Emerson E2 Hardware Overview, Learning Mode, Circuit Load Analysis, Control/Cycles Parameter

cycled ON or OFF. Unlike the Suction Group application, which uses a PID percentage to determine how many stages to turn ON or OFF, the Enhanced Suction Group keeps historical data of the effects each compressor stage has on the suction pressure or temperature, and analyzes that data to determine which stages to cycle.

The Enhanced Suction Group application is designed to balance tight control of suction pressure with economic management of compressor cycling to reduce power usage and compressor wear.

11.1.3.1Learning Mode

When an Enhanced Suction Group application runs for the first time, it undergoes a “Learning Mode” period to collect data on the compressor stages. During Learning Mode, the Enhanced Suction Group will control suction pressure, but it will purposely cycle the compressor stages in different combinations to measure the effect they have on the suction input value.

The Learning Mode lasts for several minutes. After Learning Mode ends, the Enhanced Suction Group will require up to 24 hours of operation before compressor cycling is operating at maximum efficiency. If compressor cycling seems too frequent after 24 hours of operation, you may reduce compressor cycling by changing the Con- trol/Cycles parameter (see Section 11.1.3.3, The Control/ Cycles Parameter).

11.1.3.2Circuit Load Analysis

Unlike the standard Suction Group algorithm, the Enhanced Suction Group includes Circuit Setup where you associate all circuits connected to the suction group. Once the circuits are set up, the suction group will use the circuit states to help determine current loads on the suction group. For example, when one or more circuits go into defrost, the Enhanced Suction Group determines that there is less of a load on the suction group than if all circuits were in refrigeration. With the appropriate circuits associ- ated, the Enhanced Suction Group tailors its capacity to meet the load. Over time, the Enhanced Suction Group will build and store a profile for all the different combina- tions of circuit states encountered in the algorithm.

11.1.3.3The Control/Cycles Parameter

Unlike the standard Suction Group, which used PID constants as a means of optimizing suction control and had limited features for controlling compressor cycle counts, the Enhanced Suction Group has one parameter with five preset settings to allow users to alter suction control per- formance or compressor cycling frequency.

The default setting, “Moderate Control,” seeks to bal- ance good suction pressure control with efficient cycling. If tighter control is needed, setting the field to “Tight Con-

trol” or “Tightest Control” will increase the application’s reaction to suction changes, resulting in tighter control (usually at the expense of more frequent cycling). If fewer compressor cycles are desired, setting the field to “Less Cycling” or “Least Cycling” will decrease the number of cycles but also increase the amount of fluctuation in the suction pressure.

11.1.3.4Variable-Speed, Digital Scroll, and Digital Discus Compressor Support

The Enhanced Suction Group supports variable-speed compressors similar to the Suction Group application. When a variable-speed compressor is present, it is the first compressor stage ON and the last stage OFF, and its capacity is varied to attempt to correct small fluctuations in the suction pressure or temperature.

In addition, the Enhanced Suction Group application supports use of one or multiple Copeland Digital Scroll or Digital Discus compressors for use as a variable-capacity compressor. With several Digital Scroll or Digital Discus compressors, the Enhanced Suction Group will modulate one of those compressors at a time to control suction pres- sure. As compressor capacity is added or removed, the Enhanced Suction Group may modulate another Digital Scroll compressor to distribute compressor resources and solenoid wear.

The operating capacities of the Copeland Digital Scroll and Copeland Digital Discus compressors are determined in the same way as a variable-speed compressor, except the Copeland Digital Scroll and Copeland Digital Discus controlled by pulse-width modulation (PWM).

11.1.3.5Floating Suction Control

Floating suction control in the Enhanced Suction Group behaves identically to the way it works in the Suc- tion Group application. Refer to Section 11.1.2.3, Floating Setpoint Control.

11.1.4 Hardware Overview

An overview of the input and output devices that make up a Suction Group is shown in Figure 11-1.These devices should be wired to input and output boards in the manner outlined in Table 11-1and Table 11-2.

11-2 • E2 RX/BX/CX I&O Manual 026-1610 Rev 13 14-SEP-2011