1. Low pump current (pump cavitating) 



2. Suit water temperature too high [>110 F (43 C) ] 



3. Cell temperature below 140 F (60°C) 



The control panel also contains two off /on switches — a diver-operated 

 one for suit circulation, and another one for activation of the elec- 

 trolyte pump and electronics. Thermistors sense the cell and suit-water 

 temperatures. The electronic components are housed in a watertight 

 pressure housing attached to the pump motors. The electronic/electrical 

 control circuit is shown in Figure 28. 



Power for operating the pump motors and electronics is supplied 

 from three parallel sets of four D-size lithium primary cells connected 

 in series to provide 10.5 volts and 17 A-hr. The batteries are contained 

 in watertight housings (Figure 29) that are mounted external to the 

 heater case. 



Safety Considerations 



Safety is an inherent characteristic of the heat source; the reaction 

 produces no toxic substances, and the high reaction temperatures that 

 might result from overheating are limited to the local boiling point of 

 seawater. If the temperature of the electrolyte exceeds 140°F, which 

 could occur if the diver load were to be less than the anticipated 1,000 

 watts, the electrolyte/suit-water heat exchanger will transfer the 

 additional heat to the diver circuit and elevate the suit-water tempera- 

 ture. This immediately activates the temperature control valve, which 

 causes the hot water to be dumped and cold water to be taken in at the 

 circulation pump. The incoming cold water creates a load that exceeds 

 the capacity of the cell, thereby causing a subsequent reduction in 

 the electrolyte temperature. As an additional thermal safety device, if 

 an excessive electrolyte temperature were to occur, the extra hydrogen 

 produced would cause a higher internal case pressure and subsequent 

 dewatering of the cell. 



By adjusting the temperature control valve, the diver can automa- 

 tically control the temperature of his suit water at any point within 

 the 100°F-to-110°F (38o-to-43°C) range. If the diver sets the valve 

 below the automatic control range, he can dump any portion or virtually 

 all of the heater output and circulate cool water through the suit. If 

 the temperature control valve should fail, the diver could remain 

 comfortable by periodically connecting and disconnecting couplings in 

 the suit-water hoses. The only possible hazard from the heater is the 

 accumulation of an explosive concentration of hydrogen if the heater is 

 operated in a closed space for a prolonged period of time. 



15 



3 ■ 



I 



