SCADA on a refrigeration system is not about having a nice screen to look at. Its real value lies in two things: knowing before something fails, and being able to prove the storage conditions when a customer or an audit team asks.
How SCADA differs from a conventional controller
A temperature controller does switching: above the setpoint it runs, at the setpoint it stops. It deals with the present and remembers nothing of the past.
SCADA collects data from many points, stores it over time, displays it centrally and raises alarms against preset conditions. The core difference: SCADA shows you the trend — something a standalone controller never does.
Why the trend matters more than the instantaneous reading
Most serious refrigeration failures give off signs of gradual drift beforehand: the discharge pressure creeping up, the pull-down time getting a little longer each week, the compressor current edging higher.
Look at any single moment and everything is still "within limits". Look across a month and it is clear where the system is heading. That interval is the window in which a business can act deliberately, instead of waiting for the plant to stop mid-shift.
What is worth monitoring
- The temperature of each room, at agreed representative points
- Suction and discharge pressures for each compressor set
- Compressor current and run/stop status
- Defrost cycle status and the duration of each cycle
- The status of the protection devices — whether they have tripped
- Water inlet and outlet temperatures on chiller systems
- Store door status — a door left open is a common cause of sudden heat load spikes
- Power supply and the status of any transfer to standby power
You do not need every signal from day one. Start with the group that directly affects the product and the risk of a shutdown, then expand.
Alarms: design them badly and they get ignored
This is where many SCADA systems fail. Set the thresholds too tight and the alarms sound constantly; within a few weeks nobody pays attention — and when something real happens, it gets ignored like all the rest.
Principles for designing alarms:
- Grade them by severity — alarms to be aware of, alarms to deal with during the shift, and alarms that must call someone immediately
- Build in a sensible delay so they do not sound for the temporary rise when the door opens for an intake
- Send them to the right person by severity and by shift roster
- Record the acknowledgement — who saw it, and what they did about it
One final point that matters for food and pharmaceutical stores: an audit team does not only ask whether you have alarms — they ask whether there are corrective action records for the alarms that have already occurred.
Remote monitoring and the security question
Remote access brings real value: managers can see the state of the store out of hours, and a technician can make a preliminary diagnosis before travelling to site. It comes with information security requirements.
The principle to apply: separate viewing rights from control rights. Most users only need to see the data; the right to change settings should be limited to a few people, with a log of who changed what and when.
What it does for documentation and traceability
For stores serving export food or pharmaceuticals, continuous temperature data is evidence, not a convenience. When there is a problem with a consignment, the business has to be able to prove that it stayed within the temperature range for the whole time it was stored.
Three requirements to settle when designing the system: how long the data is retained, whether it can be extracted by batch and by time period, and whether the sensors have calibration records. See also documentation requirements for GSP stores.
When SCADA is worth the investment
- The system has multiple rooms and multiple compressor sets — manual operation cannot cover it all
- High-value goods, where the loss from a single incident exceeds the cost of the monitoring system
- There are traceability requirements from customers or regulators
- Continuous operation, where knowing in advance allows planned maintenance instead of reactive repair
- Several storage sites in different locations that need central management
Tan Long designs and fabricates SCADA control cabinets for industrial refrigeration systems, programmed to each plant's operating requirements.
Two projects where Tan Long integrated SCADA
- NECS – New Era Cold Storage: control cabinets, PLC, control programming and SCADA connection for a system of around 3 MW, with online monitoring and alerts to mobile devices.
- AJ Total Vietnam – Long Hau Industrial Park: power electrics, PLC, HMI and SCADA providing central monitoring of the compressors, pumps, valves and ancillary equipment of a multi-area cold storage centre.
Frequently asked questions about SCADA for refrigeration systems
How does SCADA differ from a conventional temperature controller?
A controller only switches on the current temperature and remembers nothing of the past. SCADA collects data from many points, stores it over time, displays it centrally and raises alarms against set conditions — which is how it reveals the trend.
Why does the trend matter more than the instantaneous reading?
Because most serious failures show gradual drift beforehand — the discharge pressure edging up, the pull-down time getting longer. At any single moment it is still within limits; only across a month is it clear where the system is heading.
Why do so many alarm systems end up ignored?
Because thresholds set too tight make the alarms sound constantly, and within a few weeks nobody pays attention. They need grading by severity, a sensible delay so they do not sound during an intake, and routing to the right person by shift roster.
Does remote monitoring carry any risk?
Yes — viewing rights should be separated from control rights. Most users only need to see the data; the right to change settings should be limited to a few people, with a log of who changed what and when.
What needs settling about data when designing a monitoring system?
How long the data is retained, whether it can be extracted by batch and by time period, and whether the sensors have calibration records. For export food or pharmaceutical stores, these three questions are mandatory.
When is SCADA worth the investment?
When the system has multiple rooms and compressor sets, when the goods are high-value, when there are traceability requirements, when continuous operation calls for planned maintenance, or when several storage sites in different locations need central management.
Related pages
- SCADA control cabinet
- PLC control cabinet
- Data loggers: temperature monitoring and recording
- Cold store temperature sensors: where to place them
- GSP cold stores: from documentation to acceptance
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
