2.8 NSTM 330 Lighting S9086-K9-STM-000_1_A.pdf

S9086-K9-STM-000/CH-330

FIRST REVISION

NAVAL SHIPS' TECHNICAL MANUAL

CHAPTER330

LIGHTING

THIS CHAPTER SUPERSEDES CHAPTER 330 DATED 1 JUNE 1977

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330-1.1 330-1.1.1 330-1.1.2 330-1.1.2.1 330-1.1.2.2 330-1.1.2.3 330-1.1.2.4 330-1.1.2.5 330-1.1.2.6 330-1.1.2.7 330-1.1.2.8 330-1.1.2.9 330-1.2 330-1.2.1 330-1.2.2 330-1.2.3 330-1.2.4 330-1.2.5 330-1.2.6 330-1.3 330-1.3.1 330-1.3.3 330-1.3.4 330-1.3.5 330-1.3.7 330-1.3.7.1 330-1.3.7.2 330-1.4 330-1.4.1 330-1.4.2 330-1.4.2.1 330-1.4.2.2 330-1.4.2.3 330-1.4.3 330-1.4.5

S9086-K9-STM-000/CH-330

TABLE OF CONTENTS

CHAPTER330

LIGHTING

SECTION 1. DESCRIPTION

GENERAL

PURPOSE

DEFINITIONS

General Illumination Detail Illumination Special Illumination Red Illumination Low Level White (LLW) Illumination Broad Band Blue (BBB) Illumination Darkened Ship Emergency Illumination Yellow Illumination

REFERENCE PUBLICATIONS

THEORY AND DESIGN

NAVIGATIONAL LIGHTING

VISUAL LANDING LIGHTING

USE OF SYMBOL NUMBERS

LIGHTING FIXTURES

LIGHTING FIXTURE AVAILABILITY

LIGHT AND VISION

GENERAL

HOW THE EYE SEES

VISUAL PROCESS

TWO KINDS OF VISION

ADAPTATION

Mechanical Response Chemical Response

PRINCIPAL FACTORS AFFECTING VISION

GENERAL

PHYSICAL FACTORS

Size Brightness Contrast

VISIBILITY

ILLUMINATION LEVELS

Page

1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-1 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-3 1-3 1-3 1-3 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4

S9086-K9- STM -000/CH -330

330-1.5 330-1.5.1 330-1.5.5 330-1.5.5.3 330-1.5.5.5 330-1.5.5.7 330-1.5.6 330-1.5.6.1 330-1.5.6.2 330-1.5.6.4 330-1.5.6.8 330-1.5.6.9 330-1.5.6.15 330-1.5.6.18 330-1.5.6.24 330-1.5.6.28 330-1.5.6.30 330-1.5.6.34 330-1.5.6.35 330-1.5.6.37 330-1.5.6.38 330-1.5.7 330-1.5.7.1 330-1.5.7.2 330-1.5.7.3 330-1.6 330-1.6.1 330-1.6.1.1 330-1.6.1.3 330-1.6.1.5 330-1.6.2 330-1.6.2.1 330-1.6.2.2 330-1.6.2.3 330-1.7 330-1.7.1 330-1.7.2 330-1.8 330-1.8.1 330-1.8.3 330-1.8.4 330-1.9 330-1.9.1 330-1.9.2 330-1.9.2.1 330-1.9.2.3

II

LIGHT SOURCES

GENERAL

INCANDESCENT LAMPS

Effect of Voltage Lamp Mortality Lumen Depreciation

FLUORESCENT LAMPS

Definition Auxiliary Control Equipment Starters Ballasts High Efficiency Ballasts Direct Current Operation Radio Interference Dimming Stroboscopic Effect Effect of Temperature Effect of Frequency Effect of Voltage Lamp Mortality Depreciation

LOW PRESSURE SODIUM LAMPS

Starting Time Restrike Time Color Rendition

POWER SUPPLY

SURFACE SHIPS

Ship Service Lighting System Isolation of Lighting in Machinery Spaces Ship Emergency or Alternate Lighting System

SUBMARINES

General ACSystem DC System

GENERAL ILLUMINATION

PURPOSE

CONTROL

DETAIL ILLUMINATION

PURPOSE

CONTROL

BERTH LIGHT LOCATION

SPECIAL ILLUMINATION

PURPOSE

TYPES

Weather Deck Lighting Fixtures Boom Lights

1-4 1-4 1-5 1-5 1-5 1-5 1-6 1-6 1-6 1-7 1-7 1-7 1-8 1-9

1-10 1-10 1-12 1-13 1-13 1-13 1-13 1-13 1-13 1-13 1-14 1-15 1-15 1-15 1-15 1-15 1-15 1-17 1-17 1-17 1-17 1-17 1-17 1-18 1-18 1-18 1-18 1-18 1-18 1-18 1-21

330-1.9.2.4 330-1.9.2.5 330-1.9.2.6 330-1.9.2.7 330-1.9.2.8 330-1.9.2.9 330-1.9.2.11 330-1.9.2.12 330-1.9.2.13 330-1.9.2.14 330-1.9.2.15 330-1.9.2.16 330-1.9.2.17 330-1.9.2.18 330-1.9.2.19 330-1.9.2.20 330-1.9.2.23 330-1.9.2.24 330-1.9.2.25 330-1.9.2.26 330-1.9.3 330-1.9.3.1 330-1.9.3.2 330-1.9.3.6 330-1.9.3.7 330-1.10 330-1.10.1 330-1.10.2 330-1.10.4 330-1.10.6 330-1.10.6.1 330-1.10.6.2 330-1.10.6.6 330-1.10.6.8 330-1.10.7 330-1.10.7.1 330-1.10.7.2 330-1.10.7.3 330-1.10.7.4 330-1.10.7.7 330-1.11 330-1.11.1 330-1.11.2 330-1.11.3 330-1.11.4 330-1.11.5

S9086-K9-STM-000/CH-330

Anchor Detail Lights Gangway and Accommodation Ladder Lights Weapon Mounts ASROC Security Lights Aircraft Elevator Safety Lights Weapons/Cargo Elevator Lighting Flight Deck Firefighting Hose Reel Stations Flight Deck Catwalk Emergency Lighting Flight Operations in Progress Warning Lights Well Area Lighting Submarine Log Desk and Gangway Lights Floodlights (Weather Deck) Waterline Security Lights Dress Ship Lights Ship Numeral Lights Surgical Lights Conventional Landing Craft Docking and Control Lights LCAC Optical Alignment System Boat Handling Station Lighting Control Portable Extension Lights

BATTERY POWERED LIGHTS

Damage Control Floodlanterns Relay Lanterns Portable Lanterns Flashlight

RED ILLUMINATION

PURPOSE

BACKGROUND INFORMATION

LIGHTING FIXTURES USED

WHERE PROVIDED

Living Spaces Access Routes Special Compartments and Stations Replenishment-at-Sea Stations

RED LIGHTING CONTROL

Compartment Lighting Replenishment-at-Sea Stations Weather Deck Red/Yellow Floodlighting Hangar Space Weapons/Cargo Elevator Lights Contro

BROAD BAND BLUE ILLUMINATION

PURPOSE

BACKGROUND INFORMATION

EFFECT ON CRT

OTHER EFFECTS

LIGHTING FIXTURES

1-21 1-21 1-22 1-22 1-22 1-22 1-22 1-22 1-22 1-23 1-23 1-23 1-23 1-23 1-23 1-24 1-24 1-24 1-24 1-25 1-26 1-26 1-26 1-27 1-28 1-28 1-28 1-28 1-28 1-29 1-29 1-29 1-29 1-29 1-30 1-30 1-30 1-30 1-30 1-30 1-32 1-32 1-32 1-33 1-34 1-34 iii

89086-K9- STM -000/CH -330

330-1.11.6 330-1.11.7 330-1.11.8 330-1.12 330-1.12.1 330-1.12.2 330-1.13 330-1.13.1 330-1.13.2 330-1.13.2.1 330-1.13.2.2 330-1.13.3 330-1.14 330-1.14.1 330-1.14.2 330-1.15 330-1.15.1 330-1.15.2

330-2.1 330-2.1.2 330-2.1.3 330-2.1.4 330-2.1.5 330-2.1.6 330-2.1.8 330-2.1.9 330-2.2 330-2.2.2 330-2.2.3 330-2.2.4 330-2.2.5 330-2.2.6 330-2.2.7 330-2.2.9 330-2.2.10 330-2.2.11 330-2.2.12 330-2.2.13 330-2.2.14 330-2.3 330-2.4 iv

CONTROL

MAINTENANCE (WHITE) LIGHTING

SUPPLEMENTARY ILLUMINATION

LOW-LEVEL WHITE (LLW) ILLUMINATION

LOW-LEVEL WHITE (LLW) ILLUMINATION - SURFACE SHIPS .. .

LOW-LEVEL WHITE (LLW) ILLUMINATION- SUBMARINES

DARKENED SHIP ILLUMINATION

PURPOSE

METHODS

Lightltaps Door Switches

CONTROL

EMERGENCY ILLUMINATION

PURPOSE

SOURCES

YELLOW ILLUMINATION

PURPOSE

METHOD

SECTION 2. OPERATION

SAFETY PRECAUTIONS

SHATTERED LAMPS

FUSES

FIXTURES

PORTABLE/EXTENSION LIGHTS

LAMP REPLACEMENT

WIRING

EXPOSED METAL PARTS

OPERATING PROCEDURES

UNSHIELDED LIGHTS

REFLECTED GLARE

LAMP SIZE

LIGHTING EXTREMES

SHIELDED FIXTURES

DARK ADAPTATION

LIGHT TRAPS

REPLACING LAMPS

LOCATION

PAINTING

VOLTAGE REGULATION

MAINTENANCE

POWER SUPPLY

QUALITY OF ILLUMINATION

1-34 1-34 1-35 1-35 1-35 1-35 1-35 1-35 1-36 1-36 1-36 1-36 1-38 1-38 1-38 1-38 1-38 1-38

2-1 2-1 2-1 2-1 2-1 2-1 2-1 2-1 2-4 2-4 2-4 2-4 2-4 2-4 2-4 2-4 2-4 2-4 2-4 2-5 2-5 2-5 2-5

330-3.1 330-3.1.5 330-3.2 330-3.2.3 330-3.2.8 330-3.2.10 330-3.2.11 330-3.2.12 330-3.3 330-3.3.1 330-3.3.1.1 330-3.3.1.2 330-3.3.2 330-3.3.2.1 330-3.3.2.2 330-3.3.3

330-3.3.4 330-3.3.4.2 330-3.3.4.4 330-3.3.4.8 330-3.3.5 330-3.3.5.1 330-3.3.5.2 330-3.4 330-3.4.1 330-3.4.2 330-3.4.2.1 330-3.4.2.2 330-3.4.2.3 330-3.4.3 330-3.4.5 330-3.5 330-3.5.1 330-3.5.2 330-3.5.3 330-3.6 330-3.6.1 330-3.6.4 330-3.6.6 330-3.6.7 330-3.6.9 330-3.6.10

S9086-K9- STM -000/CH -330

SECTION 3. MAINTENANCE

GENERAL

ADDITION OF LIGHTING FIXTURES

CAUSES OF LIGHT LOSS

DIRT ON LAMPS AND FIXTURES

DIRT ON ROOM SURFACES

LAMP LUMEN DEPRECIATION

BURNOUTS

IMPROPER OPERATION

LAMP REPLACEMENT

REPLACEMENT OF INCANDESCENT LAMPS

Blackening When to Replace

REPLACEMENT OF FLUORESCENT LAMPS

Cause of Trouble When to Replace

REPLACEMENT OF EXPLOSION-PROOF EXTENSION

LIGHT LAMPS

PLANNED RELAMPING

Spot Relamping Group Relamping Spot Versus Group Relamping

DISPOSAL OF OLD LAMPS

Incandescent Lamps Fluorescent Lamps

FIXTURE CLEANING

AUTHORIZED PERSONNEL

CLEANING METHODS AND FREQUENCY

'!Ype of Fixture Location Type of Dust

CLEANING OPEN TYPE FIXTURES

CLEANING ENCLOSED TYPE FIXTURES

MAINTENANCE OF LIGHTING FIXTURES

WINDOW ASSEMBLIES

INTERNAL COMPONENTS

SHOCK MOUNTS

MAINTENANCE OF BATTERY POWERED LIGHTS

DAMAGE CONTROL FLOOD LANTERNS

RELAY AND PORTABLE LANTERNS

FLASHLIGHTS

DARKENED SHIP DOOR SWITCHES

PORTABLE EXTENSION LIGHTS

EXTENSION LIGHTS FOR SMALL BOATS

3-1 3-1 3-1 3-1 3-2 3-2 3-2 3-2 3-2 3-2 3-3 3-3 3-3 3-3 3-3

3-3 3-3 3-3 3-4 3-5 3-5 3-5 3-5 3-5 3-5 3-6 3-6 3-6 3-6 3-6 3-6 3-7 3-7 3-7 3-7 3-7 3-7 3-9

3-11 3-11 3-14 3-14 v vi

Figures

330-1-1 330-1-2 330-1-3 330-1-4 330-1-5 330-1-6 330-1-7 330-1-8 330-1-9 330-1-10 330-1-11 330-1-12 330-1-13 330-1-14 330-1-15 330-1-16 330-2-1 330-2-2 330-2-3 330-3-1

S9086-K9- STM -000/CH -330

LIST OF ILLUSTRATIONS

Camera/Eye Similarities Effect of Voltage on Lamp Life and Lumen Output Lumen Depreciation of Incandescent Lamps Basic AC Circuit of a Preheat Fluorescent Fixture '!Ypical Circuit for DC Operation of Fluorescent Lamps Reduction of Fluorescent Lamp EMI by Installation of a Copper Strip Grounding Metal Louvers in Shielded Fluorescent Lighting Fixtures '!Ypical EMI Filter Lamp Mortality Curve Lumen Depreciation of Fluorescent Lamps '!Ypical Wiring for Lighting Distribution System '!Ypical Wiring of Three-Lamp Fluorescent Lighting Fixture Control of Lighting Fixtures by Individual Switches Berth Light Location '!Ypical Light Trap Light Fixtures (Sheet 1 of 2) Approved Lighting Fixture Grounding Methods in Order of Preference Relay Lantern Grounding Method Portable Light Grounding Method Fluorescent Lamp End Blackening

Page

1-3 1-6 1-6 1-8 1-9

1-11 1-11 1-12 1-14 1-14 1-16 1-19 1-20 1-21 1-37 1-40 2-2 2-3 2-3 3-4 vii viii

Tables

330-1-1 330-1-2 330-3-1 330-3-2

330-3-3 330-3-4 330-3-5

S9086-K9- STM -000/CH -330

LIST OF TABLES

Hangar Space Lighting Control System Lighting Fixtures Window Assemblies for Fluorescent Lighting Fixtures Window Assemblies, Globes, and Roundels for Incandescent Lighting

Fixtures Standard Parts for Fixtures Using 8-Watt Fluorescent Lamps Standard Parts for Fixtures Using 15- or 20-Watt Fluorescent Lamps Repair Parts for Relay and Portable Lanterns

Page

1-31 1-42 3-8

3-10 3-11 3-12 3-13

IX

X

CHAPTER330

LIGHTING

Section 1. DESCRIPTION

330-1.1 GENERAL

330-1.1.1 PURPOSE. Chapter 330 contains gener al information regarding the proper operating and maintenance procedures for lighting installations.

330-1.1.2 DEFINITIONS. Terms used in this chap ter are defined in the following paragraphs.

330-1.1.2.1 General Illumination. The white illu mination from all lighting fixtures on the overhead and bulkheads, except detail lighting fixtures.

330-1.1.2.2 Detail Illumination. The illumination provided for specific visual tasks, such as lights on desks, log desks, berths, and machine tools.

330-1.1.2.3 Special Illumination. The illumination from miscellaneous fixtures for purposes other than those covered by general and detail illumination.

330-1.1.2.4 Red Illumination. The red illumination that minimizes interference with dark adapted vi sion, including certain special applications involving darkened ship operation and red illumination in berthing areas for safety and sleeping comfort.

330-1.1.2.5 Low Level White (LLW) Illumination.

LLW lighting is used in command and control spaces of submarines and some surface ships where color display consoles are used.

330-1.1.2.6 Broad Band Blue (BBB) Illumination.

The blue illumination, in command and control spaces containing cathode ray tube display consoles, that provide illumination under conditions which re sult in minimum interference with display reading.

330-1.1.2.7 Darkened Ship. The ship condition es tablished to insure light security. This is achieved through the use of light traps, door operated switches, darkened ship control circuits, and material classifications assigned to certain doors and hatches.

330-1.1.2.8 Emergency Illumination. The illumina tion from lighting systems designed to provide illu mination during emergencies or conditions which in terfere with normal lighting systems.

330-1.1.2.9 Yellow Illumination. During peace time, yellow illumination is used to substitute for all external red illumination (except for navigation and signal lights) and all internal red lighting that can be seen directly from another ship. The purpose of this substitution is to eliminate possible confusion with red navigation lights.

330-1.2 REFERENCE PUBLICATIONS

330-1.2.1 THEORY AND DESIGN. Information regarding the theory and design of lighting equip ment and instal-

1-1 lations, such as the fundamentals of light and vision, illumination levels, light sources, general and detail lighting fixtures, lanterns, typical installation meth ods, photometric surveys, and other lighting informa tion, is contained in Lighting on Naval Ships, DoD

HDBK-289.

330-1.2.2 NAVIGATIONAL LIGHTING. Informa tion regarding navigation lights, signal lights, and searchlights is contained in chapter 422, Navigation and Signal Lights.

330-1.2.3 VISUAL LANDING LIGHTING. In formation concerning visual landing aid lighting is contained in Naval Air System Command (NAVAIR) technical manuals and bulletins.

330-1.2.4 USE OF SYMBOL NUMBERS. Symbol numbers specified herein and as shown on the equip ment nameplates are numbers assigned to electrical equipment covered by standard electrical drawings and military specifications and standards for ship board applications. Symbol numbers are a shorthand means of identifying electrical equipment. Symbol numbers are in accordance with Standard Electrical Symbol List, MIL-HDBK-290.

330-1.2.5 LIGHTING FIXTURES. Navy standard lighting fixtures are listed in MIL-HDBK-290. In formation concerning the design of most lighting fix tures (and their repair parts) is contained in MIL-F -16377 (with its associated specification sheets).

330-1.2.6 LIGHTING FIXTURE AVAILABILITY.

Availability of lighting fixtures in the supply system is shown in the following Federal Supply Classes (FSCs):

1-2

1. FSC 6210 -- Electrical Lighting Fixtures

2. FSC 6230 - Electrical Portable and Hand Lighting Equipment

3. FSC 6240 -· Electric Lamps

4. FSC 6250 - Ballasts, Lampholders, and Starters

330-1.3 LIGHT AND VISION

330-1.3.1 GENERAL. The lighting system has been designed to provide adequate illumination for per forming visual tasks with maximum speed, accuracy, and comfort, and with minimum effort and fatigue.

The importance of operating and maintaining the lighting system as it was designed cannot be over stressed.

330-1.3.2 The following discussion of the human eye, and its reaction to various levels and types of illu mination, is presented as background information relative to understanding the purposes of the various types of lighting installations on naval ships.

330-1.3.3 HOW THE EYE SEES. The eye is fre quently compared to a camera (see Figure 330-1-1) because camera designs are based on the functioning of the human eye. In both cases, light reflected by an object passes through a lens and is focused on a light-sensitive surface. There the similarity ends. In the camera, the light-sensitive surface is film and the process is complete. In the eye, the light-sensitive surface is the retina and the pro cess is just beginning.

330-1.3.4 VISUAL PROCESS. Vision is both a me chanical process and chemical process. In the me chanical process, the pupil (or opening of the eye) ad justs automatically to allow enough light to

IMAGE

OBJECT

LIGHT

REGULATING

DIAPHRo\M

S9086-K9- STM -000/CH -330

FOCUSING

LENS

LIG..CT

SENSITIVE

FIE TINA

FOCUSING

LENS

LIGH,

SENSITIVE

FILM

Figure 330-1-1. Camera/Eye Similarities enter in order to fonn a clear image on the retina.

From the retina, vision is a chemical process. Varia tions in the frequency in the light spectrum cause a variety of chemical changes in the eye receptors which, when transmitted to the brain, cause the sensation of vision.

330-1.3.5 TWO KINDS OF VISION. The retina contains two sets of receptors: cones and rods. The cones function in bright light (day-photopic vision) and make possible discrimination of fine detail and the perception of color. The rods are sensitive to low levels of illumination, function in dim light (night scotopic vision) but have no color response.

330-1.3.6 Because the cones are not affected by low-level illumination, the eye is able to readily ad just to changes in light intensity when the change is from low to high levels of illumination. The eye re sponse to a change in illumination from high to low, however, is much slower because the more light -sen sitive rods are adversely affected by bright light. Af ter exposure to bright light, it takes a finite time in a semidark environment before the rods can function effectively.

330-1.3.7 ADAPTATION. Adaptation is the ability to adjust to any given illumination level within the vis ible spectrum. In the process of adaptation, both me chanical and chemical changes take place within the eye.

330-1.3.7.1 Mechanical Response. The mechanical response takes place at the pupil of the eye. The size of the pupil opening is determined by the amount of light received at the eye. In very dim light, the pupil opens wide and as light intensity increases, the size of the pupil opening decreases proportionally. This mechanical response is almost unnoticeable within a limited range of light intensities or when the change in light intensity is gradual. Sudden, dramatic changes in intensity may cause a momentary loss of vision while the pupil adjusts to the change.

330-1.3.7.2 Chemical Response. The chemical re sponse within the eye is much slower, especially to abrupt changes from bright light to semidarkness.

The time it takes for the eye to become adapted to the dark when going from a brightly lit area to semidark ness is usually complete within 25 to 30 minutes, al though it has been known to take longer than an hour.

The transition can be accelerated if a person has been exposed to low -level red il-

1-3

89086-K9-STM -000/CH -330

lumination since the rods that are used in night vision are relatively insensitive to red light. Besides reduc ing transition time, red illumination permits the per formance of useful visual tasks. Also, personnel can move between darkened areas and red illuminated areas without impairment of vision in either area.

The wearing of red goggles for about 30 minutes in bright light before moving into darkness will provide the same benefits as exposure to red illumination.

330-1.4 PRINCIPAL FACTORS AFFECTING

VISION

330-1.4.1 GENERAL. The principal factors affect ing vision include physiological (physical construc tion and age of the eyes), psychological (tension, dis tractions), and physical (size, brightness, contrast).

Of these, the physical factors concern us most be cause they are the tangible factors that dictate the lighting requirements for any given area.

330-1.4.2 PHYSICAL FACTORS. The physical fac tors are the external factors affecting the visibility of an object. There are three such factors.

330-1.4.2.1 Size. Visual size is the combination of actual size and distance from the observer.

330-1.4.2.2 Brightness. Brightness is determined by applied light intensity and reflectance of the ob ject.

330-1.4.2.3 Contrast. Contrast refers to the grada tions of brightness or color of objects within the field of view.

1-4

330-1.4.3 VISIBILITY. If there were no gradations in brightness or color, the eye would be unable to dis tinguish objects from their background. Contrast is necessary to enable the eye to detect the presence, size, and shape of objects, and also to reveal every de tail that can be seen.

330-1.4.4 In general, visibility improves as contrast is increased. For example, other things being equal, black print on white paper is easier to read than black print on gray paper because the former combination represents the greater brightness contrast between the object of interest and the background.

330-1.4.5 ILLUMINATION LEVELS. Visibility is also affected by the :ratio of the illumination on the object to the illumination on its surroundings. Con trasting levels of illumination in the same area where visual tasks are performed are undesirable and could cause eye fatigue.

330-1.4.6 To illustrate, during the performance of prolonged tasks, the eyes frequently (and often invol untarily) move away from and toward the task at hand. The contrasting illumination levels will cause the pupils of the eyes to constantly readjust in order to accommodate the different amounts of light enter ing the eye. This constant readjustment of the pupils over long periods of time eventually will lead to eye fatigue.

330-1.5 LIGHT SOURCES

330-1.5.1 GENERAL. Incandescent and fluores cent lamps are the most common sources of light used in naval ships.

330-1.5.2 For light production, the efficiency of a lamp is expressed in terms of lumens emitted per watt of power consumed.

330-1.5.3 The incandescent filament lamp has cer tain characteristics that make it inherently inefficient as a source of light.

330-1.5.4 The fluorescent lamp produces light by an entirely different process, and is capable of achieving much higher efficiencies. Present fluorescent lamps have efficiencies of up to 53 lumens per watt, while incandescent lamps have only 12 lumens per watt.

330-1.5.5 INCANDESCENT LAMPS. Because of their low efficiency, incandescent lamps are used less frequently as light sources on naval ships. They pro duce light by means of a tungsten or carbon filament that is heated to incandescence by an electric current.

Oxidation and consequent failure of the filament, which occurs in air, are prevented by surrounding the filament with an inert gas or by operating it in a vacu um.

330-1.5.5.1 The incandescent lamps most used for general lighting on shipboard are 115 or 120 volt (50, 100, 110, and 200 watt rough service lamps). These lamps have specially constructed filaments that are supported at several points to increase their ability to withstand vibration and shock.

330-1.5.5.2 The most commonly used lamp on ship board is the inside frosted lamp consisting of a glass bulb with the entire inside surface frosted. Frosting conceals the filament and diffuses the light emitted

S9086-K9-STM -000/CH -330

from the lamp. These lamps can be used with or with out reflecting equipment.

330-1.5.5.3 Effect of Voltage. Figure 330-1-2 shows the effect of voltage variation on the life and lumen output of incandescent lamps.

330-1.5.5.4 Overvoltage operation results in great er light output, but shortens lamp life. Undervoltage operation, while increasing lamp life, causes a reduc tion in light output.

330-1.5.5.5 Lamp Mortality. Testing has proved that in any large group of lamps, failures which occur will generally correspond to the mortality curve which is discussed in paragraph 330-1.5.6.37.

330-1.5.5.6 In any large group of lamps some will fail relatively early in life, whereas others will still be burning long after the end of rated life. The average life, however, is the point at which approximately 50 percent of the lamps burn out.

330-1.5.5.7 Lumen Depreciation. As an incandes cent lamp burns at constant voltage, the filament gradually evaporates or sublimes, causing a slow but continuous reduction in power consumption and light output. The normal end of life is reached when the wire breaks or burns through at its thinnest point.

Further light output reduction results from the ab sorption of light by the vaporized tungsten, which col lects as a black deposit on the inner surface of the bulb.

330-1.5.5.8 The curve in Figure 330-1-3 shows the typical range of lamp depreciation in light output versus time.

1-5

S9086-K9-STM -000/CH -330

170 •so ., 110 z &U t50 ~· 1.0 -c 130 w

120 ~ Ct 110 ...

'00 z ""' u 10 rr r 10

...... {~~ ~'i.~s~ ,,.,. -

I""'- t:-~ , ,_ -"-, .. oo w

350 -300 c w

250 ~ a:

200 ~ 150 0 ...

100 z w 50 t.> a:

0 w

Q.

12 t• Ia 18 tOO 102 104 tO& 108

PERCENT OF RATED VOUS

Figure 330-1-2. Effect of Voltage on Lamp Life and Lumen Output •

~ 40o~~20~~.~o---a~o---a·o---,~o~o--,-20 w PERCENT RATED LIFE CL

Figure 330-1-3. Lumen Depreciation of Incandescent Lamps.

330-1.5.6 FLUORESCENT LAMPS. Fluorescent lamps are now used for the majority of interior light ing on naval ships. The Navy has standardized on three lamp sizes: 8-watt, 15-watt, and 20-watt cool white lamps. The use of fluorescent lamps over 20 watts has been limited to special installations because their fragility and length require special design and fabrication of the lighting fixture.

330-1.5.6.1 Definition. Fluorescent light sources are electric discharge lamps consisting of a glass tube coated on the inside with a fluorescent phosphor and

1-6 enclosing two electrodes (one at each end), a drop of mercury, and a small amount of argon gas. A fluores cent lamp produces invisible, shortwave (ultraviolet) radiation by the discharge through the mercury vapor in the tube. The phosphor absorbs the invisible ra diant energy and re-radiates it over a band of longer wavelengths to which the eye is sensitive.

330-1.5.6.2 Auxiliary Control Equipment. As in all discharge light sourcc~s, fluorescent lamps require special auxiliary control equipment for proper operation.

330-1.5.6.3 The auxiliary components of a preheat fluorescent lamp system include a ballast and a start er (see Figure 330-1-4).

330-1.5.6.4 Starters. Preheat lamps are activated by a starter that completes the circuit which permits a heating current to flow through the electrode at each end of the lamp. When the switch is opened, a high -voltage pulse is transmitted across the lamp and strikes the arc. Starters are either a thermal or a glow-switch type, with the latter in more common use today.

330-1.5.6.5 Glow-switch starters contain two elec trodes, one of which is a bimetallic strip, enclosed in a small glass bulb filled with an inert gas such as neon or argon. When voltage is applied, a small current flows through the circuit as a result of a glow discharge between the two electrodes. The heating effect of the current expands the bimetallic element, causing the electrodes to touch. Closing the switch stops the flow discharge, but allows a substantial flow of current to preheat the lamp electrodes during the short period of time when there is enough residual heat in the switch to keep it closed. As the bimetal cools, the switch opens and the resultant high -voltage pulse starts normal lamp operation. If the lamp arc fails to strike, the cycle is repeated. The condenser sup presses electro-magnetic interference (see para graph 330-1.5.6.21).

330-1.5.6.6 The switch does not glow after the lamp arc is established because the remaining available electrical potential is insufficient to cause a break down between its electrodes. Thus, the switch con-

S9086-K9- STM -000/CH -330

sumes no power. When the lamp is turned off, it can be immediately restarted.

330-1.5.6.7 Thermal-switch starters must be used in operating conditions involving low temperature, direct current, or widely varying line voltage. This type of starter has a heating coil in series with the bal last and lamp. Since the thermal switch is closed, pre heating occurs immediately when voltage is applied.

The heating coil actuates the bimetallic strip in the starter switch and after sufficient preheat time elapses, the thermal switch opens, starting the lamp.

Thermal starters consume only a small amount of en ergy during lamp operation.

330-1.5.6.8 Ballasts. The principle function of a ballast is to limit current to a fluorescent lamp. A bal last also supplies sufficient voltage to start and oper ate the lamp. In case of rapid -start circuits, a ballast supplies voltage to continuously heat the lamp cath odes.

330-1.5.6.9 High Efficiency Ballasts. General trends in lighting design are moving toward the instal lation of high efficiency ballasts for new and retrofit lighting applications. This practice has proven to save relatively large amounts of energy without sacrificing lighting quality. When a ballast failure is encoun tered in such an installation, the replacement ballast should not only be compatible with the lamps and cir cuit parameters, but should also have a similar effi ciency rating. This will ensure that high efficiency installations continue to function as intended.

330-1.5.6.10 Because a fluorescent lamp is an arc discharge device, the more current in the arc, the low er the resistance becomes. Without a ballast to limit current, the lamp would draw so much current that it would destroy itself.

1-7

FIXED CONTACT

(El..ECTRODEl

CONDENSER

/BIMETALLIC STRIP

(E-ECTRODE)

MOVABLE CONTACT

115 VAC

GLOW·SWITCH

STARTER

Figure 330-1-4. Basic AC Circuit of a Preheat FluoresCE!nt Fixture.

330-1.5.6.11 Inductive ballasts constitute the most practical solution to limiting lamp current. The sim plest inductive ballast is a coil, inserted into the cir cuit to limit current.

330-1.5.6.12 Single-lamp ballasts are used in stan dard Navy lighting fixtures because of space and weight limitations, and the peculiar application of lighting fixtures in split circuits for red/yellow and white illumination.

330-1.5.6.13 Each lamp requires a ballast specifical ly designed for its electrical characteristics, the type of circuit in which it is to be operated, and the voltage and frequency of the power supply. Generally, bal lasts are incorporated as an integral part of a lighting fixture.

330-1.5.6.14 External ballasts housed in a separate box, are required on certain de taillights such as those on the secretary bureau, radio operator's desk, and berth lockers.

1-8

330-1.5.6.15 Direct Current Operation. Although fluorescent lamps are basically ac, they can be oper ated on de with proper auxiliary equipment. The cur rent is controlled by an external resistance in series with the lamp (see Figure 330-1-5). Since there is no voltage peak, starting is more difficult and ther mal-switch starters are required.

330-1.5.6.16 When a fluorescent lamp is operated in an ac circuit, an inductive ballast limits current to the lamp without consuming an appreciable amount of power. This is possible because of characteristics exhibited by inductance in an ac circuit. However, the resistance ballast usc~d for de operation consumes about the same amount of power as the lamp. Be cause of the greater voltage loss in resistance, the overall lumens per watt efficiency of de system is about 60 percent of the ac system.

330-1.5.6.17 Fluorescent lamps operated on de have a tendency to become dim at one end after sev eral hours of operation. Dimming is a result of con tinuous current flow

S9086-K9-STM-OOO/CH-330

POLAR ITV

REVERSING

SWITCH

RESISTANCE

BOX

R - 30 WATT RESISTOR

e 150 OHMS FOR

20-WATT LAMPS

e 330 OHMS FOR

8-WATT LAMPS

S - THERMAL STARTER

Figure 330-1-5. 1Ypical Circuit for DC Operation of Fluorescent Lamps.

in one direction, which eventually causes the mercury to accumulate at the negative (cathode) end of the lamp. A line-reversing switch is often used to re verse the electrode functions every few hours of op eration, thus overcoming the tendency to dim more at one end. Lamps operated on de may function for only 80 percent of their rated life. Because of these limitations, de operation of fluorescent lamps should be limited only to detail illumination of berths, desks, and offices.

330-1.5.6.18 Radio Interference. The mercury arc in a fluorescent lamp emits Electro-Magnetic Inter ference (EMI) radiation. This radiation may be picked up by nearby radios causing an audible sound.

Because of the frequencies generated by the fluores-cent lamp, EMI is ordinarily limited to the AM broadcast band and nearby amateur and communica tion bands. The FM, television, and higher frequency bands are very rarely affected.

330-1.5.6.19 Identification of EMI from fluores cent lamps can readily be made by tuning the set to a point where the interference is most pronounced, and then turning off the lamps. If the noise persists, it is from some source other than the lamps.

330-1.5.6.20 EMI from fluorescent lamps may reach the radio in three ways: by direct radiation from the lamp to the radio antenna circuit, by line radi ation from the electric supply to the antenna circuit, and by line feedback from the lamp through the pow er line to the radio.

1-9

330-1.5.6.21 Elimination of most EMI from pre heat lamps is by a small condenser ordinarily mounted in the starter-switch container. With rap id-start and instant-start systems, the condenser is mounted in the ballast.

330-1.5.6.22 EMI may be eliminated by moving the radio antenna farther from the lamp, 5 feet is usually sufficient. Where this is not practical, shielding me dia, such as those shown in Figure 330-1-6 and Figure 330-1-7, will suppress the noise below the interference level.

330-1.5.6.23 Conducted EMI may be suppressed by EMI filters that are commercially available. The sim plestofthese is a three-section delta-connected ca pacitor that is grounded to the fixture and connected across the supply lines as they enter the fixture, as close to the lamps as possible. A larger capacitor type filter is also available for installation in laborato ries, radio repair shops, and other places where conditions are not favorable for good radio reception.

Figure 330-1-8 shows a typical filter circuit.

330-1.5.6.24 Dimming. The light output of some fluorescent lamps (rapid-start) can be adjusted or dimmed by a number of special circuits. All of these circuits incorporate one essential principle: the bal last must keep the cathodes of the lamp energized at the proper voltage regardless of the amount the lamp is to be dimmed.

330-1.5.6.25 Current passing through the lamp or lamps in the dimming system may be controlled by a number of methods. The methods used include thy ratrons, silicon-controlled rectifiers, and other sol id-state devices. Also, variable inductors, auto-

1-10 transformers, saturable core reactors, magnetic am plifiers, and other similar devices may be used.

330-1.5.6.26 Dimming of Navy standard lighting fix tures can be accomplished by replacing the standard ballast with a dimmable type, and by employing a rheostat to control the voltage. Dimmable ballasts are considered special equipments, weigh more, and because of their dimensions, must be separately mounted from lighting futures. This system has prov en unreliable and is no longer used.

330-1.5.6.27 The preferred method of varying illu mination levels aboard Naval Ships, where fluores cent lighting fixtures are used, is accomplished by se lecting the number of lighting fixtures or lamps within a fixture to be energized. This is most easily accom plished by wiring and switching arrangements. (Re fer to paragraph 330--1.7.2) This method is preferred because it is more reliiable, lighter in weight and occu pies less space than the dimmable ballast method.

330-1.5.6.28 Stroboscopic Effect. When a fluores cent lamp is operated on ac, the voltage passes through zero and reverses in direction twice for each cycle. In 60-Hz circuitry, this occurs 120 times per se cond. The light from the lamp decreases momentari ly each time the voltage reverses, but no telltale flick er is visible since the eye does not respond to a fre quency of this magnitude.

330-1.5.6.29 However, an interesting phenomenon called a stroboscopic ~~ffect (the tendency to see mov ing objects in repetitive flashes at successive posi tions) may sometimes be observed on rapidly moving or rotating objects. In an unusual combination of cir cumstances, where tht~ stroboscopic effect might be a problem, the following actions (listed in order of preference) can be taken:

ELECTRICAL BONO AT BOTH ENOS

OF STRIP AND FIXTURE ENCLOSURE

COPPER STRIP (0.20 INCH WIOE BY

0.013 INCH THICK) PERPENDICULAR

ACROSS THE MrDPOtNTS OF THE

FLUORESCENT LAMPS

Figure 330-1-6. Reduction of Fluorescent Lamp EMI by Installation of a Copper Strip.

GAOUNDING

LOUVER ASSEMBLY

NOTE:

.. STALL GROUNDING STRIPS BETWEEN

LEATHER WASHER AND ALUMINUM

BUSHING. GROUND LOUVERS TOGETHER

ON SPLIT LOUVER INSTALLATIONS.

GROUNDING MUST BE CONTINUOUS FROM

ONE ENO MOUNTING SCREW TO THE

OTHER.

Figure 330-1-7. Grounding Metal Louvers in Shielded Fluorescent Lighting Fixtures.

1-11

200 u. H

I

I ~ F ,.... F I 0.25 I 0.25

..z:::::: -- I o.25 »F 10.25 "'F

200 » H

Figure 330-1-8. 'JYpical EMI Filter.

1. Use two or more adjacent lighting fixtures and connect them to different phases of the lighting power supply.

2. Use a two-lamp fixture and connect each lamp to a different phase of the lighting power sup ply.

3. Use a three-lamp fixture and connect each lamp to a different phase of the lighting power sup ply.

330-1.5.6.30 Effect of Temperature. The light out put of any fluorescent lamp depends on the mercury vapor pressure inside the lamp. Optimum pressure for maximum light output for most fluorescent lamps occurs when the coolest spot on the lamp is about 100° F. Lamp wall temperature is affected by lamp wattage, and lamp diameter by the design of the light ing fixtures, and by the ambient temperature and draft conditions.

1-12

330-1.5.6.31 As lamp wall temperature is raised above 100° F, the me,rcury vapor pressure within the lamp increases causing the light output and lamp wattage to slowly drop. At lower lamp wall tempera tures, the mercury condenses on the tube, pressure drops, light output falls sharply, and wattage drops slowly. This characteristic is common to all fluores cent lamp designs.

330-1.5.6.32 For maximum efficiency, lamp wall temperatures should be within a range of 100° F to 120° F. Light output decreases about 1 percent for each 1 o F drop in lamp temperature below 100° F, and a like amount for each 3 o F rise between 120° and 200° F.

330-1.5.6.33 Low temperatures may also cause starting difficulty. Preheat-type lamps will give reli able starting at ambient temperatures of 50° F and above. Preheat lamps can be started at lower temper atures by the use of thermal rather than glow-switch starters.

330-1.5.6.34 Effect of Frequency. The current -lim iting characteristics of a ballast directly depend on the frequency of the power supply. For this reason, ballasts must be used only at the frequency for which they were designed. When operated at a frequency lower than the design frequency, the inductive reac tance of a lag ballast is reduced, and higher current flows through the lamp, resulting in shorter lamp life and an overheated ballast. At a frequency higher than the design frequency, lamp current is reduced, resulting in lowered light output.

330-1.5.6.35 Effect of Voltage. The voltage of the fixture should be kept well within the normal operat ing range for the ballast. Low voltage, as well as high voltage, reduces efficiency and shortens life. This is in contrast with filament lamps where low voltage re duces efficiency but prolongs life. Low voltage on fluorescent lamps may also produce instability in the arc and cause starting difficulty.

330-1.5.6.36 Voltages below the specified range may lower the preheat current to a point where the electrodes fail to emit their proper quota of elec trons. Such a condition may cause the lamps to flash on and off without starting. Under these conditions, if the lamps do start, the emission material may waste away too rapidly, shortening lamp life. On voltages above the specified range, operating current becomes excessive and may not only overheat the ballast but cause premature end-blackening and early lamp failure.

330-1.5.6.37 Lamp Mortality. Fluorescent lamp life is influenced greatly by operating conditions. For example, operation with frequent starts shortens life appreciably. On the other hand, operation with many burning hours per start lengthens lamp life. For this

S9086-K9- STM -000/CH -330

reason, lamps have several different life ratings, based on the number of hours per start. When a large group of lamps is tested it will be found that failures occur very nearly in accordance with the mortality curve in Figure 330-1-9.

330-1.5.6.38 Depreciation. A fluorescent lamp de creases in lumen output most rapidly during the first 100 hours of operation; therefore, the rated initial lu mens is the measurement of the value obtained after 100 hours of burning. The curve in Figure 330-1-10 shows the typical range of lamp depreciation in light output versus time. The vast majority of lamps de preciate along a line near the upper limit of the curve.

Depreciation in light output is due chiefly to a gradu al deterioration of the phosphor powders, and a blackening of the inside of the tube.

330-1.5.7 LOW PRESSURE SODIUM LAMPS.

Low Pressure Sodium (LPS) also known as SOX lamps have been installed in flight deck and hangar bay areas on aircraft carriers. These lamps produce a characteristic yellow light with efficiencies in excess of 170 lumens per watt. Compared to other light sources, LPS lighting can be installed with fewer fix tures to provide the same amount light for a given area.

330-1.5.7.1 Starting Time. A drawback of LPS lighting is the starting delay-time required to bring a lamp up to full brilliance. Because the sodium in the lamp must first vaporize, it may take anywhere from 7 to 15 minutes before the lamp reaches full bril liance.

330-1.5.7.2 Restrike Time. The restrike time of a light source is the time it takes for a lamp to return to full brilliance after being subjected to a momentary power loss. LPS lamps are known to have varying

1-13

S9086-K9-STM -000/CH-330

100 f20

PERCENT OF RATED LFE

Figure 330-1-9. Lamp Mortality Cunre.

10C ...

i s 75..,__...., __ i 50~--._--~--~~--r---~--~ .J ...

ffi 25~~---+--~--~--r-~

~ 0 ~--~--~--~--_.--~--~ 2 41 e e to 12

BURNING HOURS

(BURNING HOURS IN THOUSANDS)

Figure 330-1-10. Lumen Depreciation of Fluorescent Lamps.

restrike times from instantaneous, to several minutes.

This occurs because when aLPS lamp is operating at its full brilliance, it has reached its design tempera ture and pressure, and the sodium inside has vapor ized. When power is interrupted, temperature and pressure begin to decrease and the sodium begins to condense. The amount of light output immediately following a momentary power interruption depends on the state of these parameters. In general, if the power interruption is only a few cycles in duration, there is a good chance that the lamp will restrike instantly. If the power interruption is a few seconds or longer, restrike time will be longer. In any case, if the sodium is allowed to condense, and the tempera ture and pressure are allowed to return to ambient, it will take the normal starting time of 7 to 15 minutes to restart.

1-14

330-1.5.7.3 Color Rendition. LPS lamps produce a characteristic yellow light that will affect the appear ance of colors. Many colors will appear to be black, a shade of gray, or blend in with the background col ors. Problems such as these can be reduced by the use of localized white lighting.

330-1.6 POWER SUPPLY

330-1.6.1 SURFACE SHIPS. On surface ships, two lighting systems are utilized; the ship service lighting system and the emergency or alternate lighting sys tem.

330-1.6.1.1 Ship Service lighting System. The ship service lighting system provides a distribution system for ship service lighting and 120-volt auxiliaries.

These auxiliaries include hotel loads, such as coffee makers, drinking fountains, toasters, small tools, and photographic auxiliaries.

330-1.6.1.2 The ship service lighting system dis tribution (see Figure 330-1-11) is by radial feeders from the ship service switchboards or load centers to local lighting load center panels. It is designed for maximum continuity of service and minimum vulner ability to mechanical and battle damage. The num ber and location of load centers and transformer banks are chosen to keep the amount of cable to a minimum. The feeder and mains are three-phase, with single-phase loads divided as evenly as practical between the three phases.

330-1.6.1.3 Isolation of lighting in Machinery Spaces. During emergency situations such as compartment fires or floods, life threatening, electri cal hazards may exist due to energized circuits coming in contact with water. It is essential that all electrical circuits be de-energized in a flooded compartment, but it is also essential to have adequate lighting to permit personnel to carry out emergency procedures.

This situation has led to the re-design of lighting cir cuits for machinery spaces on new construction ships.

To enhance fire fighting efforts in machinery spaces, the lighting within that space is isolated from other non -lighting loads on new ship design. On older

Change A

S9086-K9-STM-OOO/CH-330

ships, all electrical equipment may be required to be de-energized during fire fighting efforts.

330-1.6.1.4 Most lighting fixtures are provided with power only from the ship service lighting systems.

Others are normally provided with power from the ship service system and are automatically connected to the emergency power supply when the ship service power supply fails. Surface combatants do not have an emergency light system. Lighting that is consid ered "vital" is supplied by normal and alternate pow er.

330-1.6.1.5 Ship Emergency or Alternate Lighting System. The emergency or alternate lighting system is designed to provide a suitable distribution system that, upon failure of the ship service lighting system, will assure continuity of service in vital spaces and in board watch stations. Continuous illumination is es sential in these areas because of functional require ments, and when personnel are expected to remain on duty.

330-1.6.1.6 The emergency or alternate lighting sys tem consists of a selected group of fixtures that are fed from the emergency or alternate switchboard through automatic bus transfer equipment. Normally the supply is from the ship service distribution system with automatic transfer to the emergency or alternate system only when the ship service supply is inter rupted. Where generator capacity permits, all fix tures in a space requiring emergency lighting are sup plied from the emergency system. This obviates the need for duplication of fixtures or control equipment.

The emergency feeders are either 450-volt or 120-volt.

330-1.6.2 SUBMARINES. A submarine has only a ship service lighting system, but it functions in two ways.

1-15

Q l:ol

(1>

I

0'1

INCANO~SCENT LIGHTING FIX. flUORESCENT LIGHTING FUC. BLK

I- .... c::,,:J

CABLE SUPPLIED LRAENLATEY •N·

Wt T'H F'LUORESENT " s llOX

FIXTURES

.--t-1--. 110 FEE TJ

TO OTHER

LANTfRNS tNCANDESCENT ~ S DOOR CPERAT!O SWITCHES FIXTURE ALSO t3l.l. WITCH (WHEN REODI

~ll?1:: ~g:- s::?L_'=' AL TEI!!fATE TO OTHER GROUND ~ r: -, LANTERNS COHN.

GRDUNO ~ f,-~ ,-..... CONN. BOX

_-m._

~ ~I

EMERGENCY

SWITCHBOARD

(450 YJ

-11'"- !m.

Sit i!E

SHIP SERVICE

SWI TCHSOAHD

(4,0 Y)

~~fT~R ~ 11 FUSS BOX RElAY

SYMBOLS ? II SYY 871.1 LANTERNS

AUTOMATIC BUS

TRANSFER SWITCH

TO EMERGENC 'I

1/i--F}-:------1-~=- li:T~~:ER

LOADS ....----,,..,

FEEDER I J I

(3 REO'D ) 460/120V.

80Hz, 1 t (3,5,7.5, 15,25

OR 37.5 KVA).

MIL-T-15108

- I

~~~HER rH. I

LOADS TEE~EI==~ FOR INSTALL-ATIONS ONLY WHERE

LIGHTS ARE CONTitOL LED BY CIRCUIT BKRS -!If SUB-MAIN

FUSE BOX

MIDGET FUSES

ISOLATION XFMR

120/120 V. 60Hz 1 t(1,3 __ _, SKVA)MIL-T-16108

CONNECT LAN~-RN TO

SAME PHASE AS LIGHTS

Figure 330-1-11. 1)'pical Wiring for Lighting Distribution System.

C/}

I

I

C/}

I

~ n = I

330-1.6.2.1 General. Submarines are normally sup plied with an ac and a de ship service lighting system.

The ac system provides for normal illumination, which consists primarily of fluorescent lighting fix tures and the 120-volt auxiliaries. The de system provides for a limited number of 50-watt, 120-volt incandescent lighting fixtures installed to produce a minimum of illumination for safe movement in oper ating areas, manned spaces, and access routes during periods when ac power is not available for the normal lighting system.

330-1.6.2.2 AC System. The ac system is supplied through 450/120-volt, 3-phase, 60-Hz transformer banks energized from the primary 450-volt (port and starboard) power systems. To insure continuity of illumination in all major compartments and oper ating stations either of two schemes are used:

1. the lighting transformer banks are fed through automatic bus transfer switches for automat ic restoration of power from the alternate system, or

2. the power supply to the lighting fixtures in each compartment is divided between feeders that derive power from port and starboard lighting trans former banks.