3RF2020-1AA42

What type of device is this?

This is a SIRIUS 3RF20 single-phase solid-state relay designed to switch AC loads using a low-voltage DC control signal. It has no moving contacts, making it suitable for frequent switching applications.

What load voltage can the relay switch?

The relay is rated for AC operating voltages from 24 to 230 V at 50 or 60 Hz. Its specified operating range extends from 20 to 253 V AC.

What control voltage does the relay require?

The control input operates from 4 to 30 V DC. A signal of at least 4 V DC is recognized as ON, while 1 V DC or less is recognized as OFF.

What is the rated load current?

The rated operational current is 20 A for AC-51 loads. The application must also account for ambient temperature, heat dissipation, load characteristics, and the thermal resistance of the selected heat sink.

Does the relay use zero-cross switching?

Yes. The 3RF2020-1AA42 uses zero-cross switching, which turns the AC load on near the voltage zero point. This can reduce switching disturbances when controlling suitable resistive loads.

What types of applications is this relay commonly used for?

It is commonly used for frequent single-phase switching of resistive AC loads, including industrial heaters, heating elements, ovens, molding equipment, packaging machinery, and process temperature-control systems.

Is a heat sink required?

Thermal management is required because the relay dissipates up to 28.6 W at rated current in a hot operating state. The correct heat sink should be selected according to load current, ambient temperature, enclosure conditions, and the thermal derating curve.

What are the relay's dimensions?

The unit measures approximately 58 mm high, 45 mm wide, and 48 mm deep. It is secured by screw fixing and can be mounted side by side when installation conditions permit.

What terminal types are provided?

Screw terminals are used for both the main current circuit and the DC control circuit. The main terminals use M4 screws, while the control terminals use M3 screws.

Which terminals are used for the load and control circuits?

The AC main circuit connects through terminals 1L and 2T. The DC control signal connects to A1 positive and A2 negative, so the control polarity must be observed.

What conductor sizes can be connected?

The main terminals accept solid or stranded conductors from 1.5 to 6 mm², with finely stranded conductors and suitable end preparation accepted up to 10 mm² in specified configurations. The control terminals accept conductors from 0.5 to 2.5 mm², depending on conductor type and quantity.

What are the recommended terminal tightening torques?

The main screw terminals should be tightened to 2 to 2.5 N·m. The control terminals should be tightened to 0.5 to 0.6 N·m. The equipment fixing screw has a maximum tightening torque of 1.5 N·m.

What is the operating temperature range?

The specified ambient operating temperature range is -25 to +60 degrees Celsius. Current derating begins at 40 degrees Celsius, so the allowable load current may be lower at higher ambient temperatures.

What enclosure protection rating does the relay have?

The relay has an IP20 rating, with finger-safe protection from direct front contact when approached vertically. It is intended for installation inside an appropriate industrial control enclosure.

How quickly does the relay switch?

The specified turn-on and turn-off delay is 1 ms, plus up to one additional half-cycle of the AC waveform because switching is synchronized with the zero-crossing point.

What is the minimum load current?

The minimum specified operational current is 100 mA. Loads drawing less than this may not switch as intended, and the relay's thyristor leakage current should also be considered.

Does the output fully isolate an AC load when switched off?

A solid-state relay can allow a small leakage current while switched off. For this model, the specified reverse current of the thyristor is 10 mA, so the output should not be treated as a physical isolation point.

What short-circuit protection should be used?

A correctly coordinated semiconductor fuse should be installed to protect the relay against short circuits. Suitable fuse selection depends on the circuit design, prospective fault current, load, and applicable electrical requirements.

Can this relay switch DC loads?

No. The control input is DC, but the main output is intended for single-phase AC loads. A relay specifically designed for DC load switching should be selected for a DC output circuit.

What should be checked when selecting this relay as a replacement?

Confirm the AC load voltage, continuous current, load category, DC control range, zero-cross switching requirement, terminal arrangement, dimensions, mounting method, heat-sink capacity, ambient temperature, and protective fuse coordination.