RDM controls needs of food plant

UK: A control system installed by refrigeration specialist, Personal Refrigeration, is said to have helped deliver energy savings of 22% for dairy produce manufacturer FJ Need.

A specialist in providing dairy products to the food service and wholesale markets since 1973, FJ Need recently underwent an expansion programme with the construction of a new state-of-the-art factory in Nantwich. Following previous successful collaborations project manager, Alistair Clark of Clark Solutions, approached Personal Refrigeration to support him in the delivery of the project.

FJ Need wanted to ensure efficient and accurate temperature management of the goods in, despatch, and production areas. Careful consideration was given to energy consumption due to the site’s semi-rural location, and existing demand. Another primary objective was to deliver immediate value for money while also delivering long-term financial and environmental benefits.

The system uses R407F, a lower GWP (1824) alternative to R404A. Marketed by Honeywell as Performax LT, R407F is a non-flammable blend comprising 40% R134a, 30% R125 and 30% R32.

Centred on two independent refrigeration packs, Personal Refrigeration’s bespoke system design incorporates inverter technology, with PLC software written in-house, by Personal Refrigeration, using control manufacturer Resource Data Management’s (RDM) free license PLC editing software, TDB. The Intuitive TDB controllers provide independent control of the two packs and associated evaporators.

Multiple control algorithms were written, including inverter rest condition upon detection of stable load, auto balance of fixed speed compressor run hours, floating head pressure, and adaptive suction pressure, when necessary. This is in addition to compressor envelope monitoring, including evaporating temperature/pressure, and discharge temperature.

To facilitate refrigerant control, an Intuitive Stepper controller and Sporlan valve, were selected to provide seamless individual evaporator satellite control, along with evaporator EC fan modulation, to save energy under varying loads.

Each fully independent system features RDM’s Intuitive TDB and Mercury controllers, a semi-hermetic compressor pack, complete with inverter-driven lead compressors, and individual compressor de-super heater heat exchanger, for hot water recover. Also included are a three fan condenser with inverter driven condenser fans, four MT evaporators with modulating EC fans, split across two areas, and a HT evaporator with modulating EC fans.

RDM’s control system front end, the DMTouch, provides communication across all controllers via an integral PLC program. This is said to ensure that critical alarms are detected, and that reactive action is taken to maintain stable operation of the systems. One feature of this is to ensure that the EEV is driven closed should a failed fan be detected, preventing any flood back to the packs.

Temperature sensors and pressure transducers analyse system conditions to maintain optimum design evaporator and condensing criteria, using Intuitive TDB controllers. The refrigeration pack’s lead compressor is inverter driven for speed modulation, to enhance energy efficiency at variable load conditions. Control algorithms are also provided, for additional energy efficiency, to implement floating evaporating and condensing temperatures to adapt, and control, to real time refrigeration demands. This control technique allows system pressures to automatically adjust and regulate to suit low or high load conditions.

Each evaporator EC fan’s speed is independently managed within the PLC software. The fan speed modulates to match the refrigeration duty required for each zone of the refrigerated areas. As a result energy consumption is reduced when low loads are detected. Independently managed, each evaporator satisfies the temperature set point, minimising defrost clashes. Sporlan EEV’s are controlled, ensuring that the evaporators are efficiently utilised under varying loads by controlling the flow of the refrigerant R407F.

A major consideration for the installation was environmental impact. High efficiency heat exchangers were selected, with reduced refrigerant charge. Custom PLC software for the Intuitive controllers communicates with the fixed leak detection sensors and the DMTouch to warn of any increased levels of refrigerant within the plant area. PPM levels for delayed and immediate alarms are built in; along with a knock system, if refrigerant levels are raised intermittently over a period of time.

The new factory, which is double the size of the previous cold store has the capacity to cope with nearly twice the throughput. It is operating at 78% of the projected energy use and 73% of projected maximum demand and delivering estimated energy savings of around 22% on the anticipated site loading.

On learning of the project Andrew Chandler, RDM’s managing director, said “For me, technology has always been something that is exciting, something to be pushed to the limit. Our objective is to give customers the flexibility to create a bespoke system that specifically meets each individual requirement. It is this type of project, and the ingenuity that has been applied that motivates us.’’