Existing controls for the refrigeration plant were manual on / off switches.Four operators were required to operate the plant on a rotating shift basis. The only feedback for the manual controls were individual thermostats and thermometers. There was no scheduling or optimization of the system, resulting in inefficiencies and high cost of operation.
Refrigeration Plant Control System
Control the sequence of operations in a collection of refrigeration compressors, evaporative
condensers and evaporators to maintain the temperature requirements in the refrigerated spaces.
Key Business Activities:
Automate and Retrofit Chiller Plants and Refrigeration Plants to Save Time and Money
For this opportunity we decided to try the TIA Portal Basic software with S7-1200 1214C, Analog Input signal module SM 1231 AI4 and KTP600 Basic Panel HMI.We chose the TIA Portal after attending a seminar hosted by AWC, our local distributor. The S7-1200 and Basic Panel fit the I/O and visualization requirements of the application and were cost effective enough to keep us in line with competition. Our competitors sell a simple front end screen that has pretty pictures of what is going on, but offers no central control or optimization capability. We brought in all of the inputs and outputs of the existing hardware into the S7-1200, developed the code and PID loops to optimize coordination, and created informative screens to view and control the entire system from one HMI.
It was much faster to program in the TIA Portal (vs. STEP 7 v5.5 and WinCC Flexible).
Before, whenever you configured the HMI, you had to import the tags from the PLC as an additional step. Now with the TIA Portal, once the tag is created, it is automatically
available for use in the HMI. This saves time and prevents engineering errors. It was simple to tune the PID loops with the included loop tuner. We quickly determined the target limits to
maintain temperatures, programmed the set-points into the PLC and easily integrated the HMI to display critical values and control functions.