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Shoebox Dimmer Question

Discussion in 'Lighting and Electrics' started by mbandgeek, Aug 10, 2008.

  1. mbandgeek

    mbandgeek Active Member

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    I have 4 Elation DP-415 Packs that i am going to be using for some lighting this upcoming Friday. On each pack i plan on running 2 Altman 360Q ellipsoidals and
    2 ETC Pars.

    The Altman 360Qs are Lamped at 575 Watts and the Pars have HPL 575 Watt Bulbs in them.

    On the pack itself, it says that each channel can have a maximum of 5 amps. Overall Amperage in the pack is rated for 15 Amps maximum.

    Here is my question. Can I run the 4 lights at the same time? Or only 3? How long can i have all 4 lights running before i blow a fuse? Is it instantaneous?

    Thanks,
    Kevin
     
  2. Footer

    Footer Senior Team Senior Team Premium Member

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    So, you can have 600 watts per channel, but a 15amp max. It depends on how the dimmer is set up what you will blow. If the dimmer has a fuse on the incoming line, you will blow that. If it does not, then you run the risk of over-drawing the circuiting inside-pre dimmer. Now, I have a feeling that you will be limited by the power that is coming into the dimmer before anything else, so I think that will be a non issue. The final answer, only run 3 lights at a time. Also, I would not take anything up to full, you only have 25 watts of headroom which on those type of packs is nothing.
     
  3. len

    len Well-Known Member

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    IIRC each channel has a fuse. I believe they're fast blow. I have a couple of them also and put 575 hpl on them so I try to keep them below 80%, just in case.
     
  4. waynehoskins

    waynehoskins Active Member

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    As I understand dimming (which is apparently not as well as I had thought, my understanding being about 30 years out-of-print), if you have a fixture with a 1K lamp and you run the control down to 8, the lamp does not draw 80 percent of its "full" current; it's virtually unchanged. As I remember, it draws nearly full current from well below half.

    I could be wrong. Back in college, before I figured that part out, we had the same idea for a show: we could overload a 7.2K with six 1K scoops and three 1K 64s safely if we ran the handle down to 8 maximum. Now, it worked fine for the show (houselights), but at strike we found out that most of those scoops we thought were 1K were really 1.5K. Oops. Somehow we didn't blow up the SCRs in the old Hunt rack, and the breaker never tripped on the module. Then again, knowing the story of Dimmer 7 of that rack (a 3.6K whose shell lives in my parents' garage), I don't know how much, if any, breaking those breakers actually did. Dimmer 7 had a very bad short on its output and consequently blew up and launched itself out of the rack. It was before my time.

    Back to the shoebox pack, I don't think running the handle down will do what you think it will. I would plan to stick to only three units on at a time. But chances are that the 15A limit is chiefly because of the rating of the connector on the inlet cable. If it's bulit with 12/3, or even a quite short length of 14/3, I wouldn't be terribly worried.
     
  5. JD

    JD Well-Known Member

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    The line cord is 14/3 and the crimps & plugs are of the 15 amp variety. There is no main fuse so I suspect you will not have a problem unless your run everything flat out for a long time and burn up a crimp. (Doubtful though, because they use the same 15 amp crimps on the 20 amp unit ;) ) As for running 20 amps through 14/3, well, that's been covered on other threads I suspect. I've had problems on its bigger brother due to the use of 15 amp triacs on 10 amp dimmers, but I suspect they are using the same triacs in that unit as well, so 5 amps should not be a problem.
     
  6. mbandgeek

    mbandgeek Active Member

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    I just checked and it is indeed 14/3 cable.

    Footer, I just read in the manual, that they actually use 6 amp midget fuses. I guess that is where the headroom actually comes into play.
     
  7. JD

    JD Well-Known Member

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    Breakers are a funny lot. They have a "trip curve." The higher the overload, the faster they trip. Some marginal overloads can remain on for surprisingly long times with no trip! As for SCRs, some of those older dimmers were brick s**t-houses. I had (still have in my shed) a bunch of EDI 2.4k dimmers in which each one uses two back-to-back 65 amp SCRs! That's a bridged rating of 130 amps for a 2.4k dimmer!
     
  8. waynehoskins

    waynehoskins Active Member

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    With this one we had what was a solid 12K load on a Hunt 7.2 (Warranty Expires Oct 1977) (and Hunt folded less than a decade later). Never once did the 60A breaker on that thing trip: during focus, cueing, show, anything. Come to think of it, I don't believe I ever saw any of the breakers on that Hunt rack trip, though it and I were only acquainted for two or three years before it was replaced with a Sensor 96.

    The individual ramp trimmers on each module (24 modules) was a *****, though. Not adjustable from front either, at that. Pull the module, adjust one of the four trimmers, put it back in, see if it's good, repeat.

    In any event, even with a soft trip curve, this stupid breaker should have tripped. By comparison, there was one MD288 module, same show, that had to be swapped during performance because its breaker had a hard trip curve and wouldn't hold 2.5K. Swap it with another 2.4, and the moon stayed on in Scene One the next night...
     
  9. JD

    JD Well-Known Member

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    Yea, at 200% it should have tripped in about 10 seconds:

    [​IMG]

    And then you have the Federal Pacific breakers, which liked to let the full pole current through and use your wiring as a fuse ;)
     
  10. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    You can have them all plugged in at the same time, but not operating.

    Amps x Volts = Watts
    Watts / Volts = Amps

    120 * 6 = 720 - Each channel can pull 720 tops.

    120 * 15 = 1800 - You can run 1800 watts total on each pack at a time
    575w * 3 fixtures = 1725w
    575w * 4 fixtures = 2300w

    If you turn four fixtures on at once, you will toss the breaker, blow the fuse, whatever the protection may be. It doesn't matter what you have plugged in, only what you have turned on. It also doesn't matter which percentage you run a fixture at, the fact that it's turned is all that matters. If you run four fixtures at 50%, you're still pulling a lot more than 1150w due to the way dimmers operate. That said, you should not turn on more than three fixtures on per pack at a single time.
     
  11. waynehoskins

    waynehoskins Active Member

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    I remember hearing stories of electricians tracing wiring in conduits fed with Fed Pac breakers by putting a short on the load end and listening to the wire bang around inside the conduit, the breaker of course holding strong the whole time. Maybe it was an exaggeration, but not much, no. :)

    Thread hijacked long enough for me.
     
  12. dramatech

    dramatech Well-Known Member

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    Most of the shoebox dimmers limitation to 15 amps total per pack is ususally the input power cable and the trace on the circuit board that feeds the triacs. I usually upgrade them by changing the input power cable to a 12/3 with a high quality 20 amp rated edison. Then I take a piece of bare 12 ga wire and lay it parallel to the trace on the circuit board and solder it to the trace wherever possible. That done the total is now 20 amps, but you are still limited by the wall outlet that you plug into. Most commercial buildings will have 20 amp breakers on the wall outlets, but their will also be multiple outlets on that circuit. Make sure that only the one you are plugged ito will be used.
     
  13. mbandgeek

    mbandgeek Active Member

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    I might do this after the gig. If i do, i will have my brother in law help me. He is a certified electrician. Same goes out to all other member that are considering modding a pack like this, Seek professional help.
     
  14. dramatech

    dramatech Well-Known Member

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    I agree, that modifications to any type of lighting equipment should be done by people with the knowlege to do so. When ever possible, assist the professional with the modifications, so that you can learn how to do it, and then when you do your first mod have the professional watch and supervise you.
    I probably should have explained that I have been doing this sort of thing for 59 years. I am a certified Master electrician (the licensed kind, not theater), have graduated from the NASA soldering school and built more than half of the dimmers of the "Community Theater" where I volunteer, as the theater type master electrician. It is what I do instead of golfing or fishing in my retirement.
    ALWAYS learn first and follow common sense and electrical codes, and keep the blue smoke in the wire during "Smoke tests"
     
  15. n1ist

    n1ist Well-Known Member

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    If you are upgrading a shoebox dimmer, don't forget to check the current ratings on the rest of the parts. I was working on one that claimed 10A/channel, 20A max but it used a 14/3 cord, 10A IEC inlet, 6A switch, and 15A fuse holder. The manufacturer couldn't understand why I was concerned :)
     
  16. waynehoskins

    waynehoskins Active Member

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    Oh, that's easy to fix: to make it do more, get a 2/0 IEC feeder and plug it in. That'll make it do more than 10A, right? :)

    Yes, the 6A switch on a "20A" dimmerpack would have me worried too.
     

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