--- title: ALr 21 - How the 'Max Compressor Starts' alarm works description: If the cooler compressor repeats over temperature events equaling the high temperature lockout count within a period you set, the SCS Controller can switch off the compressor and trigger an AL21 alarm. --- [Skip to content](https://support.aofrio.com/al21-how-the-max-compressor-starts-alarm-works#main-content) - [English](https://support.aofrio.com/al21-how-the-max-compressor-starts-alarm-works) - [Español - México](https://support.aofrio.com/es-mx/al21-cómo-funciona-la-alarma-de-máximos-arranques-del-compresor) - [Português - Brasil](https://support.aofrio.com/pt-br/al21-como-funciona-o-alarme-de-máximos-inícios-do-compressor) English Show submenu for translations ![](https://support.aofrio.com/hs-fs/hubfs/e7b764c0-c89a-4e26-92a2-ab6256f23c6a_medium.png?width=100&height=75&name=e7b764c0-c89a-4e26-92a2-ab6256f23c6a_medium.png) Open main navigation Close main navigation - - [English](https://support.aofrio.com/al21-how-the-max-compressor-starts-alarm-works) - [Español - México](https://support.aofrio.com/es-mx/al21-cómo-funciona-la-alarma-de-máximos-arranques-del-compresor) - [Português - Brasil](https://support.aofrio.com/pt-br/al21-como-funciona-o-alarme-de-máximos-inícios-do-compressor) English Show submenu for translations - Contact us Contact us How can we help you? - There are no suggestions because the search field is empty. 1. [Help Center](https://support.aofrio.com/?hsLang=en) 2. [IoT hardware operation & behavior](https://support.aofrio.com/iot-hardware-operation-behavior?hsLang=en) 3. [SCS Controller - Faults & Alarms](https://support.aofrio.com/iot-hardware-operation-behavior?hsLang=en#scs-controller-faults-alarms) August 26, 2025 # ALr 21 - How the 'Max Compressor Starts' alarm works ## If the cooler compressor repeats over temperature events equaling the high temperature lockout count within a period you set, the SCS Controller can switch off the compressor and trigger an ALr 21 alarm. Review the fault logic for the 'Max Compressor Starts' alarm in the following graph: ![Max Compressor Starts alarm ](https://support.aofrio.com/hs-fs/hubfs/faultlogic_MaxCompressorstarts_ENG1.jpg?width=670&height=624&name=faultlogic_MaxCompressorstarts_ENG1.jpg) ### Possible causes and actions The compressor has had repeated over temperature trips equaling the high temperature lockout count, within the specified period (This alarm is disabled by default. Parameter access is available upon request). The condenser sensor keeps seeing a high temperature. 1. 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