In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

PhilC

On Sun, 24 Sep 2006 18:13:14 +0100, PhilC wrote:

In the interest of fuel saving could there be any saving in having a 12v
lighting circuit?

Energy consumption is a function of wattage, not voltage alone.

As a very simple rule-of-thumb, lighting level is a function of bulb
wattage - a 40w bulb is much dimmer than a 100w bulb.

I'm sure the theorists will be popping up to argue over those points, but
they're close enough for the purposes of your question.

Whilst 12v halogen bulbs can appear to give a relatively higher light
output than 230v bulbs, they tend to be fairly directional, so you'd have
to rethink your overall lighting scheme to give good lighting levels, and
probably use more 12v bulbs.

Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

Transformers have two losses, iron and copper. The iron losses are incurred
in magnetising the core of the transformer - they happen just by switching
on the transformer. In addition, when you put a transfomer on load, the
windings actually incur some losses.

Ask yourself, if there was some merit in your suggestion/question,
whole-building lv lighting circuits would be commonplace.

--
the dot wanderer at tesco dot net

"PhilC" wrote in message
...
In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be
justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

PhilC



No! Just change to a cheaper gas and electricity supplier to save money.
You can save a lot more for electricity by looking at costs per unit. I
changd over and have now got a cheaper unit price and no standing charge.
For gas I pay less than half of what british gas want, and no standing
charge.
Why pay more than you need to?

In article ,
"PhilC" writes:
In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?

Possibly, but 12V is the wrong voltage. The most efficient 100W
filament lamp will be designed for 55V operation, so if you
were going to design a circuit for efficient filament lighting,
it would likely be at least 55V. I²R losses in the copper
will be very much higher than for mains lamps, and when you
factor in that and the consequential cost of thicker conductors,
you would probably go for a higher voltage.

In the US, a range of 85V filament lamps was produced. These
included a diode in the lamp base so they could be run from 120V
mains supply (RMS voltage of half-wave rectified 120VAC is 85V).
These were more efficient than the same power rated 120V filament
lamps, because they are nearer to the optimum filament lamp
operating voltage.

However, this is all rather academic now. No one who is concerned
with lighting energy efficiency will be using filament lamps any
more.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

Transformers aren't generally left on with no load. Actually,
electronic ones often won't work below a certain minimum load.

--
Andrew Gabriel

On Sun, 24 Sep 2006 20:01:58 +0100, Paul wrote:

You can save a lot more for electricity by looking at costs per unit.

Agreed and using CFLs.

I changd over and have now got a cheaper unit price and no standing
charge. For gas I pay less than half of what british gas want, and no
standing charge.

Do you really mean "no standing charge" or a tarrif that says it has "no
standing charge" but the first X units cost more than those after?
Curiously the price difference between the two rates times the number of
units at the higher rate equals the standing charge...

There are tarrifs that truely have no standing charge and have a single
rate for all units. Equipower and Equigas I know of, there may be others.
Very handy if you have a low usage. However if you always use enough
units to pay all the hidden standing charge you'll probaly be better off
looking at standing charge tarrifs with a single, lower, per unit cost.

--
Cheers
Dave. pam is missing e-mail

PhilC wrote:

In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

PhilC

12v halogens are more efficient than mains halogens, but 240v CFLs are
much more effieicnt than either, and 12v CFLs cost more and are a bit
less efficient than 240. So no, theres nothing to gain.

CFl or linear fl are the energy saving options.

There would be savings if you had a LV system that you could plug small
appliances into, to replace wall warts, but the savings would be too
small to be worth installing a system for.


NT

PhilC wrote:

In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

PhilC

12v halogens are more efficient than mains halogens, but 12v CFLs are
much more effieicnt than either, and 12v CFLs cost more and are a bit
less efficient than 240. So no, theres nothing to gain.

CFl or linear fl are the energy saving options.

There would be savings if you had a LV system that you could plug small
appliances into, to replace wall warts, but the savings would be too
small to be worth installing a system for.


NT

PhilC wrote:
In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?
This being in addition to the normal mains circuit.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

PhilC



Ther could be in that the bulbs last longer and give more light as tehy
run hooter, for a given power.

However you have also identified that there will be losses associated
with the transformers, and the wiring losses will likeley be greater,
and the currents will necessitate a lot of thick cable, and the switches
would need uprating to deal with the currents.

Which is why we run 240v lighting circuits and switches, and use local
transformers for 12v lighting.

Since these are mostly spot lights, the advantages are lessened by the
smaller illumminated foot print. I guess you COULD use car headlamp bulbs...

The Natural Philosopher wrote:

Since these are mostly spot lights, the advantages are lessened by the
smaller illumminated foot print. I guess you COULD use car headlamp bulbs...

relatively short lamp life though

NT

wrote:
The Natural Philosopher wrote:

Since these are mostly spot lights, the advantages are lessened by the
smaller illumminated foot print. I guess you COULD use car headlamp bulbs...

relatively short lamp life though

I don't think so. Not comppared with a normal incandescent bulb anyway.

NT

In article ,
The Natural Philosopher writes:
wrote:
The Natural Philosopher wrote:

Since these are mostly spot lights, the advantages are lessened by the
smaller illumminated foot print. I guess you COULD use car headlamp bulbs...

relatively short lamp life though

I don't think so. Not comppared with a normal incandescent bulb anyway.

Something like 250 hours. (Some of the boy-racer high
temperature ones are much less.) At 12V, they would last
longer than at the battery charging voltage they are
designed for, of course.

--
Andrew Gabriel

The Wanderer wrote:
On Sun, 24 Sep 2006 18:13:14 +0100, PhilC wrote:

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

Transformers have two losses, iron and copper. The iron losses are incurred
in magnetising the core of the transformer - they happen just by switching
on the transformer. In addition, when you put a transfomer on load, the
windings actually incur some losses.

Someone did the calcs in this newsgroup a while ago, regarding how much
power the average wallwart consumed while left plugged in - can't
remember the figure but a few quid per annum IIRC?

Ask yourself, if there was some merit in your suggestion/question,
whole-building lv lighting circuits would be commonplace.

I've mused about this myself; not particularly in connection with
lighting, but because of the huge number of wall-warts which you now see
festooned around most houses these days; the majority of which get left
plugged in and switched on when not in use. All LV appliances have
different requirements of course, but wouldn't it be better if there was
a standard LV circuit(s) wired into houses, with uniform wall-mounted
sockets, which all manufacturers of electronic appliances could design
their kit around?


Without even trying, I can think of 25 wallwarts in my house, most of
which stay plugged in 24/7 despite my nagging! and this list is
certainly not exhaustive:

Mobile phones (x4)
Printer
Router
Monitor
PC speakers
Kids games/toys (x6)
Playstation
Ipod basestation
AA battery charger
DECT phones (x3)
Power tool chargers (x3)
Clock
Laptop
....

David