out of curiosity what would a typical load for a 192
dimmer system be? i know my high school had 96 20 amps fused at 400 amps.
The US Nat'l code allows a lot of leeway as to how you feed your *
stage* dimming
system. As it was once explained to me many, many years ago, by Steve Terry - now at
ETC, shortly after the section 520 segment was changed, "As far as the code's concerned, you can feed a 96
dimmer Sensor with 10 amp
zip cord".
That said, the expected demand load is a good starting
point, plus some allowance for future expansion of inventory, plus 20% or so.
Here's one case where known requirements helped plan the install. An existing lighting rig, partially consisting of 2 new
ETC permanent Sensor 96x2.4kw racks
fed off one 800 amp, 3
phase feed (in any event, that's all the extra
power that was available). The local
distro panel for these racks has 2 - 600 amp breakers, one per rack. Thus the maximum load for BOTH racks cannot exceed 800 amps per
phase, but there's no real limit as to how you load ea. rack - I.E. we insisted that the original plan for 2x400 amp/ 3
phase breakers be sized up so as to not "Zone Limit" ea. rack to 400 amps. That effectively down rates ea.
dimmer. Note that we had an existing lighting rig, with known plans for expansion, that in no case would pull more then a total of 600 amps per
phase off BOTH racks, so we were at 80% feed capacity. This rig is mostly setup with unit-per-circuit and as many fixtures are in the 575w to 1000w range, we stay well under the
feeder capacity.
Other conditions change this equation. A film or TV studio may well need a lot more capacity as the fixtures are often (somewhat) larger in wattage and may well sit on at full
intensity - all day long, 12-16 hrs. or so. In that scenario, an 800 amp per
phase feed PER rack may well be called for (in any case that's the bussbar
rating of a Sensor SR48).
As an interesting side note, Steve Terry initiated an
ETC survey of
current dimming systems in use. The survey indicated that theatrical lighting loads in permanent installs have been dropping, pretty much all a result of the S4 and it's copies, with loads on individual dimmers generally around 1150 watts per 2.4kw
dimmer. So don't be surprised if dimmers start moving towards 1.2kw capacity.
SB