The Allen-Bradley 1764-RTC is a Real-Time Clock (RTC) module that is used with MicroLogix 1500 controllers. This module is typically used to implement scheduled plant operation and processes, popular with Heating, Ventilation and Air Conditioning (HVAC) systems, Building Management systems (BMS) and some other applications. This accessory module is installed by removing the MicroLogix 1500 front panel cover. It provides accurate time and clock reference which can be accessed by the program through built-in instructions.

The 1764-RTC features clock accuracy that varies depending on the operating temperature. It has an accuracy of +34 to -70 seconds/month at 0°C or +32°F); +36 to -68 seconds/month at +25°C or +77°F); +29 to -75 seconds/month at +40°C or +104°F) and -133 to -237 seconds/month at +55°C or +131°F. When data to be written to the RTC module is verified valid by the system, the data is written immediately however, an invalid data cannot be written to the module. This prevents system and programming error from occurring to the controller.

Additionally, the 17640RTC comes with a non-replaceable battery. This battery is expected to operate at a minimum of 5 years when the host controller is operated at 0°C to +40°C or +32°F to +104°F). When stored, the RTC battery life expectancy is 5 years, minimum at -40°C to +25°C (-40°F to +77°F) and 3 years minimum at +26°C to +60°C (+79°F to +140°F). If the RTC battery is low but the controller remains powered, the RTC module operation is normal. If controller power is removed along a low-battery RTC, the RTC data may be lost upon completion of power cycle. The RTC can be disabled to lengthen the device’ operation.