NA?Dimmers Use More Wattage?NA?

Jim Rosenow

Jim Rosenow

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Jim Rosenow
Ok...it's 7 degrees and a wind chill of -17...I'll annoy you folks.

We had halogen track lighting over the counter in the kitchen....7 of 'em at 35 watts a shot. Just finished replacing them with 4 50 watt (8.5 watt draw) LED's. Cool... 245 watts to 35....same hardware.

I had taken the dimmer switch out, as the halogens didn't really like it...didn't dim well and hummed. I told my better half I was going to put it back in, and she suggested against it. Her rational was that some lights in the Citation she flies actually consume more wattage dimmed than they do at full bright.

Interesting....both the fluorescents she referenced in the airplane, and the track lighting go thru transformers (down to 12v for the track lighting). So..... would the track lighting also use more wattage when dimmed. Electricians....what say you?

Jim
 
She's full of it. The bulbs do not consume more wattage dimmed. Some tiny amount of energy is wasted in the dimmer but it's still a net savings. 120V halogens shouldn't have a problem with a semiconductor dimmer though some filament sing at half brightness is not uncommon. If you've got low voltage fixtures you shouldn't have the sing, but some of the dimmers won't work well with it.

The other issue for running halogens dim is that it may leave them cold enough to inhibit the halogen cycle, but frankly there is less filament boiling going on at the lower settings as well. Working for a long time with halogen stage lights, I can tell you that the benefits outweigh the problems.
 
flyingron said:
She's full of it. The bulbs do not consume more wattage dimmed. Some tiny amount of energy is wasted in the dimmer but it's still a net savings. 120V halogens shouldn't have a problem with a semiconductor dimmer though some filament sing at half brightness is not uncommon. If you've got low voltage fixtures you shouldn't have the sing, but some of the dimmers won't work well with it.

The other issue for running halogens dim is that it may leave them cold enough to inhibit the halogen cycle, but frankly there is less filament boiling going on at the lower settings as well. Working for a long time with halogen stage lights, I can tell you that the benefits outweigh the problems.
Click to expand...

I'll let YOU tell her that, Ron :) After reading the the page 172guy referenced above....maybe she was saying the NET savings are not AS MUCH as one would anticipate. I dunno....I'm happy going from 245 watts to 35, so I"ll leave it at that. Thanks!

Jim
 
My parents house had basically the same setup. It should all work fine. However, you have to make sure you bought "dimmable" LED lights, and have an LED compatible dimmer switch.

Originally, when my parents swapped fixtures, some LEDs wouldn't turn off, others would be either on or off only, while others would hum...Just my experience, and something to watch out for.
 
Thanks for the info, guys! It's getting interesting...I had bought top-of-the line (based on the probably 40 in the house) Feit dimmable LED's. Swapped 'em out as I mentioned above. (Remember, no dimmer in place right now) Fired 'em up...gorgeous. Better half started making Christmas goodies under 'em yesterday, and everyone once in awhile, one (indivdually) will blink out for a second. Maybe once every 5 minutes... different bulbs, at different times.

Some prior history (pre-current-LEDs) for those, if any, who care... This fixture has an internal transformer of course, and originally came with the halogens (245 watts of) and a dimmer. Energy-efficient house, so that was killing me. The halogens' light seemed to 'waver', anyway. Bought some cheap (non-dimmable) Chinese LED's, and swapped an on/off for the dimmer. Had essentially the same issue with the LED's as now.

Put the halogens back up, left the on/off in place, and the 'wavering' went away, for the most part. Left it that way 'til colder weather, and I decided to try the Feit dimmables (remember....still on the on/off switch...no dimmer).

I'm almost to the point to just go buy a new fixture....but who knows if it would have the same issues. Oh...and it's not voltage or power parameters....voltage meter says those are fine. Wiring is 4 years old new install.

Jim
 
Most cheap dimmers are only good for incandescent load. A straight 120V Halogen isn't a problem (it is an incandescent bulb, just one that's designed to burn hotter due to the halogen gas inside the envelope that migrates the boiled off tungsten back to the filament). However, as I mentioned in my earlier post, if you have a low voltage fixture with halogens, then the dimmer may indeed gag on it. There are dimmer that can handle the transformers in the loop.
 
Understood....and during the process I purchased a dimmer recommended by the manufacturer of the first set of LEDs for that purpose....no joy. Currently, there's no dimmer in place....straight on/off. It's just nuts!

Thanks, Ron!

Jim
 
Um..."wattage" is not consumed at all, current is consumed. Wattage is output (in most electronics as unwanted heat, in bulbs as desired light and unwanted heat) and is the result of current X voltage.

Also there are different types of dimmers, a very simple one would simply divide the current, allowing less to go through the lamps, but the rest back to ground through resistance, but the total would be the same?
 
LongRoadBob said:
Um..."wattage" is not consumed at all, current is consumed. Wattage is output (in most electronics as unwanted heat, in bulbs as desired light and unwanted heat) and is the result of current X voltage.

Also there are different types of dimmers, a very simple one would simply divide the current, allowing less to go through the lamps, but the rest back to ground through resistance, but the total would be the same?
Click to expand...

Thanks! You sound like you know what you're doing, Bob....(and others) riddle me this. As noted above, I replaced the halogens with LED's, and after awhile they started blinking individually, randomly. We left them on for a couple hours that way, as we were in the middle of a project. Next day we turned them back on to do more baking, and not one blink......for 3 hours...nor any time since then. Remember, there is NO dimmer in the circuit at this point. I think it's haunted!

Jim
 
LongRoadBob said:
Also there are different types of dimmers, a very simple one would simply divide the current, allowing less to go through the lamps, but the rest back to ground through resistance, but the total would be the same?
Click to expand...
There is no dimmer that works like that.

A simple dimmer would be a resistor in series with the bulb. Lets say you have a 60W bulb at 120V. Without the dimmer, the bulb is flowing .5A and has a resistance of 240 Ohms. We put another 240 Ohm resistance in series, the voltage across the bulb is half. The current flow is now only .25A (that's all that is flowing, nothing is redirected anyhow). The bulb now only dissapates .25A*60V or about 15 Watts.

The truth is, that your in-the-wall dimmer is not a resistor. One major reason is size, the other is that changing the size of the load (your bulb wattage) causes the dimmer to have different response over it's range. I've worked in a theatre with an old resistance dimmer board. Often we had additional lights (not pointed at the stage), to put a load on the resistance dimmer to get the response right.

The in-the-wall dimmer (and all modern stage dimmers) are TRIACS. This is a semiconductor device that has very high resistance in its OFF state and very low resistance once it "fires". The dimmer "fires" the appropriate point in the waveform to give the brightness requested. It's more of a duty cycle thing than controlling the absolute current. Still the average power consumed by the bulb (in light and heat) is adjusted based on where the dimmer is set.

Resistance or triac or magnetic amplifier or auto transformer or thyratron (I've worked with all of those except the last), less power in the entire system when you dim the bulbs. There's a bit lost in dimmer itself (so maybe at 99.5% brightness, you may be using the same power as at 100%), but for most settings it's negligible.
 
Jim Rosenow said:
Thanks! You sound like you know what you're doing, Bob....(and others) riddle me this. As noted above, I replaced the halogens with LED's, and after awhile they started blinking individually, randomly. We left them on for a couple hours that way, as we were in the middle of a project. Next day we turned them back on to do more baking, and not one blink......for 3 hours...nor any time since then. Remember, there is NO dimmer in the circuit at this point. I think it's haunted!

Jim
Click to expand...

As flyingron pointed out, I oversimplified (or just plain misled) about what a dimmer is, how it works. I'm a little rusty, on electronics, been programming and away from electronics a while.

With LEDs, I'm not quite sure what the setup you are using is, but it sounds a little troubling that they were blinking randomly. An LED is a light emitting diode. A diode is basically a kind of a switch. There is something calle forward bias, which means the voltage (and polarity) has to be over the forward bias voltage for it to turn on. Up until forward biased it is seen as equivalent to an open switch, no current will flow through the diode (light emitting or regular). Once forward voltage is achieved it will flow as if it were a closed switch, with little resistance. Because of this there needs to be current limiting, which means resistors that will not allow the current to go "infinite" or max out. These LEDS you have are still using a DC power supply correct? A supply running ac on one side and DC feeding the LEDS?

Because the thing I was thinking it might be that the power supply is not up to the demands of so many LEDs, or right at its limit, so when all turned on it was struggling to supply the correct voltage and as each turned on drew more current than the supply could supply, which brought the voltage down temporarily which meant that some LEDs were no longer forward biased (and I'm not sure if yours are all series or parallel or series-parallel wired) for a brief bit, the power supply caught up, they were, but drew too much etc.

This is just wild guessing, as I don't still really know the setup you are using but I would be careful and check the supply, see if it is hot, and would double check the setup.
 
It's got really squat to do with BIAS. The problem with LEDs is they have hardly any internal resistance and if you put one against a 120V, it's going to flow so much current it is going to burn up instantly. You can restrict the current flow with a simple resistor (we do this commonly when running them on lower voltages), but then you're dissipating power in the resistor. The guts of an LED bulb designed for normal 110V fixtures is a small power supply that efficiently provides the proper voltage, current limited.

The problem with a regular "designed for incandescent and other resistive loads" when you throw something like a transformer, or a fluorescent, or similar load on them, is they cheap diac that they use to detect the zero crossing may be confused. Then add to that the power supply (or non-incandescent bulb) may not handle having the AC wave form chopped like the TRIAC dimmer does, means that the bulb may indeed be incompatible with the dimmer. You need a dimmer designed for non-resistive loads and you need a bulb that's designed to handle TRIAC modulated AC.
 
Previous set-up...7 halogens @ 35 watts per. Current set-up 4 LED's @50 watts equivalent per (but advertised draw of 8.5 each)....and 100% same fixture, minus the extra 3 'light units' (for lack of a better term).

"These LEDS you have are still using a DC power supply correct? A supply running ac on one side and DC feeding the LEDS?".... 100 percent correct..... and to emphasize, there is NO dimmer in the circuit. :)

Jim
 
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A F4 sitting on the ground uses the same amount of fuel cruising up at altitude. Pulse Width Modulation PWM is your friend with LEDs
 
Jim Rosenow said:
Previous set-up...7 halogens @ 35 watts per. Current set-up 4 LED's @50 watts equivalent per (but advertised draw of 8.5 each)....and 100% same fixture, minus the extra 3 'light units' (for lack of a better term).

"These LEDS you have are still using a DC power supply correct? A supply running ac on one side and DC feeding the LEDS?".... 100 percent correct..... and to emphasize, there is NO dimmer in the circuit. :)

Jim
Click to expand...

Hey, a couple of things. For one, using a voltmeter the voltage won't tell you the whole story necessarily.
Let me just get one more thing straight, you bought the LEDs but are they led assemblies? Meaning led (which are simple and small, and just single items) or rather led modules, where they may have a circuitous board, etc?

So I'm getting that you didn't buy the whole thing, LED lights plus new power supply designed for those led specifically?

And no, I get there is no dimmer, it's just a simple circuit, but something is wrong if your LEDs are turning off intermittently. Right away I would suspect the power.

Here's why simply using voltmeter doesn't tell you what you need to know...I would use an oscilloscope to look at the voltage looking for ripple voltage, or power cycles looking wrong. Cheaper power supplies rectify AC and may be designed with filtering. Often good ones use capacitors to smooth out the fluctuations in voltage that are on the output. If you looked at ripple voltage it would stay positive, but look like an AC wave riding up above zero. Or just bumps.

Not sure what to say to help. Again, I would check how hot the power supply is getting. It seems that sometimes the LEDs intermittently turn off and on, and other times not? What about if you turn on and off a bunch of times, does it sometimes get flaky but other times seem stable?

Ambient heat? Notice of it happens when the area around the power supply is colder, warmer, whatever?
I'd consider only setting in two of the four....see if they turn off and on. Try and test them, and if they are solid, try just the other two. Same thing there. If this only happens when all four are on, that would point even more at the power supply. If it follows one or two of the LEDs (assembly's?) then it might be isolated.

I would really suspect the power supply and buy the one designed for these led units. Good luck!

One thing you could do, is set the voltmeter up, have it continuously read out, and while one of you is watching the voltage display, the other tells you when lights go dark, see if it just the power supply struggling.
 
But...but....but....It's really impossible to troubleshoot at this point. As noted above, the issue happened the first time the LED's were powered up. Since then, nary a flicker. Maybe next I'll add a dimmer :) A lot of good information, folks....thanks!

Jim
 
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LongRoadBob said:
Um..."wattage" is not consumed at all, current is consumed. Wattage is output (in most electronics as unwanted heat, in bulbs as desired light and unwanted heat) and is the result of current X voltage.?
Click to expand...

That's an interesting heresy. Wattage is the ONLY thing that can be consumed. It is consumed as light and heat. Current and voltage are the mechanisms by which power is manufactured.

Jim
 
Let me get this straight. You had 12v halogens, and replaced the lamps (bulbs) with 12v LEDs? Then you get a flicker, then no flicker.
Something tells me that you are running 12v AC, into a 12v DC apparatus. Hence the flicker. When you turned them off, and back on, the individual LEDs got out of phase, so you don't notice the flicker, but the flicker is still there. LEDs are a DC apparatus. A diode to be precise.
A diode only conducts in one direction. AC supplys current in two directions, swapping direction at a frequency of about 60 times per second.
You can actually use 4 LEDs as a rectifier, to produce pulsing DC. But they won't last very long doing that as the current going through them to feed the load will most likely be more than they can handle. Along with the reverse voltage applied when the load is switched off, and on.
The incandescent Halogen lamp doesn't know if it's being fed AC or DC, nor does it care. So it's power supply probably consists of a transformer,
and that's about it. The LED requires a transformer, rectifier, and filter. Or you'll get what you have.
 
bluerooster said:
Let me get this straight. You had 12v halogens, and replaced the lamps (bulbs) with 12v LEDs? Then you get a flicker, then no flicker.
Something tells me that you are running 12v AC, into a 12v DC apparatus. Hence the flicker. When you turned them off, and back on, the individual LEDs got out of phase, so you don't notice the flicker, but the flicker is still there. LEDs are a DC apparatus. A diode to be precise.
A diode only conducts in one direction. AC supplys current in two directions, swapping direction at a frequency of about 60 times per second.
You can actually use 4 LEDs as a rectifier, to produce pulsing DC. But they won't last very long doing that as the current going through them to feed the load will most likely be more than they can handle. Along with the reverse voltage applied when the load is switched off, and on.
The incandescent Halogen lamp doesn't know if it's being fed AC or DC, nor does it care. So it's power supply probably consists of a transformer,
and that's about it. The LED requires a transformer, rectifier, and filter. Or you'll get what you have.
Click to expand...

Do I understand you to say that you think there's an issue with the transformer that goes from 110 AC to 12 volt DC?....and that it's outputting 12VAC? Remember, only the bulbs were changed. How would that have affected the halogens prior to the change? Would it have been noticeable on them also? Too confusing!! Thanks!

Jim

Edit...re-reading your post, you're saying that it needs additional 'stuff' to work LED's? Seems odd that they would sell LED's that would fit in fixtures they won't work in. Like I said... too confusing!
 
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Halogen/incandescent bulbs don't really care if they're being fed AC or DC... but LEDs do.
 
Looks like it's time to climb up, disassemble the fixture and see what the transformer inside says.... 120 VAC to 12 VAC or 12 VDC?

Edit- Uh-oh....just checked one of the LED bulbs......8.5W 12VAC 60Hz 700mA 500 lumens. The halogens just say 35W. They came with the fixture.
 
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I do hope that you all don't mind that I use this entire post for a final exam next semester. The student(s) that pick out the best fallacies and incorrect statements get an A.

Example: The "transformer" that converts 110AC to 12DC. I want to by a hundred million of those transformers and win the Nobel next year for something that we always thought was impossible.

Dozens more.

Keep it up. You are making my job a LOT easier.

Jim
 
weirdjim said:
That's an interesting heresy. Wattage is the ONLY thing that can be consumed. It is consumed as light and heat. Current and voltage are the mechanisms by which power is manufactured.

Jim
Click to expand...

It is not really consumed, it is output. In most of electronics it is an undesirable by product of inefficiency, but we use it here for light.
 
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weirdjim said:
I do hope that you all don't mind that I use this entire post for a final exam next semester. The student(s) that pick out the best fallacies and incorrect statements get an A.

Example: The "transformer" that converts 110AC to 12DC. I want to by a hundred million of those transformers and win the Nobel next year for something that we always thought was impossible.

Dozens more.

Keep it up. You are making my job a LOT easier.

Jim
Click to expand...

......and the bonus essay question is, "Why exactly did those lights blink first-run, and not once the week since?"....."Buehler?...Feris Buehler??" LOL!

Jim (the electrically-uninformed one)
 
My dimmers in the Twin Beech use more wattage.....but then they are also double as feathering pumps. Holy crap, you should see how the cabin/panel lighting dims when you test those pumps during a night runup!
 
LongRoadBob said:
It is not really consumed, it is output. In most of electronics it is an undesirable by product of inefficiency, but we use it here for light.
Click to expand...

No, that's quite wrong. Wattage is simply a measure of power. In electronics it's the product of voltage times current, and in general it is energy per unit time. Power can be produced, transmitted or consumed, depending on the specific situation and perspective. It's wrong to say in general that "power is not consumed" (since it often is), or that "power is output" (because it's often input). Also, it is not "undesirable"; it is simply the rate of energy production, transfer or use, and it can be either desirable or undesirable, depending on your goal or perspective.
But what do you expect from an internet forum where everyone is an expert?
 
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Jim Rosenow said:
Looks like it's time to climb up, disassemble the fixture and see what the transformer inside says.... 120 VAC to 12 VAC or 12 VDC?

Edit- Uh-oh....just checked one of the LED bulbs......8.5W 12VAC 60Hz 700mA 500 lumens. The halogens just say 35W. They came with the fixture.
Click to expand...
So integral to the LED "bulb" is a rectifier, (4 diodes, and a filter capacitor, probably all on a tiny silicon chip) to convert that 12vac to 12vdc.
 
The cheap christmas light strings don't even have the rectifier. They only half-wave filter the AC, you can tell if you move your head (or the string) as you can see the 30Hz flicker.
 
Old school dimmers (some anyway) most definitely were resistors (variable resistors or rheostats) and when "on" increased the load in a circuit, increasing power usage. My understanding is that some new AC dimmers work differently (modulating on and off at varying frequency) to dim and actually reduce power usage. Power consumption is for conductor rating and billing purposes.
 
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2 pages and i still be confused:eek: can someone do cliff notes:)
 
GlennAB1 said:
Old school dimmers (some anyway) most definitely were resistors (variable resistors or rheostats) and when "on" increased the load in a circuit, increasing power usage.
Click to expand...

I'm sorry Glenn, but that is 100% wrong. No "in the wall" dimmers were resistive. They would never have fit. The 1000W stage dimmers had plates over a foot in diameter. They did not work by increasing the dissipated power. As I described above, they were used in SERIES with the load and the added resistance overall, decreased the current flowing and hence (since voltage was constant) the power.

Power = E**2/R. E is constant (120V). Increasing the load resistance changes the power consumed in inverse proportion.

As I stated, the main reason resistive dimmers were problematic, is that you had to size the resistance of the dimmer with the load to get a nice full range of dimming. Often theatres had to add phantom loads if they need to dim a smaller instrument. Resistive boards are real antiques. I restored one at the Utopia theater in Greenbelt, MD. They were quickly replaced in practice with autotransformers which essentially was a continuously tappable transformer which was smaller (albeit not lighter) and simply modulated the voltage which was independent of the load.

My understanding is that some new AC dimmers work differently (modulating on and off at varying frequency) to dim and actually reduce power usage. Power consumption is for conductor rating and billing purposes.
Click to expand...
Actually the frequency is constant, but they turn on conduction of the semiconductor device at different portions of the waveform depending on the dimmer setting (essentially varying the duty cycle). They still run at 60HZ.

Semiconductor dimmers are more efficient than resistive dimmers, but it's not the case that resistive dimmers consumed as much power while dimmed as they did at full brightness.
 
hotprops said:
2 pages and i still be confused:eek: can someone do cliff notes:)
Click to expand...

Ok...

Don't replace halogen lighting with LED lighting unless you know what you're doing -- and you'll likely need a new dimmer switch to accomplish it.

:)
 
ok but i just replaced every bulb in the house. all lites are dim able store brand from home deep,also EVERY lite is wired to older leutron skylark 600 watt dimmers . every thing works fine. sooo do i save on power when i dim the lites ??
 
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