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Fibaro Dimmer module melt down


budda

Question

I've had the Fibaro Dimmer module controlling 4 x MR16 halogen lights in my bathroom for over a year - without problem.

About a month ago 3 of the 4 12V transformers packed up within the space of about 1 week. The 4th transformer that continued to work was one I had replaced a few years ago.

So the dimmer module only had 1 working transformer and MR16 bulb connected this month.

Whilst I was hoovering the hallway I kept smelling hot plastic as i moved around. After a lot of sniffing I unscrewed my light switch to discover the Fibaro had melted the corner of its casing and could see a spark/arching from within the unit.

In the corner next to the 'L' connection block terminal I can see inside the unit where it looks like a component casing has popped/cracked too.

I immediately turned off the mains power and removed the unit from the light switch. I'm just glad I noticed it during the afternoon and it wasn't sat there cooking through the night!

I have more of the same Dimmer modules installed and so far have not experienced the same problem, but they were bought around the same time so maybe from the same batch.

Photo attached of the damage.

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Guest lochnesz

budda, that sounds seriously dangerous, and it is not the first time we read about melting dimmers. So the dimmer was turned on when it happened? What dimmer level was it set to?

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  • Inquirer
  • No the dimmer light was off at the time. It was during the afternoon daylight.

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    Guest lochnesz

    Oh, that is even worse...

    Please login or register to see this image.

    /emoticons/default_icon_curve.gif" alt=":-/" />

    [ Added: 2014-11-21, 09:50 ]

    Anyone tested Qubino? Are they the same size as the Fibaro modules? How do they work with HC2?

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    What kind of transformer have you been using? And what type of bulbs did you connect to the transformer?

    There is a wellknown issue with dimmers like the Fibaro unit related to the dimming electronics. It is the type known as a leading edge dimmer. The issue is that swithc mode DC power supplies can potentially overload the TRIAC-circuitry in the dimmer. Do you know if the power supply is a switchmode power supply or an old-fashioned iron core transformer? If you don't know the difference, the switchmode supply will be much lighter than the iron core transformer.

    If the three old supplies were iron core and the new one that is still working is a switch mode, that might be the explanation; Putting it a bit simple, the three can have worked as a buffer, ensuring that the dimmer doesn't experience the inrush issues that causes the overheating.

    This has been highlighted before and I have suggested to Fibaro, that they move to the much safer (but also slightly more expensive) trailing edge dimmer, which does not have the inrush problems and therefore not the same risk of overheating. They replied (on this forum somewhere) that they knew the risk of the dimmer, but claimed that the disclaimer in the instructions warned of this. So they know the issue, but they refuse to do anything about it. The disclaimer does not cover the inrush risks from using the cheaper leading edge dimmer type - but hey, if one of mine catches fire, I know exactly where to send the bill.

    Anyway, due to LED bulbs making their way into the market, this will eventually be such a big issue that the EU will be forced to ban leading edge dimmers from European markets because of the fire hazard associated with the leading edge dimmer. So if Fibaro won't listen to the concerns of their customers, they'll eventually have their hand forced if they want to stay in the European market.

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    No, the problem is related to how the dimmer is modulating current. This means that it cuts off the current for a part of each alternating current pulse, this means that instead of the voltage "slowly" increasing, the voltage will just cut in at a given point (at 50% dim it will cut in at the top of the sine curve equating to approx 340 V for a 240VAC system). This means that the electronics will be energized at a much higher voltage than usual, as the current will be greatly in excess of the capacity of the dimmer circuitry, it will overheat and potentially catch fire.

    But this can only be the case when the dimmer is on and not set at or close to 100% dimlevel. If it melted at full power or when the light is switched off, it indicates that something else was wrong with the dimmer module. But damage from inrush currents can ofcause have damaged the curcuitry in a way that made it melt even though it wasn't in operation - but that is purely speculative!

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  • What kind of transformer have you been using? And what type of bulbs did you connect to the transformer?

    There is a wellknown issue with dimmers like the Fibaro unit related to the dimming electronics. It is the type known as a leading edge dimmer. The issue is that swithc mode DC power supplies can potentially overload the TRIAC-circuitry in the dimmer. Do you know if the power supply is a switchmode power supply or an old-fashioned iron core transformer? If you don't know the difference, the switchmode supply will be much lighter than the iron core transformer.

    If the three old supplies were iron core and the new one that is still working is a switch mode, that might be the explanation; Putting it a bit simple, the three can have worked as a buffer, ensuring that the dimmer doesn't experience the inrush issues that causes the overheating.

    The transformer is a SKOT ET60T-5 20-60 Watts maximum 4.9A "Fully dimmable".

    Quite thin and small, light weight.

    Searching for the model number brings up all sorts of re-branded versions with slightly different label and symbols on it.

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    Dalle, I can only bow to your electrical knowledge here, but surely there is a major problem here. These modules are marketed as being easy to install and simple setup, and although they recommend using a qualified electrician to install them, there is no mention that you need a degree in electrical engineering to ensure you don't burn your house down. The electrician is generally not involved at the planning /purchase stage, so unless they read the instructions back to front and realise its not safe to install, you are then left with a bunch of modules you never realised you would have a problem installing. Or they will plough ahead with the install as per the diagram which is what they work do, and not assess tall the pre-requisites

    Personally I think these pre-reqs need to be clearly highlighted, not buried in the instructions in size 4 font, or the modules withdrawn from sale until they are safer

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    I can only agree here.

    Dimmers must be safe no matter what!

    Safeguards must be built in to consumer electronics to be fool proof.

    There are more things to consider, what happens if you move and the new owner of the house decides to replace the halogen light with LEDs?

    Everything works fine but all of a sudden your house might burn down.

    To me it should work like this:

    The dimmer works with X but if you plug in Y the dimmer stops working as a safeguard.

    There are safety built in to the dimmer for overheating, why didn't that function kick in?

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    Under British law, installing this module would be "non notifiable" meaning anyone vaguely competent can do it. It's pretty common for ordinary people to change their own light switches etc.

    Whilst it is not unheard off for anything with electronics in on the mains (like ordinary dimmer switches) to do a meltdown, it does suggest that the product may have a design flaw given teh Swedish reports.

    My personal slightly qualified opinion is the risk is low if this is installed in a metal back box in a brick wall.

    However as lighting back boxes are generally very shallow in Britain, this type of module is far more likely to get installed in the attic or under the upstairs floor where the lighting wiring goes. That would be a far more dangerous scenario. As would being installed in a plastic backbox on wooden panelling, or in a drywall.

    For in ceiling/attic installations, under the IET Wiring Regulations, this device would need to go inside an enclosure (box) such boxes are commonly plastic so would afford no fire containment.

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    Also, the installation in a metal box could cause interference with the Z-Wave signal so its most likely these are installed in plastic back boxes where they can be, and as such increases the risk significantly.

    I have pushed in the other thread for an answer from Fibaro as to whether they can disprove the Swedish findings, and I can only assume from there lack of response that they can not and the dimmers and relays will remain banned.

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    I completely agree that this should be clearly stated. i'm not even sure the instructions mention that this is a leading edge dimmer. I've deducted it from it's operational hum and the fact that it shows this sort of behaviour when exposed to led light sources.

    TimJWatts, most countries don't use metal backboxes because they are - well dangerous. So two things, if the device catch fire inside your backbox, it can still create enough heat for the fire to propagate through the backbox. If it propagates through the wires, the insulation will burn off and you have a far bigger fire hazard. So if it melts, and you realise it - pull out the module and install a switch, you still have a hidden fire hazard inside your walls! Underestimating the dangers of electrical fires is very dangerous.

    I only have fib dimmer modules in visible lighting fixtures where i can see if something is happening where I have an isolator between the module and the in wall wiring.

    Leading edge dimmers should, and probably will be, banned from sale as switch mode supplies and leds can make them catch fire. An intermediate solution is to ensure that to NEMA SSL7.

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    I completely agree that this should be clearly stated. i'm not even sure the instructions mention that this is a leading edge dimmer. I've deducted it from it's operational hum and the fact that it shows this sort of behaviour when exposed to led light sources.

    So are you saying that trailing edge dimmers should be fine with these dimmers modules?

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    TimJWatts, most countries don't use metal backboxes because they are - well dangerous.

    With all due respect the British Institution of Engineering and Technology (formerly the IEE) disagree with you.

    Metal back boxes must be earthed for all the reasons you state (insulation failing for one). And this is based on the 17th Edition of the Wiring regulations which is heavily harmonised with the rest of the EU. However, with that proviso, metal boxes are not considered unsafe in teh slightest.

    And there are many places where metal surface boxes like these:

    Please login or register to see this link.

    would be the preferred solution due to the need for additional mechanical protection (eg workshops).

    In fact the IET is considering rather the opposite point of view now and is concerned, after a report by the London Fire Brigade, as to the suitability of plastic enclosures for Consumer Units (fuseboxes). We expect a recommendation to move towards metal units in a year or two, unless manufacturers can produce fire resistant non metal boxes.

    [ Added: 2014-11-21, 16:31 ]

    But I take the (obvious in hindsight!) point about trying to put an RF device in a fully metal box (not just a metal backbox, though that mey have a problem if the switch plate is also metal!).

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    I think you need to do a re read of the IEC 60364 on which the BS7671 is based. Metal casings are only good for mechanical protection. All equipment inside must be at least IP2X under normal operation and must måbe electrically isolated from the casing. Same goes for DIN rails - which must also be earthed. The requirement according to 60364 is that the casing can provide, mechanical, electrical, thermal and chemical protection. Metalic boxes does not provide electrical insulation, even when earthed. Therefore you need added protection when using metal backboxes. Danish regulations doesn't allow them for home installationa all together - same is the case in many other european countries.

    Most european installation material for home installation is plastics and that is very well in line with the regulations in IEC 60884 regarding wall outlets and plugs.

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    I think you need to do a re read of the IEC 60364 on which the BS7671 is based. Metal casings are only good for mechanical protection. All equipment inside must be at least IP2X under normal operation and must måbe electrically isolated from the casing. Same goes for DIN rails - which must also be earthed. The requirement according to 60364 is that the casing can provide, mechanical, electrical, thermal and chemical protection. Metalic boxes does not provide electrical insulation, even when earthed. Therefore you need added protection when using metal backboxes. Danish regulations doesn't allow them for home installationa all together - same is the case in many other european countries.

    Most european installation material for home installation is plastics and that is very well in line with the regulations in IEC 60884 regarding wall outlets and plugs.

    This must be a misunderstanding.

    Metal enclosures are not only permitted, they are routinely used in the UK for both surface and flush mounted accessories.

    Of course you have basic insulation on the live parts inside. And the enclosure must be earthed (unless somehow you have met conditions for classifying it as a Class II double insulated device).

    I'm quite happy with my understanding of BS7671. And I'd much rather have a metal enclosure for fire reasons than anything made of a thermoplastic.

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    Safety of our users is the highest priority, hence we decided to assign highest urgency to investigation of your case. budda please contact me with PM, we will send courier with door to door service. The most probable cause of failure is inappropriate choose of transformer. Only ones designed for dimming should be used. Nevertheless we have to examine this specific device to commission that. Please contact me soon. I'm

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    Safety of our users is the highest priority, hence we decided to assign highest urgency to investigation of your case. budda please contact me with PM, we will send courier with door to door service. The most probable cause of failure is inappropriate choose of transformer. Only ones designed for dimming should be used. Nevertheless we have to examine this specific device to commission that. Please contact me soon. I'm

    If that is the case, you should seriously consider switching to a trailing edge dimmer type.

    This will not display any of the issues that a leading edge dimmer does, as it does not suffer from inrush. Another benefit is also that a leading edge dimmer will have a tendancy to have a just visible flash when at low dim, because the off periods become quite long ahead of the bulb powering up, this will be less noticeable with a TE dimmer). Also, the irritating buzzing noise of the leading edge dimmer will also be a thing of the past.

    So not only will you have happier customers, you'll also have safer customers. And as I wrote, with the inrush (no pun intended) of LEDs to the market, sooner or later, the EU will be forced to ban the leading edge dimmer as it is inherently dangerous. And since you have already been banned from Sweden and apparently need to redesign your dimmers to get back in that market (and apparently risk loosing the rest of EU to the same issue), you might as well go the full distance and switch to a trailing edge design. It isn't that much more expensive to build and it is so much nicer.

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  • For what its worth my melted FGD211 has no version number printed on the white label.

    The other two FGD211s I also removed from my installation did have v1.9 printed on their white labels. They have not melted, but I was not confident in trusting them!

     

    The melted unit has a lower serial number of 011-0990

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    Hi guys please give me an advice about the following:

    We are going to install like 150meters of RGB led strip 12volts. They will be dimmable and the power consumption will be like 800W. The transformers are dimamble DALI led drivers. The total wattage for 1 dimmer is 500w and i am planning to install like 1 dimmer for 2 transformers in order not to burn the dimmers. So for 7 transformers it will be like 4 dimmers which will be associated in the HC2. When you dim 1 of them, the others will dim aswell. What do you thing about the idea (the number of dimmers and transformers and the association in the HC2)? Any ideas and suggestions are going to be welcomed!

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