Theory Of Operation - Genie Z-25/8 Service Manual

First Edition • Third Printing
Power Source
The Genie Z-20/8N & Genie Z-20/8 &
Genie Z-25/8 machines are powered by eight six-
volt (255 AH) batteries. Each 4-battery pack, is
wired in series/parallel to produce 24V DC. The
two battery packs are then wired in series to
produce 48V DC. The drive system uses 48V DC
and the control system uses 24V DC.
Hydraulic System
All machine functions are performed by the
hydraulic system. The hydraulic system is
powered by a two-section pressure balanced gear
pump. The lift and steer functions use pump #2.
The drive function utilizes pump #1 combined with
pump #2 for a total of 12 cc's displacement per
revolution. To protect from over-pressurization of
the hydraulic system, the pumps are provided with
a pressure relief valve set at 3500 psi (241 bar).
Activating a machine function is accomplished by
actuating or moving a toggle switch and/or control
handle, which sends voltage to the appropriate
directional control valve. The directional control
valve determines which direction the hydraulic fluid
will travel. The amount of hydraulic fluid volume is
determined by the proportional valve input voltage
from the boom function speed controller at the
platform controls. The boom lift cylinder and the jib
boom lift cylinder incorporate counterbalance
valves to prevent movement in the event of a
hydraulic line failure.
Part No. 41314 Genie Z-20/8N & Genie Z-20/8 & Genie Z-25/8

Theory of Operation

Electrical System
Drive speed limit switch
The drive speed limit switch, located in the boom
storage area, is used to restrict drive speed when
the boom is raised. An improperly functioning drive
speed limit switch will allow the boom to raise
and/or drive into an unsafe position.
Machine Controls
The Genie Z-20/8N & Genie Z-20/8 &
Genie Z-25/8 machines are equipped with
operational controls which are found in two
locations: the ground controls, and platform
controls. All lift and drive functions are available at
the platform controls. Only boom functions are
available at the ground controls. Moving a boom
toggle switch in the direction indicated on the
control panel decal will indicate which boom
function will operate and its direction of travel.
The platform controls incorporates a boom
function speed controller which, by varying the
position of the controller, controls the amount of
voltage sent to the proportional valve. This
determines the speed at which the function will
operate.
The drive controller (joystick) is fitted with a
potentiometer that communicates the joystick
position with the motor controller. A thumb rocker
switch on the top of the joystick is used for
steering.
Washing electronic components is not suggested.
Instead, use compressed air to remove debris
from these components.
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