Over-Lamping Dimmer Packs

Discussion in 'Lighting and Electrics' started by Heckle, Apr 18, 2018.

  1. Heckle

    Heckle Member

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    Hey all,
    So I am doing a show and have ran into a a bit of an issue. The fixtures I am wanting to use have 2000 watt lamps. The dimmer packs I am using are 600 Watts. Can I use these dimmer packs with these lights, I can’t figure out if the lights will just use less than 100 percent, or if it will trip the breaker or potentially burn out the dimmer.

    Thanks,
    Heckle
     
  2. Brentgi

    Brentgi Active Member

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    It will most likely, if not definitely, trip to breaker.
     
  3. JD

    JD Well-Known Member

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    Considering the nature of the inrush current on a 2k lamp, the pack will probably blow before the breaker gets to trip. If it is a "shoe box" dimmer (small stand alone 4 or 6 channel dimmer), it is most likely using a 16 amp triac. A 2kw lamp at 120 volts will draw a pulse of about 160 amps when cold. (Inrush can be 10 times the operating current.) Although dimmers are designed to handle inrush, such a pack would only support 1/4 of that amount. Add to that, shoe box dimmers do not have a good reputation for handling inrush even at their rated loads.
    To run a 2k load you would want a dimmer that has a minimum rating of 2.4Kw. Most of us would want more headroom and if available would go with an even larger dimmer.
     
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  4. Brentgi

    Brentgi Active Member

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    TL;DR - Don't do it.
     
  5. Chase P.

    Chase P. Well-Known Member

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    My experience has been that many shoebox dimmers use even smaller triacs. If the individual channels are rated for 10A, as is true for many packs, the triac may be exactly that.

    Combine that with the way that every shoebox I've seen places the breaker upstream of the triac, instead of between the triac and the outlet, you stand a good chance of burning out the pack. Any electrical engineers out there know why? It seems that that breaker should be placed to protect the dimmer from damage. Putting it between the triac and the power source makes the pack more susceptible to damage. Built in obsolescence, maybe?

    While we're on the subject, I've worked at a number of venues with fried triacs. If you're handy with a soldering iron, they're actually pretty easy to repair. The hardest part is disassembling the entire pack to get to the part of the circuit board that you need.
     
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  6. STEVETERRY

    STEVETERRY Well-Known Member

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  7. JD

    JD Well-Known Member

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    The reason the protection is prior to the triac as compared to after it is that you also want to protect against a failure where the triac may short to the case. For example, most triacs have an insulated tab, or the mounting tab is insulated from the heat sink by a mica washer. In either case, this insulation may break down especially if there is some burning involved when it fails. This will pop the upstream fuse or breaker. Better it be a 10 amp fuse than a 20 amp breaker, or in the case of larger systems, a MUCH higher higher limit.
     
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  8. josh88

    josh88 Remarkably Tired. Fight Leukemia

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    Can't get much clearer and to the point than that. Thanks Steve.
     
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  9. Chris Pflieger

    Chris Pflieger Well-Known Member

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  10. JD

    JD Well-Known Member

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    Pretty much changed out all the 16 amp triacs for 25 amp triacs on the shoe boxes I have. Not to increase the rating, but just to make them more reliable regarding inrush issues. Details on another older thread, packages are the same, same gating etc. Thermal becomes an issue as systems get bigger, but always figure on one watt of heat for every amp of current going through the triac. Basically, a Triac drops about 0.8 volts when on. Round that up to 1 and 1 x 1 = 1 , 2 x 1 = 2, etc.
     
  11. Control point

    Control point Member

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  12. Richard Young

    Richard Young Member

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    If it is one of those plug in the wall dimmer packs, first is it yours, second are you willing to give up 4 dimmers to dim one light?
    This trick is not for those not knowing anything of the electronics & more advanced electrical knowledge than is usually discussed here.
    If you own it and give all 4 dimmers up for a single 2k .
    Open it up (unplugged) locate the low voltage control input wires on the SSR blocks. Remove the control leads from dimmers 2-3-4. Find some small gauge wire ( striped out piece of Cat5 or phone wire) will work. Jump from control on #1 to 2-3-4. Find some 12 or 14ga wire on the back of the outlets fashion some u shaped jumpers and connect all the hot (black in us) togeather. Most of these things have outlets with push in wire connections.
    If it has 2 power cords eliminate one and connect to just one of them interaly or make sure they both get plugged into the same outlet and that both outlets are on the same phase.
    If it’s a rental, call and get them to send a bigger pack or
    Build 3 suicide cords 9” or so. Jump all 4 outlets on the pack togeather. When fading the light up take all 4 faders at full, put them on a sub master and bring all 4 up at the same time. This does work but needs knowledge some fool putting up a single channel and not all 4 will blow it in grand fassion
     
  13. TJCornish

    TJCornish Well-Known Member

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    No. What may be fine in a basement workshop is not fine for a public venue. Absolutely nothing you post here is acceptable to do.
     
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  14. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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  15. n1ist

    n1ist Well-Known Member

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    No! In addition to violating type acceptance and the NRTL listing, the line cord, inlet, fuse, switch, and wiring aren't rated for 20A (many are barely rated for 10A...) and the SSRs aren't rated for being paralleled. You need either smaller lamps or a bigger dimmer and circuit to feed it from.
    /mike
     
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  16. TimMc

    TimMc Well-Known Member

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  17. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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  18. TimMc

    TimMc Well-Known Member

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  19. JD

    JD Well-Known Member

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    Firing Thrysistors (SCR, Triac, SSR) in parallel is never a good thing. Inevitably, slight variations in production cause devices to have slightly different turn-on times. Although the single half-wave surge current of modern devices is pretty high, it is still most likely that one of the devices will always be the first one to go into conduction. It is also possible that if the lag is great enough, secondary device firing will not occur as the needed drop voltage is no longer present after the first device fires. I have seen designs that use paralleled devices in non-lighting applications, but the designs allow for safe variations.
    Needless to say, all of the statements about modification and liability are right on the money. In other words DON'T DO IT. The cost of a higher powered dimmer is far cheaper than a lawsuit. My comment above simply reflects that even if these other factors were not in play, you are still creating a very unreliable device at best.
     
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  20. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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