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Thread: 1000 watt air cooled transformer

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    1000 watt air cooled transformer

    Please excuse me but I do not have much experience with low voltage. I stopped by a mansion today that had LED strip lights installed in the cove molding in a ballroom. The lights were supplied by two 1000 watt air cooled 24 volt transformers located in the basement. Each transformer was connected via 12-2 NM to an 8 amp controller/dimmer. None of the lights worked and one of the dimmer/controllers had melted.

    Does this sound like a typical install? Someone suggested this may have been an older installation that used Halogen lights? I don't understand using 12-2 NM on the load side of a 1000 watt transformer.

    It has been suggested to bypass the controllers and go directly from the transformer to the LED lights.
    Any thoughts?

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    We need more detail.but a 1000 watt xfmr at 24 volts puts out 41 amps which would be more than twice what the 12 is rated .
    Tom
    TBLO

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    Quote Originally Posted by ptonsparky View Post
    We need more detail.but a 1000 watt xfmr at 24 volts puts out 41 amps which would be more than twice what the 12 is rated .
    If each transformer is driving one 8A dimmer/controller at 24V, then I do not think the main problem is in the wire size. I would definitely see how the connected lamp load compares to the 8A rating of the controller though.
    Last edited by GoldDigger; 03-06-18 at 08:29 PM.

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    Quote Originally Posted by GoldDigger View Post
    If each transformer is driving one 8A dimmer/controller at 24V, then I do not think the problem is in the wire size. I would definitely see how the connected lamp load compares to the 8A rating of the controller though.
    You’re right, I’m sure the secondary has been fused properly and no loads have been exceeded.
    Tom
    TBLO

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    A standard dimmer switch is only good for 600 watts. I've seen numerous ones pushed beyond their design capacity and they all have one thing in common: they were melted.

    LED lighting I think you'll find that a standard dimmer is only good for 150 watts.

    Yes I have seen old lighting that ran halogen bulbs at 24 volts. I consider them Legacy or obsolete systems.

    Eta : as mentioned above 1000 watt Transformer can put out 41 amps at 24 volts which is significantly more than either the cable or dimmers are rated for. If they have LED lights chances are they only need 300 watt Transformers.
    Electricians do it until it Hertz!

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    180307-1011 EST

    The following information is inadequate, and thus, a useful answer is very difficult to provide.
    Please excuse me but I do not have much experience with low voltage. I stopped by a mansion today that had LED strip lights installed in the cove molding in a ballroom. The lights were supplied by two 1000 watt air cooled 24 volt transformers located in the basement. Each transformer was connected via 12-2 NM to an 8 amp controller/dimmer. None of the lights worked and one of the dimmer/controllers had melted.
    What is an LED strip light? I will assume it is what I might call a DC load or more particularly a load that should normally driven by a DC or modulated DC source. I believe what is call an LED strip light will consist of two power distribution wires run the length of the strip. One labeled + and the other -. Distributed along these bus bars are many parallel light items each consisting of a series string of several LED chips and a series resistor.

    An LED chip is a semiconductor component that is a diode that in the forward direction that emits light, and in the reverse direction is a high resistance until a breakdown voltage.

    In the forward direction there is a maximum allowed current, the series resistor helps keep this current within an acceptable maximum with varying input voltage.

    The resistor is of virtually no use relative to protection in the reverse direction. The voltage source has to be designed to never produce too much reverse voltage.


    What is a transformer? I have no idea here.

    What is a dimmer/controller? I have no idea here.

    Where is the dimmer/controller located in the circuit?

    Can a DC light strip be supplied by a sine wave AC source? Possibly. It will depend upon the peak inverse voltage rating of the DC LED light strip. Would you want to? Doubtful.

    Two general ways to dim a DC light strip. An adjustable, but otherwise constant DC voltage source, or a constant DC voltage source with a pulse width modulated output (might be preferred method).

    A more complete description of this circuit is needed.

    .

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    I highly doubt the lights are LED up in the cove. You would need an insane amount of LEDs probably miles of strip to draw that much current.

    Sent from my A574BL using Tapatalk
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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    180307-1352 EST

    Some data from an actual DC LED light strip. This is a normal brightmess unit 2.5 meters (100", 8' 4") long. I have just one Armcost medium brightness strip. At 12.08 V DC I read 1.45 A, the far end of the strip is 11.36 V.

    Armcost claims about 19 W at 12 V. This calculates to 1.58 A. The number of LEDs per meter is 60, or about 12 LEDs per ft. Looks like 3 LEDs per resistor. LEDs are about 0.65" apart which corresponds with 60 per meter.

    Their high brightness strip is 120 per meter, and that would double the current.

    If the area being covered is large, then required current can add up quite easily.

    In my opinion the best way to dim DC LEDs is with pulse width modulation. This provides 100% range control, linear brightness adjustment, and no quirkiness in adjustment.

    As with most products today there is inadequate technical information.

    On-line I could not find good information aboit the Armacost DC dimmer. On the package is listed 12 and 24 V DC loads. No maximum input voltage. 8 A is mentioned with the 12 V comment, might be the same at 24 V since this is an on-off modulation at several thousand Hz. Would I run it at 8 A? Probably not.



    Greg1707:

    You probably need to find out more about your circuit before you can make progress in solving the problem.

    If the dimmers are on the DC side of the circuit, then find out what your total load current is per dimmer at full brightness. This will be the worst power dissipation in the dimmer for a pulse width modulation dimmer because the full current is passing thru the switching device (likely an FET) 100% of the time.

    .

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    problem solved

    OP We removed the controllers and and wired the lights directly to the transformers. I spoke with the manufacturer before doing this. I believe the transformers were for an older lighting system.
    In the cove there were 4-16' LED strips. There were two on each transformer.

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    189307-1711 EST

    Greg1707:

    What is a transformer? If you take a Fluke 27 or 87 or similar instrument what voltage do you read at the transformer output using the AC range, and then using the DC range?

    .

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