Siemens SIRIUS 3RK3111 MSS Basic: Enabling Force in Test Mode

Overview: When the Force Option Becomes Available

The Force function on the Siemens SIRIUS 3RK3111 MSS Basic modular safety system is not available in the default configuring (online) mode that opens immediately after a download. The Force command is only enabled once the central unit is switched to test mode through Target system > Test mode in the SIRIUS Safety ES (formerly MSS-ES) configuration software. Test mode is the engineering diagnostic state in which I/O signals, function blocks, and logic states can be observed, overridden, and forced for commissioning without affecting the final safety logic on the device.

This article explains why Force is hidden in configuring mode, the exact procedure to enable it on a 3RK3111 central unit, the password handling rules, and how to verify that the option has been activated. It also documents troubleshooting cases where Force remains greyed out, the password prompt fails, or the download cannot be completed.

1. Product Context: SIRIUS 3RK3 MSS Basic Family

The 3RK3 Modular Safety System (MSS) is the Siemens SIRIUS safety controller family for small to mid-sized safety applications, used as an alternative to conventional hard-wired safety relay chains and to larger SIMATIC F-CPU systems when only a few safety functions are required. The MSS family is split into two product lines:

The 3RK3111 central unit covered here is the Basic variant: it has an integrated set of safety logic blocks (emergency stop, safety gate, two-hand, muting, light curtain, etc., depending on firmware) and is configured with SIRIUS Safety ES (the engineering tool, downloadable from the Siemens Industry Online Support portal). For general product information and ordering data see the Siemens SIRIUS product family page.

2. Why Force Is Locked in Configuring Mode

The Force function directly writes to the I/O image of the safety central unit during online operation. Because every forced value temporarily overrides a real safety signal (sensor state, output to contactor, feedback circuit), SIRIUS Safety ES gates the function behind two controls:

1. Mode gate – the engineering PC must be in test mode, not configuring mode. This is the primary reason Force remains disabled right after a download.
2. Password gate – test mode itself is protected by a password that defaults to 0000. If the password has been changed and lost, the device must be reset to factory settings (which removes the safety configuration).

Only when both conditions are satisfied will the Target system > Force (or Force I/O) command activate, allowing per-channel forcing of inputs, outputs, and selected internal flags while online.

3. Prerequisites

Before attempting to enable Force on the 3RK3111, confirm the following:

• Configuration software: SIRIUS Safety ES installed and licensed on the engineering PC. The tool is the successor of the older MSS-ES software and is required for current 3RK3 firmware generations.
• Project consistency: The open project must match the configuration stored on the device. Run Edit > Check consistency and resolve any reported errors before downloading.
• Serial connection: A serial (RS-232) point-to-point link from the PC to the 3RK3111 is configured, e.g., COM1 at 57.6 kbit/s or 115.2 kbit/s, 8 data bits, no parity, 1 stop bit. Some versions expose a USB service interface (3RK3911-0BA00 USB-to-serial adapter) instead of a native COM port.
• Power supply: The 24 V DC supply to the 3RK3111 must be present and the device must complete its self-test without errors (all status LEDs green or as expected).
• Operating state: The controlled machine or process must be in a safe stopped / de-energized condition so that any forced I/O does not cause unexpected machine motion.

4. Step-by-Step: Function Test of the 3RK3111 in Test Mode

The numbered procedure below matches the official Function test of the MSS 3RK3 Basic workflow documented in the SIRIUS Safety ES help and the 3RK3 Basic operating instructions. It is the precise sequence that unlocks the Force option.

1. Switch on the power supply. The safety relay executes a self-test. Wait for the status LEDs to settle (READY/CPU LED steady green; no SF/DIAG LED).
2. Check consistency. Choose Edit > Check consistency. If the output window shows no messages, the configuration is internally consistent and may be downloaded.
3. Download to the switching device. Choose Target system > Load to switching device. Confirm the memory dialog (whether to keep the existing configuration in RAM) with Yes. The Save switching device as dialog opens.
4. Save the project. Confirm the storage location. The Load to switching device dialog then opens to select the interface.
5. Set the interface. Pick the COM port that the 3RK3111 is connected to (e.g., COM1) and confirm with OK. The configuration is transferred; a completion message appears.
6. Confirm download completion with OK. The engineering tool is now online in configuring mode. In this state the Force command is greyed out.
7. Switch to test mode. Choose Target system > Test mode. Confirm the prompt Activate test mode with Yes. The Change password for test mode dialog opens.
8. Assign the test-mode password. The default is 0000. If you change it, record the new password; the device does not store a copy that can be retrieved later.

After step 8 the MSS transitions from configuring mode to test mode. The status bar of SIRIUS Safety ES now shows Online – Test mode, and the Force entry under the Target system menu (or the right-click context menu of an I/O signal) becomes available.

5. Using the Force Function

Once test mode is active, Force is opened from the Target system menu or via the Force button on the online toolbar. The Force window presents a tabular list of every I/O signal and selectable internal variable in the active configuration:

Common Force workflows on a 3RK3111 include:

• Forcing a safe sensor input LOW to simulate an open safety gate while watching whether the assigned output drops out.
• Forcing an output HIGH to verify wiring to the downstream contactor or drive, bypassing the safety logic for a single test cycle.
• Forcing flags or counter values to step through muting sequences or two-hand control logic.

6. Password Management for Test Mode

The password dialog shown during the transition to test mode has three behaviors:

• Default password 0000: Used on a freshly delivered device or after a factory reset. Enter 0000 in both fields and confirm.
• New password assignment: If the default is still active, the dialog prompts to assign a new password. Choose a password of at least the minimum length required by the installed firmware (typically 4 numeric characters; later firmware may accept alphanumeric).
• Existing non-default password: If a password was previously assigned, the dialog asks for the current password before a new one can be entered.

If the password is lost and the device is not in protection mode, the only recovery is a factory reset from SIRIUS Safety ES (Target system > Reset to factory settings) or by holding the service button during power-up, depending on firmware. A factory reset erases the safety configuration – the project file on the engineering PC must be available to restore it. Re-validate the safety function after restoration.

7. Verification: Confirming Force Is Enabled

After completing the procedure above, verify Force is actually available before relying on it for commissioning:

1. Look at the SIRIUS Safety ES status bar – it must read Online – Test mode, not Online – Configuring mode.
2. Open Target system > Force. The dialog should open without error.
3. Right-click an input signal in the configuration view and confirm that the context menu contains the Force value… entry.
4. Apply a harmless force (e.g., force an unused spare input) and watch the Force dialog status change to Forced. Clear the force immediately after the check.

If any of these checks fail, see the troubleshooting matrix below.

8. Leaving Test Mode

When commissioning is complete:

1. Clear every forced value in the Force dialog (right-click each entry and choose Remove force, or use Remove all forces).
2. Close the Force dialog.
3. Choose Target system > End test mode (or Target system > Go offline). The device returns to configuring mode; production logic is now governed by the stored configuration and the live sensor signals.
4. Document the version of SIRIUS Safety ES, the project file hash, and the date in the commissioning report.

9. Troubleshooting Matrix

10. Field-Proven Caveats

• One engineer at a time. Test mode is exclusive on the serial interface. A second PC attempting Go online while Force is active will be rejected.
• Cross-device projects. Projects created for a 3RK3122 (Advanced) or 3RK3125 (PROFIsafe) will not download to a 3RK3111 (Basic). The central-unit type is encoded in the project file.
• Password storage. Test-mode passwords are stored locally on the 3RK3111; SIRIUS Safety ES does not retain them between sessions.
• Online help. The most authoritative reference for the Force dialog is the Online Help > Forcing topic inside SIRIUS Safety ES itself – it is context-sensitive to the open window and is updated with each tool version.

11. Related Documentation Pointers

Official Siemens SIRIUS MSS documentation is available on the Siemens Industry Online Support portal at support.industry.siemens.com. From there, search by the article number of your 3RK3111 (printed on the front label, e.g., 3RK3111-1AA10) to retrieve:

• Operating Instructions for the 3RK3 Basic central unit
• SIRIUS Safety ES user manual and release notes
• Function block catalog for the Basic firmware version installed on the device
• Application examples for emergency-stop, safety gate, and two-hand control circuits

The general SIRIUS product landing page at siemens.com/sirius provides the family overview, selection tools, and links to the modular safety system configuration guides.

Frequently Asked Questions