Finder 77.F1.9.024.8250 – 77 Series Modular solid state relays

Why Choose the Finder 77.F1.9.024.8250 Solid State Relay?

The Finder 77.F1.9.024.8250 is a high-capacity 80 A single-phase solid state relay (SSR) designed for reliable, silent and contactless switching of industrial AC electrical loads. Part of the Finder Series 77 industrial solid state relay range, this device combines a nominal 24 V DC control input, a 3–32 V DC operating input range and a 24–280 V AC output switching range in a robust hockey puck-style housing.

Featuring zero-crossing switching technology, the Finder 77.F1.9.024.8250 activates its semiconductor output close to the AC voltage zero crossing. This helps reduce switching disturbances in suitable applications, particularly resistive heating and other compatible AC loads.

Unlike conventional electromechanical relays, the Finder 77.F1.9.024.8250 operates without moving power contacts. Its semiconductor switching mechanism provides silent operation, rapid switching response and freedom from mechanical contact bounce, making it suitable for industrial heating systems, process equipment, lighting circuits and automated machinery.

The relay features a single normally open equivalent output, screw terminal connections and a hockey puck-style housing with folding terminal covers. Designed for panel or heatsink mounting, it can be installed on suitable control cabinet sheet metal or an appropriately rated heatsink. Correct thermal management is essential when operating at higher load currents.

Key Advantages

• 80 A single-phase solid state relay for high-current industrial AC switching.
• 24 V DC nominal control input for compatible industrial automation systems.
• 3–32 V DC control input range for flexible electronic control.
• 24–280 V AC output switching range for suitable AC electrical loads.
• Zero-crossing switching technology helps minimise switching disturbances in compatible applications.
• 800 A maximum peak current for 10 ms under specified conditions.
• Contactless semiconductor operation eliminates mechanical contact wear.
• Silent, spark-free and bounce-free switching during normal operation.
• Single normally open equivalent output for straightforward AC load control.
• Hockey puck-style industrial housing with folding screw terminal covers.
• Relay-style terminal arrangement with control and load connections on opposite sides.
• Panel or heatsink mounting for industrial electrical cabinets.
• Screw terminal connections for practical electrical wiring.
• 47–400 Hz output operating frequency range for compatible AC applications.
• −30 to +80 °C ambient temperature range, subject to thermal derating.
• IP20 protection rating for appropriately protected installations.
• Suitable for industrial heating, lighting, process equipment and automated AC load switching.

Key Features

• Finder Series 77 industrial solid state relay.
• Single-phase AC output switching.
• Output configuration: 1 normally open equivalent (SPST-NO / 1 Form A).
• Rated output current: 80 A.
• Output switching voltage: 24–280 V AC.
• Nominal control voltage: 24 V DC.
• Control voltage range: 3–32 V DC.
• Control input type: DC.
• Switching characteristic: Zero crossing.
• Maximum peak current: 800 A for 10 ms.
• Output operating frequency: 47–400 Hz.
• Hockey puck-style housing.
• Folding screw terminal covers.
• Relay-style input and output terminal arrangement.
• Panel or heatsink mounting.
• Screw terminal connections.
• Operating ambient temperature: −30 to +80 °C.
• Protection rating: IP20.
• Silent semiconductor switching without moving power contacts.

Advanced 80 A Zero-Crossing Switching with 24 V DC Control

The Finder 77.F1.9.024.8250 is designed to switch high-current single-phase AC electrical loads using a compatible low-voltage DC control signal. When a voltage within its specified 3–32 V DC input range is applied, the relay enables its semiconductor output close to the next AC voltage zero crossing.

Zero-crossing switching means that the relay begins conducting when the instantaneous AC voltage is close to zero. This can help reduce switching disturbances and electromagnetic interference compared with switching at arbitrary points in the AC waveform, particularly when controlling suitable resistive loads.

For industrial heating applications, zero-crossing switching is especially useful where electric heating elements are repeatedly switched by temperature controllers. The Finder 77.F1.9.024.8250 allows heating circuits to be controlled without the audible clicking and mechanical contact wear associated with conventional electromechanical relays.

The relay's 80 A rated output and 24–280 V AC switching range make it suitable for appropriately rated industrial heaters, process machinery and high-current AC switching installations. Its 800 A maximum peak current for 10 ms describes a short-duration surge withstand capability and must not be confused with the permissible continuous load current.

Because the relay uses semiconductor switching rather than moving contacts, it provides silent operation, fast switching response and freedom from contact bounce. This makes it particularly useful in automated systems requiring frequent switching, provided that the load current and thermal conditions remain within the manufacturer's specified limits.

The 24 V DC nominal control input is also well suited to industrial automation systems using low-voltage control circuits. The relay can be operated from a compatible PLC output, temperature controller or other electronic interface capable of supplying the required control voltage and current.

Thermal Management and Safe Installation

Correct thermal management is essential when installing the Finder 77.F1.9.024.8250. Solid state relays generate heat while conducting current because their semiconductor outputs have an inherent voltage drop. The amount of heat increases with load current, making the relay's 80 A rating dependent on appropriate heatsinking and installation conditions.

The relay is designed for mounting onto suitable control cabinet sheet metal or an appropriately rated heatsink. The required thermal arrangement depends on the continuous load current, ambient temperature, enclosure ventilation and mounting conditions. The manufacturer's thermal derating information should be used when selecting the heatsink and determining the permissible continuous current.

For high-current installations, the thermal interface between the relay and its mounting surface is particularly important. Correct mounting pressure and suitable thermal interface materials should be used where specified by the manufacturer to ensure effective heat transfer.

Appropriate upstream short-circuit protection must also be provided. Solid state relays can be sensitive to excessive fault currents, so protective devices should be selected according to the manufacturer's recommendations and the electrical characteristics of the installation.

As with other solid state relays, the Finder 77.F1.9.024.8250 may allow a small leakage current when the output is switched off. It does not provide mechanical contact separation and must not be used as the sole means of safety isolation. A suitable mechanical disconnecting device should be installed wherever safe isolation is required.

Typical Applications

• High-current single-phase AC load switching.
• Industrial electric heating element control.
• Industrial ovens and process heating systems.
• Temperature-controlled manufacturing equipment.
• Industrial drying and curing systems.
• Resistive heating load switching.
• Commercial and industrial lighting control within suitable ratings.
• Automated manufacturing and processing machinery.
• Industrial temperature control panels.
• Solenoid and contactor coil switching where electrically compatible.
• Industrial process control and automation systems.
• PLC-controlled AC switching through compatible DC outputs.
• Electrical control cabinets and panel-mounted switching equipment.
• OEM equipment requiring silent high-current AC switching.
• Frequent-duty switching applications within the relay's specified limits.