Chapter XVIII: Theater Wiring (1)

The wireman should not fail to consult local rules or inspection departments as to whether any rules conflict with those given below. He must be warned to consult local authorities or rules, too, because safety rules are liable to change.

The purpose of this chapter is to furnish a ready reference work concerning questions of electrical construction in theaters which come up daily in all progressive play houses. To this end the subjects have been arranged in alphabetical order and the practical considerations, as well as extracts from the National Electrical Code governing construction, have been given together. The aim has been to enable the workman to find all information concerning construction work grouped together, so as to obviate the necessity of looking through various parts of the book for the information sought. This order of things will probably avoid the troubles now often caused by overlooking certain points that should be considered.

_Aisle Light._--Figure 151 is an illustration of an aisle light. Such lights are often placed along steps and aisles. The light illuminates only the floor. Aisle lights should be arranged on a separate circuit and controlled by a switch at the door.

_Alternating Current._--All wires of any circuit or mains or sub-mains of any system must be run in the same conduit. Failure to do this will cause an unnecessary drop in voltage and heating of the conduit.

_Arc Lamps._--For treatment and construction of portable arc lamps, see the chapter on “Portable Stage Equipment”.

Permanently located arc lamps are used about theaters mostly for out-door lighting. Very often, two or more lamps are arranged in front of the house. Such lamps are mostly of the flaming arc lamp type and are hung up high.

In some of the cheaper theaters a pair of arc lamps is used on the stage, but they do not give satisfaction. The light is not even and steady enough and cannot be properly “dimmed”. Where arc lamps are to be arranged for stage illumination they must be suspended amid the scenery and enclosed with wire guards. In some cities the use of arc lamps suspended above the stage is prohibited.

In the auditorium, arc lamps are sometimes installed, but this practice can not be recommended and, with the present high efficiency incandescent lamps, there is but little excuse for it. The only advantage in using arc lamps lies in the first cost of wiring, and this is more than balanced by the difficulties of trimming lamps located in such places. Wherever arc lamps are used it is essential that they be hung high and those that do not naturally throw the light downward must be equipped with suitable reflectors. The question of drop in voltage need not be considered with arc lamps unless runs are very long.

_National Electrical Code Rules for Arc Lamps._

_Arc Lamps in General._

Must be provided with reliable stops to prevent carbons from falling out in case the clamps become loose.

All exposed parts must be carefully insulated from the circuit.

Must, for constant-current systems, be provided with an approved hand switch, and an automatic switch that will shunt the current around the carbons, should they fail to feed properly.

The hand switch to be approved, if placed anywhere except on the lamps itself, must comply with requirements for switches on hanger-boards.

Terminals must be designed to secure a thoroughly good and permanent contact with the supply wires, which contact must not become loosened by motion of the lamp during trimming.

Spark arresters must so close the upper orifice of the globe that it will be impossible for any sparks, thrown off by the carbons, to escape.

_Series Arc Lamps._

Must be carefully isolated from inflammable material.

Must be provided at all times with a glass globe surrounding the arc, and securely fastened upon a closed base. Broken or cracked globes must not be used.

Must be provided with a wire netting (having a mesh not exceeding one and one-fourth inches) around the globe and an approved spark arrester, when readily inflammable material is in the vicinity of the lamps, to prevent escape of sparks of carbon or melted copper.

Outside arc lamps must be suspended at least eight feet above sidewalks. Inside arc lamps must be placed out of reach or suitably protected.

Arc lamps, when used in places where they are exposed to flyings of easily inflammable material, must have the electrodes enclosed completely in a tight globe in such manner as to avoid the necessity for spark arresters.

“Enclosed arc” lamps, having tight inner globes may be used, and the requirements of b and c above would, of course, not apply to them.

Where hanger-boards are not used, lamps must be hung from insulating supports other than their conductors.

Lamps when arranged to be raised and lowered either for carboning or other purposes, shall be connected up with stranded conductors from the last point of support to the lamp, when such conductor is larger than No. 14 B. & S. gauge.

_Arc Lamps on Constant-Potential Circuits._

Must have a cut-out for each lamp or each series of lamps.

The branch conductors must have a carrying capacity about fifty per cent in excess of the normal current required by the lamp.

Must only be furnished with such resistances or regulators as are enclosed in non-combustible material, such resistances being treated as sources of heat. Incandescent lamps must not be used for this purpose.

_Arc Lamps Used as a Part of a Moving-Picture Machine._

Must be constructed, so far as practicable, similar to arc lamps of theaters, and wiring to same must not be of less capacity than No. 6 B. & S. gauge. See “Portable Stage Equipment”.

_Stage and Gallery Pockets._

Must be of approved type, insulated from ground and controlled from switchboard, each receptacle to be of not less than 35 ampere rating for arc lamps nor 15 amperes for incandescent lamps, and each receptacle to be wired to its full capacity. Arc pockets to be wired with wire not smaller than No. 6 B. & S. gauge and incandescent pockets with not less than No. 12 B. & S. gauge.

Plugs for arcs and incandescent pockets must not be interchangeable.

_Armored Cable._--All wires in the stage part of theaters must be enclosed in conduit or armored cable. Armored cable is thus the only flexible conductor allowed for permanent work. This cable is very convenient where wires must be “fished”, or run around beams or other obstacles making many bends necessary. It should, however, be used only where the rigid conduit cannot well be installed and it is advisable to use the latter, even where the additional expense is considerable. Wires run in rigid conduit can be taken out and replaced by new ones at any time, while this is not the case with armored cable. Should a wire incased in armored cable develop a serious fault, the old cable would have to be abandoned and a new circuit run, which in many cases would mean the tearing up of parts of the building.

Where armored cable is to be used great care should be exercised to see that bends are not made too short, and that each length of cable is tested for grounds, short circuits, and open circuits. Special attention must be given to the wires at the place where the armor has been cut. Careless workmen can do great damage at this point. The manner of cutting the armor is shown in Figure 152. Each strand of the armor is partly cut with a saw and may then be broken off, taking care that no sharp edge is left in position to pierce the wire.

Installation rules are given below. Before installing any armored cable, be sure that it is of approved make and guaranteed to pass inspection.

_National Electrical Code Rule for Armored Cables._

Must be continuous from outlet to outlet or to junction boxes or cabinets, and the armor of the cable must properly enter and be secured to all fittings, and the entire system must be mechanically secured in position.

In case of service connections and main runs, this involves running such armored cable continuously into a main cut-out cabinet or gutter surrounding the panel board, as the case may be.

Must be equipped at every outlet with an approved outlet box or plate, as required in conduit work.

Outlet plates must not be used where it is practicable to install outlet boxes.

For concealed work in walls and ceilings composed of plaster on wooden joist or stud construction, outlet boxes or plates and also cut-out cabinets must be so installed that the front edge will not be more than one-fourth inch back of the finished surface of the plaster, and if this surface is broken or incomplete it shall be repaired so that it will not show any gaps or open spaces around the edges of the outlet box or plate or of the cut-out cabinet. On wooden walls or ceilings, outlet boxes or plates and cut-out cabinets must be so installed that the front edge will either be flush with the finished surface or project therefrom. This will not apply to concealed work in walls or ceilings composed of concrete, tile or other non-combustible material.

In buildings already constructed where the conditions are such that neither outlet box nor plate can be installed, these appliances may be omitted by special permission, provided the armored cable is firmly and rigidly secured in place.

Must have the metal armor of cables permanently and effectually grounded to water piping, gas piping, or other suitable grounds, provided that when connections are made to gas piping, they must be on the street side of the meter. If the armored cable system consists of several separate sections, the sections must be bonded to each other, and the system grounded, or each section may be separately grounded, as required above.

The armor of cables and gas pipes must be securely fastened in outlet boxes, junction boxes, and cabinets, so as to secure good electrical connection.

If armor of cables and metal of couplings, outlet boxes, junction boxes, cabinets, or fittings having protective coating of non-conducting material, such as enamel, are used, such coating must be thoroughly removed from threads of both couplings and the armor of cables, and from surfaces of the boxes, cabinets, and fittings where the armor of cables or ground clamp is secured in order to obtain the requisite good connection. Grounded pipes must be cleaned of rust, scale, etc., at place of attachment of ground clamp. Connections to grounded pipes and to armor of cables must be exposed to view or readily accessible, and must be made by means of approved ground clamps, to which the ground wires must be soldered.

Ground wires must be of copper, at least No. 10 B. & S. gauge (where largest wire contained in cable is not greater than No. 0 B. & S. gauge), and need not be greater than No. 4 B. & S. gauge (where largest wire contained in cable is greater than No. 0 B. & S. gauge). They must be protected from mechanical injury. The ground for the armored cable system is not to be considered as a ground for a secondary system.

When installed in so-called fireproof buildings in course of construction, or afterwards if exposed to moisture, or where it is exposed to the weather, or in damp places, such as breweries, stables, etc., the cable must have a lead covering placed between the outer braid of the conductors and the steel armor. The lead covering is not to be required when the cable is run against brick walls, or laid in ordinary plaster walls unless same are continuously damp.

Where entering junction boxes, and at all other outlets, etc., must be provided with approved terminal fittings which will protect the insulation of the conductors from abrasion, unless such junction or outlet boxes are specially designed and approved for use with the cable.

Junction boxes must always be installed in such a manner as to be accessible.

For alternating-current systems must have the two or more conductors of the circuit enclosed in one metal armor.

All bends must be so made that the armor of the cable will not be injured. The radius of the curve of the inner edge of any bend not to be less than 1-1/2 inches.

_Asbestos._--As all wiring in theaters is required to be run in conduit, and metal cabinets are compulsory in this connection, there is but little opportunity to use asbestos. Wherever the use of asbestos is advisable it must conform to the general requirements as given for wooden cutout cabinets, viz.: “for lining wooden cabinets, one-eighth inch rigid asbestos board may be used when firmly secured in place by screws or tacks”.

_Attachment Plugs._--Attachment plugs should be used to connect all portable apparatus. All plugs should be of approved type and constructed so as to pull out in case strain is put on them. On the stage, pin-plug connectors should be used in place of attachment plugs, as none of the latter are sufficiently rugged to withstand the hard usage.

_National Electrical Code Rules for Attachment Plugs._

Link fuse attachment plugs of the types now on the market are considered unsafe, as under entirely possible conditions an arc may be produced when the fuses blow, damaging the plug and perhaps causing fire. Attachment plugs are not approved for more than six hundred and sixty watts or two hundred and fifty volts.

_Auditorium._--Two separate systems of lighting are required: See emergency or exit lighting. Metal moulding, as well as armored cable or conduit, is permissible in wiring the auditorium part of the theater.

_Auto-Starters._--Auto-starters perform the same service with alternating-current motors that resistances do with direct-current motors. They are used with motors from two or three horse power upward, and not generally with the smaller motors.

The following are extracts from the “National Electrical Code” concerning their use:

In all wet, dusty, or linty places, auto-starters, unless equipped with tight casings enclosing all current-carrying parts, must be enclosed in dust-tight fireproof cabinets. Where there is any liability of short circuits, caused by accidental contacts, across their exposed live parts a railing must be erected around them.

The switch on the auto-starter must provide an off position, a running position, and at least one starting position. It must be so arranged that it will be held in off and running position, but not in starting position or without the proper running overload-protection devices in the circuit.

For currents above 30 amperes, lugs, into which the connecting wires may be soldered, or approved solderless connectors must be used. Clamps or lugs will not be required when leads are provided as a part of the device.

The following rules are drawn for rheostats but may also apply to auto-starters:

Where the circuit-breaking device on the motor-starting rheostat disconnects all of the wires of the circuit, the switch called for in this section (to disconnect all apparatus) may be omitted.

Overload-release devices on motor-starting rheostats will not be considered to take the place of the cutout required to protect the motor and the rheostat.

_Balconies._--The illumination of balconies is a difficult matter. The ceilings under galleries above are always low, and to obtain even illumination requires the use of many small candle-power lamps. These should be set well back so as not to be visible too much to the audience.

Stage-pocket capacity for one or more arc lamps should always be provided. Where there are galleries above, the arc lamps used for stage illumination are generally placed there, but it often happens that a moving-picture machine must be installed and it is very disadvantageous if this must be located in the galleries. Balconies require the same exit and emergency light service as is required in the auditorium.

_Batteries._--See Portable Stage Equipment.

_Bells._--Systems of call bells are generally arranged between the box office or the manager’s office and the stage switch board; also from the stage switch board to the fly floor by which signals for raising and lowering the curtain may be given; also to the orchestra leader. In some cities all of this wiring is required to be in conduit. These signaling circuits should be carefully installed, for they are as important as any part of the wiring. Only the very best bells and push buttons should be used, and it is advisable to avoid the use of the ordinary annunciator wire so often seen in connection with bell work. Numerous diagrams and much information concerning bell wiring is given in “Modern Wiring Diagrams and Descriptions”, which should be consulted in case some complicated annunciator system is to be installed. Figure 153 is a diagram of a simple call-and-return-call system.

_Borders._--The number of borders used in theaters varies from one to six, the latter number being sufficient for almost any stage. They are generally made of a length about equal to the proscenium opening. The borders placed in the rear are of less importance than those in front and consequently are made shorter and are not provided with so many lights. Each border should have at least three circuits, one for each color; each circuit being taken through a separate dimmer so that any color may be used alone and dimmed as desired.

Figures 154 and 155 show types of borders, and the method of wiring is shown in Figure 156.

Large borders are very heavy and are usually suspended by wire rope and provided with counterweights to make handling easy. The wire rope should be kept well protected by oiling; the moisture given off by fireproofed scenery is liable to rust them very fast, and as the ropes are made up of very fine strands the rust soon cuts entirely through them. The suspending ropes and also cables supplying lights must be long enough to admit of bringing the border within five or six feet of the stage floor for lamp renewals and cleaning. The cleaning is very important as the dust which accumulates may absorb a large part of the light.

_The National Electrical Code Rules Governing Border and Proscenium Sidelight Construction._

Must be constructed of steel of a thickness not less than No. 20 U. S. sheet metal gauge; treated to prevent oxidation; be suitably stayed and supported; and so designed that flanges of reflectors will protect lamps.

Must be so wired that no set of lamps requiring more than 1,320 watts nor more than 26 receptacles shall be dependent upon one cut-out.

Must be wired in approved conduit or armored cable, each lamp receptacle to be enclosed within an approved outlet box, or the lamp receptacles may be mounted in an iron or steel box, metal to be of a thickness not less than No. 20 U. S. sheet metal gauge treated to prevent oxidation, so constructed as to enclose all wires. Wires to be soldered to lugs of receptacles.

Must be provided with suitable guards to prevent scenery or other combustible material coming in contact with lamps.

Cable for borders must be of approved type and suitably supported; conduit construction must be used from switchboard to point where cables must be flexible to permit of the raising and lowering of border.

For the wiring of the border proper, wire with approved slow-burning insulation must be used.

Borders must be suitably suspended, and if a wire rope is used same must be insulated by at least one strain insulator inserted at the border.

_Box Office._--The box office is often a very stuffy place in summer and very cold in winter. There should be an outlet for a fan motor, and also one for a heater. Very many box offices depend upon electric heating for comfort in winter. Plenty of light should be provided and the light should be at the ceiling, out of the way, and directly over the ticket window.

_Brackets._--Any brackets used in theaters should be at least seven feet above the floor. Brackets used for emergency or exit lights must be fitted with keyless sockets. See “Fixtures”.

_Branch Circuits._--The term, “branch circuit”, as here used refers to the wires leaving the last cut-outs and connecting directly to the lamps or other devices. Mains are often run from the switchboard to various parts of the building to feed cut-out centers, and the branch circuits are then run from these centers. This is often the cheapest method, but it is by no means the best. In a well designed theater all branch circuits lead out from the vicinity of the switchboard so that, in case of any trouble with fuses, they may be replaced without interfering with any part of the audience and in the shortest possible time. This method of wiring involves some long runs of branch circuit wires and Table V, which shows the drop in voltage, was prepared for the convenience of wiremen. If possible the circuits should be so arranged that the lamps fed are closely together so all may receive nearly the same voltage. The drop should not much exceed two per cent.

Table showing drop in voltage due to 6 amperes, with sizes of wire and distances given:

TABLE V.

DROP IN VOLTAGE DUE TO 6 AMPERES WITH SIZE OF WIRE AND DISTANCE GIVEN.

--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----
Distance| 50 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 300
in feet | | | | | | | | | |
--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----
Size of | | | | | | | | | |
Wire | 1.58| 2.37| 3.16| 3.95| 4.74| 5.53| 6.32| 7.11| 7.90| 9.48
No. 14 | | | | | | | | | |
--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----
Size of | | | | | | | | | |
Wire | 0.99| 1.48| 1.98| 2.47| 2.97| 3.45| 3.96| 4.45| 4.95| 5.94
No. 12 | | | | | | | | | |
--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----
Size of | | | | | | | | | |
Wire | 0.63| 0.94| 1.25| 1.56| 1.87| 2.19| 2.50| 2.81| 3.12| 3.75
No. 10 | | | | | | | | | |
--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----
Size of | | | | | | | | | |
Wire | 0.39| 0.59| 0.78| 0.97| 1.17| 1.36| 1.56| 1.75| 1.95| 2.34
No. 8 | | | | | | | | | |
--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----

_National Electrical Code Rules Governing Size of Wire for Branch Circuits and Fuses for Same._

No wire smaller than No. 14 B. & S. gauge must be used.

Each branch circuit must be protected by fuses, which must be so placed that no set of small motors, small heating devices, or incandescent lamps, whether grouped on one fixture or on several fixtures or pendants (nor more than 16 sockets or receptacles) requiring more than 660 watts, will be dependent upon one cut-out.

By special permission, in cases where wiring equal in size and insulation to No. 14 B. & S. gauge approved rubber-covered wire is carried direct into keyless sockets or receptacles, and where the location of sockets and receptacles is such as to render unlikely the attachment of flexible cords thereto, the circuits may be so arranged that not more than 1,320 watts (or thirty-two sockets or receptacles) will be dependent upon the final cut-out.

Except for signs and outline lighting, sockets and receptacles will be considered as requiring not less than 40 watts each.

All branches or taps, from any three-wire system, which are directly connected to lamp sockets or other translating devices, must be run as two-wire circuits if the fuses are omitted in the neutral, or if the difference of potential between the two outside wires is over 250 volts, and both wires of such branch or tap circuits must be protected by proper fuses.

The above shall also apply to motors, except that small motors may be grouped under the protection of a single set of fuses, provided the rated capacity of the fuses does not exceed 10 amperes.

When 1,320 watts are dependent upon one fusible cut-out, as is allowed in theater wiring, outline lighting and large chandeliers, the fuses may be in accordance with the following:

125 volts or less 20 amperes
125 to 250 volts 10 amperes

_Bus-Bars._--Bus-bars may be made of bare metal. They must, however, be protected against accidental contact. The metal should be ample so that it will not heat more than 50 degrees Fahrenheit above the surrounding air.

It is customary to calculate the metal needed, on the basis of 1,000 amperes per square-inch cross section. On this basis bars of the sizes given below would have the carrying capacities in amperes given in the body of the table.

TABLE VI.

CURRENT-CARRYING CAPACITY OF BUS-BARS.

-----------+----+----+----+----+----+----+----+----+-----+-----+-----
Thickness |2/32|3/32|4/32|5/32|6/32|7/32|8/32|9/32|10/32|12/32|16/32
-----+-----+----+----+----+----+----+----+----+----+-----+-----+-----
| 1/2 | 30| 45| 60| 75| 90| 105| 120| 135| 150| 165| 180
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
| 5/8 | 37| 57| 75| 94| 108| 132| 150| 168| 188| 206| 225
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
| 6/8 | 45| 68| 90| 112| 135| 158| 180| 202| 225| 248| 270
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
Width| 7/8 | 53| 79| 105| 130| 158| 184| 210| 236| 263| 289| 315
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
in | 1.0 | 60| 90| 120| 150| 180| 210| 240| 270| 300| 330| 360
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
In- |1-1/4| 75| 112| 150| 188| 225| 263| 300| 338| 375| 412| 450
ches +-----+----+----+----+----+----+----+----+----+-----+-----+-----
|1-1/2| 90| 135| 180| 225| 270| 315| 360| 405| 450| 495| 540
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
|1-3/4| 105| 157| 210| 263| 315| 367| 420| 473| 525| 577| 630
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
| 2.00| 120| 180| 240| 300| 360| 420| 480| 540| 600| 660| 720
+-----+----+----+----+----+----+----+----+----+-----+-----+-----
| 3.00| 180| 270| 360| 450| 540| 630| 720| 810| 900| 990| 1080
-----+-----+----+----+----+----+----+----+----+----+-----+-----+-----

_Cabinets._--Cabinets are required to enclose all fuses. It is advised that they be arranged so that it will not be necessary to open the fuse compartment to operate switches.

Care should be exercised in locating cut-out cabinets. They should be in a dry place, easily accessible to authorized persons, and not accessible to the general public or miscellaneous employes. If too accessible they are likely to be made receptacles for all sorts of rubbish. Wooden or composition cabinets must not be used in theaters. Use only approved cabinets.

In some cities special rules, governing the construction of cabinets for theaters, exist and these should be looked up.

_Cables._--For construction rules, see “Stage Cables” in the chapter on “Portable Stage Equipment”. Cables are required to connect border lights. The cable is usually run from an outlet on the grid floor above the center of the border. It must be long enough to allow the border to be lowered for the cleaning and renewal of lamps. The slack cable must be taken up when the border is raised and some provision must be made to support the cable without injury to the insulation. Wire ropes or cables are generally used to support the borders, but the lower end, which is handled by the stage crew, is of ordinary manilla rope. Wire cables must be insulated from the border by strain insulators.

_Canopies._--Very many theaters are provided with canopies which extend over the street. Sometimes these are fitted out with glass signs behind which incandescent lamps are installed. Often, also, a row of lights is arranged around the bottom of the canopy ceiling. The number of lights to be used depends upon the design of the canopy, but the effect is best if a large number of small candle-power lamps are used. These lamps should be of low intrinsic brilliancy. If possible, the lamps and sockets should be arranged to be out of the weather. In addition to the small outline lamps, other lights are often placed under canopy to provide bright illumination. Each circuit may carry 1,320 watts.

_National Electrical Code Rule._

Where insulating joints are required, fixture canopies of metal must be thoroughly and permanently insulated from metal walls or ceilings, or from plaster walls or ceilings on metal lathing, and from outlet boxes.

Canopy insulators must be securely fastened in place, so as to separate the canopies thoroughly and permanently from the surfaces and outlet boxes from which they are designed to be insulated.

_Carriage Call._--See “Program Board”.

_Carrying Capacity of Wires._--Table VII is designed to help the wiremen select the proper size of wire to use in supplying a certain number of lights. The first column at the left gives the B. & S. gauge number. The second column gives the number of amperes allowed on each wire according to the National Electrical Code. The third column gives the distance in feet which will cause a loss of 2 volts with the current given; thus a current of 70 amperes in a No. 4 B. & S. gauge wire will lose 2 volts over a distance of 56 feet. The proper size of wire to be used can easily be determined from the table. The loss will always be in proportion to the product of distance and current. The balance of the table is devoted to showing the number of watts and lamps of various sizes the wires will be allowed to supply.

_Ceiling Fans._--Must be hung from insulated hooks, or else there must be an insulator interposed between the motor and its support. Not more than 660 watts may be on one circuit.

_Chandeliers._--Large and elaborate chandeliers are sometimes used in the center of the auditorium ceiling for purposes of illumination. Such chandeliers should be suspended in a manner which will admit of readily raising or lowering them for lamping up or repairs. For rules governing wiring, see “Fixtures”.

TABLE VII.

TABLE SHOWING CARRYING CAPACITY OF WIRES; DISTANCE TO WHICH FULL LOAD MAY BE CARRIED AT 2 VOLTS DROP AND NUMBER OF LIGHTS EQUIVALENT TO FULL CURRENT GIVEN.

=======+=======+========+============+=============================
B. & S.|Rubber |Distance| Total | Total Number of Lamps of
Gage | Insu- |in Feet |Capacity in | Different Voltages and
|lation |Causing | Watts |Wattages that may be supplied
|Amperes|a Loss | +---------+---------+---------
| | of 2 | | 25-Watt | 40-Watt | 60-Watt
| | Volts +-----+------+----+----+----+----+----+----
| | | 110 | 220 | 110| 220| 110| 220| 110| 220
| | | V. | V. | V. | V. | V. | V. | V. | V.
-------+-------+--------+-----+------+----+----+----+----+----+----
14| 15 | 26 | 1650| 3300| 66| 132| 41| 82| 27| 54
12| 20 | 30 | 2200| 4400| 88| 176| 55| 110| 36| 73
10| 25 | 38 | 2750| 5500| 110| 220| 68| 137| 46| 91
8| 35 | 43 | 3850| 7700| 154| 308| 96| 192| 64| 128
6| 50 | 50 | 5500| 11000| 220| 440| 137| 275| 91| 183
5| 55 | 56 | 6050| 12100| 242| 484| 151| 302| 100| 201
4| 70 | 56 | 7700| 15400| 308| 616| 192| 385| 128| 256
3| 80 | 61 | 8800| 17600| 352| 704| 220| 440| 146| 292
2| 90 | 68 | 9900| 19800| 396| 792| 247| 494| 165| 330
1| 100 | 67 |11000| 22000| 440| 880| 275| 550| 183| 366
0| 125 | 78 |13750| 27500| 550|1100| 343| 686| 229| 458
00| 150 | 82 |16500| 33000| 660|1320| 412| 824| 275| 550
000| 175 | 89 |19250| 38500| 770|1540| 481| 962| 320| 640
0000| 225 | 87 |24750| 49500| 990|1980| 618|1236| 412| 824
200000| 200 | 92 |22000| 44000| 880|1760| 550|1100| 367| 734
300000| 275 | 101 |30250| 60500|1210|2420| 756|1512| 504|1008
400000| 325 | 114 |35750| 71500|1430|2860| 893|1786| 596|1192
500000| 400 | 117 |44000| 88000|1760|3520|1100|2200| 733|1455
600000| 450 | 123 |49500| 99000|1980|3960|1237|2474| 825|1650
700000| 500 | 130 |55000|110000|2200|4400|1375|2750| 916|1832
800000| 550 | 135 |60500|121000|2420|4840|1512|3024|1008|2016
900000| 600 | 139 |66000|132000|2640|5280|1650|3300|1100|2200
1000000| 650 | 143 |71500|143000|2860|5720|1787|3574|1191|2382
1100000| 690 | 147 |75900|151800|3036|6072|1897|3794|1264|2528
1200000| 730 | 151 |80300|160600|3212|6424|2007|4014|1338|2676
1300000| 770 | 155 |84700|169400|3388|6776|2117|4234|1412|2824
1400000| 810 | 161 |89100|178200|3564|7128|2227|4454|1485|2970
1500000| 850 | 164 |93500|187000|3740|7480|2337|4674|1558|3116
-------+-------+--------+-----+------+----+----+----+----+----+----

=======+=======+========+============+=============================
|Rubber |Distance| Total | Total Number of Lamps of
| Insu- |in Feet |Capacity in | Different Voltages and
B. & S.|lation |Causing | Watts |Wattages that may be supplied
Gage |Amperes|a Loss | +--------+--------+-----------
| | of 2 | |100-Watt|150-Watt|250-Watt
| | Volts +-----+------+---+----+---+----+---+-------
| | | 110 | 220 |110| 220|110| 220|110|220
| | | V. | V. |V. | V. |V. | V. |V. |V.
-------+-------+--------+-----+------+---+----+---+----+---+-------
14| 15 | 26 | 1650| 3300| 16| 33| 11| 22| 6| 13
12| 20 | 30 | 2200| 4400| 22| 44| 14| 29| 8| 17
10| 25 | 38 | 2750| 5500| 27| 55| 18| 36| 11| 22
8| 35 | 43 | 3850| 7700| 38| 77| 25| 61| 15| 30
6| 50 | 50 | 5500| 11000| 55| 110| 36| 73| 22| 44
5| 55 | 56 | 6050| 12100| 60| 121| 40| 80| 24| 48
4| 70 | 56 | 7700| 15400| 77| 154| 49| 99| 30| 61
3| 80 | 61 | 8800| 17600| 88| 176| 58| 117| 35| 70
2| 90 | 68 | 9900| 19800| 99| 198| 66| 132| 39| 78
1| 100 | 67 |11000| 22000|110| 220| 73| 146| 44| 88
0| 125 | 78 |13750| 27500|137| 274| 91| 182| 55|110
00| 150 | 82 |16500| 33000|165| 330|110| 220| 66|132
000| 175 | 89 |19250| 38500|192| 384|128| 256| 77|154
0000| 225 | 87 |24750| 49500|247| 404|165| 330| 99|198
200000| 200 | 92 |22000| 44000|220| 440|146| 292| 88|176
300000| 275 | 101 |30250| 60500|302| 604|201| 402|121|242
400000| 325 | 114 |35750| 71500|357| 714|238| 476|143|286
500000| 400 | 117 |44000| 88000|440| 880|293| 586|176|352
600000| 450 | 123 |49500| 99000|495| 990|330| 660|198|396
700000| 500 | 130 |55000|110000|550|1100|366| 732|220|440
800000| 550 | 135 |60500|121000|605|1210|403| 806|242|484
900000| 600 | 139 |66000|132000|660|1320|440| 880|264|528
1000000| 650 | 143 |71500|143000|715|1430|476| 952|286|572
1100000| 690 | 147 |75900|151800|759|1518|506|1012|303|606
1200000| 730 | 151 |80300|160600|803|1606|535|1070|321|642
1300000| 770 | 155 |84700|169400|847|1694|564|1128|338|676
1400000| 810 | 161 |89100|178200|891|1782|594|1188|356|712
1500000| 850 | 164 |93500|187000|935|1870|623|1246|374|748
-------+-------+--------+-----+------+---+----+---+----+---+-------

_National Electrical Code Rules for Fusing Chandelier Circuits._

When 1,320 watts are dependent upon one cut-out, as is allowed in theater wiring, outline lighting, and large chandeliers, the fuse may be in accordance with the following:

125 volts or less 20 amperes
125 to 250 volts 10 amperes

_Circuit Breakers._--Circuit breakers are not used much about theaters. They are used mostly in connection with motors and on switchboards of isolated plants. They are more sensitive and quicker to act than fuses and, in case of a blow-out, can be more easily replaced. Where circuit breakers are used it is good practice to set them for a higher amperage than the fuses so that, in case of a heavy short circuit, the breaker may act while the fuse will take care of an overload which comes on more gradually.

_National Electrical Code Rides for Circuit Breakers._

With motors an automatic circuit breaker, disconnecting all wires of the circuit, may serve as both switch and cut-out.

Where the circuit-breaking device on the motor-starting rheostat disconnects all wires of the circuit, the switch may be omitted.

Circuit breakers must not be set more than thirty per cent above the allowable carrying capacity of the wires, unless a fusible cut-out is also installed on the circuit.

When installed without other automatic overload protective devices, automatic overload circuit breakers must have the poles and trip coils so arranged as to afford complete protection against overloads and short circuits and, if also used in place of the switch, must be so arranged that no one pole can be opened manually without disconnecting all the wires.

_Concealed Work._--All concealed work must be in conduit or armored cable. Wherever possible, rigid conduit should be used. Armored cable should be used only where the whole cable may at any time be withdrawn, or where it is impracticable to use rigid conduit.

_Conduit Work._--This is now considered the standard method of construction. It is, however, somewhat over-rated and, especially in wet places, has led to much disappointment. It is generally recognized that wires, placed in conduit, will cause more trouble than those placed in any other standard manner. The trouble is, however, confined to the interior of the conduit and, if the conduit system be kept in good order, and fuses at their proper limit, there is no chance of fire from the wire confined within the conduit.

There are three points which, if carefully observed, will avoid most, if not all, of the conduit troubles:

Avoid as far as possible locating conduit in wet or damp places.

Run all conduits so that they will drain.

Give particular attention to joints in outlet or junction boxes; tape them heavily; and arrange them so they are not pressed against metal more than is necessary; use large boxes.

Wires used in conduits must have approved rubber insulation and double braid.

_National Electrical Code Rules for Wires and Interior Conduits._

_Wires for Conduit Work._

Must have an approved rubber insulated covering (Type Letter R. D.), and must within the conduit tubing be without splices or taps.

Must not be drawn in until all mechanical work on the building has been, as far as possible, completed.

Conductors in vertical conduit risers must be supported within the conduit system in accordance with the following:

No. 14 to 0 every 100 feet
No. 00 to 0000 every 80 feet
No. 0000 to 350,000 C. M. every 60 feet
350,000 C. M. to 500,000 C. M. every 50 feet
500,000 C. M. to 750,000 C. M. every 40 feet
750,000 C. M. every 35 feet

The following methods of supporting cables are recommended:

(1) A turn of 90 degrees in the conduit system will constitute a satisfactory support.

(2) Junction boxes may be inserted in the conduit system at the required intervals, in which insulating supports of approved type must be installed and secured in a satisfactory manner so as to withstand the weight of the conductors attached thereto, the boxes to be provided with proper covers.

(3) Cables may be supported in approved junction boxes on two or more insulating supports so placed that the conductors will be deflected at an angle of not less than 90 degrees, and carried a distance of not less than twice the diameter of the cable from its vertical position. Cables so suspended may be additionally secured to these insulators by tie wires. Other methods may be used if specially approved.

Must, for alternating-current systems, have two or more wires of a circuit drawn in the same conduit. It is suggested that this be done for direct-current systems, also, so that they may be changed to alternating systems at any time, induction troubles preventing such a change if the wires are in separate conduits.

Except in the case of stage pocket and border circuits the same conduit must not contain more than four two-wire, or three three-wire circuits of the same system, except by special permission, and must never contain circuits of different systems.

_Interior Conduits._

No conduit smaller than one-half inch electrical-trade size shall be used.

Must be continuous from outlet to outlet or to junction boxes or cabinets, and the conduit must properly enter, and be secured to all fittings and the entire system must be mechanically secured in position. In case of service connections and main runs, this involves running each conduit continuously into a main cut-out cabinet or gutter surrounding the panel board, as the case may be. Departure from this rule may be authorized in case of underground services by special permission.

Must be first installed as a complete conduit system, without the conductors.

Must be equipped at every outlet with an approved outlet box or plate. At exposed ends of conduit (but not at fixture outlets), where wires pass from the conduit system without splice, joint, or tap, an approved fitting, having separately bushed holes for each conductor, must be used. Departure from this rule may be authorized by special permission. Outlet plates must not be used where it is practicable to install outlet boxes.

For concealed work in walls and ceilings composed of plaster on wooden joist or stud construction, outlet boxes or plates, and also cut-out cabinets must be so installed that the front edge will not be more than one-fourth inch back of the finished surface of the plaster; and if this surface is broken or incomplete it shall be repaired so that it will not show any gaps or open spaces around the edges of the outlet box or plate or of the cut-out cabinet. On wooden walls or ceilings, outlet boxes or plates and cut-out cabinets must be so installed that the front edge will either be flush with the finished surface or project therefrom. This will not apply to concealed work in walls or ceilings composed of concrete, tile or other non-combustible material.

In buildings already constructed where the conditions are such that neither outlet box or plate can be installed, these appliances may be omitted, providing the conduit ends are bushed and secured.

It is suggested that outlet boxes and fittings, having conductive coatings, be used in order to secure better electrical contact at all points through the conduit system.

Metal conduits, where they enter junction boxes and at all other outlets, etc., must be provided with approved bushings or fastening plates fitted so as to protect wire from abrasion, except when such protection is obtained by the use of approved nipples, properly fitted in boxes or devices.

Must have the metal of the conduit permanently and effectually grounded to water piping, gas piping, or other suitable grounds, provided that when connections are made to gas piping, they must be on the street side of the meter. If the conduit system consists of several separate sections, the sections must be bonded to each other, and the system grounded; or each section may be separately grounded, as required above. Where short sections of conduit (or pipe of equivalent strength) are used for the protection of exposed wiring on side walls, and such conduit or pipe and wiring is installed as required by the Code Rules, the conduit or pipe need not be grounded.

Conduits and gas pipes must be securely fastened in outlet boxes, junction boxes, and cabinets, so as to secure good electrical connections.

If conduits, couplings, outlet boxes, junction boxes, cabinets or fittings, having protective coating of non-conducting material such as enamel, are used, such coating must be thoroughly removed from threads of both couplings and conduit, and such surfaces of boxes, cabinets, and fittings, where the conduit or group clamp is secured, in order to obtain the requisite good connection. Grounded pipes must be cleaned of rust, scale, etc., at place of attachment of ground clamp.

Connections to grounded pipes and to conduits must be exposed to view or readily accessible, and must be made by means of approved ground clamps to which the ground wires must be soldered.

Ground wires must be of copper, at least No. 10 B. & S. gauge (where largest wire contained in conduit is not greater than No. 0 B. & S. gauge), and need not be greater than No. 4 B. & S. gauge (where largest wire contained in conduit is greater than No. 0 B. & S. gauge). They shall be protected from mechanical injury. The ground on the conduit system is not to be considered as a ground for a secondary system.

Junction boxes must always be installed in such a manner as to be accessible.

All elbows or hands must be so made that the conduit will not be injured. The radius of the curve of the inner edge of any elbow must not be less than three and one-half inches, and must have not more than the equivalent of four quarter bends from outlet to outlet, the bends at the outlets not being counted.

_Contacts._--Must be mounted on non-combustible non-absorption insulated bases. Other materials than slate, marble, or porcelain must be submitted for special examination before being used.

_Cord._--The use of flexible cord should be reduced to a minimum. Wherever drop lights are necessary they should be wired with reinforced cord or stage cable.

_Current Taps._--Must be of approved construction and may be used if properly installed.

_National Electrical Code Rules for Current Taps._

Where, in addition to sockets or receptacles already installed, connections are desired to lighting circuits for portable lamps, for motors, or other special appliances requiring only small amounts of current, multiple-current taps may be used, provided the entire circuit does not require more than 660 watts, and provided their use will not, under any conditions, involve a departure from the requirements of Rule 23-d of the National Electrical Code. Current taps must not be used in key or pull sockets if the device, controlled through such sockets, requires more than 250 watts.

_Cut-Outs._--All cut-outs should be on the stage switchboard. This requires considerable extra wire, but it will be profitable in the end. Fuses should be inspected occasionally to see that contacts are bright and screws kept tight. There is everywhere a very strong tendency to over-fuse, and the principal reason for it is the failure to keep screws tightly fastened.

There is no fuse better than the plug fuse but it is not permitted with voltages higher than 125 or with more than 30 amperes. Refillable fuses must not be used. Cartridge fuses, especially, require to be kept clean. The spring contacts on these often grow weak and cause heating which helps to blow the fuse. The neutral fuse in three-wire installations should be larger than the outside fuses. Link fuses should be avoided on account of the delay that may be caused through difficulty of installing.

It is advisable not to place switches in the same cabinet with fuses.

_National Electrical Code Rules for Automatic Cut-outs (Fuses and Circuit-Breakers)._

_Constant-Potential Systems._

Must be placed on all service wires, either overhead or underground, in the nearest accessible place to the point where they enter the building, inside the walls, and arranged to cut off the entire current from the building. Departure from this rule may be authorized only under special permission in writing. Where the service switch is inside the building, the cut-out required by this section must be placed so as to protect it.

For three-wire (not three-phase) systems the fuse in the neutral wire may be omitted, provided the neutral wire is of equal carrying capacity to the larger of the outside wires and is grounded.

Must be placed at every point where a change is made in the size of wire (unless the cut-out in the larger wire will protect the smaller). For three-wire direct current or single-phase systems the fuse in the neutral wire, except that called for under Section d, may be omitted, provided the neutral wire is grounded.

Must be in plain sight, or enclosed in an approved cabinet, and readily accessible. They must not be placed in the canopies or shells of fixtures. Link fuses may be used only when mounted on approved bases and must be enclosed in dust-tight, fireproofed cabinets, except on switchboards.

Must be so placed that no set of small motors, small heating devices, or incandescent lamps, whether grouped on one fixture or on several fixtures or pendants (nor more than 16 sockets or receptacles) requiring more than 660 watts, will be dependent upon one cut-out.

By special permission, in cases where wiring equal in size and insulation to No. 14 B. & S. gauge approved rubber-covered wire is carried direct into keyless sockets or receptacles, and where the location of sockets and receptacles is such as to render unlikely the attachment of flexible cords thereto, the circuits may be so arranged that not more than 1,320 watts (or thirty-two sockets or receptacles) will be dependent upon the final cut-out. Except for signs and outline lighting, sockets and receptacles will be considered as requiring not less than 40 watts each.

All branches or taps from any three-wire system which are directly connected to lamp sockets or other translating devices, must be run as two-wire circuits if the fuses are omitted in the neutral or if the difference of potential between the two outside wires is over 250 volts, and both wires of such branch or tap circuits must be protected by proper fuses.

The above shall also apply to motors, except that small motors may be grouped under the protection of a single set of fuses, provided the rated capacity of the fuses does not exceed 10 amperes. When 1,320 watts are dependent upon one fusible cut-out, as is allowed in theater wiring, outline lighting, and large chandeliers, the fuses may be in accordance with the following:

125 volts or less 20 amperes
125 to 250 volts 10 amperes

The rated capacity of fuses must not exceed the allowable carrying capacity of the wire. Circuit breakers must not be set more than 30 per cent above allowable carrying capacity of the wire, unless a fusible cut-out is also installed on the circuit. Fixture wire or flexible cord of No. 18 B. & S. gauge, will be considered as properly protected by 10-ampere fuses.

Each wire of motor circuits, except on main switchboard or when otherwise subject to competent supervision, must be protected by an approved fuse whether automatic overload circuit breakers are installed or not. Single-phase motors may have one side protected by an approved automatic overload circuit breaker only if the other side is protected by an approved fuse.

For circuits having a maximum capacity greater than that for which enclosed fuses are approved, circuit breakers alone will be approved. The ordinary porcelain link fuse cut-out will not be approved. Link fuses may be used only when mounted on slate or marble bases conforming to the rules, and must be enclosed in dust-tight, fire-proofed cabinets, except on switchboards located well away from combustible material, as in the ordinary engine and dynamo room, and where these conditions will be maintained.

_Damp Places._--It is best to avoid wiring in damp places if possible. If wires must be run in such places, they should be lead covered. If armored cable is used, the wires in cable must be incased in lead. Weatherproof sockets must be used and the use of cords should be avoided. Where cords must be used they should be of the brewery or packing-house type. If outside of the theater, proper open work may be used. Conduit work is permissible but not advisable, except where wires are subject to mechanical injury.

_Decorative Lighting Systems._--The commercial decorative lighting systems are not suitable for use inside of theaters and should be used only outside.

_National Electrical Code Rule for Decorative Lighting Systems._

Special permission may be given in writing for the temporary installation of approved systems of decorative lighting, provided the difference of potential between the wires of any circuit shall not be over 150 volts and also provided that no group of lamps requiring more than 1,320 watts shall be dependent on one cut-out.

_Dimmers._--“Dimmer” is the name given to the resistances which are used to dim the electric lights on the stage. They are usually mounted at the top or bottom of the switchboard with the operating handles in easy reach of the operator. A dimmer should be provided for each color in every border light and also for the foot lights. In some cases the proscenium side lights are also arranged for several colors. The dimmers should be mounted so that each one is directly above the switch which controls the circuit to which it belongs. They should be protected by wire guards against rubbish, which is likely to accumulate among them if they are not enclosed. Good ventilation must be provided. A certain dimmer can be used only while the amperage remains within the proper limitations. If carbon lamps, for instance, are changed for tungsten, the amperage will be much reduced and the dimmer may not work properly.

Modern dimmers are all of the interlocking type so that the whole bank may be worked together or any one singly. Figure 157 is an illustration of a small bank of dimmers.

_Door Switches._--Door switches are used mostly in connection with dressing rooms. When the light in the room is burning, opening and closing the door will turn it out.

_Dressing Rooms._--Many dressing rooms are wired with lights on pendant cords, but this method is not to be recommended. It is better to arrange the lights in sockets fitted into the outlet boxes. It will be well if each dressing room is provided with a circuit for flatirons. If this is considered too expensive, the fuses on circuits leading into dressing rooms must be kept small enough to blow in case a flatiron is connected. Many actors are in the habit of carrying flatirons and will use them on incandescent-light circuits if no other circuit is provided. If metal guards are fastened on securely, much of the trouble from flatirons will be avoided, but they must be fastened so that an ordinary screwdriver will not loosen the screws.

Dressing room illumination, if properly carried out, will save the proprietor much annoyance. Actors have ways of obtaining the light they want by fair means or foul, and it is much better to arrange the lighting so that it will be satisfactory to those using it, than to have it continually tampered with.