RDM’s Control System Front-End Lowers Refrigeration Energy Use
RDM is proud to be a strong proponent of energy savings through inherent controller features and our system architecture. We have also developed, over years of research and development, six core energy-saving software features for refrigeration temperature control applications. These features can be enabled on either of RDM’s control systems front-end: miniDM or DMTouch.
Pack (Rack) Optimisation
Pack optimisation enables the target pressure of a pack controller to be adjusted in response to the average valve openings of all the evaporators connected to that pack. If the evaporators are satisfied, the pack suction pressure setpoint floats up to improve system efficiency, resulting in decreased energy usage of pack compressors. Overall, the Pack Optimisation feature typically leads to a 10-30% reduction in pack power, without any interruption or deterioration in case temperature control.
Optimisation requires an RDM pack controller to be used in conjunction with a DMTouch or miniDM and a number of networked case and coldroom (evaporator) controllers. A DMTouch can be configured for up to 50 packs, whilst a miniDM supports up to five packs.
Condenser TD (Temperature Differential)
The Condenser TD feature provides monitoring of the efficiency of up to 50 condenser units for the DMTouch and up to 5 condensers for the miniDM. Three probes are fitted to the condenser to measure liquid return, discharge and ambient air temperature. Two measurement methods are available: Discharge to Liquid Return and Liquid Return to Ambient Air On. The DMTouch and miniDM will report three escalation levels of alarm, providing early notification of a condenser performing inefficiently.
Network Trim (Anti-Sweat) Control
A typical supermarket consumes 20-30kW of constant trim (anti-sweat) heater load. RDM’s Network Trim feature can be used in conjunction with networked RDM case controllers with trim heater control. The DMTouch or miniDM will instruct the controllers to adjust their trim heater output levels according to either of two measurement methods: ambient humidity only, or dew point using a humidity sensor and ambient temperature probe. The output level of the trim heaters will be enough to prevent condensation forming without using unnecessary power and will constantly adjust to changing atmospheric conditions. Using the Network Trim energy feature can lead to an overall 30-50% reduction in trim heater load power.
The trim level settings can also be automatically reduced at night time to provide further energy savings when the facility is unoccupied. Even by simply reducing the maximum output of the heaters to 70% (as opposed to always on), energy consumption is instantly reduced by 30%.
Night Blinds Check
Night blinds installed on an open-air refrigerated case, when deployed after store trading hours, can reduce the power requirement of the case by up to 40%. This of course is dependent on the night blinds actually being utilised. By comparing the temperature sensors that are already installed in the refrigerated cabinet, a DMTouch or miniDM can ascertain if the night blinds have been used and generate an alarm if they have not. Both front-end systems can also produce a report detailing night blind use for the store.
The Defrost Warning feature provides a warning when a consecutive number of defrost cycles on a particular evaporator terminate on time setpoint as opposed to the temperature limit. The number of consecutive defrosts before a warning is issued is user-configurable on either control system front-end. If a defrost cycle terminates based on time limit, then it may indicate that the evaporator has not cleared all the ice which will affect efficiency and use more power. Users can also configure a defrost limit setting. This will produce an alarm if an evaporator has more than the pre-set amount of defrost cycles per day, highlighting potential energy waste.
Case Performance (TPI)
This feature monitors the performance of a refrigeration case or coldroom, allocating a score for easy monitoring. The Temperature Performance Indicator (TPI) provides a predictive maintenance solution by informing users of poorly performing equipment, helping them to easily identify faults before they become a costly issue.
Based on a number of variables such as over-temperature alarms and under-temperature alarms, a TPI score is determined for a case or coldroom. A score of one equates to a good performance, whilst a score of ten equates to a poor performance. The performance indicator is also displayed in the Device List of the DMTouch of miniDM for individual devices and as a summary of all configured devices.
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