What a temperature log should tell you
A good logger gives you the time, the temperature and enough history to see a pattern. For shops, farms and packhouses in the Western Cape, that pattern matters because heat, humidity and frequent door opening can change performance quickly. Do not look only at the highest or lowest number. Look at how fast the unit returns to set point, how often it overshoots, and whether the trend gets worse over several days.
If the room should hold at 2 to 5 C, a short rise during loading may be normal. A slow climb every afternoon, or a room that takes longer to pull back after load-shedding, is a sign that something is drifting. The logger is not there to impress anyone, it is there to help you catch a problem early.
Start with the set point and the normal band
Before you read any chart, confirm the target temperature for that space. Fresh produce, dairy, frozen goods and medication all have different limits. Once you know the set point, mark the normal band around it. Many sites in Cape Town and the Winelands work with a narrow band because product quality depends on it.
- Check the set point against the actual room use.
- Confirm whether the logger shows air temperature or product temperature.
- Note the acceptable swing for that site, not just a generic figure.
- Record the date, time and who checked the log.
If the logger is in the return air path, the room may look warmer than the product really is. That is fine, but the same position must be used every time so your readings stay compareable.
Read the shape of the graph, not only the numbers
The shape of the line tells you what the system is doing. A steady saw-tooth pattern often means normal cycling. Wide swings can point to poor door seals, overloading, fan faults or a coil that needs cleaning. A flat line that sits too high may mean the unit is running but cannot bring the room down. A sudden step change can follow a power interruption, thermostat fault or someone changing the settings without logging it.
In coastal areas like Cape Town and Vredenburg, higher humidity can make doors sweat and ice build-up worse. That often shows up as a slow drift upward before anyone notices water on the floor. If the line becomes more jagged than usual, look at the door usage, defrost timing and the condition of the drainage first.
Use spikes, drops and recovery time as clues
Short spikes are not always a fault. A delivery, cleaning shift or a long door open can cause a brief rise. The real question is how quickly the room recovers. If a room used to recover in 20 minutes and now takes 50, something has changed. That could be a weak condenser fan, a refrigerant leak, dirty coils or a damaged door curtain.
- Spike with quick recovery: likely normal activity.
- Spike with slow recovery: inspect doors, seals and fan operation.
- Repeated spikes at the same time daily: check routines, loading and shift handover.
- Drop below normal after defrost: look at sensors, control settings and drainage.
On farms around Paarl, Stellenbosch and Malmesbury, a unit working harder in hot weather may also show longer recovery after midday loading. That trend should be tracked over several days, not one afternoon only.
Link the log to what happened on site
Temperature data means more when you match it to site events. Write down cleaning, maintenance, stock changes, power interruptions and any alarm call. Then compare those notes with the log. If the room warmed after a coil clean, that may be because the unit was off for service. If the warming starts days later, there may be an unrelated issue that needs checking.
For planned maintenance, this step is essential. A clean log before and after service shows whether the work improved pull-down time, reduced cycling or stopped ice formation. It also helps when you need to explain a temperature excursion to a manager or auditor.
A simple weekly check for shops and farms
Most sites do not need complicated analysis every day. A weekly review is enough to catch early changes if it is done properly. Keep the printout or digital record, and review the same points each time. Small drift is often the first sign of a bigger failure later.
- Compare this week’s average with last week’s average.
- Check for repeated highs at the same time each day.
- Look for longer recovery after door use or defrost.
- Confirm the logger clock is correct after load-shedding.
- Inspect the room for blocked vents, ice, water or abnormal noise.
If the trend is moving the wrong way two weeks in a row, do not wait for a full breakdown. Arrange an inspection and make notes while the issue is still small.
When to call for service without delay
Some readings need a technician straight away. If stock safety is at risk, act early. A log that shows repeated excursions, rising average temperature or sudden loss of control should never be ignored. The same applies if one room behaves differently from similar rooms on the same site.
Call for help when you see any of these signs: alarms that repeat after resets, temperature climbing through the day, long compressor run times, heavy frost on the coil, water on the floor, or poor cooling after a power cut. In Montague Gardens, Cape Town and the wider Western Cape, our team handles emergency call-outs, leak detection, coil cleaning, drain clearing and cold-room servicing for shops and farms. Early action costs less than lost stock, and usually saves a second fault from developing.
