LXQ: How Do I Spec a Small Theatre Lighting Rig? – Learn Stage Lighting .com

LXQ: How Do I Spec a Small Theatre Lighting Rig?

Theatre Lighting

Photo Credit: Thomas Hawk via Compfight cc

Lighting Questions are sent in from readers of our FREE email newsletter, or via our contact page.  With the permission of the writers, we share the Q&A’s here so that we can help others who have the same questions!

This week, Carlos writes in asking about how to install a small theatre lighting system.

Specifically, what components are needed and suggested, and how do we specify all that to the electrician for installation?

In our email conversation, Carlos and I discussed a lot of questions and answers revolving around this installation.  When I brought all of that info into this post, it got pretty long winded.

I’ve copied and pasted the most important bits and pieces of our conversations here, with Carlos’s words in italics and mine in the regular text, so we’ll  go back and forth a good bit.

Question & Answer

—-

Thanks so much for your site and willingness to help others. I’d like to “hear” your thoughts about my project and dilemma. To help you better understand it, I structured my message in three parts; my experience; my project; my dilemma.

Please know that I’m not expecting you to do my work for me, I just ask you to please point me to the right sources; I’m willing to do the reading/studying.

My Current Experience:

I’m an electrical engineer with a major in theater.

The courses I took in stage lighting design were mostly geared toward the design part of stage lighting, not the technical part.  I have also acquired some design experience as I have designed about 4 plays on my own already.

As an electrical engineer, I understand the power considerations of stage lighting.

However, although I understand how the lighting control equipment works in general, I have no hands on or practical experience with some of its components such as: dimmers, consoles, etc.

Some of my doubts are also related to the actual electrical wiring of the system components.

My Project:

A friend of mine asked me to help him set up the lighting system from scratch for a small theater venue.

Theatrical Lighting InstallationHe asked me to specify the whole system in detail.

My knowledge allows me to come up with a lighting system plan in general.   However, I have difficulties with some of the specifics regarding the lighting control aspect of the plan, as well as with the electrical wiring of the components.

For instance, given theater dimensions and budget constraints, I’m able to specify:

  • The amount and position of electrical bars:
    • A back, a center, and an FOH bar;
  • Types and amount of instruments per bar;
  • Make console selection
  • Specify amount of dimmers:
    • Either 12 @ 2400 Watt/Channel or 24 @ 1200 Watt/Channel, to add flexibility
    • Other options with less channels are possible;
  • Understand the need to specify non-dimmable power in general, for purposes such as lighting effects, working lights, house lights, etc.

My dilemma:

My dilemma is twofold:

First, even after reading your site and other sources, I have doubts about what specific lighting control equipment to get.  

In particular, what type of dimmer equipment to consider?  Should I consider the boxes that hang directly on electrical bars or a dimmer rack?

Dimming: Packs or Racks?

theater dimmer rack

The Original Dimmer Rack. These worked by literally pushing the huge handles on individual lights! Photo Credit: rustyjaw via Compfight cc

As Carlos alluded to, there’s really 2 options for a small dimming setup like this.  For an theatre installation like this, I’d suggest going with a centralized dimmer rack in an accessible place.

The benefits of this are that:

a) It’s easy to troubleshoot dimmer and fixture problems from the ground.  You can quickly check the dimmer to see if it’s getting signal from the console.  Then, you can see the dimmer’s breaker or fuses, and determine whether or not you need to drag out a lift to access a light that’s not working.

b) Decreased noise level out in the audience.  Some small dimmer packs make a good bit of noise when you dim lights down really far.  Dimmer racks make this noise too, but if it’s in a closet across the hall, there’s no buzzing for your audience to hear!

c) You only have to run DMX data to one place.  This is assuming that your lighting positions don’t have any LED’s/movers/scrollers that already have data out there.

Dimmer packs, on the other hand, are more flexible.

You hang it where you want circuits, and run power and non-dim power to the pack.  Want a big, rock and roll backlight show one week, and then a frontlight-heavy theatre show the next – no problem – you just have to move the packs around.

I know dimmer racks can be several thousand dollars and that’s out of the question in this project. Are there some affordable options?

Thankfully, that’s not always the case.  Yes, full-blown dimmer racks like an ETC Sensor rack or similar are pricey.  But, for a small installation, you can have an electrician hardware in dimmer rack packs like the ETC smart rack, Leprecon VX and others.

As far as dimmer packs, I read the info about the Leviton D4DMX-MD5 you suggest in your site and seemed like a good option for this project.

However, I don’t understand the specs.

It says that it is a 4 channel dimmer. The unit is rated for 20A (2400w) total/10A (1200w) per channel. But then this doesn’t make any sense to me.

Theatre Seats

Photo from M. Pratter on Flickr

To me, if it is a 4 channel unit rated for 20A (2400w) total, then it should be rated 5A (600w) per channel. But then you go on to say that “you can use lamps brighter than 600w!”.

Obviously, I’m missing something but I cannot see what is it? Do you mean that I have the option of plugging 3 x 750w lights, for instance?

But that would make it a 3 channel dimmer essentially, wouldn’t it? This is the kind of stuff I’m not following.

This is an interesting feature of dimmer packs that I do like.  The individual channels are indeed rated higher than the total pack when you add them all together- and that’s okay.

You can’t fill all of the channels up to capacity, because you must stay within the packs total capacity.  However, like you mentioned, you can put a hotter lamp into 1 channel or 2 if you want, and you wouldn’t have that option if the 4 channels were simply rated at 1/4 of the pack capacity.

So yes, you’ll reduce the number of channels that you have available to use, but if you want that one brighter fixture, it may make sense to have it and reduce the number of channels by one.

Second, how is the whole system wired?

For a dimmer rack based system, I know the power will come to the safety breaker first and then to the dimmer rack.

The dimmer rack in turn will be connected to the console on one hand and to the lighting instruments on the other. The console itself will be plug to a non-dimmable plug. However, I don’t know how to specify the actual wiring: what specific cables are used, how they are connected to the equipment and routed from one piece of equipment to the other.

stage lighting console

Photo Credit: B Rosen via Compfight cc

Exactly.  So, the power does hit the circuit breaker first and then moves along to the dimmer rack itself.

As for the specific type of cable, that depends on your local wiring codes, so leave that to your electrician!  They’ll be able to look up what wiring is appropriate, then run and terminate it for you.

However, if dimmer packs are used, how does the wiring change?

The first and most obvious change is that you need to run data out to your lighting position.  The second is that non-dimmed power needs to be run out to the packs, as opposed to a dimmer rack in the proverbial closet that runs dimmed power out to the lighting position.

Finally, does the non-dimmable power go in a different breaker than the dimmer rack or packs?

For an installation, the easiest way to do this is have the electrician wire up a separate panel with regular breakers for the non-dims.

The most flexible method of doing this involves purchasing special non-dimming modules for your dimmer rack, and then you can move them around to any circuit on your rack.

For what I understand, I’ll have to specify all this to the licensed electrician as I believe he doesn’t have any experience wiring stage lighting equipment.

Exactly.  And you can give him the spec sheets for all of the gear, provided from the manufacturer, and that will have the information he needs.

Well David, I appreciate you taking the time to read this message first and mostly any suggestions you can make.

Thanks so much,

Carlos

You’re welcome!  Have a great day!

-David


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