SECTION 4. PRINCIPLES OF OPERATION
Figure 4-1 Pictorial Diagram, Steam and Water Circuits
4.3.1.1 60 MINUTE TIMER/CONSTANT STEAM
The timer contains a 120-volt AC synchronous
motor that drives a timing dial through a gear re-
duction and clutch mechanism. The timer dial is
manually set for any interval of operation from 0
to 60 minutes or constant steam as read on the
calibrated dial face. The manual rotation of the
dial moves the common element (1) of the timer
switch from the neutral (OFF) position to contact
(3), which connects with the steam inlet solenoid
valve operating circuit.
The cooker is placed into automatic operation
with the setting of the timer dial. Its timing cycle,
however, is automatically delayed by a thermo-
static switch, which assures operating tempera-
ture is achieved before the timer motor begins to
“time out.” When the timer motor has operated
for the preset duration, the common element is
transferred to contact (4), returning the inlet sole-
noid valve to the closed position and energizing
the buzzer. Contact to the buzzer circuit remains
closed until the dial is manually turned to the OFF
position, returning the common element (1) of the
timer switch to the neutral position.
4.3.1.2 INDICATOR LIGHTS
An indicator light is included for both compart-
ments. The light remains on (red) at all times
when the coinciding timer dial is set and the door
interlock switch is closed. The light turns off at the
end of the timed cooking duration.
4.3.1.3 BUZZER
The buzzer is an alarm device that operates by
oscillation of a striker against the core of an elec-
tromagnet. When the 60-minute timer dials reach
the “0-Minute” position, the buzzer coil is ener-
gized to sound the buzzer. Movement of the timer
dial to the OFF position opens the contact to the
buzzer coil to shut it off.
4.3.1.4 DOOR INTERLOCK SWITCH
The interlock switch is a single-pole proximity
switch with normally open contacts. The switch is
operated by the proximity of a magnet within the
door. When the door is open, the switch contacts
remain in the open position. When the door is
closed and securely latched in place, the magnet
is near the switch to close the contacts. Connect-
ed between the operating contact (3) of the timers
and the steam inlet solenoid valve, the door switch
acts as a protective device to interrupt valve op-
eration unless the door is closed.
4.3.1.5 THERMOSTATIC SWITCH
The thermostatically operated switch is a two-po-
sition, normally open switch mounted on the cook-
ing compartment. The switch functions to activate
the cold water solenoid valves of the steam con-
densing system and to delay timer motor opera-
tion until the compartment temperature reaches
195°F, thus assuring that cooking temperature ex-
ists throughout the timed duration.
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