Bulbs blowing wireless switches

Discussion in 'C-Bus Wireless Hardware' started by lpeterson, May 8, 2011.

  1. lpeterson

    lpeterson

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    Hi all, possibly stupid questions follow which may have been posted before, apologies if this is the case.

    I have saturn wireless switches which we retro fitted into our house some 6 odd years ago now. When we did it we found that they were not very good for fan control (probably more the idiot (me) programming them) so also added at the time a relay unit and some wired switches for fans and non dimable lights. Both of these are bridged together so that all lights and fans can be controlled in some fashion.

    Anyway, what I'm finding is that when a bulb blows (i.e. pops rather than a simple die piecefully and dont turn on) in one of the downlights on a circuit, the switch itself gets blown, and as a result we have to replace the switch as well as the bulb. Furthermore when this happens the remaining downlights on the circuit remain on, and in a dimmed fashion, so to turn them off until I get a new switch I have to physically remove the switch. Having just removed my fourth switch its starting to irk me.

    So my question is, why does the blown bulb blow the saturn wireless switch? Is there something that I need to do to isolate the switch or do I need to have specific downlights or something special functionwise in the downlights to stop them blowing the switches?

    Appreciate any thoughts as to what might be done to save the reamining switches from the fate of the others.

    Lawrence
     
    lpeterson, May 8, 2011
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  2. lpeterson

    ashleigh Moderator

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    Sounds like you have trailing edge dimmers, probably attached to mains downlights.

    You have the wrong type of dimmer - the trailing edge should not be used on a mains bulb of any kind.

    Whats happening when the lamp goes is that in one form or another there is a current surge (perhaps depending on where a broken filament falls) which is taking out one of the power switching transistors. The reason the lamps stay on is that they are actually running on every 1/2 cycle (you should see they are on but not full brightness). One leg of the switching circuit is blown and short (can't switch any more). The other leg is still working.

    You need to replace the saturn dimmer with the leading edge model, this uses a TRIAC and is more robust.

    Basically: using the wrong product for the load type.
     
    ashleigh, May 8, 2011
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  3. lpeterson

    lpeterson

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    Thanks Ashley for the assist. And yes, having now gone back to the original invoice and paperwork, they are Trailing edge dimmer switches, and in all cases both channels are wired to circuits containing downlights powered by mains current. Might have been nice to have this explained to me by either the electrician or the guys who suplied the switches 6 years ago, but hey you cant have everything you ask for I guess.

    So this leads to the next question. Is this inherantly dangerous, and should I be looking to swap out all the switches immediately? Or can I simply wait till each dies and replace them with leading edge dimmers as they die?

    Thanks again for explaining an obvious flaw in "the original plan".
     
    lpeterson, May 8, 2011
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  4. lpeterson

    Newman

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    Using trailing edge dimmers for 240V halogens is definitely a bad idea. The surge currents when the bulbs fail can be extremely high, and this is what is damaging the switches. As Ashleigh says, Leading Edge dimmers should be used with this kind of load.

    It's not dangerous in any way. You'll just have to put up with there being a chance that the dimmer gets damaged when the bulbs blow and the other bulbs on that circuit getting stuck half on.

    Depending upon how many downlights you have, it might be cheaper or a better long-term investment to replace the downlights with dimmable electronically-ballasted 12V halogens or dimmable LED downlights. Both of these types of lights should work great on your trailing edge dimmers (there are exceptions of course). Restrictions are coming for 12V halogens too, that will force people to use the higher efficiency types such as the Osram IRC lamps, but they'll at least be around for a few more years yet, unlike 240V halogens.

    Later in 2012 (currently planned for October) the sale of 240V reflector halogen lamps is going to be banned, which may force you to change your lamps over to a different type anyway and there's a good chance that whatever you replace them with will require a Trailing Edge dimmer, not Leading Edge. You don't want to change your dimmers over to LE versions only to suddenly find out that you need TE dimmers in a year or two.
     
    Newman, May 9, 2011
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  5. lpeterson

    ashleigh Moderator

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    Just wait until they die. It's not inherently dangerous, its just that because they use FETs they can get killed. The trailing edge units are designed for LV downlights using electronic transformers (as far as I can remember). They also have a marking on them that shows this :)

    They are not suitable for iron core transformers or direct mains lamps of any kind (halogen or otherwise).

    Some newer dimmers out there (eg 32E450 stand-alone dimmer) can be used on mains lamps - this is a later design generation which includes modifications to be short-circuit proof. These mods have not made it into the wireless products.
     
    ashleigh, May 9, 2011
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