Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default COMPUTING ELECTRIC USAGE

Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.

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"Tony" wrote in news:1169676266.575825.307060
@k78g2000cwa.googlegroups.com:

Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.



35 Watts from a 12 volt system is the same as 35 Watts from a 115 volt
system, one uses less current...

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me writes:

"Tony" wrote in news:1169676266.575825.307060
@k78g2000cwa.googlegroups.com:

Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.


35 Watts from a 12 volt system is the same as 35 Watts from a 115 volt
system, one uses less current...


But if it's the lamps that are rated 35 W, the 115 VAC circuit uses more
power because the conversion from 115 VAC to 35 V isn't 100 percent
efficient.

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Sam Goldwasser wrote in
:

me writes:

"Tony" wrote in
news:1169676266.575825.307060 @k78g2000cwa.googlegroups.com:

Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit
operating at regular household current of 115V?? I assume it is less
on the 12V??? Thank you very much.


35 Watts from a 12 volt system is the same as 35 Watts from a 115
volt system, one uses less current...


But if it's the lamps that are rated 35 W, the 115 VAC circuit uses
more power because the conversion from 115 VAC to 35 V isn't 100
percent efficient.


I take it you mean the 12 V system uses more because the losses in
thransforming from 115 V. (?) Then sure the low voltage system will use
slightly more, but the original question really didn't appear to need finer
technical detail.

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On 24 Jan 2007 14:04:26 -0800, "Tony" wrote:

Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.


It is a case of comparing apples with apples....

Both the 115Vac and 12Vac lamps consume a total of 105W if we assume
that the same lamp technology is used. However, there may be a
considerable difference in the light output from both lamps even
though the power consumption is the same. Also, because the
transformer or electronic ballast, which converts the 115Vac to 12Vac
is not 100% efficient, some loss will occur in this device. Therefore,
some additional power will be consumed in this device for the 12Vac
lamp arrangement.

A 12Vac halogen lamp will produce a higher light output at lower power
consumption than a 115Vac tungsten filament lamp having the same
wattage rating. For the 115Vac tungsten lamp to produce an equivalent
light output to the 12Vac halogen lamp it would have to consume more
power and it would thus have a higher wattage rating because it is
relatively inefficient at converting energy to light.

It all comes down to the efficiency of converting AC power into light
output, and of course personal preferences and economics. Converting
house lighting from tungsten filament lamps to 12Vac halogen can be
more efficient in energy consumption but it also depends to some
extent on aesthetics and whether the light pattern produced is
suitable for the intended living area. Halogen lighting generally
tends to be more "beamed or focussed" so to fill a room with even
light may require more 12Vac lamps than for a system using say
tungsten filament or high efficiency flouro lamps, which means you end
up using a similar amount of power to produce that even lighting.

Horses for courses...


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Tony wrote:
Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.



Watts are watts, the current will be much lower on the 120V circuit but
the consumption will be identical.
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"Tony" wrote in message
oups.com...
Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.


Nope, slightly more. There are various losses involved in running from 12 V.


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So, I can assume it would be cheaper in terms of KWH to operate the
12VAC system than the 115VAC? Is this correct please?
Thankx

On Jan 24, 10:58 pm, James Sweet wrote:
Tony wrote:
Can anyone tell me please tell me the difference in electric
consumption between a low-voltage AC circuit containing three, 35-W
bulbs on a 12-Volt AC circuit as opposed to the same circuit operating
at regular household current of 115V?? I assume it is less on the
12V??? Thank you very much.Watts are watts, the current will be much lower on the 120V circuit but

the consumption will be identical.


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Tony wrote:
So, I can assume it would be cheaper in terms of KWH to operate the
12VAC system than the 115VAC? Is this correct please?
Thankx



Hi...

Yes, in pure theory. A power transformer is about the most efficient
thing there is, so in practical terms the effect would be virtually nil.

Suggest you make your decision on which to use based on other factors.

12 volts is much safer than 120 volts. Cost of bulbs? Don't know where
you are, but in some places an electrician is required to run 120, but
you can do 12 yourself. Location of transformer if you go that way -
there's a slight possibility it may hum a bit. (like the isolation
transformer shaver outlet in my bathroom... durned thing

There are more considerations. In or near a swimming pool? Hot tub?

Take care.

Ken
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"Ken Weitzel" wrote in message
news:n2buh.785813$5R2.264143@pd7urf3no...

So, I can assume it would be cheaper in terms of KWH to operate the
12VAC system than the 115VAC? Is this correct please?


Yes, in pure theory. A power transformer is about the most efficient
thing there is, so in practical terms the effect would be virtually nil.


But the current is higher so the wiring losses are as well. That's why most
countries went with 220 - 240 volts and not the Edison 100 volt system.

"Edison's DC distribution system consisted of generating plants feeding
heavy distribution conductors, with customer loads (lighting and motors)
tapped off it. The system operated at the same voltage level throughout; for
example, 100 volt lamps at the customer's location would be connected to a
generator supplying 110 volts, to allow for some voltage drop in the wires
between the generator and load. The voltage level was chosen for convenience
in lamp manufacture; and at the time it was felt that 100 volts was not
likely to present a severe hazard of electrocution. To economize on the cost
of copper conductors, a three-wire distribution system was used. In the
Edison system, the three wires were at +110 volts, 0 volts and -110 volts
relative potential. 100-volt lamps could be operated between either the +110
or -110 volt legs of the system and the 0-volt "neutral" conductor, which
only carried the unbalanced current between the + and - sources. The
resulting three-wire system used less copper wire for a given quantity of
electric power transmitted, while still maintaining (relatively) low
voltages. However, even with this innovation, the voltage drop due to the
resistance of the system conductors was so high that generating plants had
to be located within a mile (1.6km) or so of the load, otherwise very large
expensive conductors would be needed or else very high voltage drops (and
efficiency losses) would result."





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"Tony" wrote in message
oups.com...

So, I can assume it would be cheaper in terms of KWH to operate the
12VAC system than the 115VAC? Is this correct please?


Nope. You are better off using CFL off 115 for lighting in my experience.
There is no cheaper source of power than the stuff the electric co sells.


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