Siemens · SIRIUS ACT Series

3SU1150-1HB20-3CH0

Active
UL CSA CE

SIRIUS ACT E-Stop Twist Release 2NC

Part number: 3SU1 - 1 - 50 - 20
Siemens SIRIUS ACT Series Introduced circa 2013

Siemens SIRIUS ACT e-stop with plastic front ring — budget option.

Common Applications

Same function as the metal 3SU1150 but with plastic front ring. Costs 40% less. For indoor panels where the premium metal look isnt needed. 2NC contacts for dual-channel safety.

Specifications

Actuator Function
Twist-release
Actuator Type
Mushroom 40mm
Certifications
UL, CSA, CE
Color
Red
Contact Configuration
2NC
Cutout Diameter
22mm
IP Rating
IP67
Material
Plastic front ring

Installation Quick Reference

Panel cutout: 22mm. Mount with the yellow backing plate visible (required by EN/ISO 13850).

Wiring: Wire NC contacts in series with the safety relay input channels. Use dual-channel wiring for SIL 3 / PLe applications. Never wire directly to a motor contactor.

Testing: Press the e-stop and verify the machine stops within the required time. Test the reset mechanism. Repeat monthly per EN/ISO 13850.

Dimensions

Front 22mm cutout 40mm head Side panel terminals

Wiring Diagram

21 22 NC Ch.1 31 32 NC Ch.2 Dual-channel safety

Troubleshooting

E-stop won't reset (twist/pull doesn't release)

Check for debris in the mechanism. For twist-release: turn clockwise 45-90 degrees. For push-pull: pull straight out firmly. If the mechanism is stuck, the internal latch may be damaged — replace the entire head assembly.

Machine doesn't stop when e-stop is pressed

Critical safety issue. Immediately lock out the machine. Check wiring — NC contacts must be in series with the safety relay. Verify the safety relay is functioning. A broken wire in an NC circuit should cause a stop, so check for a wiring bypass.

Safety relay faults after e-stop reset

The safety relay detects a cross-fault between the two monitoring channels. Check that both NC contacts on the e-stop are switching simultaneously. One contact may be welded closed — replace the contact block.

Where to Buy

Price range

$31.37 — $79.54

across 2 distributors

Quick Specs

Actuator Function
Twist-release
Actuator Type
Mushroom 40mm
Certifications
UL, CSA, CE
Color
Red
Contact Configuration
2NC

What People Are Saying

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“Same function as the metal 3SU1150 but with plastic front ring. Costs 40% less. For indoor panels where the premium metal look isnt needed. 2NC contacts for dual-channel safety.”

Reddit r/PLC 30 upvotes View thread →