VIII. AIR PRESSURE SAFETY SWITCH (PS200-SERIES, PS555/570-SERIES, PS360EWB, PS360WB70)

Middleby ovens have a safety feature that prevents the burner/heating elements from activating if the blower(s) are not in operation. On PS200-series ovens and PS555/570- series ovens, this feature is controlled by a separate air pressure switch that reads air flow from the blower. One switch is used for each blower (1 for the PS200-series, 2 for the PS555/570 series).

These ovens cannot use a centrifugal switch on the motor because they use an indirect, belted drive system. If a belt fails, it is possible for the motor to operate normally while the blower itself is stopped.

In addition, gas ovens with a line-voltage burner blower mo- tor use an identical air switch to check that the burner blower motor is operating before burner activation. These ovens include the PS360EWB, PS360WB70, PS555, PS555G, and PS570G, as well as PS200-series ovens equipped with the modulating gas system. This additional air switch is not necessary on ovens with a 120V burner blower motor

SECTION 3 - SERVICING COMPONENTS

because of the presence of a centrifugal air switch inside the motor housing (see Section VII, Burner Blower Motor Centrifugal Safety Switch, on the previous page).

The switch is an assembly that includes a normally-open microswitch and a diaphragm. When the blower is at speed, pressure is applied to the diaphragm which in turn closes the microswitch. This completes the heat circuit, allowing the burner/heating elements to activate.

If a blower is not operating, the microswitch receives no signal from the diaphragm and cannot close, preventing burner/heating element activation.

A. Part Number Reference - Air Switches

Middleby has used four different types of air switches for these applications. See Figure 50.

When replacing one of these switches, note that the “cur- rent” Yamatake-Honeywell air switch (#4 below) cannot be used as an upgrade for an older switch. If you are replacing Switches #1, #2 or #3 as shown in Figure 50, you should use the Service Kits described for Switch #2.

Figure 50 - Air pressure safety switch models

1.

 

2.

 

Original-style round air switch

Dungs square-case air switch with dial adjustment

Replace with #2

Replace with same

 

 

 

Positive

 

 

 

 

pressure

Adjustment dial

 

 

 

 

(in. W.C. or

 

 

 

 

mbar)

 

Adjustment

 

 

screw

 

 

 

 

 

Positive

 

 

 

 

pressure

 

 

 

 

Negative

 

 

 

 

pressure

 

3.

 

4.

 

Dungs square-case “replacement” air switch with screw adjustment

Yamatake-Honeywell air switch, non-adjustable

Replace with #2

Replace with same

 

Adjustment

 

 

screw

 

 

 

 

 

Adjustment

 

 

 

 

screw

 

 

 

 

(fixed at proper

 

Positive

setting - cannot

 

be adjusted)

 

pressure

 

 

 

Negative

 

 

pressure

 

 

 

 

 

Positive

Negative

 

 

 

pressure

pressure

81

Page 81 Page 83
Page 82
Image 82
Middleby Marshall PS220, PS570, PS360, PS200, PS555, PS224 PS310 manual Air pressure safety switch models
Page 81 Page 83

PS224 PS310, PS220, PS555, PS200, PS360 specifications

The Middleby Marshall PS555 is a standout commercial pizza oven renowned for its performance, efficiency, and advanced technologies. Designed with the modern pizzeria in mind, the PS555 delivers exceptional cooking results while maximizing energy efficiency and throughput.

One of the key features of the PS555 is its innovative cooking technology, which incorporates both convection and radiant heat. This unique combination ensures that pizzas are cooked evenly and quickly, achieving a perfectly crispy crust and evenly melted cheese every time. The oven’s high-speed air impingement system accelerates cooking times, allowing pizzerias to serve more customers in less time without compromising quality.

The PS555 is designed with a spacious cooking chamber that can accommodate multiple pizzas simultaneously. With its ability to fit pizzas up to 18 inches in diameter, the oven is ideal for establishments with high demand. Additionally, the adjustable conveyor speed allows operators to customize the cooking time based on their specific menu items, enhancing versatility and productivity.

Energy efficiency is a hallmark of the Middleby Marshall PS555. The oven utilizes advanced insulation materials to minimize heat loss, ensuring that it operates at optimal temperatures while consuming less energy. This efficiency not only reduces operating costs but also contributes to a more sustainable kitchen environment.

User-friendly controls make it simple for operators to manage the cooking process. The PS555 features digital controls with programmable settings, enabling quick adjustments to temperature and cooking time. This ensures consistent quality across different shifts and helps maintain product standards while simplifying staff training.

Durability is another defining characteristic of the PS555. Built with high-quality materials, the oven is designed for heavy use in busy commercial kitchens. Its stainless steel construction ensures resistance to wear and tear, making it a worthwhile investment for any pizzeria.

In summary, the Middleby Marshall PS555 pizza oven is a high-performance piece of equipment that combines advanced cooking technologies, efficiency, and durability. Its ability to deliver consistently excellent results while streamlining operations makes it an essential asset for any pizza business aiming to enhance its productivity and customer satisfaction.
Top Page Image Contents