Refrigeration energy monitoring
Meter the whole refrigeration plant, split out compressors and fans, and compare periods with the same controller state and load.
- Measure
- Refrigeration power monitoring for the whole plant, selected component circuits and controller operating state
- Calculate
- Cold storage energy monitoring as whole-system kWh, component shares and a site-defined specific-energy denominator NEA
- Sensors
- ZEM-65, meters each three-phase electrical boundary with its selected CT set Wireless 3-Phase Electricity Monitor datasheet
- On site
- ZGW-20 Gateway, Edge keeps the measured totals, component context and calculated comparisons locally Gateway datasheet
Define the electrical boundary before choosing meter positions
Start with a one-line diagram of every compressor, condenser fan, evaporator fan, pump, defrost heater and auxiliary that belongs to the refrigeration system. Put one parent meter around the complete declared boundary. Add component meters only where a separate supply can answer a useful question. A controller register adds operating context beside the electrical measurement.
| Measurement layer | EpiSensor route | Question it answers |
|---|---|---|
| Whole refrigeration system | ZEM-65 at the refrigeration board | How much electrical energy crossed the complete declared boundary? |
| Selected component circuits | One ZEM-65 per separately supplied compressor, fan, pump or defrost group | Which non-overlapping component changed, and does the split reconcile with the parent? |
| Controller operating context | ZMB-31 on a documented Modbus RTU segment | Which compressors, stages, fans or defrost states were active when the electrical pattern changed? |
Hardware for refrigeration power monitoring
Use one ZEM-65 for the parent electrical boundary and additional units only for non-overlapping circuits worth separating. Add a ZMB-31 when the controller has a published Modbus RTU map.
Measures the complete refrigeration board or a selected compressor, condenser, evaporator or defrost supply
1 per declared electrical boundary three-phase, 3 or 4 wire
- Choose the CT rating for each monitored supply: 120 A split-core, or 300 A, 1 kA and 3 kA Rogowski coils
Class 0.5S to IEC 62053-22 with its CTs, 0.1 A to 3 kA
Collects the electrical and controller records, retains local history and calculates declared comparisons
1 per surveyed coverage area coverage and capacity checked on site
If the controller has a published register map and a suitable RS-485 segment
Reads compressor, capacity-stage, fan, defrost, setpoint or pressure values that the refrigeration controller documents
1 per RS-485 segment up to 30 configured registers
Modbus RTU master over RS-485, up to 30 configured registers
Cold storage energy monitoring boundaries
The parent meter owns the total. Component meters explain selected parts of it. Keep the operating state and comparison denominator beside both, so a change in load, weather, setpoint or defrost schedule is read as a change in conditions.
How refrigeration energy reaches Edge
The plant's electrical supplies and documented controller data follow separate measurement paths before they are aligned locally in Edge.
- Wired
- Zigbee
- Edge
- Platforms
| Position | What it tells you | Reference | Sensor |
|---|---|---|---|
| Complete refrigeration board | Total kW, kWh and demand for every electrical load inside the declared refrigeration boundary | Include or explicitly exclude compressors, condenser and evaporator fans, pumps, defrost, drain and anti-sweat heaters DOE | ZEM-65 (on this page) |
| Compressor supply | The compressor pack's electrical share, starts and changing capacity signature | Use a separate meter only where the supply is electrically distinct; retain the parent meter as the system total NEA | ZEM-65 (on this page), selected child boundary |
| Heat-rejection and distribution loads | Condenser fans, evaporator fans and pumps that may move differently from compressor electricity | Whole-system measurement keeps an apparent compressor saving from hiding a fan or pump penalty NREL | ZEM-65 (on this page), selected child boundary |
| Defrost and auxiliary loads | The timing and energy of electric defrost, drain, anti-sweat or pan heaters where separately supplied | Record both power and operating time; the daily energy is their product DOE | ZEM-65 (on this page), selected child boundary |
| Controller operating context | Which stage, fan, setpoint, pressure or defrost state accompanied the measured electrical pattern | Use only the documented model and firmware register map, with address, type, byte order, scale and unit recorded Modbus Interface datasheet | ZMB-31 (on this page) |
Count child meters once. A compressor meter is already inside the refrigeration-board total. Use it to calculate a share or reconcile a residual.
State what each figure is divided by. Tonnes stored, tonnes handled, cubic metres, operating hours and cooling output answer different questions. Record which one you used, and the period, beside every specific-energy figure.
Read controller data as context. A compressor run flag or calculated load percentage says what the controller asked for; the electrical measurement at the chosen boundary says what it used.
How to calculate refrigeration energy performance
Calculate from interval energy inside one stable electrical boundary. Use non-overlapping component meters for shares, and divide by a declared operating denominator only when that denominator is measured over the same period.
component share (%) = Ecomponent ÷ Esystem × 100
specific energy = Esystem ÷ D- Ecomponent
- interval energy for one non-overlapping component boundary, kWh
- Esystem
- interval energy for the complete declared refrigeration boundary, kWh
- D
- the recorded denominator for the same interval, such as tonnes stored, tonnes handled, refrigerated volume or directly measured cooling output
Worked example
During one recorded day, the complete refrigeration boundary uses 720 kWh. The separately metered compressor pack uses 504 kWh, so its share is 70%. If the site's agreed denominator is an average 90 tonnes stored during that same day, the recorded specific energy is 8 kWh per tonne for that day. It is comparable only with periods that use the same boundary, denominator and operating context.
In Edge
Edge can sum explicit separate inputs and calculate guarded ratios. Keep source identities, units, interval alignment, stale-input action and output timestamp policy with the result. Record a missing component as a gap, and calculate kWh from cumulative registers rather than from repeated instantaneous kW.
Commissioning checks
Commission the parent total first. Component analysis is useful only after the complete boundary is credible.
-
Freeze the one-line boundary
Mark every compressor, fan, pump, heater and auxiliary as included, excluded or separately metered on the current electrical one-line diagram.
Pass when the diagram, meter labels and Edge point names describe the same physical boundaries.
-
Prove each electrical channel
With a competent electrical person, verify voltage references, phase order, CT orientation and ratio against a known operating state or reference instrument.
Pass when phase values, total kW and direction are plausible, and the check is recorded for every ZEM-65.
-
Reconcile parent and children
Compare the parent interval energy with the sum of non-overlapping child meters and list every load that remains only in the parent.
Pass when the residual is explainable and every physical load is counted once.
-
Walk the controller states
Observe a normal compressor stage change, fan change and defrost cycle while checking each selected register's value, unit and timestamp.
Pass when every state changes with the plant and restores correctly after a communication interruption.
-
Validate the comparison basis
Record setpoints, ambient condition, door or production activity, inventory or throughput denominator, defrost schedule and any maintenance change for the baseline and comparison periods.
Pass when the two periods are comparable, or every material difference is disclosed with the result.
-
Test missing and stale inputs
In an approved test window, stop one input and inspect the parent total, component share and specific-energy output before and after reporting resumes.
Pass when a missing input is visible, a partial total is labelled partial, and the gap is still there after restoration.
Limits of this measurement
Electrical and controller records explain when and where the plant used energy. They do not, by themselves, prove cooling efficiency, product compliance or a safe control strategy.
- Electricity, runtime and operating temperatures do not measure useful cooling output, so they are not enough to calculate COP without a separately engineered cooling-output measurement.
- This page does not replace mapped product-temperature monitoring, food-safety procedures or alarm response; those belong to the cold-chain temperature guide.
- Energy monitoring does not detect or quantify refrigerant leakage, charge condition, oil condition, vibration faults or mechanical wear.
- Observing a controller does not authorise setpoint changes, load shedding or demand response; controlled flexibility needs its own engineered permissions, interlocks and recovery test.
- A lower kWh total is not automatically an efficiency improvement when weather, product load, doors, setpoints, operating hours or the measurement boundary changed.
Sources
- Commercial Refrigeration Equipment Technical Support Document (opens in a new tab) US Department of Energy
- Commercial Refrigeration: Heat Transfer Optimization and Energy Reduction (opens in a new tab) National Renewable Energy Laboratory and US Department of Energy Better Buildings
- Energy Efficiency Opportunities Assessment and Energy Performance Measurement Guidelines for New Ventures (opens in a new tab) National Environment Agency, Singapore
- Wireless 3-Phase Electricity Monitor datasheet (opens in a new tab) EpiSensor. Specifications, ranges and ordering codes.
Related
Third-party devices for this application
More in the Device Directory: Energy meters (62), Current transformers (7)
Start with the boundary
An engineer can map the refrigeration circuits and controller, choose each metering path, and define a comparison that shows every missing load.