Case controllers are used to control the temperature at the evaporator during the heat transfer, for instance, between the air circulating through the refrigerated cabinet and the refrigerant. Whether used locally or centrally, i.e. in refrigerated cabinets or in switch cabinets, case controllers optimise this process and improve energy efficiency.
Refrigeration case controllers
UA 400 series – the next generation of case controllers
The case controllers of the UA 400 range for thermostatic expansion valves (solenoid valves in the evaporator line) and electronic expansion valves are suitable for controlling and monitoring two temperature zones in all kinds of refrigerated cabinets and cold rooms for normal and low temperature (NT and LT).
- The UA 400 series includes the following models:
- UA 400 for thermostatic expansion valves
- UA 400 E for electronic expansion valves
- UA 410 L for temperature data logging
The respective use for multi-deck cabinets, cold counters, freezer islands, walk-in freezers, etc. can be selected via a DIP switch at the controller. Approved factory settings for the desired application are, then, loaded via plug & play.
The UA 400 series is backward compatible and a much more powerful replacement for the case controllers of the UA 300 series. As well as the extension of the analog in-/outputs other features of the UA 400 Family has been improved:
- Spring terminals for easy installation
- Two-rowed CAN bus terminal for fast connection on the bus
- Non-polar connector coding for all terminals
- More compact dimensions than UA 300
More details about news and differences can be found at the E°EDP.
UA 400 E – for electronic expansion valves
The UA 400 E case controller for the continuous control of electronic expansion valves controlls two electronic valves independently of one another. The pulse-width modulation at the valves is the control-technological presupposition for optimal refrigerant superheat.
Continuous control – why and wherefore?
Continuous control of the evaporator temperature has the major benefit of precisely controlling the heat transfer at the refrigeration point, by which the coefficient of performance (COP) and/or the figure of merit is increased and energy efficiency, enhanced. Controlling via temperature is possible, since in the so-called two-phase zone (where the refrigerant boils) there is a close connection between pressure and temperature.
The temperature difference between refrigerant and heat transfer medium (i.e. in refrigerated cabinets, the air) can be precisely controlled. The UA 400 E continuously aligns the refrigeration capacity of the evaporator with the evaporating temperature control error and in this way ensures the lower superheat. This is economical because the precisely controlled increase of the evaporating temperature by 1 Kelvin reduces energy consumption by up to 3 percent.
Unless the requested refrigeration capacity is too low, there is no switch-off state in the continuous control of temperature at the refrigeration point (other than in the discontinuous control). Continuous control therefore offers advantages, particularly in case of load fluctuations.
UA 410 L – for recording and controlling temperatures
According to EC regulation 37/2005, walk-in freezers with a volume of more than 10 cubic metres need to be equipped with separate temperature documentation. The UA 410 L temperature recording controller with its 10 inputs for temperature sensors is a convenient solution for this need. In markets without a system centre of their own, it can also be used for monitoring tasks. Particularly when it comes to retrofitting and monitoring of plug-in refrigerators, the UA 410 L is an interesting option.
All case controllers of the UA 400 range are equipped with an emergency operating programme that includes all normal control functions. The case controllers are available for installation both in refrigerated cabinets and switch cabinets. They are optionally fitted with a CAN bus interface (if networked and connected with the system centre) or with an integrated real-time clock (for stand-alone operation).
Defrosting is controlled via internal clock or freely programmable via external command, and can be conducted via enthalpy. Defrosting is optimally controlled, when it is combined with the freely parameterisable ventilation control.
Stand-alone refrigerated cabinets are operated via operator interface.
For extended operation with CAN bus, a system centre or an operator interface is used. Optionally, laptops and PCs can be used for operating and optimisation tasks.
UA 30 Rx – the compact case controller
The spectrum of case controllers is rounded off with the UA 30 RC and UA 30 RS compact controllers for DIN rail and panel mounting. They are equipped with a modbus interface for networking and connection with the system centre, but can also be operated as stand-alone units. Interval defrosting or external defrost commands are used as defrost methods.
- Case controllers for integration via Modbus and stand-alone operation
- Control of thermostatic expansion valves
- Freely parameterisable defrost times and ventilation control
- Temperature recording with case controller for monitoring tasks