Dimmer 2 Melted

[Kennet N 0]

Hi

 

I have been using a dimmer 2 for some years now in an installation in my bedroom.

Originally I had 9 halogen spots (12 V / 20 W ) and two transformers to power them.

I have been using the dimmer 2 to allow dimming the lights and this has been working fine.

The transformers was connected in a two wire installation without a bypass.

 

I then gradually started replacing the halogen lights with Dimmable LEDs.

Naturally the dimming did not work so well for the LEDs when they were replaced but this was ok for me. 

Eventually when I got down to only to halogen lights the lights started flickering at some brightness levels so I thought I just that to install a bypass 2 and this would fix that.

So I bought a bypass 2 and installed it in parallel with the two transformers, but this did not fix the issue.

I also tried replacing all the spots to LED but this did not work either now the lights would not turn on at all. So I returned to having 2 halogen lights and the rest as LED.

But shortly after this I found that something in the dimmer had burned up and I quickly removed it again.

 

Details:

Transformer 1: TD 6721.2 (12V / 80 VA)

Transformer 2: Noratel mini 120/1-kt ( 12V / 120 VA )

LEDs : 3W Dimmable

  

I have attached a picture of the melted dimmer 2.

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So the question is what when wrong ?

If the installation was working with halogen lights and I replaced them with LEDs that require less power why did the Dimmer burn up ?

 

Thanks for any input on this.

[Tim__ 126]

Wow, I have not seen something like this here before. I presume the unit self extinguished, and thankfully no fire in your house??

 

It doesn't look like poor terminations were the issue. However, the manual for the device has these precautions listed. Using two transformers and mixing light sources is a no-no. I'm also going to guess that these rules are more important in a 2 wire scenario, and again where a bypass is fitted. My theory is that these factors all contribute to the device needing to manage multiple power factors. While the device survived the multiple transformers, the different light types would have had different harmonics and this overwhelmed the power semiconductor in the Dimmer. Anyone else have a different theory?

 

Applied load and the Dimmer 2 itself may be damaged if the applied load is inconsistent with the technical specifications!

When connecting FIBARO Dimmer 2 act in accordance with the following rules:

• Do not connect loads greater or less than those recommended
• Do not connect different types of light sources simultaneously
• Do not connect the power supply without a load
• Do not connect more than one transformer with Dimmer 2 output
• When using magnetic transformer load it with 50% of its nominal power at minimum
• Minimize number of electronic transformers in a circuit, noises caused by them in electrical grids may affect Dimmer’s operation

[Kennet N 0]

Hi Tim

 

Thanks a lot for the reply.

No I did not have a fire at my house thanks for asking, luckily I could smell the issue before it caught fire.

 

I was also thinking that the multiply transformers was not a good thing. They were designed for higher power loads.

So I have now replaced the two transformers with a single LED driver. 

The new driver is a GTPC-50-D from 

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On the page where I bought it is says it should work with 10 to 50 Watts. Packages says.

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I have also changed so that I only have LED's and they are all the same type.

I have 9 LEDs with 3 watts each so I am guessing this is a good size for the driver.

They are connected in parallel on LED driver.

I have then bought another Dimmer 2 and connect all of this still in 2 wire mode.

 

Unfortunately this did not go so well.

When I initially started it, it was working and I thought everything was good.

I still have the bypass installed in parallel on the 240 V side of the LED driver. (Manual is unclean if it should be on the 12V side ?) 

Anyway I remembered that according to the dimmer manual I have to configure use of bypass by setting parameter 13 to 2.

So I did that, The dimmer did the auto calibration, but then the dimming stopped working.

Looking at the parameters I could see that parameter 1 "Minimum brightness level" was set to something like 40.

So I tried to change that but that was not possible. 

It was about this time I started smelling something burned again, So I quickly turned it off and tried to revert parameter 13 to 1.

Now the dimmer 2 configured the Minimum brightness level to 53 and the dimming still did not work.

 

It can turn on and off, but I have removed the dimmer again, until I understand the issue.

 

So the question is again what is it that I am doing wrong ?

 

[RH_Dreambox 189]

Could it be the bypass unit that causes the problems.
It is intended to be placed in parallel over low power lamps so that they can be dimmed correctly.
But you have connected it in parallel over the transformer, which I think is wrong.

[Tim__ 126]

You can not use a LED driver with the Dimmer 2. The dimmer is varying its average output voltage in order to dim lights, but in your setup this is going to the LED driver which is trying to provide a constant 12V  voltage to the LEDs.

 

With Dimmer 2, you need to use dimmable 240V LED bulbs or strips, without a driver.

 

If you have 12V LEDs, you should use the Fibaro RGBW Controller 2. No bypass needed. You will still need the 12V power supply (assuming it is not fried!). See the online manual for how to wire it up.