Eight Working Dimmers, a Two-Story Unit, and a Fire Marshal
A black-box theatre measures 40 by 40 feet with a 14-foot grid. The lighting inventory includes twelve dimmers, but four have failed; the remaining eight are 20-amp circuits at 120 volts, fed from a 100-amp service. The board has 24 channels and no spare DMX universes. The set designer's model shows a two-story interior with a practical table lamp, a window for moonlight, and a staircase. The budget for scenery and lights combined is $1,200, of which $700 is already committed to lumber. The fire marshal requires flame-retardant treatment for all fabric and a clear 36-inch egress path. The director wants four warm interior areas, two blue moonlight washes, the practical lamp, and two downlight specials. The technical director must submit a plan that will pass inspection and not overload the service.
1. Allocate the eight working dimmers among the required lighting looks and explain your priorities, including how you would handle the practical lamp and any two-fer.
Read the worked answer
The first priority is visibility of faces and the actor's spatial relation to the staircase, because the set's two levels create shadows and blind spots. I would allocate four dimmers to the warm interior areas, but not as four separate 500-watt fixtures if the service calculation becomes tight; two warm dimmers can feed two-fers of matched 300-watt fresnels aimed at adjacent areas, provided the total load per dimmer stays within 80 percent of its 20-amp capacity. Two dimmers go to the blue moonlight washes, one to the two downlight specials (again, matched fixtures on a two-fer), and one to the practical lamp through a non-dim relay or a dimmer kept above the lamp's flicker threshold.
The practical should not share a dimmer with a stage fixture because its heat and color temperature are different and because the actor may need to switch it on physically. If the lamp is LED, a non-dim circuit is preferable; if it is incandescent, keep it on a dedicated dimmer and treat the shade with flame retardant. Two-fers are acceptable only when the fixtures are the same type, color, and function, and when the combined wattage is calculated. Do not two-fer the specials with the washes; losing independent control would flatten the climax.
2. Recommend a scenery plan that meets the fire code and egress path within the remaining $500, including material substitutions for the two-story unit.
Read the worked answer
The two-story unit is the budget's main threat. A full second level with a staircase, railings, and a practical window can consume the remaining $500 in lumber alone, before flame retardant and hardware. I would reduce the unit to a single elevated platform at 4 feet with a built-in ladder-stair and a railing, and use stock or rented platforms if the theatre has them. The window can be a flame-retardant muslin flat with a painted moon and a cut-out, lit from behind by a single blue fixture; it does not need glass or a full frame. The practical lamp sits on a small table that is part of the platform, not a separate scenic piece.
All fabric-drops, curtains, lamp shade, and any upholstery-must be treated with an approved flame retardant and documented. The 36-inch egress path must remain clear at all times, including during scene changes; mark it on the deck and rehearse crossings so actors do not stand in it. Keep the staircase open on both sides or provide a handrail. The remaining budget should go to flame retardant, hardware, and a fire-rated practical shade before decorative trim. If the platform cannot be built safely, cut the second level and use level changes on the deck; the play's function is the actor's isolation, not architectural realism.
3. Identify the load calculation and one safety risk you would flag to the technical director before opening.
Read the worked answer
A rough load calculation: four warm fixtures at 300 watts each equal 1,200 watts; two blue washes at 500 watts equal 1,000 watts; two specials at 300 watts equal 600 watts; the practical lamp at 60 watts. Total is 2,860 watts. At 120 volts that is about 23.8 amps, well under the 100-amp service, but the relevant constraint is per-dimmer load and continuous-use derating. A 20-amp dimmer should not carry more than 16 amps continuously, or 1,920 watts; each of the above dimmers is comfortably below that, but if the warm two-fer combines two 500-watt fixtures, it reaches 1,000 watts, still acceptable. The calculation must be redone if any fixture is swapped.
The safety risk I would flag most urgently is the practical lamp: an incandescent bulb close to a flame-retardant-treated but still combustible shade, placed on a platform where actors move, is a burn and fire risk. Use a cool LED lamp, secure the cord, keep the shade clear of the bulb, and place the lamp where it cannot be knocked into the egress path. The second risk is the staircase railing and the platform edge in low moonlight; mark the edge with glow tape and rehearse the climb under the actual cue levels.