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Old 01-18-2009, 06:49 PM   #1
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...using a dimmer requires more power and will increase your electric bill if you dim the lights often?
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Old 01-18-2009, 06:56 PM   #2
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Dimmed lights use less power. It does reduce efficiency slightly, but in absolute terms you will be using less power.
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Old 01-18-2009, 06:58 PM   #3
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See that's what I thought. My buddy seems to think that dimmers use MORE power.
My buddy must be...wrong.
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Old 01-18-2009, 08:49 PM   #4
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I believe that it will use the same amount of power at all times. The way a dimmer works is it cuts the sine wave. By doing this you still have 120v all the time and it is pulling the same amount of amps. All it does is makes it like you are turning it on and off really really fast. If you had a high speed camera you could record it and see this.
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Old 01-18-2009, 08:55 PM   #5
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I believe that it will use the same amount of power at all times. The way a dimmer works is it cuts the sine wave. By doing this you still have 120v all the time and it is pulling the same amount of amps. All it does is makes it like you are turning it on and off really really fast. If you had a high speed camera you could record it and see this.

Put an amprobe on one next time.

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Old 01-19-2009, 12:25 PM   #6
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Two ways to reduce power to lamp; put a resistor in series with the lamp or turn on/off the power at some duty cycle less than 100%.

The first wastes power in the resistor; the second theoretically uses no power at all in the control element. In the real world, though, the dimmer's internal Triac needs a heat sink, so it must use some small amount of power, a watt or two.

For a lamp filament having a thermal time constant of a few dozen milliseconds you want a high switching freq., e.g., 60 Hz. For a house thermostat, the air in the house and the house structure has a long thermal time constant so a switching freq. of 1 cycle per 10 minutes or longer is probably OK.
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