster you mentioned says....


note the bolded and underlined

Yes, it's an acknowledgement of the common denomination. The wit in those posts says they know it's one phase, split.

I now understand the denomination and use it without getting any conceptual confusion from that. I suspect it's a necessary misnomer, as I said above.

 

[aleCcowaN]

It was very bizarre. Some kitchen appliances were working. Others weren't. There didn't seem to be any logic to what was working and what wasn't.

It's customary mixing circuits in every room. I mean, if you have different "phases" or phases, or even different circuits with independent breakers on the same phase, it's always expected you have at least two different circuits in every room so when one of them fails you don't wind up without power in the whole room.

That is specially important in kitchens, utility rooms, pump rooms and workshops.

 

[aleCcowaN]

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).

There's no reason to bill three-phase power. The electricity provider balances the load by assigning different phases to different customers. In any building I know all three phases go into the metre room and 1/3 of flats or offices gets each phase. The three-phase service is reserved for water pumps, lifts and, if they exist, escalators and central air conditioners.

 

[aleCcowaN]

Easy fixed. Mandatory Earth Leakage Current Detectors.

But for high loads they are usually trigger by leakages currents that might be mortal.

I my country it's mandatory to have 3ma breakers with any circuit breaker up to 30A. From that value on, it increases to 30ma for 65A breakers. You won't want those if you have a baby in the house.

 

[CORed]

Easy fixed. Mandatory Earth Leakage Current Detectors.

I think that's the same thing that's called a "ground fault interrupter" in the US. I think they are required by current codes, but a lot of older houses still don't have them.

 

[psionl0]

There's no reason to bill three-phase power.

The electricity supply companies could charge a lower supply (not per unit) fee for single phase customers if they wished but they don't. Once 3 phase power is connected to a house, it costs the same to supply the electricity.

The electricity provider balances the load by assigning different phases to different customers.

Good googling.

In any building I know all three phases go into the metre room and 1/3 of flats or offices gets each phase. The three-phase service is reserved for water pumps, lifts and, if they exist, escalators and central air conditioners.

There are detached dwellings known as houses where this doesn't apply.

I mean, if you have different "phases" or phases, or even different circuits with independent breakers on the same phase, it's always expected you have at least two different circuits in every room so when one of them fails you don't wind up without power in the whole room.

That may be the case in the US. For 240V residences, a modest dwelling may only have one power fuse (or circuit breaker) so if it goes then all the power points go dead. Lighting is on a separate circuit though.

 

[Dabop]

It matters not a whit how the electricity arrives either via a single phase, 2 phases or three, so once the cost of installing the meters and street supply cabling is met via the installation fee, of course the price is the same

it is ALL billed in Kw/hrs on either 1,2,3 (or more even!!) meters, the totals added up and that amount is the total POWER CONSUMED by that customer...

(The only cavat to that is some suppliers may have tiered costings like off peak charges, that are usually on their own meter which has a subtone controlled relay or timer on it, this is usually NOT available the full 24/7, but is often at a greatly reduced price in an effort to get customers to shift HWS etc to different times of the day/night so they can lessen peak loads)

All billing is done by Kw/hrs or equivalent measurements for those strange countries that still measure cars petrol consumption in hogsheads per staff or whatever.. Many people still dont seem to get power consumption, but it's really very simple.
When consuming electricity you use a certain amount of power (usually expressed as watts eg 100W lightbulb) or sometimes as VA (many tvs have that for some reason 100VA is 100W) or they will have an Amp rating eg 2.4A (this needs a calculator- you need to multiply the voltage and the amperage to get the wattage eg 240v x 2A = 480W)

now you need to time it- say a 100w lightbulb left turned on all the time day and night- uses 100w every hour- so its usage is 100w/hr ie 0.1Kw/hr... left running for 10 hrs it has used exactly 1Kw/hr and after a full day has used 2.4Kw/hr... if you are billed say $0.34 per Kw/hr (my bill) then leaving that light on 24/7 costs me $0.77 a day to leave it running

 

[jsfisher]

When consuming electricity you use a certain amount of power (usually expressed as watts eg 100W lightbulb) or sometimes as VA (many tvs have that for some reason 100VA is 100W) or they will have an Amp rating eg 2.4A (this needs a calculator- you need to multiply the voltage and the amperage to get the wattage eg 240v x 2A = 480W)

Minor quibble: VA is not equivalent to W. VA is simply the product of RMS amperes and RMS volts. It doesn't account for the effect reactive and capacitive loads have on power consumption. That's where the so-called power factor comes in: VA x power-factor = W.

...if you are billed say $0.34 per Kw/hr (my bill)...

Really? $0.34 / KwH? ...and I assume that's in AUS$. Wow.

 

[Dabop]

I was trying to keep it simple and in most cases it works out near enough- plus most people dont have the equipment to accurately measure the power factor anyway

;-)

and yes thats the price on my last bill, and its going to be going up another 20% next bill according to the local news on tv the other day...
No wonder solar panels and now things like the tesla powerwalls are selling so fast they cant import enough into the country- my new house is going to be offgrid simply due to the fact it will actually be cheaper than getting the grid connected (rural property, expected min install cost of OVER $20 grand.... then the $$ per quarter on top means its actually cheaper to buy the batterys and offgrid inverter (I already have a 8Kw inverter) and still come out ahead...

 

[psionl0]

it is ALL billed in Kw/hrs on either 1,2,3 (or more even!!) meters, the totals added up and that amount is the total POWER CONSUMED by that customer...

Another minor quibble. Not all of the billing is based on consumption.

Electricity bills usually contain a fixed charge (known as the "supply" charge) and a variable charge which is based on consumption. As solar penetration increases, the fixed charge is likely to be increased to protect the profits of the supply companies. (We have heard a Western Power spokesperson try to argue that solar users are being "subsidized" by non-solar users).

 

[ceptimus]

In the UK, three-phase is usually billed by the amount of VA-hours used. This gives factories an incentive to run at unity power factor in order to save on energy costs so it is common to see power factor correction equipment installed.

However, single phase meters fitted to most residential properties only measure kWH, so there is no financial incentive for single phase users to optimize their power factor. In any case, it's not really an issue as the majority of power consumed by home equipment tends to be near unity power factor.

 

[Dabop]

Another minor quibble. Not all of the billing is based on consumption.

Electricity bills usually contain a fixed charge (known as the "supply" charge) and a variable charge which is based on consumption. As solar penetration increases, the fixed charge is likely to be increased to protect the profits of the supply companies. (We have heard a Western Power spokesperson try to argue that solar users are being "subsidized" by non-solar users).

The ALL mentioned was of course the electricity consumed and indeed it is all metered, and billed at the appropriate rates. I wasnt talking about extra added fees such as supply or administration or meter reading fees (of which I am rapidly approaching unity with the actual cost of the electricity consumed in my existing house, having solar hws, led and cfl lighting and having eliminated parasitic loads), but the apparent misconception that some electricity wasnt being metered or required metering ie

There's no reason to bill three-phase power.

As many Oz homes do have 3 phase power these days, but the amount of power consumed on each phase may differ dramatically depending on usage patterns in the house- Aircon with 3 phase compressor will be approximately the same draw on each phase, while the kitchen will be on one phase only, thus the requirement for 3 separate meters (or a combination meter) to account for the difference in power consumption of the different phases. If they didnt meter each of the 3 phases individually, there would be one of two situations, they meter only the phase of the rest of the house- ie giving you the electricity on the other two phases for free (as if THAT would happen) or bill you the usage of the monitored phase on the other two as being a given (as if I want THAT to happen)ie charging you for electricity you didnt actually use

Nothing was stated or implied about other service charges, I was only talking about consumption charges

 

[Dabop]

In the UK, three-phase is usually billed by the amount of VA-hours used. This gives factories an incentive to run at unity power factor in order to save on energy costs so it is common to see power factor correction equipment installed.

However, single phase meters fitted to most residential properties only measure kWH, so there is no financial incentive for single phase users to optimize their power factor. In any case, it's not really an issue as the majority of power consumed by home equipment tends to be near unity power factor.

That used to be the case here as well, but the introduction of the smart meters (with the public unhappiness with them as they 'charged more' than the old spinning wheel meters)
What actually happened was that because some loads in the houses werent at unity ie having a power factor of one (and with the increasing popularity of led and cfl lighting, and switchmode powersupplies in most modern electronic devices this was increasingly the case) most houses were actually being undercharged for their electricity.
With the introduction of smart metering, and its ability to calculate true usage rather than apparent usage peoples bills went up- hence the often claimed 'they rip people off with the smart meters'

 

[lomiller]

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).

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.

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

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.