Emerson E2 operation manual Refrigeration Control, Defrost Control

11.3.1 Refrigeration Control

A Standard Circuit application may apply one of four different control methods to a case circuit: the Tempera- ture Monitor method, the Temperature Control method, and the Line Up(ESR)/Defrost method, and the Lineup(MFESR)/Defrost method.

11.3.1.1Temperature Monitor

The Temperature Monitor method does not control case temperature. The application will read and record case temperature inputs, but it will not make any attempt to control temperature. The application will still initiate and control defrost, cycle fans, and perform other neces- sary functions.

11.3.1.2Temperature Control

A Standard Circuit application using the Temperature Control method will pulse the refrigeration liquid line solenoid OPEN and CLOSED so as to control the case temperature to the user-defined setpoint. The application monitors up to six different temperature sensors in the cir- cuit and combines them into a single value that is com- pared to the setpoint.

11.3.1.3Line Up(ESR)/Defrost

In Line Up ESR, circuit temperature is controlled by an electronic evaporator pressure regulator (EEPR). The EEPR is controlled by a PID algorithm that steps the valve open from 0% to 100% based on how far away the circuit temperature is from the setpoint.

This strategy requires the use of the Echelon-based ESR8 stepper regulator output board, which has been dis- continued and replaced by the I/O Network-based Multi- Flex ESR.

11.3.1.4Line Up(MFESR)/Defrost

In Line Up MFESR, circuit temperature is controlled by an electronic evaporator pressure regulator (EEPR). The EEPR is controlled by a PID algorithm that steps the valve open from 0% to 100% based on how far away the circuit temperature is from the setpoint.

This new strategy requires the use of the I/O Network- based MultiFlex ESR and should not be used with the Echelon-based MultiFlex ESR.

11.3.2 Defrost Control

Defrost cycles in a Standard Circuit application may be initiated in either of three ways: by schedule (at specific times of the day, programmed by the user), by external trigger (a user-initiated signal such as a switch or button), or by manual command (initiated on the E2 front panel by the user).

11.3.2.1Defrost States

The defrost cycle for a Standard Circuit application consists of three steps.

1.Pump Down (Elec & Hot Gas only) - The defrost cycle begins with this step immediately after the refrigeration solenoid is turned OFF. During the Pump Down phase, the application waits for a user-specific amount of time to elapse before turning on the defrost heat. This allows refriger- ant in the evaporator to be evacuated before defrost heat is activated. The compressor(s) remain ON during Pump Down.

2.Defrost - During the defrost phase, refrigeration is disabled. If using electric defrost heaters will be ON. If using hot gas, heated refrigerant will be pumped through the coil. This phase will con- tinue until the defrost is terminated (see Section 11.3.2.3 for information on how defrost is termi- nated).

3.Run-Off (Elec & Hot Gas only)- After defrost heat is deactivated, the application waits for the Run-Off time to pass before re-entering refrigera- tion mode. This allows melted frost on the evapo- rator to drain from the coil so that it will not re- freeze when refrigeration begins again. After the user-specifiedRun-Off time has passed, the defrost cycle has ended.

11.3.2.2Defrost Types

There are many different ways used to defrost a refrig- erated case. A Standard Circuit application is capable of employing five different strategies to accommodate five different types of defrost.

Timed and Reverse Air

Timed defrost and Reverse Air defrost are two differ- ent defrost strategies, but both are alike in the way they are controlled by a Standard Circuit application. In both defrost types, no heat is applied to the evaporator. The application simply turns the refrigeration solenoid OFF for the duration of the defrost cycle.

When these defrost types are used, Pump Down and Run-Off times are not necessary; therefore, they will not be part of the defrost cycle.

Hot Gas and Reversed Cycle Hot Gas

Hot Gas and Reversed Cycle Hot Gas require the use of hot gas from the refrigeration lines. During these types of defrost, the application will open the circuit’s liquid line solenoid AND will send a command to the refrigeration rack to open the Master Liquid Line Solenoid. As a result, heated refrigerant will be pumped through the evaporator coil.

11-6 • E2 RX/BX/CX I&O Manual 026-1614 Rev 4 5-JAN-2013