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Old 11-02-2008, 10:38 AM   #16
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Higher wattage dimmer switches?


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The dimmer installed should be able to handle the fixtures with their maximum wattage bulbs installed. You don't know what the next person will install in the fixtures.
Good point. I thought about that after my post. He should use the max allowed in the fixture for his calculations. Even with the resistor installed to look like it is a factory piece, it still could be removed and the benefit lost.

Jamie, Either slip it up or get one that can handle the wattage.

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Old 11-03-2008, 11:50 AM   #17
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Higher wattage dimmer switches?


Hi Guys;

Thanks so much for the responses. Don't worry about me frying myself or anything. I don't know everything about electrical work, but sure understand all of the basics well enough not to get a shock from any setup.

I am farmilar with the varivac's, many people use them on there coffee roasters to make sure they have consistant voltage comming to them.

Bottom line, the question that really comes to my mind, that I am still a bit confused about is this;

What advantage would resistors, a transformer, a varivac, etc, have over one or two of the correct size dimmer switches? Assuming I put the dimmer switches in a correct box so there is not a heat issue that is going to cause a problem.

Are we talking about any electrical savings with any of these vs the others?

Regardless of what option I use to get the bulbs down to say 20 watts (varivac, resistors, dimmers), they are only going to use 20 watts each right? I assume there is a bit of overhead for the dimmer switches and the varivac, so they draw a bit of there own power?

Thanks for all the imput.

Jamie
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Old 11-03-2008, 03:03 PM   #18
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Higher wattage dimmer switches?


The resistor will be the cheapest and easiest to install. But if someone removes the resistor then the fixture will pull the full voltage and watts depending on the bulbs used.

The transformer is over kill IMO. And the most expensive and labor sensitive. You will need an enclosure too with this method.

Getting the correct size dimmer or dimmers is probably the best way to go.

I had a customer once that was blowing bulbs in his soffit lights prematurely. I installed a 100 watt resistor in each fixture and covered it with shrink wrap. Never heard from him again about burning out bulbs. No dimmer was used in this application, but could have been.

If you go the resistor route, go to a electronics supply store. Tell them what you are doing. Tell them you need a big barrel type, one that will give off heat easily. The bigger (dimension) the better.
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Old 11-03-2008, 07:35 PM   #19
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Higher wattage dimmer switches?


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Originally Posted by J. V. View Post
The resistor will be the cheapest and easiest to install. But if someone removes the resistor then the fixture will pull the full voltage and watts depending on the bulbs used.

The transformer is over kill IMO. And the most expensive and labor sensitive. You will need an enclosure too with this method.

Getting the correct size dimmer or dimmers is probably the best way to go.

I had a customer once that was blowing bulbs in his soffit lights prematurely. I installed a 100 watt resistor in each fixture and covered it with shrink wrap. Never heard from him again about burning out bulbs. No dimmer was used in this application, but could have been.

If you go the resistor route, go to a electronics supply store. Tell them what you are doing. Tell them you need a big barrel type, one that will give off heat easily. The bigger (dimension) the better.
JV, you might try diodes next time. No problem with heat then.
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Old 11-04-2008, 11:29 AM   #20
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Higher wattage dimmer switches?


Tell me how a diode works in this application? A diode only allows current to flow in one direction, where a resistor affects the voltage. I will be looking for your reply. Yes, I agree about the heat produced from the resistor. Thanks
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Old 11-04-2008, 01:24 PM   #21
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Higher wattage dimmer switches?


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Tell me how a diode works in this application? A diode only allows current to flow in one direction, where a resistor affects the voltage. I will be looking for your reply. Yes, I agree about the heat produced from the resistor. Thanks
Hi JV
Rather than go through a long drawn out explanation, will it suffice to say its current flow that causes heat/light!
With a diode the current is reduced to one half of a cycle!
There is little resistance in the forward flow of current through the diode. On the reverse, there is no flow. No current flow, no heat. And if there is little resistance, no heat is generated either.
So during the positive cycle the full current will flow through the load. This will start to heat the lamp element. Giving off some light.
But, on the negative cycle no current flows so the element starts to cool. And the light produced will start to reduce.
Hence, the reduction of light output.
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Old 11-04-2008, 01:40 PM   #22
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Higher wattage dimmer switches?


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Hi JV
Rather than go through a long drawn out explanation, will it suffice to say its current flow that causes heat/light!
With a diode the current is reduced to one half of a cycle!
There is little resistance in the forward flow of current through the diode. On the reverse, there is no flow. No current flow, no heat. And if there is little resistance, no heat is generated either.
So during the positive cycle the full current will flow through the load. This will start to heat the lamp element. Giving off some light.
But, on the negative cycle no current flows so the element starts to cool. And the light produced will start to reduce.
Hence, the reduction of light output.
Have you actually put this into use or is this just theory based? It makes sense in theory, but i'd be interested to see if this has actually been done and proven to work....
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Old 11-04-2008, 05:32 PM   #23
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Higher wattage dimmer switches?


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Have you actually put this into use or is this just theory based? It makes sense in theory, but i'd be interested to see if this has actually been done and proven to work....
This is not a theory! In an earlier post I mentioned that I wired diodes into illuminated EXIT signs. These diodes were manufactured by LEVITON for the specific purpose of reducing the power draw and extending the lamp life in these signs.
The use of diodes is not a new idea. We were using diodes for this purpose back in the early 70's.
I must say, that I was surprised to read that some people are using resisters for this purpose!
Using resistors is pre- 1950 technology!
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Old 11-04-2008, 08:05 PM   #24
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Higher wattage dimmer switches?


Using diodes manufactured for the purpose is a big difference from going to radio shack and buying some diodes.
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Old 11-04-2008, 08:12 PM   #25
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Higher wattage dimmer switches?


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Using diodes manufactured for the purpose is a big difference from going to radio shack and buying some diodes.

Haha, I don't go to radiosmack for anything (other than the occasional roll of solder). I buy all my electronic parts online at www.newark.com where I've had an account for quite some time.
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Old 11-10-2008, 09:41 AM   #26
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Higher wattage dimmer switches?


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Haha, I don't go to radiosmack for anything (other than the occasional roll of solder). I buy all my electronic parts online at www.newark.com where I've had an account for quite some time.
Hosfelt.com also has great performance/price ratios.

The rms value of half wave rectified AC from a diode is 1/2 of the peak AC (~170v) which gives half power to the lamp (~85vrms). The dissipation in the diode is only about 1w. The lamp may last 30x longer.

And the voltage the diode applies to the lamp is more or less independent of the lamp resistance (just like a dimmer or a Variac).

But an incandescent lamp pulls 10x to 15x normal current for a few dozen milliseconds so the diode's I squared T rating has to be high enough to withstand this current pulse.
For a 1N4004 diode this rating is about 7 amps-squared-seconds.

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