Posted on 06/30/2010 7:35:39 PM PDT by mowowie
Say i have three 60 watt bulbs blazing in my kitchen at it's 180 watts total.
Then say i use the dimmer switch i installed a few years ago and dim the 3 bulbs 75%. My question is am i saving electricity and money by dimming them or is the dimmer mechanism itself just absorbing up the slack, still using the same 180 watts as before but i'm just seeing less light?
I believe the answer is in between. The dimmer gets warm, so it is using some energy. What you won’t get is the most efficient use of the electricity. I find that bulbs on dimmers burn out faster.
You are using less power. A dimmer works by turning the power on and off very quickly.
The larger a percentage of the time the power is on, the brighter the light and the more power is consumed.
When it’s off, it’s off and consuming no power.
Prove it to yourself, does the dimmer switch get as hot as the lightbulb when you have it set at 1/2 the brightness?
It depends. If you’re using an older type resistor dimmer, you not saving anything.
If you’re using a newer, solid-state device, then you indeed are saving some electrons from an early death. :-)
You would probably be better off getting some dimmer bulbs in another fixture. That way you could simply turn off the brighter lights and go with the lower wattage lights when you wanted.
MOSTLY, you’re saving the energy. The dimmer switch reduces the draw. Yeah, the dimmer swicth generates a little warmth, but this is negligible compared to enough heat to cause your light bulbs to glow white hot.
My Bish can cook in the dark
2. Most modern dimmers limit the power through some type of pulse width modulation. Rather than put a resistor in the circuit (which would heat up a lot), they turn on and off the electricity so current only flows during part of the 60 Hertz cycle. Here is a page which describes it from a dimmer manufacturer. http://www.lutron.com/Education-Training/LCE/Pages/DimmingBasics.aspx
I put (rather expensive) dimmers throughout my home except for hallways. Glad I did.
Definitely saved money. I say go for it.
LOL
I’ve always wanted to learn to read braile.
I did the same and then ripped them all out when I converted my PAR30’s to CFL’s. The dimmable CFL’s cost a fortune!
I’m happy to be saving money with CFL’s. My kitchen has a plethora of cans and I went from 700+ watts down to about 40.
But in terms of losses in the dimmer itself, they are small - usually the heat comes from a primitive power supply for the dimmer itself. The switch (a semiconductor device) is probably ice cold.
If you are really interested in efficient dimming, use LED lights. They are infinitely and linearly dimmable (using PWM) and they are very efficient.
THINK!
How hot would the dimmer have to get if it were just radiating (wasting) the energy that isn’t reaching the light bulbs?
A solid-state dimmer cuts off the current during a part of each cycle of the alternating current. If you could flip a light-switch 60 times a second, you would get the same effect.
If you have 300 Watts of bulb controlled by a dimmer, and the dimmer is sending current to the bulbs only 33% of the time, the bulbs will radiate 100 Watts of power.
But you will get less than 33% as much useful light from the bulbs, because they will be cooler, and therefore a larger relative share of the radiated energy will be infrared rather than visible light.
A light bulb is more efficient (i.e., produces more, and whiter, visible light) the hotter it is—but of course its life will be shorter.
They don’t die - they reincarnate ;-)
The basic power formula is P = I^2 / R where R is the combined resistance of filament resistance plus rheostat resistance and I is the current in the circuit.
When power is first applied, filament resistance is near zero (startup current is momentarily huge); and that filament resistance builds to a steady state as the filament heats up to produce light.
With a rheostat involved, there’s an extra resistance in the circuit and less current is applied to the filament ... decreasing the power consumed by the filament and dimming the light output
A rheostat cuts down the current (I) by increasing circuit resistance R. Without a rheostat, almost all resistance is in the bulb filament, and that resistance goes from almost zero to a higher value as the filament heats up.
If you cut the current (I) by increasing total resistance (R), the startup current is not only diminished, the total power consumed is less — because of that I squared factor in the power formula.
http://www.topbits.com/rheostat.html
Thanks everybody.
I was thinking in the past.
Beliving that dimmer swithces were still varible resistors.
I’ve actually istalled more than a few around here, now that i know for a fact that i’m saving some cash, that alone adds to the cozy atmosphere that the dimmers provide.
P = I^2 / R
Is that Kirchofs law?
It’s beeen a while for me.
Apparently thees dimmers are now solid state.
I was thinking they were rheostats myself.
I got the power formula wrong ... P = I*E
Using Ohm’s law I = E/R that formula becomes P = I^2*R
When I want to dim a room I turn on blacklights (to counteract the whitelights).
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.