Littelfuse LLC54AA Liquid Level Control Relay

The Littelfuse LLC54AA is a compact, adjustable sensitivity liquid level control relay designed for reliable detection and control of conductive liquids in industrial applications. It operates by monitoring resistance between probes to detect high and low liquid levels, triggering a relay to control pumps or valves for filling or draining operations. Key features include an adjustable sensitivity knob (1-10 scale, corresponding to 1k-250k ohms resistance), LED status indicator for relay operation, and compatibility with single or dual probe setups. This model is ideal for water treatment, sump pumps, chemical processing, and food/beverage industries where precise level control prevents overflow or dry running. Advantages over similar products include its robust construction, easy installation on DIN rails or panels, and UL/CSA certifications for safety. Drawbacks may include limited suitability for non-conductive liquids and the need for periodic probe cleaning in corrosive environments. The unit supports 120VAC input and offers general-purpose ratings, making it versatile for pilot duty applications. Based on visual analysis, this unit appears used with minor wear, cut wires, and a 2017 date code, but remains functional for refurbishment or direct use.