In early 2005, as part of our product development efforts, the marketing and R&D groups at ETC began thinking about the current global state of dimmer loading and sizing in performance lighting systems. Because of our role as the manufacturer of Source Four® lighting fixtures, we knew that the global uptake of 575W lamps in performance lighting systems had been significant over the last 13 years. Somewhat surprisingly, we saw no apparent change in direction of dimmer capacities that might reflect the large worldwide usage of 575W lamps. This caused us to scratch our heads. We had plenty of anecdotal evidence that the market trend was toward higher dimmer quantities and light dimmer loading. We needed a relatively easy method of proving or disproving our anecdotal evidence. And in order to be believable to ourselves and to the industry, we needed to gather enough data to be statistically meaningful. In initial discussions, we felt that 100,000 dimmers of connected load data would give us a representative sample.

Previous efforts to characterize dimmer system loading have focused on system feeder currents during performance, with a view to right-sizing feeders and air conditioning systems. The typical method of gathering data was to send a measurement team out with a recording three-phase ammeter to various performance venues. Feeder current data was gathered during a performance and then compared with the nameplate rating (maximum possible current) of the dimmer system. These efforts were of limited success due to high cost, cumbersome equipment connection methods, lack of volunteer time to do the work, and no good method of coordinating the effort.

We reasoned that, in order to gather effective dimmer loading data in great volume, a simpler approach was needed. It had to be painless, and we needed help from hundreds, not tens of people. First, we worked the problem from the dimmers themselves, not the system feeders. For every show, in every venue, we concluded that someone must know how much load was plugged into every dimmer. Second, we devised a pain-free, Web-based survey method of reporting dimmer loads (see graphics). Finally, we added the carrot of a small gift and an opportunity to win a drawing for an ETC product to those that responded to the survey.

An Avalanche Response

We publicized the survey in the trade press and through various industry websites. In addition, our staff worked on an outreach to various lighting designers and production electricians, who provided connected load data for productions by sending us Lightwright files containing the data.

At the end of the day, the response was overwhelming. We received data from a total of 480 individuals, consisting of 736 unique shows and 642 discrete dimming systems. We received connected load data for a total of 119,862 show/dimmers. We defined a show/dimmer as the connected load for a given dimmer for a particular production. Thus, if a respondent was reporting about a system of 500 dimmers and provided data on four separate shows, that translated to 2,000 show/dimmers.

Everyone we talked to, from theatre consultants to lighting designers to electricians, immediately grasped the goal of the survey and came up with significant data. We want to thank each and every person who took the time and energy to participate in this important effort.

Who Responded and Where are They Located?

The survey respondents cover a wide range of performance venues. The breakdown by show/dimmers for each market and voltage (120V is assumed to be North America, while 230/240V is assumed to be the “rest of the world, excluding Japan”) looks like this:

120V MARKET Show/Dimmers Reported Percent 120V Show/Dimmers Shows Reported Systems Reported
Broadway 18,836 20.93% 53 53
Educational 21,459 23.85% 160 130
Non Profit 6,804 7.56% 71 56
Touring 5,726 6.36% 34 31
Regional 12,422 13.80% 60 45
Opera House 3,821 4.25% 9 5
Concert 3,500 3.89% 24 22
TV Studio 2,473 2.75% 8 8
Film 4,182 4.65% 8 8
Theme Park 1,591 1.77% 7 7
Place of Worship 2,733 3.04% 27 27
Industrial 5,191 5.77% 30 30
Other 1,250 1.39% 13 13
120V TOTAL 89,988 100.00% 504 435
230/240V MARKET Show/Dimmers Reported Percent 230/240V Show/Dimmers Shows Reported Systems Reported
Broadway 1,180 3.95% 5 5
Educational 2,012 6.73% 38 36
Non Profit 1,033 3.46% 23 22
Touring 2,058 6.89% 26 26
Regional 8,457 28.31% 53 45
Opera House 6,413 21.47% 14 10
Concert 3,173 10.62% 33 24
TV Studio 2,121 7.10% 13 12
Film 1,131 3.79% 2 2
Theme Park 414 1.39% 2 2
Place of Worship 389 1.30% 6 6
Industrial 1,043 3.49% 11 11
Other 450 1.51% 6 6
230/240V TOTAL 29,874 100.00% 232 207
Show/Dimmers Reported Shows Reported Systems Reported Individual Respondents
119,862 736 642 480

What Size Dimmers are People Using?

The charts below show the breakdown of dimmer sizes reported. Perhaps not surprisingly, 2.4kW is the leader in the 120V markets with 91% of the reported dimmers. Likewise, 2.5kW is king in the 230/240V markets, with 58% of the reported dimmers.

What is the Dimmer Loading?

The answer to this question contains the meat of the whole survey effort. The figures below show the results for the 120V market and 230/240V markets in detail and in summary. When we identify percentages here, we refer to the 120V and 230/240V markets as separate entities. The data speaks for itself, but some results are notable:

Loading Of 120V Systems

  • In the 120V market, 72% of loaded show/dimmers reported are loaded at 1,150W or below. 28% of loaded show/dimmers reported are loaded at 1,151W or above.

  • 17% of total reported show/dimmers in the 120V market have no load at all. This is useful in evaluating whether dimming systems are too large or small by dimmer count, but a dimmer with no load cannot be characterized as “1,150W or below,” since “no load' is a unique category.

Loading Of 230/240V Systems

  • In the 230/240V market, 51% of loaded show/dimmers reported are loaded at 1,150W or below. 49% of loaded show/dimmers reported are loaded at 1,151W or above.

  • 27% of total reported show/dimmers in the 230/240V market have no load at all. This is useful in evaluating whether dimming systems are too large or small by dimmer count, but a dimmer with no load cannot be characterized as “1,150W or below,” since “no load” is a unique category.

Why Is The 1,150W Number Interesting?

We believe that the load survey data can be viewed in the context of “1,150W or less” and “1,151W or more,” for the following reasons:

  • The majority of the dimmer loads reported in the 120V market were 1,150W or less, by a significant margin. In the 230/240V markets, 1,150W or less was also the majority, but by a smaller margin.

  • 1,150W represents a load approximately half the capacity of the most popular 120V and 230/240V dimmers. Therefore, if a future reduction in dimmer capacity were made to right-size for 1,150W loads, it would be a material reduction of at least 50%.

Food For Thought

We are presenting the results of this load survey to the lighting industry as a way of starting a dialogue about dimmer sizing. We believe the data speaks for itself, but what is it saying? Here are some further questions to kick off a discussion:

  • Is there now a real requirement for 1.2kW dimmers in the performance space? As new technologies like sine wave dimming emerge, perhaps the over-sizing of dimmers that we are used to becomes a luxury in terms of cost and space. With SCR dimming, such over-sizing carries very little penalty, but a 2.4kW sine wave dimmer is four times the size of a 1.2kW dimmer and is significantly more expensive. One way to make sine wave dimming technology more accessible would be to right-size it to the loads being used. The load survey results suggest that 1.2kW might be right-sized for a significant percentage of loads.

  • If 1.2kW dimmers look desirable for a big percentage of loads, what's the best method of deploying 2.4kW dimmers where needed in the performance space? It seems to us that 2.4kW dimmers are not going away and will always be needed for some of the higher power loads like cyc lights, strip lights, and 2kW Fresnels. But where are we to put them and in what quantity? Some possibilities might include distributed dimming at or near the load, flexible cable distribution rather than hard raceways, or a percentage of 2.4kW dimmers at each physical location where there are outlets.

  • Will 1.2kW dimmers have a cost-ripple effect in wiring and cooling a performance space? Even though the National Electrical Code allows feeding a dimming system based on the connected load, and the air conditioning requirements are supposedly based on that connected load, it seems likely that current feeders and cooling plants are being somewhat oversized. There could be material savings in right-sizing feeders, branch circuit wiring, and air conditioning to match the move from 2.4kW to 1.2kW dimmers for a significant number of circuits.

We believe the next step is to listen to end users, specifiers, and theatre consultants. We welcome your reaction to this article.

Steve Terry is the vice president of Research & Development at ETC (Electronic Theatre Controls, Inc.), where he is responsible for global product development. He is also the co-chair of the ESTA Control Protocols Working Group and the alternate USITT representative to National Electrical Code Panel 15, which is responsible for the theatre, film, and television sections of the Code.