EcoChill Uses RDM Control and Monitoring System to Deliver Major Benefits in Kerifresh Chiller Upgrade.
Kerifresh is New Zealand’s largest grower of citrus fruits. Based in Kerikeri, it produces over half of the NZ citrus crop, along with blueberries and Kiwifruit, and exports it to Japan, SE Asia and Australia.
The company prides itself in the quality of its products and its approach to environmental protection, investing in the latest technology for growing, harvesting and optimizing fruit quality and shelf life.
It’s post-harvest and distribution facility holds mainly Kiwifruit and citrus fruit, at any one time storing 100-plus tons of Kiwifruit alone in specially controlled rooms. Due to the growth of the facility over time, the control and lay-out of environmental control plant was not ideal. The system was inefficient and had difficulty maintaining optimum conditions across the fruit storage rooms.
The purpose of the project, designed and installed by EcoChill, was to implement a new state-of-the-art control and monitoring system, to deliver the lowest possible energy use while maintaining optimum conditions for fruit quality and shelf life.
The system was under the control of an outdated control system that had been in use for many years. Chillers 3 and 7 were equipped with two cooling systems for each room, sharing the load. Units 3A and 7A are in a plant room situated next to the cool store, while units 3B and 7B are located in a separate plant room 50m away.
This resulted in a number of problems:
- Temperatures in the store rooms were poorly controlled, leading to large variations in core product temperature;
- The existing control system delivered poor control of cooling the plant, with multiple generic units linked with plc relay output board controlling solenoids, compressors and condenser fans;
- Electric defrost was fixed duration, controlled by a mechanical time clock with no other form of termination;
- System pump down was controlled by mechanical pressure switch.
It was clear that the problem was not the cooling plant itself, but the inadequate control system, which was failing to optimise performance energy efficiency.
Following discussions with the client, a decision was taken to install a bespoke system with specific control logic, designed and written by EcoChill for the Kerifresh cool store application.
Matthew Darby, managing director of EcoChill, advised: “We chose RDM due to the flexible nature of the product – it enables us to tailor the software to suit the specific control requirements. It is also easily expandable, and enables us to easily add to the system in future without major disruption.”
With two plant rooms in different locations, the RDM PR0650 Intuitive TDB controller was installed in the main plant room, with a PR0661 Intuitive Expansion I/O board installed into the second plant room. The two controllers communicate with each other via a CANBUS network.
A full-colour touch-screen was installed in the main plant room to allow the client to change temperature set-points, initiate emergency defrosts and view alarms with a simple touch of the screen.
Specific improvements to plant operation and control included:
- All systems can now communicate and are controlled in unison;
- Partial pump down of systems is possible, with the use of individual system pressure transactions
- Defrost termination is now controlled according to temperature/pressure via the transducers, delivering greatly improved performance and energy efficiency;
- There is now a Manual Defrost option following heavy usage, such as loading of warm product;
- The use of smart defrost logic: If the control set-point is +4degC or above, the system performs an off-cycle air defrost; if the control set-point is below +4C, electric defrost is enabled with pressure termination. This ensures energy savings by only activating electric defrosts when necessary, and allows for each of the systems to terminate individually;
- Due to limited electrical board loading sizes, an interlock was added for defrosts - so only one room can be on defrost at any one time.
The new system has achieved its objectives and is delivering significant benefits in terms of plant performance, reduced energy use and improved product quality and consistency.
By installing the RDM control system, EcoChill has achieved the following specific improvements:
- Reduced overall pull-down time, as the system now works "as one" and has significantly reduced defrosting times;
- More even pull-down of product temperature, resulting in improved quality and shelf-life;
- Reduced energy consumption due to reduced defrost times and, when possible, the elimination of power-hungry electric defrost;
- A far more user-friendly control system that is easy to operate and understand, enhancing the customer's confidence in operating and managing the facility;
- Improved reliability of the overall system due to increased control and monitoring capabilities.
Matthew Darby said: “Overall, the customer was very impressed with the user friendly nature of the system – in particular the simplicity of the touch-screen in managing operational changes with ease, and without the need for in-depth technical knowledge.”
He added: “From the designer and installer’s point of view, the system gives us the freedom to write our own programs to suit the specific requirements of each application. It enables us to say, “We can do that” to our customers, which is of course very powerful and attractive.”
Following the success of the project, he reports that the client is keen to roll out similar upgrades with EcoChill in other parts of the facility.