Section 4 Principles Of Operation; General; Plumbing Circuits; Steam Inlet Line - Market Forge Industries ST-10 Owner's Manual

SECTION 4. PRINCIPLES OF OPERATION

4.1 GENERAL

The ST-10 Pressureless Steam Cooker consists
of two identical cooking compartments, one above
the other, in a single cabinet assembly. Each com-
partment is fitted with independent electrically
controlled steam circuits and spring-loaded, self-
sealing doors with slam action latches. Compart-
ments 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.

4.2 PLUMBING CIRCUITS

The plumbing circuits consist of the piping, steam
solenoid valves, orifice, drain, and cold water con-
denser required to provide controlled steam appli-
cation to the cooking compartments. A simplified
diagram of these circuits is shown in Figure 4-1.
NOTE: Figure 4-1 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 direct-
ly into a steam boiler or direct-connected steam
plumbing enclosed within the base cabinet on
which the cooker is mounted. The boiler (or di-
rect-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.

4.2.1 STEAM INLET LINE

A steam supply line is plumbed from the boiler out-
put (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 com-
partment remains closed to prevent steam from
entering. During operation, the appropriate inlet
solenoid valve is opened by activation of the con-
trol 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.

4.2.2 STEAM EXHAUST AND DRAIN LINES

Perforated strainers at the drain line openings in-
side each compartment allow only steam, conden-
sation, 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.

4.2.3 STEAM EXHAUST CONDENSING SYSTEM

The steam condensing system consists of the
identical, two-position, normally closed cold wa-
ter solenoid valves, with outlet sides connected
into the exhaust plumbing for each cooking com-
partment. A spray nozzle directs cold water about
the inside of the drain lines to increase cold water
contact with exhausted steam. Valve inlet sides
are connected remote from the supply line of the
steam boiler (or direct-connected steam plumb-
ing). The valves respond to a thermostatic switch
located inside the compartment. When the timer
starts the cold water solenoids will energize.

4.3 ELECTRICAL CIRCUITS

The electrical circuits of the cooker control the
power to activate timer motors and energize so-
lenoid-operated valves and circuits, which in turn
control application of steam to the cooking com-
partment and condensation of steam from the ex-
haust line. The cooker operates on 120V, 2 amp,
60Hz electrical service connected to all circuits
from the circuits of the steam boiler (or direct-
connected steam controls) contained within the
cabinet on which the cooker is mounted. Power is
supplied to the control circuit at all times when the
shut-off device for the unit (supplied by the user)
is in the ON position.

4.3.1 CONTROL CIRCUIT COMPONENTS

A brief description of the electrical circuit elements
follows (see next page).
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