Circuit alarm has a sound or light display to show when the storage and-or refrigeration circuit (4) is not working. The reactivation of the system by closing of a main contact breaker (11) return the alarm to stand by and imposes a delay in start up of the storage system to prevent excessive cooling of the milk which remains in the tank (1). The alarm also operates when the milk flow (3) connects the feed pipe to the tank filling opening (2).