Float level switch AT 120

for wastewaterfor tanksfor pump control

Presentation
The AT 120 float level switch is a dry-contact (COM / NO / NC) biconical float switch designed for automatic pump control in industrial and wastewater applications. Its wide differential angle provides stable, snag-free switching to protect pump motors and electrical equipment. A high-resistance, double-envelope version is available for aggressive liquids. Note: not recommended for very slow filling rates.

Operating principle
The device operates by tipping detection: the float moves with the liquid level and tilts at a preset angle to open or close a mechanical switch. When used in pairs, two units can regulate minimum and maximum levels within the same tank.

Modes of operation

• Drain mode: switch activates the pump at the high position (anti-overflow). When the tank is emptied, the circuit opens to protect the pump.
• Fill mode: switch closes the circuit in the low position (NC) to start the pump and fill the tank.

Detection characteristics
Omnidirectional detection thanks to the biconical float shape; reliable in agitated or turbulent liquids.

Installation and adjustments
The float is suspended on its cable; the ballast fixation point on the cable adjusts the switching angle and level differential. Increasing the distance between ballast and float increases the switching differential. The ballast is adjustable and removable to set the locking ring position. Use the FIXCAB accessory for recommended fixation; avoid clamps that may damage the cable and compromise sealing. Electrical connections must be sealed and housed outside the tank. Cable extensions can be made with standard signal cable; custom cable lengths are available on request to avoid splices.

Options and variants
High-resistance double-envelope version (HR HY) for aggressive liquids (acids, solvents, hydrocarbons, etc.). On request, unit can be supplied with a multifunction plug or with a 3G1 cable for direct pump connection.

Recommended accessories

• FIXCAB: suspension fixation accessory for float switches.
• Resin ballast 175 g (adjustable cable ballast).
• Multifunction plug (convenient option for pump automation).
• Level control relays (e.g., AT series) for control and alarm functions.

Technical characteristics / specifications

• Switching angle: ±120°
• Allowed fluid density: 0.70 to 1.15 kg/dm³
• Maximum working pressure: 3.5 bar
• Maximum temperature: 85 °C
• Protection rating: IP68
• Biconical housing: copolymer polypropylene
• Cable: 3 conductors 1 mm², neoprene (HR HY for high-resistance version)
• Float weight without cable: ~200 g
• Ballast: 175–250 g loaded resin
• Cable lengths (standard): 3 m, 5 m, 6 m, 10 m, 20 m
• Contacts: COM / NO / NC (selection by wiring)
• Electrical ratings (representative examples): AC 50/60 Hz – up to 250 V resistive 20 A, inductive 8 A; DC examples: 48 V 1.5 A; 24 V 10 A; 50 V 1.8 A