Reducing mains voltage to 220V to cut bills...

[joebog1]

Thanks Penguin,
Power factor is massive, AND a massive mathematical headache.
I guess I was being polite when I first answered.

There is NO FREE LUNCH !!.
Energy is expendable, we do it every day.
The power company KNOWS this with absolute certainty, and play on it accordingly.

All I need now, is an aeroplane with no wings or engines and I have them buggered!!!.
OHH and a decent bar with a fridge.

Joe

[ppppenguin]

Power factor is a problem but relatively easy to correct with capacitor banks or rotating machines acting as synchronous capacitors (or occasionally inductors). Harmonics are harder to deal with.

I've done the basic maths for PF, nothing terribly complicated beyonds sin, cos and tan, though it helps to be familiar with j (the square root of -1, what the mathamagicians call i but electrical types don't cos it gets confused with current). It all gets a lot harder when there are distorted or non-periodic waveforms. This bit on the wiki article shows the simple stuff quite nicely: https://en.wikipedia.org/wiki/Power_factor

The whole article has a fair bit of maths which will initimidate some: https://en.wikipedia.org/wiki/Power_factor

[Paul_RK]

Seems to me he thought that as the difference between 240 & 220 is about 7% that electric gubbins would use 7% less electricity, as others have said kettles would take longer to boil, ovens take longer to get up to temp, electric fires/fan heaters wouldn't  give out so much heat. Effect on bills? I suspect not a lot...

I make it about 16% less, as power = voltage x current, and reduced voltage means reduced current too.

So, yes, kettles would take longer to boil but cost about the same as they do now. Heating controlled by a thermostat would be "on" for more of the time, consuming over time just the same power as it does now. And in this household with our fleet of Belling Champion convector heaters keeping us from being too cold - well, they would spend more of the time plugged in and/or switched to full rather than half heat to eliminate the same amount of discomfort...

Paul

[Murphyv310]

Hi.
Paul, it's not as simple as P=VxI. Look as many SMPS that have a wide input spread from 100 to 250 volts, if the required output load is constant then so is load on the mains, if it requires 1 amp at 240v it will require 2 amps at 120v.
I also remember many times industrial pressure washers that had a 3kw induction motor that blew the 13 amp plug fuse regularly, the Start/Run cap would be OK or even replaced, then you'd discover that the mains would be low at 220v and even less on remote farms especially under load, the only cure was a 16 amp socket not a cut down nail in the 13 amp plug. So the simple formula doesn't always hold up unfortunately.

PS, my own Nilfisk MH4C pressure washer is rated at 2800 watts and I've noticed on a very odd occasion a popped fuse, a quick check on the mains reveals a level of just below 230v off load, I think the fuse just slowly melts, the plug is quite hot with the live pin the hottest

[Paul_RK]

Yes, I was only considering the basic resistive loads that still constitute much the greater part of household consumption for many of us, particularly in all-electric homes - space heating, kettles and immersion heaters and so forth. Not quite so simple even then of course as lower operating voltage means lower temperature, hence lower electrical resistance, reducing to some extent the expected drop in current.

Paul

[ppppenguin]

Fuses and circuit breakers are actually quite complicated. The nominal rating is what it's meant to be able to carry indefinitely without blowing/tripping. As you go above this, it will blow or trip at some time. Ranging from milliseconds for a huge overload to many hours for a small one. These small overlaods are actually the most hazardous. A 15% long term overload can cause wiring to overheat while the fuse may not blow for many tens of hours. Even a 50% overload will not blow a fuse for quite a while.

Conversely, a short term surge can easily give a nuisance blow or trip as Trevor has described.

13A plugs can suffer from poor contact at the fuse and in the socket. The result can be nasty.

[Murphyv310]

Absolutely Jeffrey.
I've seen many melted 13a plugs and sockets with intact fuses when servicing industrial cleaning equipment, the usual answer was a 16 amp plug and socket with a suitably rated MCD.

[Mike Watterson]

Although Refugee is technically correct this is a very minor effect. To a decent approximation, anyting with a switchmode PSU will use the same amount of electricty on any voltage within its range.

Lights will be dimmer and use less. You might or might not notice this.

...

Overall effect on bills? For most people it will be negligible.

Agree with all except lights. That only slightly affects halogens (due to marked barreter like thermistor effect) and more affects non-halogen tungsten, but not by the % voltage change as the response isn't linear due thermistor effect. It would increase life of filament lamps a bit!

CFLs and LEDs might be as unaffected as a SMPSU. Even traditional tubes not much affected? You can test by measuring light output change by dropping voltage using 20V transformer correctly phased (you don't want 260V).

So, I'd agree negligible effect on bills unless you use electric room heating with no thermostat. Negligible effect if there is a thermostat.

It would make a difference if millions of AC/DC TVs with dropper resistors still in use.

[ppppenguin]

The effect of voltage on the life and brightness of standard tunsten lamps is more than you might expect. See here for example: http://www.lamptech.co.uk/Documents/IN%20Voltage.htm

5% overvoltage will halve the life, 5% under will double it.

I don't know if halogen lamps are similarly affected.

[Mike Watterson]

Some lamps or valve filaments it's 10% change is double or half life. Maybe vacuum filaments. Hence the valves in 1.5V battery sets supposed to be at 1.35V on AC mains PSU, and a 7.5V battery series system about 6.5 V to 6.8V

The bulbs for 6V battery torches can be labelled as 6.5V or 6V. Their life is short as they are really 4V lamps. Car lamps rated equivalently (not headlamps) are probably really 14V (or 7V for old mbikes and 1950s VW). Colour temperature is a guide on pilot lamps. A same voltage torch bulb can be very white and long life pilot lamps are decidedly orange.

I don't think even regular filament lamps have been a vacuum for maybe more than 100 years. Only valves have a vacuum, though I'm not sure about some straight wire tungsten (festoon?) lamps. I think the big advances in filaments were tungsten instead of carbon, platinum or nickel, coiled coils, pure nitrogen then halogen and noble gas mixes. Tungsten was harder to make and is very brittle. Oddly at first the 1941 RCA B7G 1.4V valves used nickel filaments. Philips perfected more uniform and thinner tungsten for 25mA type B7G after WWII, and also the Russians very thin filaments for rod tubes. Tungsten filaments (rather than ceramic and separate cathode types) need a spring tension at one end. You can see the spring move on some miniature direct filament valves.
Halogen are also exponential as well as Tungsten, but a different curve. They are after all still tungsten filament.