Siemens SIRIUS Safety Technology
Siemens 3TK2825-1AL20 SIRIUS Safety Relay
A 230 V AC safety relay with screw terminals, three instantaneous enabling contacts and two signaling contacts for monitored machine-safety circuits.
Product Overview
Compact Relay Logic for Monitored Machine Safety
The 3TK2825-1AL20 belongs to the Siemens SIRIUS 3TK28 safety relay family. It evaluates single-channel or two-channel safety circuits and switches three relay enabling paths without intentional delay.
Siemens specifies the device for emergency-stop circuits, movable guards, protective doors and safety mats. Automatic and monitored start are supported, together with external-device monitoring and cross-circuit detection.
| Manufacturer | Siemens |
|---|---|
| Order number | 3TK2825-1AL20 |
| Product family | SIRIUS 3TK28 |
| Product type | Safety relay, basic device |
| Terminal system | Screw terminals |
| Mounting | 35 mm mounting rail; any mounting position |
| Housing / terminals | IP40 / IP20 |
Product Specifications
Verified Technical Data
| Rated control supply | 230 V AC, 50/60 Hz |
|---|---|
| Enabling outputs | 3 NO: 13-14, 23-24, 33-34 |
| Signaling outputs | 2 NC: 41-42, 51-52 |
| Start modes | Automatic start; monitored start |
| Stop category | Stop Category 0 |
| Maximum safety level | SIL 3; PL e; Category 4 |
| PFHD | 1.5 x 10-9 per hour |
| T1 interval | 20 years |
| Thermal current | 6 A |
|---|---|
| AC-15 rating | 6 A at 230 V AC |
| DC-13 rating | 6 A at 24 V DC |
| Mechanical cycles | 10 million |
| Electrical cycles | 100,000 |
| Operating temperature | -25 to +60 °C |
| Product dimensions | 45 x 106 x 115 mm (W x H x D) |
| Net weight | 0.469 kg |
Features & Benefits
Product Functions
Dual-channel evaluation
Supports two-channel sensor wiring with cross-circuit monitoring.
Selectable restart
Provides automatic or monitored start selection.
Three enabling paths
Three instantaneous NO contacts switch downstream safety contactors.
External-device monitoring
The feedback circuit monitors connected contactors.
Long field wiring
Up to 1000 m single-channel or 500 m two-channel at 1.5 mm².
Status indication
Three LEDs provide device status information.
Applications
Industrial Application Scope
Emergency-stop circuits
Evaluation of emergency-stop control devices in machinery safety circuits.
Protective-door monitoring
Safety circuits for movable guards and protective doors.
Safety mats
Step-mat circuits using the supported safety architecture.
Lifecycle & Replacement
Official Product Status
Product Technical Images
Terminal and Safety-Path Schematic
The diagram separates sensor channels, start and feedback connections, enabling outputs and signaling contacts.
Functional schematic based on Siemens terminal assignments. Not to scale.
FAQ
Frequently Asked Questions
Is 3TK2825-1AL20 still in active production?
No. Siemens lists the product as production discontinued.
What is the official preferred successor?
Siemens identifies 3SK1111-1AW20 as the preferred successor.
Is the successor a direct terminal-for-terminal replacement?
No. Terminal mapping is required, and one signaling circuit is not available in the successor configuration.
Does this model support automatic and monitored start?
Yes. Both start modes are supported.
What should be supplied for a quality enquiry?
Provide the complete order number, quantity, nameplate photos and terminal photos.
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Contact Information
Industrial Parts Enquiry
Send the exact model, quantity and destination for a quotation.
ManagerLeonia
Emailsales@mvme.cn
Whatsapp+8618030175807
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