THEATER WIRING.
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.
[Illustration: FIGURE 151.]
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.
[Illustration: FIGURE 152.]
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.
[Illustration: FIGURE 153.]
[Illustration: FIGURE 154.]
_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.
[Illustration: FIGURE 155.]
[Illustration: 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.
[Illustration: FIGURE 157.]
_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.
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 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._--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.
[Illustration: 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.
[Illustration: 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 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._--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._--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._--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 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 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.
[Illustration: 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._--See Heaters.
_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 is not permissible in theaters.
_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._--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._--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.
[Illustration: FIGURE 161.]
[Illustration: FIGURE 162.]