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PRINCIPLES OF OPERATION
GENERAL
The ST-24 Pressureless Steam Cooker consists of two identical cooking compartments, one above the
other, in a single cabinet assembly. Each compartment is fitted with independent electrically controlled
steam circuits and spring-loaded, self-sealing doors with slam action latches. Compartments can be used
separately or simultaneously for either constant steam or 60-minute timing. The principles of operation
in this section include an explanation of steam, steam condensing, and electrical circuits and their
functioning.
PLUMBING CIRCUITS
The plumbing circuits consist of the piping, steam solenoid valves, orifice, drain, and cold water
condenser required to provide controlled steam application to the cooking compartments. A simplified
diagram of these circuits is shown in Figure 3 on page 15.
NOTE: Figure 3 on page 15 is strictly a pictorial schematic diagram and is not intended to show the
actual configuration of the plumbing. All components are shown in correct relationship with each other.
However, the diagram does not show their actual locations or position within the cooker.
As shown in the diagram, steam inlet and exhaust connections are connected at the factory directly into
a steam boiler or direct-connected steam plumbing enclosed within the base cabinet on which the
cooker is mounted. The boiler (or direct-connected steam control system) is equipped to supply
constant, regulated steam at 14–15 PSI. Steam exhaust, having been reduced to water by the cold water
condenser, is directed into the boiler (or direct-connected steam control) drain system.
Steam inlet lines for compartments are equipped with normally closed solenoid valves operated by the
electrical control circuits. The inlet valves are opened whenever the compartment control circuit is
activated by use of the 60-minute timers.
Steam Inlet Line
A steam supply line is plumbed from the boiler output (or direct-connected steam control) to a 1/2-inch
barb fitting connected to the input sides of both steam inlet solenoid valves. When a cooking
compartment is not in use, the valve for the compartment remains closed to prevent steam from
entering. During operation, the appropriate inlet solenoid valve is opened by activation of the control
circuit. Steam is projected onto the surface of pans of food loaded into the compartment by an orifice
located inside the compartment. Steam continues to flow through the compartment in this manner until
the control circuit closes the solenoid valve.
Steam Exhaust and Drain Lines
Perforated strainers at the drain line openings inside each compartment allow only steam,
condensation, and liquid cooking drainage to enter. Prior to discharge into the boiler drain system,
steam is converted to water by the cold water condensing systems for each compartment.
Steam Exhaust Condensing System
The steam condensing system consists of the identical, two-position, normally closed cold water
solenoid valves, with outlet sides connected into the exhaust plumbing for each cooking compartment.
A spray nozzle directs cold water about the inside of the drain lines to increase cold water contact with
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