LED Bulbs / Dimmer Problem?

Thread Starter

FraserJim

Joined Sep 13, 2022
3
Have a Whole Home lighting system with dimmers located in central panel. On Sunday, I replaced one halogen PAR20 bulb with an LED bulb. Now total of 5 LED bulbs on circuit. When I turn circuit off, two of the bulbs remained dimly lit. 20-volt output on dimmer output. I replaced one bulb with an old incandescent and all bulbs would go off. So the dimmers do not play nicely with 100% LED circuits. I was thinking of adding wirewound 10k 25-watt resistors in parallel on each LED circuit and would appreciate feedback on approach and if this is the best resistor choice?
 

dendad

Joined Feb 20, 2016
4,216
I would think it a lot easier to just use an incandescent lamp, even a 15W one, as the resistor. Certainly a lot cheaper than a power resistor.
 

Thread Starter

FraserJim

Joined Sep 13, 2022
3
I agree, but have the following concerns. On this circuit, the remaining bulbs would be 50-watts so lightning may not be uniform. I have one “chandelier“ circuit with a single bulb. Haven’t figured out the lumens yet, but don’t know if I can get incandescent that large. I may have other circuits that may have output voltage after shutting off, but not be enough to light bulbs, so I would have to go to each dimmer, turn circuit on and then off and see if there is any output voltage. Looking for a more permanent solution.
 

Sensacell

Joined Jun 19, 2012
3,064
All you need is one small incandescent lamp in parallel with the LED lamps.

The low cold resistance of the filament shunts the leakage currents.
Old-school dimmers have leakage, the LED fixtures are very efficient and light up a bit passing this leakage current.
A parallel resistance reduces the voltage at the LED fixture, preventing them from glowing.
 

Ian0

Joined Aug 7, 2020
6,294
I would prefer a lamp to a resistor. A lamp will at least generate some light, where a resistor generates none.
The only disadvantage is that the colour temperature of the filament lamp will vary, but the colour temperature of the LEDs will remain constant.
Does the dimmer have a series inductor? If so, and if you have access to the neutral conductor, you could put a capacitor between output and neutral. That will shunt the small amount of current away losslessly, and improve the filtering at the same time.
Some dimmers have the capacitor (or a snubber) between output and incoming live, that makes things worse!
Also worth looking to see if the lighting system has a “preheat“ setting which keeps filaments lamps slightly lit, or some other method to set zero brightness. A dimmer which has a neutral connection has no excuse to have any leakage when it is meant to be off.
 

DickCappels

Joined Aug 21, 2008
9,317
I don't know whether this solution is available to you, but I have been buying Philips LED "bulbs". They are off when they are supposed to be off and very reliable, and nearly free in terms of electricity cost. Better LED lamps have power supply that prevents the LEDs from seeing the AC line directly.
 

Ian0

Joined Aug 7, 2020
6,294
There are LED lamps which cannot be dimmed by a phase-fired dimmer.
There are LED lamps which claim that they can be dimmed by a phase-fired dimmer, and
there are LED lamps which actually can be dimmed by a phase fired dimmer.

They work by rectifying and smoothing the supply, then measuring the pulse-width of the incoming waveform, then adjusting the LED current to match what the brightness of a filament lamp would be at that phase angle.
 

Thread Starter

FraserJim

Joined Sep 13, 2022
3
Let me provide some more information. The system is Litetouch. They were acquired by a firm call Savant and then Savant closed them down, so support is very limited. I have (3) 8-channel Dimmer modules mounted in an enclosure. For a total of 24 circuits. Each module does have an input neutral, but only outputs hots. I have been told that they use Triacs and they have used resistors to solve shutoff problems. But they want $25 per resistor with pigtails.

I plan to mount my solution inside the enclosure, so light doesn't matter.

Sensacell said a small incandescent, so what would be the smallest one that I could get away with?

ThanksLitetouch 1.jpg
 

dendad

Joined Feb 20, 2016
4,216
I would use a 15W 240V lamp if you can get them where you are. These lamps are often used in microwaves, fridges, oven, sewing machines etc.
The 240V version should last a long time on 120V. 2 x 120V lamps in series would work the same too. Or just one 15W 120V lamp if that is easier.
Bulk lots are available on Ebay.
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