The Siemens 3TK2821-1CB30 is a SIRIUS 3TK28 series safety relay designed for monitoring emergency stop circuits and protective doors in industrial machinery. It operates on 24 V AC/DC supply and provides 3 Normally Open (NO) safety outputs plus 1 Normally Closed (NC) signaling contact, with screw terminals for wiring.
Item No :
3TK2821-1CB30Order(MOQ) :
1Payment :
EXWProduct Origin :
GermanyShipping Port :
Wuhan, Hubei, ChinaLead Time :
3-5 daysWeight :
0.247kgOverview
3TK2821-1CB30 Siemens Simatic PLC Module
New in stock
Origin from Germany
Payment Method: TT.Western Union
Shipping Method: DHL\UPS\Fedex\EMS\Others
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| Part Number | Description | Key Difference |
|---|---|---|
| 3TK2821-1CB30 | Safety Relay, 24V AC/DC, 3NO+1NC (this item) | Discontinued; remaining stock |
| 3SK1111-1AB30 | Successor – SIRIUS 3SK1 Safety Relay | Current platform |
| 3TK2821-2CB30 | Same function, spring terminals | Spring terminal variant |
| 3TK2830 | Expansion Module | For adding safety contacts |
Migration Note: The successor 3SK1111-1AB30 is from the newer 3SK1 series. While functionally equivalent, verify terminal layout, wiring diagrams, and panel space before substituting.
1 × Siemens 3TK2821-1CB30 SIRIUS Safety Relay
Note: Safety sensors, contactors, and DIN rail are sold separately.
In Stock – Limited remaining stock available
Tested – Each unit verified for functionality
Warranty Included – Purchase with confidence
Technical Support – Safety circuit compatibility assistance available
Q1: What is the Siemens 3TK2821-1CB30?
It is a SIRIUS 3TK28 series safety relay with 24 V AC/DC supply, 3 NO safety outputs, and 1 NC signaling output. It is used for monitoring E-stop circuits, safety doors, and position switches in industrial machinery .
Q2: Is this product still in production?
No. It is a discontinued product (phase-out started 2015) . It is available only through remaining stock or third-party suppliers.
Q3: What is the successor model?
The designated successor is 3SK1111-1AB30 from the SIRIUS 3SK1 series .
Q4: What safety rating does this relay achieve?
As a basic device, it achieves SIL 1 / PL c. When used as an expansion unit in a cascaded configuration, the system can achieve up to SIL 3 / PL e .
Q5: How many safety outputs does it have?
It has 3 Normally Open (NO) safety outputs (instantaneous) and 1 Normally Closed (NC) signaling output .
Q6: What is the difference between autostart and manual start?
Autostart: outputs energize automatically when the input circuit is closed. Manual start: operator must press a start button after the circuit is restored. The 3TK2821-1CB30 supports both modes .
Q7: Does this relay support dual-channel input?
Yes. It supports 1-channel or 1- and 2-channel sensor wiring .
Q8: What type of terminals does it use?
It uses screw terminals. For a spring terminal variant, see the 3TK2821-2CB30 .
Q9: What is the operating temperature range?
The range is -25 to +60 °C.
Q10: What is the country of origin?
Germany .
Q11: What should I verify before ordering?
Always verify the exact part number (3TK2821-1CB30), confirm that a discontinued product is acceptable for your maintenance application, check the condition and warranty of the specific unit offered, and consider whether the successor 3SK1111-1AB30 would be a better long-term choice.
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