Middleby Marshall PS536ES Section Operation, A. Door Safety Switch, B. Blower Switch

SECTION 3

OPERATION

II.COMPONENT INFORMATION AND LOCATION (Figures 3-1 and 3-2)

A. Door Safety Switch

The Door Safety Switch is located at the lower left side of control panel opening. Opening the control panel door permits this switch to open, disconnecting power to all electrical controls.

CAUTION

Do NOT touch the wires going to this safety switch. Current is always present.

B. Blower Switch

The blower switch has two positions. The switch must be “ON” or “I” for the burner to come on and permit the oven to warm up. The fan circulates the air throughout the oven and must stay on during baking and during the cool down cycle above 200°F (93°C) to prevent blower bearing damage. To protect the blower motor and bearings a thermostatic override is built into the oven. If the tempera- ture inside the oven is over 180°F (82°C) the main blower will continue to run after the blower switch is turned to the “OFF” or “O” position.

An air pressure switch monitors the air flow from the blower, acting as a safety interlock for the burner. The

burner cannot light, if the air switch does not sense air flow off the main blower fan.

C. Heat Switch

Turning the HEAT switch to “ON” or“I” will initially set up the oven purge circuit. After approximately 30 seconds, the burner lights. After the burner is lit, a flame sensor sends a signal to the ignition module to stop the spark. The burner will run unless the flame sensor does not detect a flame or the heat switch is turned to the “OFF” or “O” position.

The HEAT switch is in series with the burner blower motor centrifugal switch, the high-temperature safety switch, and the blower fan air pressure switch. All three safety switches must be closed for gas to flow and the burner to light.

D. Temperature Controller

The temperature controller is a solid-state, on/off type to maintain the operator-set temperature. The temperature controller continuously monitors the oven temperature and turns on the modulating solenoid valve in a gas-heated oven. The heat is on for the time required to maintain a constant oven temperature.

The temperature controller contains a low-limit switch which allows the oven to cool down to 200°F (93°C) before shutting off the blower. A high-limit indication (ALM 1) will appear on the display if the oven reaches 650°F (343°C).

Figure 3-2. Interior View of Machinery Compartment and Control Console

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