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LED Transformer Issue

Adrian
I have recently installed a 30 meter 24v LED Strip Lighting System powered by x1 150W power supply and x320W power supply - all parts have been supplied by Maxilux Ltd.. During installation the two power supplies were temporarily connected to the mains 240v ac via a cord and 3 amp fused plug in to a wall socket. All worked okay.


A dedicated light junction box and light switch was then installed in the downstairs light circuit. As a precaution a switched fuse spur box with 3amp fuse was installed in the switched line between the light junction box and two power supplies. The light switch purpose is primarily to turn 'on' and 'off' the two power supplies - the 320W has an internal fan that would otherwise run at all times even when the 24v LED Strip Lighting is not in use. A battery powered remote can also turn the 24v LED Strip Lighting 'on' and 'off', dim and change the colour from warm to cool white - provided that the light switch is 'on' 


When the light switch was first operated the 6amp consumer unit MCB tripped. However, if the 6amp consumer unit MCB was quickly reset and light switch operated again, the two power supplies turned 'on' okay and the 24v LED Strip Lighting worked okay. The lights could be turned 'on' and 'off' okay many times using the light switch. If left 'off' for circa 30 minutes, then light switch operated to 'on' the 6amp consumer unit MCB would once again trip.

After much searching of the Internet the problem was resolved by replacing the 6amp 'B' consumer unit MCB with a 6amp 'C' consumer unit MCB from the same manufacturer. The problem went away and for several weeks it has been possible to turn 'on' and 'off' the lights using the light switch and remote without the 6amp MCB tripping. 


This evening, the light switch was turned 'on' and the 24v LED Strip Lighting worked okay. However, when the light switch was operated to turn the lights 'off', the 24v LED Strip Lighting remained 'on'. The switch does not feel right - it is not fully returning the 'off' position; I suspect the contacts have welded closed in the 'on' position. 

There are no burning smells, nothing is getting warm or hot etc. The 6amp 'C; consumer unit MCB has not tripped. Fortunately, the switched fuse spur box with 3amp fuse has allowed the 24v LED Srtip Lighting to be turned off.


Any advise please 1) what is happening, 2) how I can resolve this issue. Thank you in advance.

  • 0
    Sounds like there's a high inrush current charging a capacitor bank in the power supplies. It's probably "ok" when turned off for a short time as the capacitors won't fully discharge, unlike when it's left off for some time.


    Does the manufacturer's data give an inrush current rating?
  • 0
    Inrush.

    This has all the hallmarks of power supplies that have a bridge rectifier feeding a capacitor as the input stage, so when the cap is empty, and you are unlucky enough to flick the switch at or near the top of the mains cycle the current surge is > 20A or so, for long enough to fire the B6. It may well be a lot higher, many tens of amps, for a very short time.

    So short of just changing the light switch for a  heavier unit, you could do to add some series impedance.

    Depending on your appetite for home construction, I have had quite a lot of success with things like - these Surge Guard lmiiters  They are essentially a negative resistance versus temp, and give a slow start by being several ohms at room temp, and then heating up, and becoming  a near short circuit over a fraction of a second (the old 'thump' degausser in TV sets used this principle)


    mounted on a bit of ceramic choc block (they do get to well over 100C) in series with the live supply they allow you to add the inrush  protection the makers really should have considered themselves, by putting 10-20 ohms in series at witch on, and removing it shortly after.

    SG 39 or SG63 would be about the right size for your load.

    edit, or as those seem to be out of stock right now  these look similar, and have the advantage of being available.

    regards

    Mike.
  • 0
    Thank you for your responses Mike and 'keyland'. Attached please find copies of the Data Sheets. Inrush current for the 320W variant is stated as 40amps there is no value for the 150W, but I assume this could be assumed as circa 50% at 20amps. This is most likely the root cause. The problem now is how to overcome. You mention adding some series impedance, also a heavier unit light switch. I am keen initially to explore the latter first . I note on the market there are light switches with ratings 10a, 15a and 20a, but also 15ax and 20ax. What are the latter, are they able to with stand such initial loads? Some information states they are suitable for high impedance loads etc.
    attachments.zip
  • 0
    Use a 20amp double pole switch or 30 amp. Just use 1 side of it unless you have a neutral at the switch as well.  

     You may need a deeper back box depending what you have.  They would need at least a 25mm box.


    Gary
  • 0
    AX rated switches were intended for high switch-on surges (originally for fluorescent lights) - so that could be part of the answer.

       - Andy.
  • 0
    Come on, this cannot be right. 500W of power supplies for led lighting? Neither of the supplies is intended for this job, they are much too powerful, and so you have the inrush problem. Just what is the power of these LEDs? The problem will go away if you choose a suitably rated supply, and it won't have a fan either! You will need to replace the switch(es).
  • 0
    colourstrip consumes   30watts per metre - I presume there is more than 10 metres of it hence 2 power supplies ?  This is not a few weedy down-lighters, but serious illumination.

    Note the lumens per watt are much lower for the muticoloured strips, (factor of 5 -10 worse ) compared to the hard white, so compare to 30-60W of white LED.


    Back to the OP another other option is a relay

    (Or in the AX switches the contacts use a metal plate on the business part of the contacts with a higher melting point - that may be enough.)

    regards Mike
  • 0
    24-Watt-CCT-LED-Tape-datasheet.pdf

    Thank you all again for your helpful responses. RE: LED wattage and length of run etc. please find attached data sheet of the LED tape.

    There are 30 meters installed; the LED tape runs along both upper and lower edges of a special light blocking coveing to provide a thin strip of illumination up on to the ceiling, and another down on to the wall, hence the 30 meters. It is also a largish room. The LEDs are of the white variety that can be changed from warm to cool and dimmed. The tape is 24W per meter = 720W total. Yes, possibly some serious illumination? 

    Being dark evenings and tendency for some residents to leave their blinds/ curtains open, I have seen a number of homes locally with LED lighting similar to mine, and in bigger homes with bigger rooms, thus I assume it must be possible to get my system to work safely and reliably. 

    So short list of options apears

    Add in series impedance

    Use an AX rated light switch - 20AX ?

    Use 20A double pole switch - wiring to one half?

    At the risk of trying each until it works, is there a clear winner here, or order in which I should try? Wife is keen the lights are fully working in run up to Christmas, thus I do not want to be forever 'saying tomorrow I this will be tried...'

    Thank you again for your continued responses, appreciated

  • 0
    The efficiency is 100 lm/W, a good figure. You have 30 metres x 2500 lm/m = 75,000 lumens! This is roughly the same as a 10kW tungsten lamp, roughly 50 times that in most living rooms. I hope you have very good sunglasses!  No wonder there is a problem. This kind of thing is sufficient to remove sun shadows on outdoor filming on a sunny day, I have never heard anything quite like it. I hope they dim right down so that you can see the TV or phone screens. The idea of a motor start contactor, or perhaps a 30A switch may work, but the life may not be wonderful even then.
  • 0
    That's not colour change as I expected it, that is just two shades of white...  However it does look like a lot of lumens, I presume you mostly use it turned down.

    The RGB colur change LEDs are a lot less efficient.


    So, first  get a 20A switch that is not derated for nasty loads

    Example may be to pop out to screwfix and pick up the MK grid switch type

    https://www.screwfix.com/p/mk-2-way-20a-sp-grid-switch-white/47845
    https://www.screwfix.com/p/mk-1-gang-grid-frame/31840
    https://www.screwfix.com/p/mk-1-gang-front-plate-white/53907


    That gets you through Christmas, after all the 6A unit did you for quite a while.

    And then perhaps organise an inrush limiter in slower time, and think about where it would fit. I tend to go for a metal box with 2 stuffing glands and a bit of ceramic choc block, but that may not fit.


    regards Mike

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