Conventional controls, including the most sophisticated Building Management Systems (BMS') and state-of-the-art refrigeration controls, operate only on reaching pre-programmed fixed (static) values to switch compressors off and on or adjust capacity. When the measured medium is within the dead band the BMS and controllers remain idle until a specific set value is reached. They do nothing to dynamically measure the heat load and adjust the control differential in proportion to the cooling demand or to dynamically control the cycle rate of the compressors. In most cases they do not perform predictive analyses as the ESM™ does.

The ESM™ microcomputer records the absolute switching values of the primary controller and also measures the 'rate of change' of both the rise and fall of temperatures or pressure during the operating cycle of the compressors. With this data the ESM™ computes a reference heat load to match the cooling capacity and then calculates variable operating parameters (we call this Load Proportional Differential Adjustment or LPDA). LPDA minimizes compressor operation within the absolute switching values, with a resultant reduction in refrigeration and air conditioning compressor run time, reduced electricity consumption (Kwh) and maximum demand (Kw/KVA) as well as the maintenance of the required temperature.

What Does "Compressor Optimization" Mean?

A refrigeration compressors' capacity to remove heat is directly proportional to the operating temperature. That is the higher the controlled temperature, the higher the suction temperature (evaporator temperature), the faster the rate of heat removal.

A refrigeration cycle is a dynamic changing cycle. From the time the compressor commences to run until it stops, the suction pressure, evaporator pressure, the rate of heat exchange, refrigerant flow and many other factors are all continuously changing.

A refrigeration system is at maximum efficiency immediately after the compressor starts. The efficiency is progressively reduced as the temperature reduces. By adjusting the suction pressure over a narrow band it is possible to maximize the compressor performance increasing cooling capacity by more than 30% and achieve compressor optimization.

ESM™ Optimization Programs

The System ESM™ operates two proprietary programs to achieve a reduction in compressor operation without affecting the cooling capacity of the refrigeration system. The programs have the acronyms LACRA and PDA1. 1LACRA and PDA are copyright protected and the exclusive property of Smartcool International

LACRA is Load Adaptive Cycle Rate Adjustment. The number and frequency of the total compressor stops and starts over the whole control differential is monitored and stored by this program. The start or stop action is logged by the LNC and referenced to a particular temperature point.

PDA is Proportional Differential Adjustment. Conventional controls operate on absolute pre-programmed static values, ie. The Switch On and Off value is fixed and not variable. Using the information gathered by the LACRA program together with the data from the analogue and digital optimization inputs, either thermostatic or suction pressure enables the LNC to calculate a more effective control differential that will reduce compressor operation and maintain the controlled variable within the required range.

The Local Network Controller (LNC) adjusts the operational parameters each 30 minute period based on the data collected on the previous 30 minute period and historical data.

Routines

The software package also consists of a number of other sub-routines that are automatically enabled by the LNC dependant on the number of loads connected, the analogue input and digital input values.

All programs are designed to achieve a minimum saving level of 15%, which can be incrementally maximized, to 50% dependant on compressor cycle rate and temperature conditions.

In addition to reducing the kWh consumption of refrigeration systems the programs also analyze the compressor operation each 30 minutes to achieve a reduction in the measured maximum demand KVA or KW.

The reduction kWh is achieved by strategically and selectively switching off the controlled loads.

Multiplex Operation

The Multiplex program is selected for parallel-connected loads such as multiple compressors on common suction and discharge manifolds, compressors with solenoid capacity control or multiple liquid line solenoid valves or a combination of all of the above.

Three sub-routines are included in the program which are automatically enabled when one, two or more than two System Interface Modules are connected to an LNC.

Simplex Operation

This program enables control of single independent loads each having their own thermostat or other control.

The Simplex program operation is the same for any number of SIM's connected to the LNC.

Chiller Interface

Most modern chillers either with screw compressors or reciprocating compressors are fitted with Micro-Processor Chiller Management Systems that usually allow a third party interface to modify the chiller capacity control.

Using a direct interface with the chiller management system ensures the integrity of the chiller safety and management systems complies with the chiller manufacturers warranty conditions and is usually more cost effective than hard wiring to the chiller control circuits.

Communication Centre Software

The ESM™ Communication Centre Software can be used to remotely monitor the operation of any ESM System™ installation either through PC, LAN, or modem connection.

As many as 10 LNCs at an installation can be interconnected through an RS485 communication link to produce a Global Network. By connecting the LNCs through the RS485 system only one connection to the external network is required for each group of 10 LNC's.

Once connected, operational data such as 'savings settings' and 'saving priority', set up information as well as logging data for each LNC on the network can be accessed, monitored, collected and amended remotely via modem from anywhere in the world.