Refrigeration and cold store temperature monitoring
Probes at the warm and cold points a mapping study found, one in the product zone, and alarms that carry a delay so a door opening is not an incident.
- Measure
- The mapped warm and cold locations, the product zone, and the refrigeration plant's electricity
- Rule
- Map the space before choosing permanent positions WHO
- Sensors
- TES-22 waterproof probes, ±0.2 °C in the normal range, down to −40 °C at ±0.5 °C TES-2X datasheet (PDF, opens in a new tab)
- On site
- ZGW-20 Gateway, alarms, records and up to 250 wireless devices ZGW-20 datasheet (PDF, opens in a new tab)
Mapping comes before monitoring
A temperature mapping study finds the warmest and coldest parts of a space under loaded, empty, defrost and door-opening conditions. Permanent probes then go where the map says, not where the cable is easiest. Without the map, a probe beside the thermostat reports the thermostat.
Hardware for cold room temperature monitoring
Two probes for the extremes of each space, one for the product zone, and the plant's electricity when the cause matters as much as the effect.
The warm and cold locations the mapping study found
2 waterproof probes, 2.5 m leads
±0.2 °C from −20 to 70 °C, ±0.5 °C from −40 to 105 °C, battery life up to 10 years at 15-minute reporting
The product zone, or a buffered probe that follows the load rather than the air
- 1 waterproof probe, 2.5 m lead
Keeps the record, runs the alarms and delivers them off site
If plant behaviour has to be explained, not only recorded
The refrigeration plant's electricity, which explains what the temperature did
- Choose the CT rating for the refrigeration board: 120 A split-core, or 300 A, 1 kA and 3 kA Rogowski coils
If the controller has a published register map
Setpoint, defrost and alarm state from the refrigeration controller
TES-22 and ZMB-31 share one enclosure with different terminals inside, so the ordering code is what you specify.
Where the probes go in a cold store
Each probe answers a question the mapping study asked. Write the question beside the probe, so a later change of layout can be judged against it.
| Position | What it tells you | Reference | Sensor |
|---|---|---|---|
| Mapped warm location | The worst case the stored product sees | Chosen from a documented mapping study, under representative conditions WHO | TES-22 (on this page), probe 1 |
| Mapped cold location | Whether anything is being over-cooled or frozen | From the same study, usually in the evaporator's discharge WHO | TES-22 (on this page), probe 2 |
| Product zone | What the load is doing, which lags the air | Say whether the probe reads air, a buffer or a product simulation | TES-21 (on this page) |
| Refrigeration electricity | Whether a temperature rise came with the plant running or with it stopped | One meter on the refrigeration board ZEM-63 datasheet (PDF, opens in a new tab) | ZEM-65 (on this page) |
| Controller state | Defrost and setpoint changes that explain a scheduled excursion | Controller registers, with the model and firmware recorded ZMB-3X datasheet (PDF, opens in a new tab) | ZMB-31 (on this page) |
Air is not product. Air temperature moves in minutes and a pallet moves in hours. A door-opening spike in the air may mean nothing to the load, which is why the alarm carries a delay.
Defrost is scheduled, not an incident. Keep the controller's defrost state so a regular rise can be recognised instead of investigated every time.
The probe has a range too. Below −20 °C the probe holds ±0.5 °C rather than ±0.2 °C. In a freezer, that is part of the measurement plan.
Alarms and records for a cold store
The rules run on the Gateway, so an alarm does not depend on somebody watching a dashboard.
- A temperature outside its limits
- A limit rule per probe, with a hold time agreed with the person responsible for the product, so a door opening does not raise an incident.
- A probe that stops reporting
- A no-data rule flags a silent sensor within a set time, from one minute to a day, because a missing reading is not a good reading.
- Who is told, and when
- Email, SMS, a webhook or an alert in Edge, with the recipients set per rule. Email and SMS need the Gateway's own settings and a connection.
- The record survives the network
- Each sensor holds up to 70,000 readings in its own memory, so an outage leaves a gap in the live view but not in the record.
Commissioning checks
Do these before the record is relied on, and repeat the mapping check after any material change.
-
Each probe matches the study
Photograph every fitted probe and mark its position on the mapping study's drawing.
Pass when every permanent probe is at a position the study identified.
-
Probes agree with a reference
Compare each installed probe with a traceable reference instrument at the operating temperature.
Pass when the differences are inside the tolerance the quality process accepts, and recorded per probe.
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High, low and silent all alarm
Force each state in turn: warm one probe, cool another, and remove a battery.
Pass when all three reach the named recipient, who acknowledges them.
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The delay is right for the product
Open the door for a normal loading period and watch whether the rule fires.
Pass when routine work does not raise an alarm, and a real excursion still does.
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Time and retention are set
Check the Gateway's clock, the reporting interval and how long the record is kept.
Pass when the retention period matches what the quality process requires.
What monitoring does not replace
Installing a probe does not turn an unvalidated room into a qualified cold chain.
- The mapping study, the qualification of the space and the quality process that owns them.
- The limits themselves: what is acceptable comes from the product and its regulator, not from the sensor.
- Calibration records, retention periods and the response procedure when an alarm fires.
- A controller reading is context. It does not replace an independent monitoring point where one is required.
Sources and related guides
Sources
- How to temperature map cold chain equipment and storage areas (opens in a new tab) World Health Organization. Mapping method and sensor placement for pharmaceutical storage. Approval for a specific product stays with its regulator.
- Cold chain equipment and dry store temperature mapping tool (opens in a new tab) World Health Organization. A worked mapping and monitoring template for storage areas.
- TES-2X Probe Temperature Sensor datasheet (opens in a new tab) EpiSensor. Specifications, ranges and ordering codes.
Related
- Refrigeration demand response Application guide Use measured thermal headroom in a cold store to shift refrigeration demand, with the product temperature holding a veto over any grid request.
- Legionella temperature monitoring Application guide Where to fit pipe probes on a calorifier loop, the HSG274 temperatures to watch, alarms in Edge, and the checks that prove the system works.
Reviewed by EpiSensor Engineering on . Revision 5.
Turn a mapping study into permanent probe positions
We will place the permanent probes against the study, and size the sensors and Gateway for the site.