3TK2828-1AJ20

What does this relay do?

This unit is a SIRIUS safety relay designed to monitor protective devices such as guard doors, position switches and step mats. It provides relay enabling circuits with both instantaneous and delayed outputs, making it suitable for applications where controlled stopping behaviour is required.

What supply voltage does it require?

It is designed for a 115 V AC control supply at 50/60 Hz. The operating range factor is 0.85 to 1.1 of the rated coil voltage.

How many output contacts are available?

The relay provides 2 instantaneous safety-related NO contacts, 2 delayed safety-related NO contacts, and 1 instantaneous NC contact for signalling.

Does it have an adjustable delay function?

Yes. The delayed enabling circuit can be adjusted from 0.5 to 30 seconds after the safety circuits are opened, which is useful where a timed stop is needed.

Is automatic start available?

Yes. This version is configured for automatic start. The typical make time on AC supply is up to 80 ms.

What applications is it suited to?

According to the datasheet, it is suited to protective door monitoring, step mat monitoring, position switch monitoring and the monitoring of floating sensors. Siemens 3TK2828-1AJ20 is also suitable for use with safety switches and safety-related circuits.

Can it be used for emergency stop monitoring?

No. This version is not intended for emergency stop circuit monitoring. It is more specifically aimed at guard door and related switching applications.

What are the mounting options?

The relay can be mounted in any position and supports both screw mounting and snap-on mounting, which helps when fitting it into a control panel layout.

What type of terminals does it use?

It uses screw terminals. The connectable conductor sizes include solid conductors from 0.5 to 4.0 mm² for single conductors, and finely stranded conductors with end treatment from 0.5 to 2.5 mm².

What are the physical dimensions?

The unit is approximately 44.8 mm wide, 138.5 mm high and 120 mm deep.

What enclosure protection does it offer?

The housing and terminals are rated IP20. The design is finger-safe for protection against electrical shock during normal panel installation.

What operating conditions is it designed for?

It is rated for operation from -25 °C to +60 °C, with storage from -40 °C to +80 °C. It can be used at altitudes up to 2,000 m and in relative humidity from 10% to 95% during operation.

What switching performance should be expected?

The relay supports up to 1,000 operating cycles per hour. Typical electrical life is 100,000 switching cycles, while typical mechanical life is 10,000,000 cycles.

What protection should be used for the output contacts?

For short-circuit protection of the NO relay outputs, the datasheet specifies a gL/gG 6 A fuse or a quick-acting 10 A fuse.

What functional ratings does it achieve?

The unit is rated up to SIL 3 according to IEC 61508, with the delayed release circuit rated up to SIL 2. It also reaches PL e for the non-delayed circuit and PL d for the delayed circuit, with Category 4 according to ISO 13849-1.