ELECTRICAL AND ELECTRONIC SYSTEMS 61 



from the benthic lab and other exterior equipment. The bottom end of the pipe shall extend to 

 the same level as the bottom of the entrance trunk. The top end of the pipe shall be approxi- 

 mately three feet above the deck. A removable watertight cover shall be provided. 



REQUIREMENTS FOR ELECTRICAL EQUIPMENT 



General 



The electrical equipment shall be standard Navy items or commercial items best suited 

 for the application or which can be modified to suit the application. 



Electric Motor and Controllers 



The electric motors and controllers selected shall be in general accordance with Section 

 9630-1 of General Specifications for Ships of the U.S. Navy. Commutator type motors shall not 

 be used. Insofar as practical, motors selected shall be three-phase. The necessary manual or 

 magnetic controllers shall be provided for each motor. Thermal overload protection shall be 

 provided for each motor, including those furnished as part of a complete unit, either from the 

 Navy supply system or commercial sources. The thermal protection shall be designed to pre- 

 vent the motor from becoming overheated and contaminating the atmosphere. Fan motors 

 should be oversized or have the pitch of the fan modified to compensate for the denser atmos- 

 phere. Precautions should be exercised in the modification of the pitch of the fan blade of 

 equipment cooling fans. 



Water Heater 



The water heater shall be a 50 to 52 gallon capacity, quick-recovery type. The preferred 

 voltage is 440 volts, three-phase; however, a lower voltage rating may be used if a 440-volt 

 unit is not available. The insulation shall be fiber glass or rock wool. 



Refrigerator 



The refrigerator shall have a net capacity of not less than 10 cu ft and not more than 14 

 cu ft, and shall be divided into a freezer compartment and a refrigerator compartment. The 

 freezer capacity shall not be more than 5 cu ft net. The refrigerator shall be capable of per- 

 forming its normal function in an 80 percent helium atmosphere at approximately 110 psig. 



Cook Top 



The cook top shall consist of four electric heating units of approximately 1250 watts each. 

 Each unit shall have a heat-control switch. Thermostatically controlled units are not required. 

 The preferred voltage is 440 volts, three-phase; however, other voltages may be used if 440- 

 volt units are not readily available. 



Radiant Heaters 



The four radiant heaters for the entrance area, as shown on MDL Dwg. 8656, shall be at 

 least 1250 watts each. Each heater shall be controlled by a double-pole switch or the circuit 

 breaker in the distribution panel. 



NOTE: Nutone Model 9290 was used in Sealab I and performed satisfactorily. 



