DMX Rack or DMX Pack

[peacefulone61]

I am trying to convince our school to upgrade the lighting system from 2 24 and 1 12 analog dimmer panels and to a 96 DMX tower. One of the parents who happens to DJ on the side recommended doing away with the Dimmer rack all together and buying the addressable DMX 4 Channel Dimmer Packs and placing them all over the theater. I was wondering if anyone wanted to weigh in on thoughts with this. I can see the potential for this but my gut tells me there are also a lot of things that could go wrong. Any thoughts.

 

[Footer]

the dimmer rack is cheap comparing to how much money it costs to get proper power to the rack and then get the power out of the rack to the lights. That can cost 1x to 10x as the rack itself. Distributed dimmers is a thing that comes and goes. Right now there are a few companies pushing for it. ETC and EDI both back distributed dimmers. ETC's are intended for small installations and portable setups. Truss mounted dimmers used to be common on the pre-rig par can rigs of years past.

If the places where the dimmer packs will be placed are easily accesable, there is nothing really wrong with doing a distrusted system. It saves a ton of money in installation. Maintence on them is greater though. Instead of having one controller card to fail, you now have 30. Instead of one cable to fix if you are getting weirdness, you now have 30. Chances for failure go much higher.

If you do go the distrubuted route, don't install any DJ class gear. If the unit that the parent wants you to buy says anything like American DJ, Chauvet, Lighttronics, or the like, stay away. You can buy the little 4 pack "shoebox" DMX dimmers online for about 70 bucks. They are not meant to be used in a theatre situation. Most people consider them disposable. Don't base and install around them.

 

[icewolf08]

Along with what Kyle said, it should also be noted that doing a distributed dimming system still requires that you get the appropriate power run to the dimmers. So, if the wiring does not already exist for that, it can cost almost as much as putting in a rack and running circuits.

With your current system, do you cable all of your units back to the dimmers or are there circuits and raceways throughout the theatre that are either connected directly to the dimmers or to a patch panel? If the circuits between the dimmers and the lighting positions already exist then installing a rack is certainly the best option.

An upgrade like this also begs the question of: what is your control console currently? If it is an analog console you would need to upgrade that as well (or at least you would probably want to). This is going to add another layer of cost.

 

[epimetheus]

What 4 channel packs did the DJ guy recommend? Elation, Chauvet, or AMDJ?

I'm actually about to write a response to the building committee at my church regarding distributed verses centralized dimmers. My stance is that the centralized system using racks such as the ETC Sensor 48 or the Strand C21 is an overall better system in the long run.

Proponents of the distributed dimming systems will tell you that the biggest advantage of their systems is that they save copper since you don't have a bunch of 20A circuits running all over the place. You also don't have the high current feeds that would supply a 96 circuit rack. I don't necessarily buy that argument though. You still have to have the source circuits that supply the distributed dimmers. And now you have to add panelboards to provide the overcurrent protection for those circuits. You also have to add in the cost of the DMX distribution since now you have (16) 6 circuit dimmers, for example, instead of 1 96 circuit dimmer. You've also got 16 devices that can fail now as opposed to just one. Of course, the proponents will say that when one of those 16 devices fail, you only lose 6 circuits. While that may be true the most common failure in a rack system is a dimmer module; you don't lose the whole rack. I don't think that same concept holds true for the distributed dimmers.

You also need to look at derating. Circuit breakers in dimmer racks such as the Sensor and the C21 are 100% rated breakers. This means they can operate at 100% indefinitely. Standard thermal breakers in commercial panelboards have to be rated to 80% for loads on for more than 3 hours (the NEC definition of continuous). This means that your (6) 1.2k dimmers are now only rated for 960W.

I don't have the time to continue this thought right now, I'll try to add more later.

 

[Footer]

What 4 channel packs did the DJ guy recommend? Elation, Chauvet, or AMDJ?

I'm actually about to write a response to the building committee at my church regarding distributed verses centralized dimmers. My stance is that the centralized system using racks such as the ETC Sensor 48 or the Strand C21 is an overall better system in the long run.

Proponents of the distributed dimming systems will tell you that the biggest advantage of their systems is that they save copper since you don't have a bunch of 20A circuits running all over the place. You also don't have the high current feeds that would supply a 96 circuit rack. I don't necessarily buy that argument though. You still have to have the source circuits that supply the distributed dimmers. And now you have to add panelboards to provide the overcurrent protection for those circuits. You also have to add in the cost of the DMX distribution since now you have (16) 6 circuit dimmers, for example, instead of 1 96 circuit dimmer. You've also got 16 devices that can fail now as opposed to just one. Of course, the proponents will say that when one of those 16 devices fail, you only lose 6 circuits. While that may be true the most common failure in a rack system is a dimmer module; you don't lose the whole rack. I don't think that same concept holds true for the distributed dimmers.

You also need to look at derating. Circuit breakers in dimmer racks such as the Sensor and the C21 are 100% rated breakers. This means they can operate at 100% indefinitely. Standard thermal breakers in commercial panelboards have to be rated to 80% for loads on for more than 3 hours (the NEC definition of continuous). This means that your (6) 1.2k dimmers are now only rated for 960W.

I don't have the time to continue this thought right now, I'll try to add more later.

The one advantage to the system is you can install it in a space that does not have space for a dimmer rack or the ability to run large conduit everywhere. These things are in churches fairly often because they are easy to install in a day and you get what you need fast. There are some theatres that are installing the EDI raceways, we'll see how that turns out in 10 years. If you need more then about 24 dimmers, distributed is not for you as far as I go.

 

[Edrick]

As has already been mentioned there's pro and cons to both sides of it. What strikes me as DANGER WILL ROBBINSON, is the fact that a DJ recommended it. Now not all DJ's are just hacks who run Chauvet or American DJ. However the majority of them seem to be and that's where I'd be cautious. Did he give you any personal reasons for using packs as opposed to a dimmer rack? What was his justification for saying that's what they should do? Did he actually evaluate the space, or just say hey I'm a professional DJ and I use them I think they're great. I recommend walking on the side of caution when a DJ recommends something unless it's specific to their task. If I need to get the most muddy sounding, ear shattering, bass shaking sound I'll ask a DJ. But if I want proper vocal enforcement or sound for corporate events / a permanent install I'm going to ask a pro.

 

[SteveB]

Some of the other issues:

- Rack system, requires a room, as Kyle mentioned, as well as air conditioning for that room. If you have the room with HVAC as well as space for a rack AND 300-400amp local sized disconnect switch, then that often is the best solution. If not, it's another cost factor.

- With a distributed system, you need to install a circuit breaker panel somewhere for the breakers to feed the remote dimmers. Note that standard panel circuit breakers get downrated 20% for loads running over 3 hrs., so with distributed you need to take that into consideration in terms of the quantity and sizing of the loads as they relate to the choice of dimmer packs.

- With distributed, you also need to install a data network, either a basic DMX distribution system, or an Ethernet system. In either case, you have to get control signal to the distributed dimmers. Basic DMX can be cheaper in the short term, but as the future is with Ethernet, that is what is often recommend in terms of what kind of wiring and connections gets installed. Going Ethernet you add on the cost of "nodes" - I.E. DMX distribution convertors that convert the backbone Ethernet signal to local DMX that the dimmers and devices use. Note that installing an Ethernet backbone makes it much easier down the road to add additional devices, moving lights, LED fixtures, etc... all of which eat up DMX bandwidth quickly.

- The choice of data backbone is driven by the current controller, DMX ?, that drives the backbone complexity.

And as FYI, Cooper Controls announced last month that they were closing the EDI facility in Oregon, moving manufacture of EDI dimming systems to the Cooper facility in Vermont. As quoted on PLSN:

Prior to this closure of the EDI facility in Hillsboro, OR on Nov. 29, Cooper Controls said it built inventory of many of the existing orders and is working toward a seamless transition.

"Cooper Controls said it would be conducting a full product evaluation to determine the final product portfolio with the goal of being fully operational by March 1, 2011."

One source told me Cooper was pulling the plug, no pun intended.

 

[lighthouse]

It took me a year, but I convinced our local HS to upgrade - the compromise was an architectural system over a full rack. 48 channels, same dimmer modules as a rack but less space. If they need to grow from there they'll have to add distributed dimmers to key locations, but they've got the power sized to allow for it.

Now to raise some $ for new fixtures...

 

[natebish]

i'm in the same posistion as Lighthouse. my school has our electrics and our one catwalk on what i think is a CD80 rack. yet with that system we have no flexability for "interesting" lighting posistions since we have very little cable. so i use portable dimmers to suppliment. and as far as i'm concerned it works very well. just be sure you have a map of which outlets around your space are on different circuits.

 

[derekleffew]

... there is nothing really wrong with doing a distrusted system. ...

Best Freudian slip ever! In my opinion, there's a lot wrong with a distrusted system of more than 24 or so dimmers.

peacefulone61, right now you have 60 dimmers. Are they hard-wired to circuits (DPC) or is there a hard-patch? If the latter, is each circuit protected by its own breaker per NEC 520.50(C): Road Show Connection Panel - ControlBooth ?

I am trying to convince our school to upgrade the lighting system from 2 24 and 1 12 analog dimmer panels and to a 96 DMX tower. ...

Why? Are the dimmers failing? Repair is (almost) always less expensive than replacement. Do you desire DMX control and don't have it? Do you need more dimmers/circuits?

(epimetheus, I'm with you. See this post (and subsequent) from this thread: http://www.controlbooth.com/forums/lighting-electrics/9344-sensor-vs-et-intelligent-raceway.html .)

 

[epimetheus]

(epimetheus, I'm with you. See this post (and subsequent) from this thread: http://www.controlbooth.com/forums/lighting-electrics/9344-sensor-vs-et-intelligent-raceway.html .)

Yep, I've already been through that thread and a couple others I could find on CB concerning this issue. My personal opinion (though I haven't actually priced this out, yet) is that distributed can be cheaper than centralized to a point. There's a point somewhere in the number of circuits where the scalability of a distributed system goes to crap and a centralized system is cheaper. The consultants for my church's new worship center have spec'ed 288 circuits with 240 of those allotted to theatrical fixtures. At this level, I don't think distributed scales very well. The panelboards alone would get you.

Assuming 6 circuits on a 3 phase, 20A supply, you'd need 40 supply circuits. Thats (40) 3-pole breakers. With NEC 2008, a single panelboard can have up to 84 breakers now, instead of 42, so that helps, but it's still a completely full 84 circuit panel and a full 42 circuit panel. The 84 circuit panel would need to rated for 600A with a 100% rated 600A main if you don't factor in diversity. The 42 circuit panel would need to be rated for 400A with a 100% rated 300A breaker or a standard 400A breaker derated to 320A. If you factor in diversity, you can cut those numbers down, but you lose flexibility in doing so. Oh, and you still have to buy the dimmers. I think Steve Terry said it in one of his articles: dimmer racks are distribution panelboards with free dimmers.

 

[peacefulone61]

With your current system, do you cable all of your units back to the dimmers or are there circuits and raceways throughout the theatre that are either connected directly to the dimmers or to a patch panel? If the circuits between the dimmers and the lighting positions already exist then installing a rack is certainly the best option.

There are stage pin Boxes already set in throughout the house and the stage (most of them are just boxes but no power is run to them) Half of the circuits are Directly tied into the dimmers and Half are Run through a patch panel. The house dimmers are on a separate system with seprate controls that require to operate just to dim the house lights, not counting a Board op to run the rest of the system.

The Board is an Expression 48/96 that is wired in a way that defy logic and i have been told in previous post on CB that actually cannot work. There are Mac 500s in the system as well but are somehow the control dimmers for pan tilt and color are assigned to some of the hard patched dimmers. so i change the color and a light on stage turns on as well.

 

[peacefulone61]

As has already been mentioned there's pro and cons to both sides of it. What strikes me as DANGER WILL ROBBINSON, is the fact that a DJ recommended it. Now not all DJ's are just hacks who run Chauvet or American DJ. However the majority of them seem to be and that's where I'd be cautious. Did he give you any personal reasons for using packs as opposed to a dimmer rack? What was his justification for saying that's what they should do? Did he actually evaluate the space, or just say hey I'm a professional DJ and I use them I think they're great. I recommend walking on the side of caution when a DJ recommends something unless it's specific to their task. If I need to get the most muddy sounding, ear shattering, bass shaking sound I'll ask a DJ. But if I want proper vocal enforcement or sound for corporate events / a permanent install I'm going to ask a pro.

I think the reason that the DJ suggested it was because it could over the next few years be upgraded and slowly added two. Also Because he seems to think that they could move them around to the needs of the show. We need all the lights in the house just pick up and move the packs kind of thing.

 

[peacefulone61]

Best Freudian slip ever! In my opinion, there's a lot wrong with a distrusted system of more than 24 or so dimmers.

peacefulone61, right now you have 60 dimmers. Are they hard-wired to circuits (DPC) or is there a hard-patch? If the latter, is each circuit protected by its own breaker per NEC 520.50(C): Road Show Connection Panel - ControlBooth ?

Why? Are the dimmers failing? Repair is (almost) always less expensive than replacement. Do you desire DMX control and don't have it? Do you need more dimmers/circuits?

(epimetheus, I'm with you. See this post (and subsequent) from this thread: http://www.controlbooth.com/forums/lighting-electrics/9344-sensor-vs-et-intelligent-raceway.html .)

The Lights 36 are DPC and 24 are Patchable. I am starting to have to canablize parts as the Brushes ware down. I have had to set most dimmers to about 90% and cannot get new brushes from most of the common supply houses in my area, and strand claims to no longer support them.

 

[derekleffew]

I am trying to convince our school to upgrade the lighting system from 2 24 and 1 12 analog dimmer panels ...

... I am starting to have to canablize parts as the Brushes ware down. I have had to set most dimmers to about 90% and cannot get new brushes from most of the common supply houses in my area, and strand claims to no longer support them.

Brushes??? The only dimmers that use brushes are Dimmer, Resistance and Dimmer, Autotransformer which Strand / Strand-Century / Century hasn't made since the early 1960s. Please post some pictures.

 

[peacefulone61]

I think that the stage lights are the auto transform type i have not had to do to much to those i know barbizon laughed when i called them to come and look at them for service. The house lights are from the mid fifties and were pulled out of the old theater. those are definitely resistance dimmers.

Also 48 dimmers are not really working effectively for the stage productions plus everything else they want to do in my poor theater.

 

[epimetheus]

Pictures please? I love older electrical equipment. Unfortunately my job generally is to relegate it to the junk yard or scrap heap.

 

[ToddH]

As an installer and systems integrator I have dealt with this many times. The little shoe box dimmers are inexpensive and great for the club/DJ market. I even like them for the small community theater tour. I cannot recommend them in a professional or school theater application. They are not the same as what ETC and Strand are doing with Smartbars and Smartmodules. The quality, durability and features of the ETC or Strand product far surpasses that of a inexpensive "four pack". Currently the cost of an installation rack is generally less than a distributed dimming system per dimmer. An SR48 has a 400A max three phase. 200A would be sufficent in most applications. If three phase is not available a Unison DRd or A21 system could be used as they will take single phase. While it is true the cost of the EC services can be as much as the cost of the rack you will end up with a higher quality system in the end. Rarely have I seen the instillation cost be more than the cost of the dimmer rack as some have suggested.

 

[sk8rsdad]

I am going to lean toward for Pack rather than Rack. Here's my reasoning:

As a caveat, in my venue I have a dimmer rack and can swap out dimmers for relays as required, but if I were starting from scratch today I might go with fewer conventional dimmers. The trend seems to be to fewer instruments with more capability and lower power consumption so maybe we won't need a lot of conventional dimming a decade from now.

The future (and the present) of stage lighting is some combination of conventional, LED, and ML lights. Investing in a dimmer rack may not be as cost-effective as running switched power and communications wire (DMX and ethernet) everywhere, especially if you have to run the data wire everywhere anyway to support all those newfangled DMX devices. LEDs have integrated dimming, as do most MLs so the dimmers are primarily for the conventionals.

There are some really good quality IGBT dimmer options out there. Getting one that can up to 1.2 kW per channel would support most conventional instruments you are likely to use.

Assuming the existing wiring is worth preserving and up to the task, replace the existing dimmer rack with a DMX-controlled circuit breaker panel and reuse the the wiring to distribute switched power throughout the venue. Extra circuits are nothing special for any licensed electrician which means there's more chance it will get done correctly. It's not quite as simple as that but a good consultant, vendor, and/or electrician can help steer you straight.

Install CAT6 and DMX drops near all the locations that have power since you are going to need it for the dimmer packs. Make sure all the DMX drops come from their own branch of a DMX splitter. Make sure all the CAT6 runs home to place where a robust router can be installed. Now that you have all that data cabling for the dimmer packs, it is also available for gobo rotators, I-cues, scrollers and other DMX toys (aka the Gafftaper Method).

This option produces a venue with lots of clean power available everywhere, and lots of data wiring. When you start supplementing your rig with LED, or MLs, or decide you need to rent another 8 channels of dimming for some production, it is easy to do so.

As others have said, there are pros and cons to both methods. Assuming the same quality, dimmer rack ought to be less expensive than distributed dimming. But if you don't need as much conventional dimming, then you don't need a large dimmer rack.

 

[epimetheus]

An SR48 has a 400A max three phase. 200A would be sufficent in most applications.

I disagree. First, an SR48 is not 400A max, it's actually 1000A. Second, 400A is pretty restrictive for (96) 2.4k dimmers. If you're going to go to the trouble of installing a 96 circuit rack, don't hobble it's power feed. At 400A (320A with derating) you're forcing yourself into 50% diversity if the rack has (96) 2.4k dimmers. Your diversity would have to be even less if you had all 50A or 100A dimmers. 50% diversity might be reasonable if you've got multiple racks, but if you've got only one, then I'd guess there might be times when you'll want more than half your circuits usable. Or at least at some point in the future.