Best practice small scale commercial refrigeration, optimisation strategies and simple maintenance Michael Bellstedt, Minus40 Pty Ltd

Refrigeration system behaviour under all conditions A well designed refrigeration system will –Run at high efficiency under full cooling load –Use LESS power during cool weather –Use LESS power when the cooling load is reduced 2

Typical techniques 1.Making plant more efficient at full load –Replace deteriorated condensers –Check refrigerant charge –Clean condensers and evaporators –Improve cool air flow to condensers 2.Making the plant more efficient at low load –Fit VSDs to compressors and fans, or use EC fans –Upgrade plant controls to run the plant smarter (defrost, fan control) 3.Reducing the load on the plant –Improve insulation, check door seals, fit quick acting doors, night blinds, etc –Optimise defrost cycles –Smart lighting in cool/freezer rooms 3

The issues Condensers deteriorated and fouled (or undersized to start with) Evaporators deteriorated and fouled Condensers/condensing units poorly located Cold room curtains and door management Insulation or lack thereof Refrigerants and refrigerant leaks 4 4

Condenser coils – clean and generously sized 5

6 Oversized (or Low TD) condensers Industry standard is “14KTD” Therefore at 30ºC ambient temperature, the refrigerant will condenser at 44ºC With larger (and more costly) condensers this can be reduced to 5-10 “KTD”. At 5KTD, the system will use 25-35% less power!!

Evaporator coils – clean 7

Retrofit Evaporator fans Old style Modern units 8 Electronically Commutated (EC) motor fans save considerable amounts of power compared to conventional fans EC fans are easy retrofitted Fan speeds can be controlled to suit the load – lower speeds when setpoint temperatures have been reached. Fan power savings >>80% possible

Curtains and door management Clear, well fitting curtains 9 9

Condensing units well located Well ventilatedShaded 10

11 Oversized (or Low TD) condensers Industry standard is “14KTD” Therefore at 30ºC ambient temperature, the refrigerant will condenser at 44ºC With larger (and more costly) condensers this can be reduced to 5-10 “KTD”. At 5KTD, the system will use 25-35% less power!! Potential for DEMAND and CONSUMPTION saving

Solenoid valves on condensing unit 12 Some condensing units are fitted with liquid line solenoid valves on the unit. These should be relocated close to evaporator unless suction lines are short. This is often omitted. Whole suction line (often in hot roof space) is cooled down whenever solenoid shuts, wasting energy 12

Solenoid valves – where they should be 13

Refrigerants – low GWP or natural Hydrocarbons for small systems – R290, R600A – zero refrigerant levy Do NOT use R404A CO 2 for LT freezer units – available soon Glycol systems for larger stores R 407F or R410A for LT – OK for now R134a for MT – OK for now 14

15 High efficiency condensing units Single compressor condensing units available with –On-board VSD for compressor –Variable speed condenser fans –Advanced controls Advantages –Better control of head pressure –Less or no compressor cycling –Optimum suction pressures Substantial CONSUMPTION savings possible

Quick “low cost” checklist Check refrigerant charge Clean condenser and evaporator coils Check temperature sensors (ice-bath) Improve cool air flow to condensers Check/replace cool/freezer room door seals, Optimise defrost cycles Timer/motion detectors on cool/freezer room lighting Relocate liquid line solenoid located on condensing unit 16

Ensure correct refrigerant charge Too much refrigerant: –Excessive head pressure –High power consumption Too little refrigerant: –Too low suction pressure –Long compressor run times –Inefficient compressor operation 17

Defrost rescheduling Most commercial refrigeration systems using electric heaters to defrost evaporator coils Mostly this is done by defrosting for a fixed time, at a fixed interval, say 30 minutes 4 times/day Left on too long, defrost heaters heat the room, causing extra load for the refrigeration system Fine tune the defrost duration and interval to save energy 18