Circuit Breakers.
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.
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 Armored cable should be used only where the whole cable may at any time be withdrawn, or where it is impracticable to use rigid conduit.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.
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.
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.
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.
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.
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.
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.
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.
FIGURE 157.
Dimmers.
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.—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.
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.
A bright illumination is essential for making up and both sides of the face should be fully illuminated. To accomplish this it is necessary to provide at least two lights for each mirror. Every lamp should be provided with a substantial guard which may be securely fastened to the outlet box. This is especially necessary if small candle power lamps are furnished. For, if the light furnished is insufficient, there will be strong efforts made to replace the small lamps by larger ones. Guards are also necessary as a protection against fire. Actors are in the habit of drying small articles of clothing on the lamps, and fires have been known to start from this cause. The guards on the lamps throw shadows on the faces of the actors, and for this reason are not liked. In order to avoid the shadows, frosted lamps may be used, or two lamps on each side of the mirror. One lamp will then illuminate the shadows caused by the other. Where there are long dressing tables, as in rooms occupied by the chorus, mirrors may be placed between each two lamps on each side of the table and the lamps staggered vertically. In this way each party will receive the benefit of at least four lamps and the shadows will be less noticeable.
The color value of the lamps used in dressing rooms should match that of the lamps used on the stage. Some stages, for instance, are illuminated by flaming arcs which may give an altogether different effect to a “make up” than the tungsten lamps, for instance.
Where there are a large number of sockets without lamps in them, it is advisable to close the socket by a fuse plug from which the fuse has been removed, or in some similar manner in order to avoid the chance of short circuits from hat pins or similar objects used in dressing rooms.
Drop Lights.
Drop Lights.—Drop lights should be avoided as much as possible. Where they must be installed reinforced cord, armored cable, or flexible steel armored cord should be used.
Emergency Lighting.
Emergency Lighting.—Every theater must have an emergency lighting system as outlined in the rules below. The object of this is to provide a double system of illumination so as to reduce the likelihood of the theater being left in total darkness. This is a frequent occurrence where the theater is supplied by an isolated plant, and may also occur where the supply is obtained from a large outside lighting system although the latter is usually more reliable.
Every unnecessary light that is added to an emergency system increases the likelihood of trouble. A sufficient number of lights added to it to illuminate the space used by the audience in getting out is, therefore, necessary but more than this is a detriment rather than a help. The practice of connecting all of the hall and lobby lights to the emergency system is to be condemned, since it defeats the purpose of the rule which provides a double illumination system for every part of the theater used by the audience. The two systems should be carried into the auditorium, all stairways, exits, and lobby clear to the street. They should, furthermore, be kept entirely separate, in separate conduits and using separate meters.
The rule does not specify the number of exit and emergency lights required. Good practice requires a light for every 400 square feet or so. If each of these outlets be fitted with a 50 watt lamp the illumination will interfere with many of the acts and so, smaller lamps are generally used. One emergency light for each 60 seats will fill the bill nicely.
FIGURE 158.
Over each exit, an exit light must be provided, but as these exit lights are usually incased in ruby glass such as shown in Figure 158 they cannot be counted as giving any illumination. In many theaters gas is used for emergency and exit lighting and in many respects this seems to be a good practice. In some quarters, however, it is believed that a fire in the scenery of a theater might create such an air pressure in the building as to overcome the low gas pressure and thus put out the gas at the very time when it is most needed. The very best suggestion that can be made is that of a storage battery to supply the emergency system. Where alternating current is used this, however, introduces some complications and becomes quite expensive. Avoid the use of key sockets, fan motors, or any unnecessary device on emergency or exit light circuits.
National Electrical Code Rules for Services.
Where supply may be obtained from two separate street mains, two separate and distinct services must be installed, one service to be of sufficient capacity to supply current for the entire equipment of theater, while the other service must be at least of sufficient capacity to supply current for all emergency lights. Where supply cannot be obtained from two separate sources, the feed for emergency lights must be taken from a point on the street side of main service fuses. By “emergency lights” are meant exit lights and all lights in lobbies, stairways, corridors, and other portions of theater to which the public have access, which are normally kept lighted during the performance. Where the source of supply is an isolated plant within the same building, an auxiliary service of at least sufficient capacity to supply all emergency lights must be installed from some outside source, or a suitable storage battery within the premises may be considered the equivalent of such service.
FIGURE 159.
Exit lights must not have more than one set of fuses between same and service fuses. Exit lights and all lights in halls, corridors, or any other part of the building used by audience, except the general auditorium lighting, must be fed independently of the stage lighting, and must be controlled only from the lobby or other convenient place in front of the house. All fuses must be enclosed in approved cabinets.
Figure 159 shows a diagram of an emergency lighting system together with that of the house lighting system. The main house switch is sometimes arranged with two sets of fuses, so that it need only be thrown over when a fuse blows. See Figure 159 at the right.
Exit Lights.
Exit Lights.—Exit lights are usually required over all doors leading from any part of the auditorium to the lobby or outside of the theater. They are usually incased in ruby glass on which the word EXIT has been etched in large letters. See also Emergency Lighting.
Fan Motors.
Fan Motors.—In large theaters, sometimes as many as ten or twelve fan motors are arranged along the walls of the auditorium, to blow air toward the audience. In small theaters there is a strong temptation to connect these to the emergency circuit, but this should never be done. The motors are too noisy to be allowed to run during an act and must be wired so that they can all be thrown on or off together from the stage switchboard. Not more than 660 watts should be connected to any one circuit and the connection should be by means of attachment plugs and reinforced cord, a bracket for the motor being placed as near as possible to the outlet, so as to reduce the amount of cord required to a minimum.
Fire Alarm.
Fire Alarm.—In some of the cities a special signal system between stage and box office is required and it is necessary to consult authorities about this. Ordinarily a bell circuit, such as shown under “Bells,” will answer.
Fish Work.
Fish Work.—The fishing of wires incased in loom, as is permitted in other places, is not permissible in theaters. If wires are to be “fished” they must be incased in metal armor.
Fixtures.
Fixtures.—Fixtures require careful inspection before installing. It is seldom that the piping is properly reamed out as required by the rule. Chain fixtures especially, must be closely watched. There is little if any trouble to be expected from the wires laced among the chain links, but there is much trouble to be looked for from the wires at the points where they leave the chain support and where they enter the socket. The openings for the wires at these points are seldom large enough to admit of the proper wire being used, and they are not well reamed either. The result of these conditions is that the wire is very quickly abraded and short circuits are common.
Fixtures may be tested for short circuit by connecting a magneto at the feed end of the wires and turning it briskly. If a ring is obtained it is an indication that something in wrong. The test for open circuit may be made with the same connection. Insert a screw driver or a plug into each socket; if it is not possible to obtain a ring there must be an open circuit. The test for “ground” may be made by connecting both feed wires to one pole of the magneto, and the other pole to the metal of the fixture taking care that there is no lacquer on that part of the fixture. If a ring is obtained it is an indication that some bare spot on the wire is in contact with the fixture. Fixtures used for emergency lighting must carry no key sockets and must not feed fan motors.
National Electrical Code Rules for Fixture Wire and Fixtures.
Wires for Fixture Work.
Must not be smaller than No. 18 B. & S. gauge, and must have an approved rubber insulating covering. In wiring certain designs of show-case fixtures, ceiling bull-eyes, and similar appliances in which the wiring is exposed to temperature in excess of 120 degrees Fahrenheit (49 degrees centigrade), from the heat of the lamps, approved slow-burning wire must be used. All such forms of fixtures must be submitted for examination, test and approval before being introduced for use.
Supply conductors, and especially the splices to fixture wires, must be kept clear of the grounded part of gas pipes, and, where shells or outlet boxes are used, they must be made sufficiently large to allow the fulfillment of this requirement.
Must, when fixtures are wired outside, be so secured as not to be cut or abraded by the pressure of the fastenings or motion of the fixture.
Wires of different systems must never be contained in or attached to the same fixture, and under no circumstances must there be a difference of potential of more than 300 volts between wires contained in or attached to the same fixtures.
On chains of similar parts where conductors are not completely enclosed in metal, wires must be stranded and must have rubber insulation not less than one thirty-second of an inch in thickness; or approved pendant or portable cord may be used.
Fixtures.
When supported at outlets in metal conduit, armored cable, or metal-molding systems, or from gas piping or any grounded metal work, or when installed on metal walls or ceilings, or on plaster walls or ceilings containing metal lath, or on walls or ceilings in fireproof buildings, fixtures must be insulated from such supports by approved insulating joints placed as close as possible to the ceilings or walls. The insulating joint may be omitted in conduit, armored cable, or metal-molding systems with straight electric fixtures in which the insulation of conductors is the equivalent of insulation in other parts of the system, and provided that approved sockets, receptacles, or wireless clusters are used of a type having porcelain or equivalent insulation between live metal parts and outer metal shells, if any.
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.
Fixtures having so-called flat canopies, tops, or backs, will not be approved for installation, except where outlet boxes are used.
In non-metallic fixtures wireways must be metal-lined unless approved armored conductors with suitable fittings are used.
Flashers.
Flashers.—Flashers are used to economize electrical energy in sign illumination. An electric sign is often just as effective if only one side or one letter is in use at a time and in such a case there is considerable saving by the use of a flasher.
FIGURE 160.
Flashers are made up in a variety of forms, one of them being shown in Figure 160. The manner of wiring to the sign will be readily understood by reference to the figure. The neutral wire is carried direct to the sign and fuses for that wire are often installed up in the sign, while those for the other side of the circuits must be close to the flasher to comply with the rule which requires fuse protection where a small wire is tapped off from a larger one, unless the fuse in the larger wire is below the carrying capacity of the smaller.
National Electrical Code Rule for Flashers.
Time switches, sign flashers, and similar appliances must be of approved design and enclosed in approved cabinets.
Flat Irons.
Flat Irons.—See Heaters.
Flexible Cord.
Flexible Cord.—The ordinary flexible cord should not be used in any part of a theater. It is recommended that only those cords described below be used, each of course in its proper place. Approved reinforced cord for pendants. Approved asbestos-covered cord for portable heaters. Approved Stage and Border Cables on Stage.
See “Stage Cables.”
Flexible Tubing.
Flexible Tubing.—Flexible tubing is not permissible in theaters.
Floor Pockets.
Floor Pockets.—These are always a source of trouble and their use should be avoided as much as possible. If it is necessary to use any they must be of a type approved by the inspection department having jurisdiction.
Fly Floor.
Fly Floor.—This is the name given to that part of the gallery above the stage upon which those employes, whose duty it is to raise and lower curtains and scenery, work. No great illumination is required, but the lights should be arranged so as to be convenient to the men for reading during long waits. If this is not done there will always be considerable objectionable cord wiring found in this place. Fly-floor and rigging-loft lights should be provided with three way switches so that lights may be turned on or off either at the stage switchboard or on the fly floor.
Footlights.
Footlights.—These form the most important and effective part of the permanently located stage lights. To locate them properly requires careful consideration. If they are brought too high they will obstruct the view of the audience; if located too low they will not illuminate the lower part of the stage.
Opinion is somewhat divided as to whether they ought to be arranged in circular form or be laid out straight across the stage. In large theaters there is a circular space between the front seats and the front of the stage. A circular stage will utilize this space and this form of stage with footlights arranged in a similar manner will also allow the actors to approach more closely to the audience and will procure for them some illumination from the side. The difficulty of making up a circular strip of footlights is somewhat greater than that of making them up in a straight line.
The footlights are generally made to extend nearly the full opening of the stage and the lights should be crowded into them as closely as possible. The lighting should be divided into three groups suitable for three colors. It is customary to have about half of the lights white and the remaining half divided into two equal parts for different colors. A small part of the white lights should be arranged upon a separate circuit so that they may be used for rehearsals or other purposes, when not very much light is needed.
No very definite recommendations concerning the type of lamp to be used can be given. In some theaters the stage is very solid and tungsten lamps are used to advantage; in others the jarring prevents their use. The white lights should be arranged so that their light need not pass through the colored lamps. In vaudeville houses some protection in the form of chains or guards is often provided to prevent objects from being rolled or thrown against the lights. Figures 161 and 162 show types of footlights and the manner of installing the sockets.
The National Electrical Code Rules for Wiring Footlights.
Must be wired in approved conduit or armored cable, each lamp receptacle being 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 and so constructed as to enclose all the wires. Wires to be soldered to lugs of receptacles. 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.
Fuses.
Fuses.—See “Cut-outs.”
Gallery Lighting.
Gallery Lighting.—The proper lighting of galleries is a difficult matter where there is another gallery above. In such a case the ceiling is always very low. An even distribution of light requires the use of many small incandescent lamps evenly distributed. This will make the wiring expensive. The light should be taken pretty well from the rear so as to avoid placing lights in the range of visions of the audience. Emergency lights should be provided here as well as in the main auditorium.
Gallery Pockets.
Gallery Pockets.—Pockets for arc lamps are often provided, as it often happens that a moving-picture machine must be placed in the gallery. The stage pockets should be wired with number 6 B. & S. gauge wire, this being the smallest wire allowed to feed a moving-picture arc. The stage pocket should be controlled by a switch on the switchboard. It often happens that the operator at the lamp has a wrong cue and his light can then be controlled by the stage manager at the stage switchboard.
Gas Lighting.
Gas Lighting.—Electric gas lighting is very little used at the present time, but in many theaters the emergency lighting is by gas and, in order to save the time necessary to light these by hand before every performance, an automatic gas lighting system has been installed in some theaters. A diagram of such a system is shown in Figure 163. A battery of considerable capacity is necessary and also a spark coil S. At each gas jet a magnet M is installed which, when energized, is capable of turning the gas on and at the same time producing a spark. This magnet is also capable of turning the gas off. Two buttons are provided, one to turn the gas on and the other to turn it off.