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Control/Dimming Duplicating/repeating circuits in a raceway

Discussion in 'Lighting and Electrics' started by Footer, Nov 10, 2008.

  1. Footer

    Footer Senior Team Senior Team Premium Member

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    I am the proud owner of a theatre that has two-fered raceways and,even better, twofered floor pockets. Just wondering what others think of this most wonderful practice. My biggest gripe about mine is how they are twofered, there is NO logical reason to why they placed circuits like they did. I have floorpockets that are ganged togther accross stage from each other. I have circutis that are a upside and backwards mirror of each other, but are offset by like 8'. It is by far the most annoying thing that can happen. Just give me a circuit, and I can cable the rest. Ug.

    Anyone else annoyed with these type of setups? Anyone else figure out how to use their setup to its fullest?
     
  2. icewolf08

    icewolf08 CBMod CB Mods

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    I have seen raceway twofering where there might be 15 circuits on the raceway and it goes 1-15 and then repeats 1-15, but from what you describe it sounds like yours go 1-15 and then 15-1, which I wouldn't understand. I don't really get the floor pockets though. However, it sort of makes sense from a modified McCandless way of thinking. In that you have ganged units into each area across the stage.

    I don't know if that is any help at all.
     
  3. porkchop

    porkchop Well-Known Member

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    While I can't comment on the backwards/mirrored nature on your pockets and raceway. They did a similar thing to your two-fered circuits in my old high school.

    The rational there was that the dimmer purchase was a two step process. They got all of the copper ran and installed 2/3 of the dimmers at initial construction. Then they did some two-fering since they had 50% more copper runs than dimmers. Things like FOH wash positions and all our floor pockets got two-fered together.

    I believe that since I've left they finally bought the last 1/3 of the dimmers and there are no longer any built-in two-fers in the auditorium. This may not be why they did it in your house, but that's why they did it in my old one.
     
  4. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    There are two philosophies on this. One is that the circuits are laid out to best suit a "house plot," usually one ill-conceived and often discarded immediately. The other is to place repeating circuits in locations highly unlikely to be used simultaneously (Pork's example of the FOH wash and floor pockets is a prime example).

    A 40' raceway with outlets every 18" is 26+ circuits. Most architects/electrical engineers feel it better to duplicate some or all circuits rather than provide 26 individual circuits/dimmers. As the cost of high density dimmers racks have come down in price, this practice is dying, albeit slowly. I'm not agreeing with, or defending the practice, as I, too, would rather have one, and only one, outlet for each dimmer.

    Planning the circuit distribution layout on a stage is more art than science, and one that few get correct. I believe I've said before that I don't think I've ever been on a stage where the circuit layout is exactly to my liking, even on a relatively small stage with 1000 dimmers.
     
  5. Footer

    Footer Senior Team Senior Team Premium Member

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    Its not even a reverse mirror really, it goes beyond that. Here is my 2nd elec, from SR to SL.

    89 90 85 86 87 88 91 73 74 75 76 77 78 79 80 81 82 83 84 89 90 85 86 87 88 91

    These are fairly new ETC raceways. I have 170 something dimmers in this space, so its not like I am short on power. It is very annoying to deal with. Its obvious to see they want the pipe ends ganged, but really who does that? Also, can anyone even give me a stupid reason why they had to skip all over the place?
     
    Last edited: Nov 10, 2008
  6. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    As I understand, a lot of "new construction" today is still based upon old methods and theories. Of course there are the repeating circuits that would have been perfectly suited for strip lights. As for the mirror floor pockets, I've heard this explained as an old concept that what a design most wants is the same color of light coming from both sides of the stage at the same time. (ugh). Repeating circuits in the cats are also part of the "old theories", aside from limiting dimmer costs, namely that mccandless rules, so might as well design your theatre that way. Take the example of a recently built theatre in Detroit. A pile of circuits on the cats, but very, very limited and repeating circuits onstage. Seems to me most "modern" designers are constantly crying for more on stage circuits. Again, I think it's just more carryover from older styles of design and lighting practice, but it just wont die, and theatre consultants seem to be doing their best to keep it alive. As Derek said, as dimmer racks have come down in price, the older, repeating circuits are dying a hard, long fought death - they need to just hurry up and die already. Lighting designers, they always want more control control control.
     
  7. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    My guess is the electricians who wired the place connected wires at random, perhaps with some thought to mix-and-match between bundles that were pulled together. When they pull wire into the conduits they tend to pull them in multiples based on the number of reels they have on the go, often multiples of 3 given 3-phase distribution.

    It may be that the circuits are twinned in the dimmer rack, or it might be that they are twinned in a splitter box somewhere but if you ever get the chance to look inside you'll see a lot of wire bundles that all look very similar. If they are twinned in the rack then it's not too big a job to get a qualified electrician to take the time to reorganize them in whatever you consider a more reasonable manner.

    My theatre is wired dimmer-per-circuit in groups of 6 (2 circuits per phase) with some twinning, using Socapex (stage circuits) and/or NEMA L5-20 receptacles depending on the location and age of the the last upgrade. With an inventory of fan-ins and fan-outs we can get power to pretty much any location in the theatre with minimal fuss and cable.
     
  8. porkchop

    porkchop Well-Known Member

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    Ok while the rest of your post has merit. My common sense, and my experiance with licensed electricians, argues against the idea of random. For a few reasons:
    • Long cable runs are hard to trace to begin with, randomizing and not labeling before you pull the cable is access work.
    • Random increases the possibility of errors, and the kind of power a dimmer often has mixed with errors is not really a fun idea.
    • Dimmers are often organized in the rack in a seemingly random order to help with load balancing. A field electrician adding another step of random with limited knowledge of how the theatre plot will be setup would be counter productive.
    • It just doesn't seem like a good idea IMHO.

    If I had to guess I would say that the seemingly odd order of your example cat is actually to fit the house plot to the board nicely. One of many possible examples of fitting your example cat to a board would be 85-88 FOH warm wash, 89 + 90 FOH Cool wash, 91 Patterns, 73 - 84 utility circuits. One can make all kinds of assertions about this setup, but if the original control device has a convinent way for this pattern to work out (say rows and/or sections of faders or on the screen depending on age in install and control device) I would say that you have found a theatre that was designed to fit the plot and the plot was designed to fit the control device.
     
  9. lieperjp

    lieperjp Well-Known Member

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    My raceways also have some twofering done, as well as some threefering and fourfering (actual words?)

    For instance, my first electric goes:

    26 34 33 32 31 25 24 34 33 32 31 23 22 34 33 32 31 21 20 30 29 28 27 19 18 30 29 28 27 17 16 30 29 28 27 15

    I found it annoying at first, and don't get me wrong, I still would rather have it done singularly, but I find that as long as I plan efficiently the twofering saves me time programming submasters/groups. I think it was done this way to save money on dimmers. For instance, on stage we have 112 outlets but only 59 channels. I would think this saves a lot of money. Sure, sometimes I have to balance power out to prevent blown breakers, but that does save a lot of money and maintenance time.

    However, my electrics seem to follow a logical order. Yours, however, would drive me crazy!!!
     
    Les and (deleted member) like this.
  10. willbb123

    willbb123 Active Member

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    my highschool stage was twofered oddly also. I finaly figured out that it was designed for a REP plot. The theater i work at now has one dimmer per plug. This works great on the on-stage electrics, where I have basically every plug filled. But in the cat and booms there are 20 to 30 circuits and corresponding dimmers that I am not using.

    At my high school I would of perfered if every plug had its own circuit number, then there was a patch bay where I could patch the circuit to the dimmer. There was like 40 some plugs but only 24 dimmers so I could have patched 2 lights together.
     
  11. Footer

    Footer Senior Team Senior Team Premium Member

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    At some point I will pull the plates on the terminal buss on the raceways and see if each run is individually ran or if each run is is split in the raceway. Who knows, maybe I can re-order it. Summer project number four million (and still going to be working summer stock... in another state... that should be interesting...)

    Now, my both my racks are old CD80 racks, back when they did not do the random ordered dimmers, so it is possible they mixed up the numbers to do load balancing. Still though, its annoying.
     
  12. midgetgreen11

    midgetgreen11 Active Member

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    Almost all of my dimmers are twofered. My first electric does this, 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31, and so does the cove, booms and third electric (With separate circuits). The second electric has a handy (more like not so handy) pattern of its own: 37 42 37 38 43 38 39 44 39 40 45 40 41 46 41
     
  13. Sayen

    Sayen Active Member

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    How many of you are in schools? The last school I worked in had a similar, bizarre twofer situation, especially when it came to floor pockets. My current place is similar, with drop box circuits over the stage wired to some of the floor pockets. With schools, I suspect some of this comes from retrofits where the original plans were long lost - that was the case in my last location of employment - or non-theater folks making their best guess during installation on how circuits should be wired.
     
  14. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    When I was suggesting random, I didn't mean to imply that the electricians are incompetent or violating code, but I was quoting from experience.

    The electricians where I live are seldom experienced with theatre, mostly with office buildings. We only have a handful of theatres and decades can pass between installations.

    In our theater the electricians pulled one colour per phase for hot (blue, red, and black are typical), white for neutral, and green ground, all according to local building codes. There was no need to label the ground or neutral wires since they all terminate in a common dimmer rack on a common bus bar. With the hot leads, as long as they kept their phase colours consistent and the bundles, or conduits they run through straight they were able to get things almost right but there were several sequence errors that needed to be corrected during commissioning, all involving mismatched circuits on the same phase within the same conduit.

    Since then, we've had a few intermittent circuits due to one bad spool of white wire but that's another story...
     
  15. Sayen

    Sayen Active Member

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    As long as you're on the subject of licensed electricians, I've worked in two districts where the district electricians were less than licensed, and were more just experts who had been doing it forever. While both were good guys, and very friendly and helpful, true experts they were not. Before someone wires about safety, schools often use safety as a public issue, while behind closed doors it's all about savign money.
     
  16. SteveB

    SteveB Well-Known Member

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    What you are describing sounds like a shared neutral for every 3 hot circuits, which is totally against US Nat'l Code for stage lighting dimmer branch circuits, which requires a separate neutral for each and every hot wire.

    One reason, is that dimmer circuits do not distribute across phases the way they might in a circuit breaker panel, where circuit 1 is A Phase, etc... In a hi-density dimmer rack (Sensor, CD80, etc...) Dimmer 1 & 2 are on Phase A, thus cannot share a neutral.

    Please tell me I'm wrong.

    As to electricians, my experiences are that they do NOT read the bloody plans !. I cannot begin to count the number of times I have had to have electricians correct installed work because they did not install according to plans. Each and every time I tell them TS and to fix it. The only electricians I have worked with that do good work are the IBEW Local 3 guys and gals on staff here at the college, or the Local 3 guys doing an install. The others may or may not have decent skills, but they still don't read the plans.

    Steve B.
     
    Last edited: Nov 10, 2008
  17. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    You're wrong. ;) Every bundle in our theatre contains 18 wires. 6 hot, 6 neutral and 6 ground. There are no shared neutrals. However, every neutral terminates on the same bus bar in an ETC Sensor Rack.
     
  18. SteveB

    SteveB Well-Known Member

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    Thank you for the clarification

    But am now curious as to why a ground for every circuit ?. That's not required and usual practice is a ground to every circuit box. 6 circuit multi cables, as example, do not usually have 18 conductors.

    SB
     
  19. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    I am probably wrong about the 6 ground wires. It's been a while since I've opened up a box. Maybe we're done hijacking this thread?
     
  20. SteveB

    SteveB Well-Known Member

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    Yup.

    But remember that even these trivial and seemingly useless thread excursions sometimes emit useful information to less learned folks who are lurking in the background. Not that there's anyone like that round these parts.

    SB
     

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