Monitoring/ alarm systems
Every freezer is equipped with an internal temperature probe to control the temperature within the chamber. Based on that measurement, the freezer firmware controls the compressor system to adapt the temperature if necessary. The alarm system of the freezer is based on this internal temperature probe. For many freezers, you can define the limit for alarms, e.g. 3 °C below the set-point. That means, when the freezer is set for -80 °C, the alarm will start at -77 °C. Be aware, the more often the freezers is opened, the more temperature buffer should be included for the alarm. Otherwise, the alarm system will be triggered all over the day.
The local alarm is generated by integrated warning lamps and audio warnings at the freezer.
If the freezer is connected to a building management system (BMS), the alarm is transferred to a central alarm control unit. This finally results in that infamous call at 3 a.m. by the guard informing you about your freezer alarm.
Especially in pharmaceutical environments, a second, independent, temperature monitoring/ alarm system is more and more requested. These independent temperature measurements are based on a completely independent system with external power supply, backup battery, and messaging system. The independent temperature probe should be installed in a proper way in the middle of the freezer compartment, in close neighborhood to the internal freezer probe.