K. Modulating Gas Valve (if so equipped)

Ovens that use a PID (modulated) gas regulation system are equipped with a modulating gas valve instead of a sole- noid valve. The valve is located between the combination gas control valve and the burner.

In response to the millivolt signal from the thermocouple, the Digital Temperature Controller sends a 4-20mA signal to an amplifer board. The board, in turn, passes on a 0- 20VDC signal to the modulating valve itself. The valve opens or closes proportionally to the signal from the amplifier board, allowing any setting from 0-100% gas flow.

When the oven is switched on, gas demand is at its peak and the valve is fully open, permitting 100% gas flow. As the oven’s temperature approaches the set point, the valve slowly begins to close, restricting gas flow to the 35-60% range. After the oven is fully preheated, the gas flow usu- ally stabilizes at about 30%. The actual oven temperature can remain constant, with NO temperature swing, because the valve is adjusted constantly according to the demand.

Modulating valves are used on all PS360EWB, PS555, and PS570G gas ovens. They are also used on PS200 ovens produced 4/02 or later and PS570S ovens produced 9/00 or later.

The Model PS360EWB oven uses a Maxitrol M520 modu- lating valve with a 3/4” gas line, P/N 32570. All other Middleby oven models equipped with a modulating valve use the Maxitrol M420 valve with a 1/2” gas line, P/N 41647.

SECTION 3 - SERVICING COMPONENTS

The modulating valve features a bypass adjustment screw, shown in Figure 71. For all ovens except the PS536, the screw should ALWAYS remain fully closed; no adjustment is necessary. The screw is pre-set to the fully-closed posi- tion from the factory. If the screw is adjusted to any setting other than fully-closed, the oven may not be able to main- tain the set point temperature.

IMPORTANT: For proper functioning of the modu- lating valve, the temperature controller MUST be set to the PID operating mode. Refer to Tempera- ture Controller on Page 31.

L.Amplifier Board (ovens with a modulating gas valve only)

Ovens equipped with a modulating gas valve have an ampli- fier board mounted inside the machinery compartment.

In response to the millivolt signal from the thermocouple, the Digital Temperature Controller sends a 4-20mA signal to the amplifer board. The board, in turn, passes on a 0- 20VDC signal to the modulating valve. The valve opens or closes proportionally to the signal from the amplifier board, allowing any setting from 0-100% gas flow.

All Middleby oven models equipped with a modulating valve use amplifier board P/N 31651.

Figure 71 - Modulating Gas System

 

Digital Temperature

To transformer

Controller

24VAC input

MUST BE SET TO PID

OPERATING MODE

 

orange/white orange

white +

 

blue

To thermocouple

blue/white

red -

 

 

 

purple/white

 

bypass adjustment

purple

 

screw (under cap)

 

 

 

MUST BE FULLY

Amplifier Board

Modulating Valve

CLOSED

 

 

To amplifier board terminal 6 To amplifier board terminal 5

purple

PS360EWB

 

with Controller 32571

purple/white

only

97

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Image 98
Middleby Marshall PS200, PS570, PS360, PS555, PS220, PS224 PS310 manual Modulating Gas Valve if so equipped
Page 97 Page 99

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.
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