Market Forge Industries ST-6E Principles Of Operation, Fill/Cold Water Inlet, Steam Generation

PRINCIPLES OF OPERATION

GENERAL:

The Steam-Tech represents the latest in counter top steam technology, designed to apply the benefits of steam cooking to today’s health-conscious menus. A “close- coupled” steam generator system gives quick start-ups and efficient steam transfer to the cooking compartment, without the use of fans or expensive blower motors. In tests for energy efficiency and cooking times performed in accordance with ASTM standards, the Steam-Tech yielded impressive results over other similar counter top steamers. This section includes explanations of the steam generation, control, and drainage.

FILL/COLD WATER INLET:

When the power switch is pressed into the “on” position, a normally closed solenoid operated fill valve energizes and opens. The valve supplies cold water to the steam generator. At the same time, a normally open solenoid operated drain valve energizes and closes allowing the steam generator to fill with water (until the factory prede- termined level is reached).

The water level in the steam generator is sensed by high and low water sensor probes which are mounted on the front of the generator. The probes are connected to the electronic water level control board which, controls the opening and closing of the generator fill valve. When the water level has reached the high water level sensor probe, the electronic board cuts power to the generator fill valve. As steam is created and used up, the water level in the steam generator will drop. When the water level falls below the level of the high water level sensor rod, the electronic board will close the circuit to the gen- erator fill valve, allowing fresh water to enter the genera- tor until the water has risen back up to the level of the high water level sensor.

PREHEATING & STANDBY:

When the water level in the generator has risen up to the low water level sensor probe, the electronic water level control board closes a circuit which activates a re- lay. This relay supplies power to the heater. The heater will stay on at full power until the water temperature is sensed by a thermostatic switch mounted inside the steam generator, below the water level. The steam gen- erator will standby or idle at 195°F ready to make steam when it is called for.

STEAM GENERATION:

The Steam-Tech will not create steam until it is called for. Steam is called for by setting the timer/selector switch to either constant steam or timed steam. The cooking compartment door contains a magnet which activates a magnetic reed switch.. The red switch is located behind the front face of the unit, next to the cooking cavity open- ing. When the door is opened, the magnet and switch are separated. This opens the circuit to the heater, which will halt the creation of steam, but allow the heater to main- tain 195°F water temperature in the steam generator. When the unit is on, the heater will maintain 195°F wa- ter temperature in the steam generator, to insure quick

generation of steam when it is called for. When steam is called for, a circuit is closed which activates a relay. This relay closes the 208v, 240v, or 480v circuit which sup- plies power to the heater. The generator now begins to create steam. Steam passes from the steam generator directly through the side of the cooking compartment.

The fresh steam entering the cooking compartment forc- es the colder air to the bottom of the compartment and down the cooking compartment drain line. The cooking compartment drain line then has cooling water is sprayed into the drain flow. The cooling water is controlled by a thermostat located downstream of the cooling water nozzle. This configuration reduces the drain flow tem- perature to below 140°F. When the unit is steaming, the cooling water flow is on continuously. The cooling wa- ter comes “on” demand during other steamer functions such as generator blow-down (drain).

HOLD FEATURE (OPTION):

The Steam-Tech has a unique hold option which allows it operate as a holding cabinet at the end of a steaming cycle. The optional hold feature is activated by selecting the hold mode using the mode switch at the end of the steam cycle. While in the hold mode the generator will idle at 195°F, ready to create steam again.

When the thermostatic switch senses that the temper- ature of the cooking compartment has dropped below 170°F, it activates the steam generator. This will raise the temperature inside the cooking compartment. When the thermostatic switch senses that the temperature of the cooking compartment has risen to 175°F, it cuts pow- er to the generator. This system insures that the internal temperature of the cooking compartment will stay within a safe holding temperature range of above 150°F. The temperature of the cooking compartment can be moni- tored by observing the temperature gauge. The tem- perature gauge is located at the bottom of the the control panel.

DRAINAGE:

COOKING COMPARTMENT DRAINAGE:

The bottom of the cooking compartment is angled slight- ly towards the rear of the unit. This assures that any con- densate build-up or spills will be directed towards the drain hole which is located at the bottom center at the rear of the cooking compartment. Any liquid exiting the cooking compartment runs down the cooking compart- ment drain tube and into the drain line.

STEAM GENERATOR DRAINAGE:

Steam generator drainage is controlled by a normally open solenoid operated drain valve. When the power switch is pressed into the “on” position, power is sup- plied to the drain valve, which causes it to close allowing the generator to fill. When the power switch is pressed into the “off” position, power to the generator drain valve is cut, causing it to open. The steam generator will now automatically drain.

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