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-   -   Higher wattage dimmer switches? (http://www.diychatroom.com/f18/higher-wattage-dimmer-switches-31012/)

jamiedolan 11-01-2008 09:36 AM

Higher wattage dimmer switches?
 
Do they make higher wattage dimmer switches? Most seem to be rated at about 600watts.

I am going to install soffit lights out front, but I don't want to have bulbs burning full brightness due to cost of electricity and that much light is not necessary. I know that bulbs also last much much longer if you run them undervoltage, (i.e. I found a 130v bulb in my house that still works that I am pretty sure was installed in 1963 and used on a regular basis).

I am thinking about 14 can lights, about I was thinking about installing 75 watt bulbs, so I could turn up the brightness if necessary, but would generally want to run it at about 20-30 watts a bulb.

I am also planing on running these through a intermatic panel style timer box.

Am I best just wiring in 2 dimmer switches, each one for about half the lights so I stay under 600 watts? Or is there a larger capicity dimmer I can get?

Thanks
Jamie

dSilanskas 11-01-2008 09:55 AM

Yup yup perhaps you want to try a 1000 watt dimmer? You can get them at any electrical whole saler or Home Depot might might sell them:thumbsup:

jbfan 11-01-2008 10:05 AM

Look at the dimmers before you decide. Some have external fins to disapte the heat better, and this style may not fit the look you are going for.

Yoyizit 11-01-2008 10:29 AM

You can also go with a buck-boost transformer. At 90% of rated voltage you should have 70% of rated brightness, for incandescents. Your lamp life at this reduced voltage should be 3.5x longer.

frenchelectrican 11-01-2008 10:54 AM

Sure there is few larger dimmer on market and yes you can get them in 1,000 watts size it should have one on hand one of the few big box store near ya.

However once you go over 1,000 watt size you will run into few issue if you are not prepared with this due the 1500 and larger dimmers have extreal cooling fins on it and it typically need it own single or two gang box for this set up.

Yeah they will cost somehow more over 600 w run of mill dimmers


Merci,Marc

J. V. 11-01-2008 12:07 PM

Jamie, 14 -75 watt bulbs are 1050 watts total. A 1000 watt dimmer will be to small. Can you use 60 watt bulbs? If so you will have only 840 watts to deal with. You could put a resistor in series with each light to lower the voltage. Try a 100 ohm first and see. Just on one for testing. You can still use the dimmer with the resistors in the lamps.

jamiedolan 11-01-2008 12:16 PM

Quote:

Originally Posted by J. V. (Post 179541)
Jamie, 14 -75 watt bulbs are 1050 watts total. A 1000 watt dimmer will be to small. Can you use 60 watt bulbs? If so you will have only 840 watts to deal with. You could put a resistor in series with each light to lower the voltage. Try a 100 ohm first and see. Just on one for testing. You can still use the dimmer with the resistors in the lamps.

Yes, I can use smaller bulbs, I just picked that number to ensure it is bright enough. I just want enough light to accent things and make the house look nice at night. I hope that I can get by with keeping the bulbs running pretty low, otherwise it is going to make a huge dent on the electrical bill.

How does a resistor work on 120v lighting? Does it it knock down the voltage that is being fed to the lights? i.e. so the lights are fed with 100V with the resistor inline? Is a 120v resistor something I would find at a big box, or is it more of a supply house item?

Thanks
Jamie

Yoyizit 11-01-2008 01:31 PM

If you ask, I can advise you on the relative risk of each method below. I've tried all of these, but I am not the NEC and I don't write fire insurance policies.

14 ea. 75w bulb draw 14(75/120) = ~9A.
9A(20V) = 180W so you need a ~300W resistor oF value 20/9 = 2.2 ohms.

Hosfelt.com, part #47-170, is a 1/2 ohm 15 w resistor. You need 20 ea. wired in series/parallel to get ~2.2 ohms and 300W. 9 cents each plus shipping, plus your labor soldering these together.

If you connect one end of this composite resistor to the AC neutral there will be only 20v across it. It needs free air circulation.

The problem with incandscent lamps is that the current drawn depends on the voltage across the lamp, so the lamp is a resistor whose value depends on the current through it.
It's very hard to calculate the correct series resistor value.

Since dimmers chop up the AC waveform you may not get as long lamp life as you would expect to get if the lamps were being fed by a sine wave source (like from a Variac, a series resistor, inductor, or capacitor).

They used to sell little flat diodes that fit in lamp sockets and gave you way long lamp life at way reduced brightness.
But, they caught fire!

You can also solder a 3A, 400 PIV diode in series with each lamp, a few inches away from the heat that the lamp socket sees. Since your lamp box is fireproof, I'd put the diode in the box.
Sizing the diode correctly is important. This method is slightly more risky than a series resistor; that's why you should put each diode in the lamp box.

You could also have each lamp with its own (higher ohms but less wattage) resistor, but at these power levels they need free air circulation.

If you want variability you could try a 10A Variac; otherwise a step down transformer.

Theatre lights used to be dimmed by huge inductors; they put the iron core in or out to control the inductance and the brightness, but finding an inductor of the right value is as hard as sizing your series resistor.

InPhase277 11-01-2008 01:42 PM

Quote:

Originally Posted by Yoyizit (Post 179568)
14 ea. 75w bulb draw 14(75/120) = ~9A.
9A(20V) = 180W so you need a ~300W resistor oF value 20/9 = 2.2 ohms.

From Hosfelt.com, part #47-170, a 1/2 ohm 15 w resistor. You need 20 ea. wired in series/parallel to get ~2.2 ohms and 300W.
9 cents each plus shipping, plus your labor soldering these together.

If you connect one end of this composite resistor to the AC neutral there will be only 20v across it.

The problem with incandscent lamps is that the current drawn depends on the voltage across the lamp, so the lamp is a resistor whose value depends on the current through it.
It's very hard to calculate the correct series resistor value.

Since dimmers chop up the AC waveform you may not get as long lamp life as you would expect to get if the lamps were being fed by a sine wave source (like from a Variac).

They used to sell little flat diodes that fit in lamp sockets and gave you way long lamp life at way reduced brightness. But, they caught fire!

If you want variability you could try a 10A Variac; otherwise a step down transformer.

Theatre lights used to be dimmed by huge inductors; they put the iron core in or out to control the inductance and the brightness, but finding an inductor of the right value is as hard as sizing your series resistor.

Jeeze Louise!! You do know that this is a residential lighting setup being installed by a DIY'r right? Rigging series resistors and variacs and buck/boost transformers are quite a different ball game than "Yes, use 65 watt lamps on a 1000 W dimmer".

Yoyizit 11-01-2008 06:22 PM

Quote:

Originally Posted by InPhase277 (Post 179570)
Jeeze Louise!! You do know that this is a residential lighting setup being installed by a DIY'r right? Rigging series resistors and variacs and buck/boost transformers are quite a different ball game than "Yes, use 65 watt lamps on a 1000 W dimmer".

Dear Ms. Louise:

If the guy survived at least 18 years he must have some common sense.

Let the OP assess the risks.
It's his/her call. Not mine. Not yours.

Why go to a DIY site if you're told, "Have a professional do it." You don't need the Internet to hear that, there is advertising everywhere.

Better yet, figure out what kind of OP we are dealing with \/ \/

An adult messing with house electrical wiring is exposing himself/herself to danger, depending on how foolhardy and/or uninformed he/she is. If he/she is advised of the risks and understands them, then fine.

An adult messing with house electrical wiring who has been advised by several books or a DIY forum is less likely to hurt him/herself. If he/she is advised of the risks and benefits and understands them, then fine.

If the OP is a person who is not curious, uninformed, perhaps lacking common sense, and wants to mess with dangerous stuff, then don't do it.

How often and under what circumstances should a DIY forum advise an OP not to do some residential elec. task because it is too dangerous? The OP will do what he/she wants in any case. The best we can do is to refuse to point the way, or to point the way and the hazards/benefits that lie along that way.

Since there is a fuse upstream of the worksite, we're not dealing with arc flash. That is a different ball game.

BTW, I don't think a series impedance is practical for this application, for a number of reasons.
The pole transformer is just outside my house, I get at least 122v, so my bulbs don't last. If I could get a buck-boost for just the lighting circuits in my house at a reasonable price, I'd do it. With no electronics involved it'd be a lot more reliable than any dimmer.

Wildie 11-01-2008 07:29 PM

Years ago, it was possible to buy a diode that fit in the lamp socket.
The diode was packaged in a module about the size of 5 cent piece and was about 3/16" thick!\
The idea was that the unit placed in the socket and held there when the bulb was screwed in.
This allowed only half the voltage wave current to flow, effectively reducing the light output.
Whether these are now available, I have no idea!
Another idea would be to wire in a diode at the switch location. It would of course have to have a rated capacity suitable for the total load.
I remember once being given the job of wiring diodes into the EXIT signs for a large institution. The intent being to increase the lamp life of these units.
If my memory serves me right, the diodes were manufactured by LEVITON. If these are still available they could be installed in the light fixture boxes.

InPhase277 11-01-2008 07:44 PM

Quote:

Originally Posted by Yoyizit (Post 179660)
Dear Ms. Louise:

If the guy survived at least 18 years he must have some common sense.

Let the OP assess the risks.
It's his/her call. Not mine. Not yours.

That isn't my point. If the OP just wanted to know what would happen theoretically, then I'm all for it. But for a DIY site, I don't think it would be appropriate to instruct a novice in the ways of resistance-based lighting control.

After all, the OP wasn't even sure IF a dimmer larger than 600 W existed. I think we should instruct the DIY'rs on the available parts and safest standards for the situation. There are plenty of questions asked here that require the "CALL AN ELECTRICIAN" answer.

220/221 11-01-2008 09:01 PM

I always recommend splitting up circuits and staying well under the 600 watts.

The 1000 watt dimmers that fit in the box like the 600's get hot as hell. Also, If you gang them the are derated.

If you want to put them all together, go with an old school dimmer with external fins.

Here is a 2000W dimmer I ran across in my warehouse.

Still in the box :thumbup:


http://i8.photobucket.com/albums/a8/...2/IMG_0316.jpg


http://i8.photobucket.com/albums/a8/...2/IMG_0319.jpg

Yoyizit 11-02-2008 08:14 AM

Quote:

Originally Posted by InPhase277 (Post 179681)
I don't think it would be appropriate to instruct a novice in the ways of resistance-based lighting control.

He specifically asked about it. I hope I dissuaded him.

joed 11-02-2008 08:21 AM

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.


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