54 ELECTRICAL AND ELECTRONIC SYSTEMS 



conveniently located switches. Switches shall be Symbol 780.1 listed in NavShips 250-560-3. 

 (Note: 50 and 75-watt bulbs may be used in Fixture No. 370, since the He atmosphere is a 

 better heat conductor than air.) 



Low -Level Lighting — A red lighting fijrture for low-level lighting shall be installed in the 

 berthing space. The fixture shall be selected from NavShips 250-560-3. 



Berth Lights — Incandescent berth lights shall be installed for each berth. The fixture 

 shall be a suitable commercial type which encloses the bulb. The fixtures may connect to a 

 convenience outlet or be permanently connected. Each fixture shall have an off-on switch. 



Hand Lanterns — Hand lanterns without relay, Symbol 100.2 of NavShips 250-560-3, shall 

 be installed throughout the interior of Sealab n to provide a limited amount of illumination in 

 the event of a power failure. The minimum number of installed lanterns shall be four, and they 

 shall be located to illuminate the following areas: (a) main entrance trunk (2), (b) electrical 

 power control area, and (c) the berthing area. 



Exterior Lighting — The exterior lighting shall consist of six semiportable lighting fix- 

 tures. The fixtures shall be Standard Navy diving lights. Symbol 313, as shown on BuShips 

 Dwg. 9000, S6405-7445. Suitable mounting brackets shall be provided at locations shown on 

 MDL Dwg. 8656 to permit the lights to be installed after Sealab is on the ocean floor, or to 

 permit movement to temporary locations. The lights located on the port and starboard side of 

 lab space shall have 150 ft of cable outside the Sealab. The remaining four lights shall have 

 50 ft of cable outside the Sealab. Suitable stowage shall be provided for the excess cable when 

 the lights are mounted on Sealab. Some convenient means shall be provided to permit the lights 

 to be installed after Sealab is on the ocean floor. Connectors capable of being plugged or un- 

 plugged underwater may be used. Cables shall not be run through the entrance trunk. 



A switch shall be provided inside Sealab for each exterior light. Each switch shall be 

 clearly labeled. If underwater receptacles are used, switches shall be Symbol 780.1 of NavShips 

 250-560-3. If an interlocking switch and receptacle is used, it shall be Symbol 900.1 of NavShips 

 250-560-3. 



Equipment and Material 



The equipment and material for the electrical system shall be as specified herein. Mis- 

 cellaneous items not specifically listed shall be Navy or commercial items best suited for the 

 application. 



Transformers — The transformers shall be dry. Naval Shipboard type in accordance with 

 MIL-T-15108. Three 450-120 volt transformers of suitable size connected delta-delta, or 

 delta-wye, shall be used to supply power for the lower voltage single- and three-phase loads. 

 A 6-kva transformer bank or transformer shall be provided to supply 240-120 single-phase 

 power for the electrical cook top if the unit will not operate on 440-volt three-phase or the 

 lower voltage of the main transformer bank. 



All transformers shall be enclosed in a gastight compartment to prevent contamination of 

 the Sealab atmosphere in case of overheating. Stuffing tubes shall be used for all cables enter- 

 ing the compartment. The compartment should be built so that one side is formed by the shell 

 of the vessel. The shell side shall not be insulated. A pressure-equalizing valve shall be pro- 

 vided to equalize the pressure of the interior of the compartment during pressurizing operations. 

 A temperature -indicating device shall be provided to monitor the inside temperature of the 

 compartment near the center transformer. A circulating fan shall be installed in the trans- 

 former compartment to provide forced circulation of the compartment atmosphere through the 

 transformers in case of a temperature buildup. The fan may be manually or automatically 

 controlled. 



Transfer Panel and 450-Volt 3-Phase Distribution Panel — The incoming power -transfer 

 panel and 450-volt 3-phase distribution panel shall be similar to NWT Type panel. Symbol 2531, 

 listed in NavShips 250-560-3. The number of circuits required shall be determined by the 



