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F411/2 keep failing on LED circuits

Questo argomento contiene 8 risposte, ha 4 partecipanti, ed è stato aggiornato da  eugeneduffy 30/07/2015 at 23:03.

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    Hi during the past 3 years I have now had 3 F411/2 replaced because they become unreliable.    This seems to happen on lighting circuits with low watt LED's.   They switch on fine but I cannot switch them off either with the wall switch or even directly on the actuator.    I find if I power cycle  the bus it sometimes works again for a while but eventually even this does not work.

    Is this a regular issue or I am just unlucky!   I am gradually changing all my lights to LED so I would like to have a solution.




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    jules_wake
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    Hi Jules,

    my experience with LED lights says that with this kind of load the problem is the power supply. If it's a low quality PSU the startup current is very high (in worst cases I reached 30 or 90A for a millisecond, even if the PSU is a 0.3A or 0.8A) and this high current glues the F411 contact that is limited to 2-4-6A (depends on load type); to 'disconnect' the load you need to shut off it and "knock" on the relay. I've solved using a thermistor that limits the initial current of the PSU but you can choose two different solutions:

    – use a zero-crossing relay, that connect and disconnect the load when the AC main line pass thru 0V (and where current is 0A), like F411/U2 (see http://www.myopen-legrandgroup.com/…/9879.aspx)

    – change the PSU with a high quality one




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    angeloxx
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    Hi Angelo thanks for the reply. I will replace the broken relays with the zero crossing ones.   I am also interested in the thermistor option can you explain how to do this?   Where do you put the thermistor and what is the specification required.




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    jules_wake
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    The thermistor is a component that you place in series, more details on sizing and working principle here.

    en.wikipedia.org/…/Inrush_current_limiter

    powerelectronics.com/…/how-do-you-choose-right-type-ntc-thermistor-limit-inrush-current-capacitive-applications

    Handle with care.




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    angeloxx
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    this is the exact reason why L/Bt came up with the zero-crossing models…




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    sxpertle
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    Just annoying that I need to spend more money. It probably works out cheaper to keep halogen bulbs and pay for electricity!




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    jules_wake
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    You can use standard relays with a 230v coil. should only cost you a couple of euro per channel.




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    eugeneduffy
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    Hi Eugene can you explain in more detail.  I am reasonably competent with circuits but this is new to me.




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    jules_wake
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    Hi Jules,

    You can connect one of the outputs of a F411/4 to the control circuit of  a relay that can switch a much higher rated load. For example you could have it switching a 4 pole 63amp contactor if you needed to!

    Regards

    Eugene.




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    eugeneduffy
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