Dimmer for LED/CFL

Little Bill

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Tennessee NEC:2017
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Electrician
Anyone know of a dimmer that will handle more than 150W for LEDs?

Most of what I've seen are dual rated for 600W incandescent and 150W LED/CFL.

I see some rated for 1000W incandescent but they aren't rated for LED/CFL.

Also, what is the reason for the 150W limit on LED/CFL, if there is a limit?
 

GoldDigger

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Staff member
Anyone know of a dimmer that will handle more than 150W for LEDs?

Most of what I've seen are dual rated for 600W incandescent and 150W LED/CFL.

I see some rated for 1000W incandescent but they aren't rated for LED/CFL.

Also, what is the reason for the 150W limit on LED/CFL, if there is a limit?
I think that the main reason for the limit of 150W for LED/CFL is that the non-linear load of the driver circuitry will look like a peak catching diode capacitor load, and the semiconductors in the dimmer will be heated much more by the pulsed current drain than they would be by a more uniform RMS current over the full cycle.
Loss based on I[SUP]2[/SUP]R will give more local heating when the current is pulsed at voltage peaks than when sinusoidal.
 

Dennis Alwon

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Chapel Hill, NC
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Electrical Contractor
Lutron makes them in all styles. They have a CL in the part number-- thus an Ariadni sp dimmer would be AY600P CL or something like that
 

PetrosA

Senior Member
Generally it's not the dimmer that you need to look at but the LED manufacturer's compatibility testing results for the lamp you're using. You need to check what they've tested for the exact lamp you're using - even color temperature can have an effect on what dimmers will work and the number of lamps you can use since each lamp in the series may use a different set of electronics. A single pole dimmer of a given series may be approved for use while the three way version is not or vice versa.

The CL dimmers are (in my humble, yet frustrated opinion) a marketing gimmick. They do not guarantee that LED lamps will work properly but they do cost more.
 

Little Bill

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Electrician
Lutron makes them in all styles. They have a CL in the part number-- thus an Ariadni sp dimmer would be AY600P CL or something like that
I prefer the Lutron CL series, but I didn't see one rated more than 150W for the LED.
Most of the time the rating is a dual rating if CL such as 600W/150W
600W being incandescent and 150W being CFL/LED.
 
Last edited:

gar

Senior Member
140324-0830 EDT

Little Bill:

Any delay to turn on phase shift dimmer for any purpose should be a 3-wire type. What I mean by 3-wire is:
1. It is not a 2-wire dimmer.
2. It requires a neutral connection.
3. It may have more than three wires.

When you have a 3-wire dimmer the electronics are powered from the full input line voltage under all conditions of the load. Under no-load the dimmer still works. Under any dimmer setting position when input power is applied the dimmer provides output current, and equivalent to when it was depowered.

Several 40 to 60 W equivalent LEDs I have measured have a PF of about 0.97 at no dimming. Close to a sine wave current load with no phase shift dimming. The ones I tested also dim very well with a Variac. Actually better because a lower equivalent voltage can be applied. These comments do not apply to any CFLs that I have tested.

With the Cree bulbs I have measured I don't think there would need to be a 150 W limit, but if you need to stay within published rating limits, then 150 is your limit. Note: an LED requires about 1/5 the power of an equivalent incandescent. 150 * 5 = 750. 150 W of 10 W LEDs is 15 bulbs.

These comments do not directly answer your question, but provide background.

You might ask the dimmer manufacturer if the 150 W limitation really applies to 0.97 PF LEDs.

.
 

PetrosA

Senior Member
140324-0830 EDT

Little Bill:

Any delay to turn on phase shift dimmer for any purpose should be a 3-wire type. What I mean by 3-wire is:
1. It is not a 2-wire dimmer.
2. It requires a neutral connection.
3. It may have more than three wires.

When you have a 3-wire dimmer the electronics are powered from the full input line voltage under all conditions of the load. Under no-load the dimmer still works. Under any dimmer setting position when input power is applied the dimmer provides output current, and equivalent to when it was depowered.

Several 40 to 60 W equivalent LEDs I have measured have a PF of about 0.97 at no dimming. Close to a sine wave current load with no phase shift dimming. The ones I tested also dim very well with a Variac. Actually better because a lower equivalent voltage can be applied. These comments do not apply to any CFLs that I have tested.

With the Cree bulbs I have measured I don't think there would need to be a 150 W limit, but if you need to stay within published rating limits, then 150 is your limit. Note: an LED requires about 1/5 the power of an equivalent incandescent. 150 * 5 = 750. 150 W of 10 W LEDs is 15 bulbs.

These comments do not directly answer your question, but provide background.

You might ask the dimmer manufacturer if the 150 W limitation really applies to 0.97 PF LEDs.

.
Gar, the last time I had to call a manufacturer about this issue was with some Seagull LEDs where the dimmer section of the instructions called for a maximum of six 15W LEDs on a single dimmer. To me that sounds crazy and it's below the 150W limit that a CL dimmer would suggest is okay to use. Their claim was that the inrush of the drivers creates a much larger load that could burn out a dimmer.
 

ELA

Senior Member
Repetitive Peak Inrush

Repetitive Peak Inrush

The reason is as GoldDigger outlined.
It is called Repetitive Peak Inrush.

While an incandescent only experiences an inrush when first turned on, an LED's capacitive input driver experiences a brief inrush current each half cycle.

 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
The CL dimmers are (in my humble, yet frustrated opinion) a marketing gimmick. They do not guarantee that LED lamps will work properly but they do cost more.

The problem is that there is no standard as to how an led is designed so Lutron has to make its best guess. They have a list as to what LED's have been tested and make no promises beyond that-- I have found that they work pretty well for most LED's but definitely not all. Some need the electronic LV dimmers-which are quite pricey.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Gar, the last time I had to call a manufacturer about this issue was with some Seagull LEDs where the dimmer section of the instructions called for a maximum of six 15W LEDs on a single dimmer. To me that sounds crazy and it's below the 150W limit that a CL dimmer would suggest is okay to use. Their claim was that the inrush of the drivers creates a much larger load that could burn out a dimmer.
It is was it is. Go with a tested component or risk problems.
In resi I can't recall the last time I placed more than 12 lights on a single dimmer. In commercial you may just need to use a lighting system with multiple dimming modules.
 

gar

Senior Member
140324-1499 EDT

I have several Cree bulbs. Recently I purchased a Utilitech Pro 0424722 60 W equivalent bulb. Its actual power input is 12.0 W with 0.97 PF at 123 V.

The Utilitech RMS current with no dimmer is 100 mA. Using my 3-wire dimmer the maximum brightness RMS current was 101 mA, and this monotonically decreased to 34 mA at minimum brightness.

.
 

PetrosA

Senior Member
The problem is that there is no standard as to how an led is designed so Lutron has to make its best guess. They have a list as to what LED's have been tested and make no promises beyond that-- I have found that they work pretty well for most LED's but definitely not all. Some need the electronic LV dimmers-which are quite pricey.
I wouldn't care so much but they're taking the regular dimmers off the market. I've had some LEDs which worked fine or better on a regular AY600P or DV600P than on either model's XXCL-153P version.

The reason is as GoldDigger outlined.
It is called Repetitive Peak Inrush.

While an incandescent only experiences an inrush when first turned on, an LED's capacitive input driver experiences a brief inrush current each half cycle.
I'm thinking more and more that I want a scope :)

Sierrasparky, Funny that you mention 12 lights ;) For a while I was selling PAR20 LEDs and 4" housings at closer spacings because the price point of the PAR30 LEDs didn't make economic sense even with fewer of them going into a ceiling. I did at least two kitchens with 12 or more lights, and the one kitchen had 12 on one dimmer. None of the recommended dimmers worked with them properly, in spite of the fact that they should have according to the manufacturer. With 12 LEDs, the lights wouldn't dim below about 70%. The workaround was to add one 38PAR20 in a far corner and that smoothed things out so that they all dimmed fine.
 

gar

Senior Member
140324-2350 EDT

Further experiments. These measurements are with either no dimmer or at the input to the dimmer. Comparing 10 W Utilitech and 60 W incandescent.

10 W Utilitech bulb:

Voltage ... RMS I ..... Watts ....... VA ........ PF

121.5 ...... 0.09 ....... 11.6 ....... 11.7 ...... 0.98 .......... Direct to bulb
121.5 ...... 0.10 ....... 10.9 ....... 12.4 ...... 0.90 .......... Maximum slider position
122.0 ...... 0.07 ....... 02.5 ....... 06.1 ...... 0.33 .......... Mid slider position
121.7 ...... 0.03 ....... 00.9 ....... 04.7 ...... 0.21 .......... Minimum slider position


60 W incandescent bulb:

Voltage ... RMS I ..... Watts ....... VA ........ PF

122.1 ...... 0.49 ....... 60.9 ....... 60.9 ...... 1.00 .......... Direct to bulb
122.2 ...... 0.48 ....... 57.6 ....... 58.6 ...... 0.96 .......... Maximum slider position
122.1 ...... 0.32 ....... 20.4 ....... 40.1 ...... 0.50 .......... Mid slider position
122.4 ...... 0.22 ....... 07.5 ....... 27.7 ...... 0.27 .......... Minimum slider position

Light output is about equal with undimmed sine wave 120 V supply.

Relatively speaking the LED vs incandescent does not dim as much for the mid and minimum slider positions. This is as expected because LED light output is more linearly related to current than is an incandescent.

In both cases it is distortion that causes bad power factor.

Any unbalanced neutral current will be greatly dependent upon on the relative dimming levels. However, if existing circuits with 60 W bulbs have LEDs used as replacements, then the heating of the branch circuit wiring will be less for the LEDs vs incandescents.

I have not plotted the current waveform.

.
 

Electric-Light

Senior Member
If it happens, I guess it's gonna have to be a microprocessor based with a soft-start sequence with the assumption that loads do not have inrush limit.
 
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