Hydraulic Control Panel

Question 1

SYSTEM HYDRAULIC PUMP LOW PRESSURE lights

Answer 1

• indicates low pump output pressure from ENG 1 or ELEC 2 pump
• ENG LOW PRESSURE lights inhibited with fire handle pulled
  fluid flow to the associated engine driven pump is shut off

Question 2

ENGINE DRIVEN PUMP switches

Answer 2

ON

• the depressurization solenoid valve is not energized; this allows pump pressure to enter the hydraulic system
• normally keep this switch in the ON position to prolong solenoid life
• loss of normal electrical power to the control circuit does not affect the output of the pumps

OFF

• energizes the depressurization valve to block pump output
• re-routes hydraulic fluid to the case drain line and back to the reservoir
• this does not stop the rotation of the pump or the internal pressure in the pump
• the pump continues to be lubricated
• not so if you pull the fire handle which closes the EDP supply SOV to block fluid flow to the pump - there is no case drain fluid in this condition

Question 3

ELECTRIC MOTOR PUMP switches

Answer 3

ON

- provides electrical power to corresponding electric motor driven pump

Question 4

Electric Driven Motor Pump Overheat lights

Answer 4

• hydraulic fluid is used to cool and lubricate the corresponding EMDP
• a temperature switch in the case drain line downstream of the pump monitors the EMDP case drain fluid for overheat
• the OVERHEAT light illuminates when the case drain fluid temp increases to more than normal (> 225F)
• there is also a temperature switch in the EMDP motor that will cause the OVERHEAT light to illuminate if the motor reaches a temperature more than normal