Dimmer intermittently going off.

Discussion in 'C-Bus Wired Hardware' started by Matthew, Nov 11, 2008.

  1. Matthew

    Matthew

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    Hi All
    I've searched previous threads that discuss dimmers pulsing to 100%,

    My problem is a dimmer that intermittently pulses to 0% (off) for less than a second and then resumesback to the set level (which is 95%).
    Dimmer is a L5504D2U
    Load is 5 x 50w LV downlights, some sort of electronic Tx.
    Simply programmed to one key input and is used for 4/5 hours a day. Dimmer is set to maximum level of 95%.
    Randomly all 5 lights will switch (pulse) off and then back on. It did it about 5sec after first turn on one morning, so not likely to be a heat issue.
    The install is about 4 years old, I removed a relay and installed a dimmer to save energy and extend potential lamp life and the problem appeared. The only other thing I did was combine the 2 switched legs into 1. (there was 1 ch with 2 LVDL, 1 ch with 3 LVDL in a small 6m2 area, I joined them together)

    I have changed the group address, swapped dimmer channel, changed unit address, swapped out dimmer, all to no avail, it still happens. :(
    It is not noticed on any other channel.
    Help!
    Matthew
     
    Matthew, Nov 11, 2008
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  2. Matthew

    ashleigh Moderator

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    The joining together worries me. Does that mean you have 2 dimmer channels linked and then feeding 5 loads?

    If you do... undo that!!!! This might be a bad thing to do.
     
    ashleigh, Nov 12, 2008
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  3. Matthew

    amberelectrics

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    Im assuming you mean you took the live feeds to the LVDL circuits and put them on one dimmer channel, rather than physically connecting two dimmer channels together, which would not be good.

    I had a similar fault on a 4 channel dimmer. One channel would either pulse off/on or would simply turn off and lock the dimmer. It turned out that there is a temp sensor in the dimmer for overheat protection, this was faulty and was causing the dimmer to protect itself. In my case it was a case of sending the dimmer off and getting a new one.
     
    amberelectrics, Nov 12, 2008
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  4. Matthew

    ashleigh Moderator

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    Yes, well, the other possibility is the dimmer is overloaded. Need to clarify that doubling up thing, first, though.
     
    ashleigh, Nov 12, 2008
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  5. Matthew

    NickD Moderator

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    This sounds like a problem we've heard of a couple of times...

    The universal dimmer has overcurrent protection built in.. this detects excessively high current through the MOSFETs on a cycle by cycle basis and will switch the load off if excessive current is detected.

    Once the channel is shut down, the dimmer monitors it and will try a few times to automatically restart it. What you're probably seeing is this overcurrent protection kicking in, and the channel restarting itself about half a second later.

    We have heard a few reports of this being tripped by large transients on the mains supply, usually caused by some other large load in the installation coming on or shutting off. The transient takes the lowest impedance path back to neutral, which can sometimes be through the dimmer channel.. particularly if it's a short wiring run, and/or running a large number of electronic transformer loads, which usually have EMC filter capacitors across their mains terminals.

    There are a number of possible solutions... tech support should be able to help you out.

    Nick
     
    NickD, Nov 12, 2008
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  6. Matthew

    ICS-GS

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    1. Can you seperate the 'joined circuit' so that only 2 or 3 lamps on the channel? Does the problem go away?

    2. may be worth investigating what brand Tx is used, there have been know o be compatability issues.
     
    ICS-GS, Nov 16, 2008
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  7. Matthew

    Matthew

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    Only 1/2 a problem

    Thanks all for your response & thoughts.
    The total load is 5 x 50Watt LV downlights, so well within the capacity of the dimmer.
    These were all on 1 channel of the dimmer.
    I have split them 2 x on 1ch, 3x on another. Apparantly the fault has stayed with the group of 3, but not the group of 2.
    I am thinking mor and more that it may have to do with the load, specifically the electronic transformers.
    I will try Tech support as well.
    Thanks Matthew
     
    Matthew, Nov 17, 2008
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  8. Matthew

    ashleigh Moderator

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    If you know and can post here the brand of the transformers, that may help :)
     
    ashleigh, Nov 18, 2008
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