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Topic Title: "Defining LED Loads"
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Created On: 07 December 2012 09:33 PM
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 07 December 2012 09:33 PM
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MrOther

Posts: 531
Joined: 08 June 2010

Looking at some Phillips Zadora downlights using MASTERLEDspot lamps.

On there information pack they suggest that they are in consultation with dimmer manufactuers about definition of what is proper loading of LED lamps. They recommend a 10% Rule of Thumb. That means if a 300w dimmer that loading should exceed 30w.

What's the hidden issue here (other then bonus/misleading information leading to selling more dimmers.) Why can't you load the dimmer up to the max. power with the LEDs?

Also, when chosing an LED lamp should I be paying attention to the type of dimmer? I'm guessing because the LED drivers are electronic a inductive dimmer should be used.

Many thanks for your help and advice.
 08 December 2012 07:11 AM
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aligarjon

Posts: 2817
Joined: 09 September 2005

Originally posted by: MrOther

Looking at some Phillips Zadora downlights using MASTERLEDspot lamps.



On there information pack they suggest that they are in consultation with dimmer manufactuers about definition of what is proper loading of LED lamps. They recommend a 10% Rule of Thumb. That means if a 300w dimmer that loading should exceed 30w.



What's the hidden issue here (other then bonus/misleading information leading to selling more dimmers.) Why can't you load the dimmer up to the max. power with the LEDs?



Also, when chosing an LED lamp should I be paying attention to the type of dimmer? I'm guessing because the LED drivers are electronic a inductive dimmer should be used.



Many thanks for your help and advice.




Are they not referring to the minimum rating of the dimmer not the maximum. ?

Gary

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 08 December 2012 09:27 AM
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monk

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Joined: 08 December 2012

Yes, they refer to the minimum rating.
Having experimented a little, i found LED GU10 (sold as Dimmable) lamps flicker when used with a "standard" dimmer, and using one halogen GU10 in line with the LEDs will stabilise them. (a dimmer's usual min load is 50W, so this makes sense)

i found that this dimmer works well with LED GU10s. It's stated minimum load is 10W, yet i found it to work ok with one 6W lamp
">http://www.tlc-direct..../Pr.....QP401W.html


ah link removed. It's code is VL JQP401W from TLC

I have not experimented with the sealed LED units, so cannot comment on their compatibility with dimmers.
 08 December 2012 05:45 PM
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MrOther

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I'll have to have a reread, but I remember reading some where else of similar issues, why do Dimmer's need a minium loading? Guess it's to get over the minimum resistence theshold of the resister (if it's that type of dimmer) for any noticable effect to take place whilst dimming?
 08 December 2012 09:32 PM
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broadgage

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Originally posted by: MrOther

I'll have to have a reread, but I remember reading some where else of similar issues, why do Dimmer's need a minium loading? Guess it's to get over the minimum resistence theshold of the resister (if it's that type of dimmer) for any noticable effect to take place whilst dimming?


Allmost all modern dimmers use semiconductors that only conduct for part of each mains cycle.
Once triggered, the semiconductor passes current for the rest of that half cycle, the dimming effect being controlled by altering the point in the cycle at which triggereing takes place.
If the load current is too low, then the semiconductor wont reliably conduct for the remainder of the cycle after being triggered and the lamp will therefore be dimmer than expected or flicker.
The minimum current varies a bit with design but is typicly about 100ma or about 25 watts for domestic dimmers and about twice that for theatre dimmers.
 08 December 2012 10:41 PM
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hifly

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JCC say a min of 5 x 7watt LED downlights on a dimmer, some dimmers now have an adjustment to stop/reduce flicker when using dimmable low enery fittings.

I have only done a few dimmable installs and never needed to adjust the dimmers but i have always had min 5 x 7w units.

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