Resetting Pump Operating Hours on CountOh via WinCC Faceplate - Preset Workaround and Logic Triggers

By default, the SIMATIC PCS 7 APL operating hours counter block (CountOh) does NOT include an operator 'Reset' button on its standard WinCC faceplate, even when LiOP=0 and Feature.Bit30=0 are configured. Siemens intentionally omitted a direct faceplate reset button to prevent accidental erasure of maintenance records. To enable operators to reset operating hours from the faceplate without modifying internal library code: use the supported 'Preset' workaround by entering 0d, 0h, and 0m into the Preset value fields and clicking the 'Preset' button in the standard faceplate. Alternatively, connect an APL operator prompt block (OpDi01) to the ResetOp input pin in CFC, allowing authorized personnel to trigger a formal reset with electronic audit logging.

Executive Summary

In continuous manufacturing and utility installations, maintenance personnel track rotating machinery runtimes using the APL operating hours counter block (CountOh). Following equipment refurbishment, pump replacement, or major overhauls, maintenance teams need to reset accumulated running hours back to zero. Engineers frequently configure LiOP := 0 (Operator control priority) and Feature.Bit30 := 0 (Reset depending on LiOP) expecting an operator 'Reset' button to illuminate on the faceplate, only to discover that no such button exists. This article clarifies the process control safety rationale behind CountOh faceplate design, outlines the zero-code 'Preset' workaround, and details how to implement secure, logged operator resets using standard APL prompt blocks.

Architecture and Fundamental Mechanics

CountOh Architecture, Operating Hours Accumulation, and Faceplate Design Rules:

Internal Mechanics of CountOh (FB1864):
CountOh accumulates elapsed time whenever the monitored equipment run feedback pin (Tracking or In) is active (TRUE).
Runtimes are tracked across multiple internal registers and output pins: TotalTim (DWORD, elapsed seconds), Days, Hours, Minutes, and Hours1 (REAL, hours with fractional precision).
Why Direct Operator Reset is Suppressed on Faceplates:
In industrial DCS environments, operating hours serve as legally binding data for predictive maintenance, warranty validation, and regulatory emissions reporting.
Siemens APL style guidelines intentionally omit an unconstrained 'Reset to 0' pushbutton on @PG_CountOh_Standard.pdl to prevent plant operators from accidentally wiping hundreds of hours of maintenance data during routine shift handovers.
The Role of LiOP and Feature.Bit30:
Input pin Reset exists on the block interface, paired with interconnected input ResetLi and operator input ResetOp.
Setting Feature.Bit30 := 0 establishes: If LiOP = 0, the block evaluates parameter ResetOp for resets; if LiOP = 1, the block evaluates interconnected signal ResetLi.
However, because the standard faceplate lacks a button tied to ResetOp, setting these bits alone does not manifest a graphical control element on the screen.
The Preset Workaround vs OpDi01 Prompt:
The standard faceplate natively contains controls for the Preset function (PresetVal), allowing operators to seed the counter with historical runtime (e.g. after replacing a controller).
Entering 0 into the preset parameters and commanding 'Preset' achieves an immediate, clean reset to zero without modifying any system PDLs.

Step-by-Step Implementation Procedure

Method 1: The Zero-Code 'Preset' Workaround (Standard Faceplate):
* In WinCC Runtime, open the faceplate for the target CountOh block.
* Switch to the 'Parameter' view (or detailed value view).
* Locate the Preset value fields (PresetVal): Days (d), Hours (h), and Minutes (m).
* Enter 0 for Days, 0 for Hours, and 0 for Minutes.
* Click the Preset command button and confirm operator execution.
* The accumulated operating hours immediately reset to 0d 0h 0m (TotalTim = 0).
Method 2: Engineering an Operator Prompt via OpDi01 (Logged Reset):
* In SIMATIC Manager, open the CFC chart containing the CountOh instance.
* From the APL library, insert an OpDi01 (Digital Operator Prompt) block.
* Connect OpDi01.Out to CountOh.ResetLi.
* Set CountOh.LiOP := 1 (allowing interconnected control via ResetLi).
* Alternatively, if maintaining operator priority, connect OpDi01.Out to CountOh.ResetOp with CountOh.LiOP := 0 and Feature.Bit30 := 0.
* Configure operator authorization level 5 (Process Controlling) or level 6 (Higher Process Controlling) on OpDi01.
Auto-Resetting the Pulse in CFC:
* To ensure Reset acts as a momentary pulse rather than remaining latched on, configure an edge evaluation or use OpDi01 configured with automatic reset behavior.
Method 3: Customizing the Faceplate (If Dedicated Button is Mandatory):
* If corporate standards mandate a dedicated Reset button in the CountOh faceplate:
* Copy @PG_CountOh_Standard.pdl from GraCS to a project backup.
* In Graphics Designer, place a standard APL command pushbutton.
* Link the mouse click action to write 1 to .ResetOp#Value.
* In OS Project Editor, protect the modified file by setting it to 'Do not overwrite' on the Basic Data tab.
Compile OS and Test Operation:
* Perform an OS compilation and activate WinCC Runtime.
* Verify that triggering the reset resets accumulated hours smoothly without controller faults.

Verification

Verify Operating Hours Counter Reset Behavior:
1. In the CountOh faceplate, verify that executing the Preset workaround resets TotalTim to 0 and displays 0d 0h 0m.
2. If using OpDi01, confirm that clicking the reset prompt generates an audit trail message in WinCC Alarm Logging recording the operator name, timestamp, and action.
3. Simulate pump running status; verify that the counter resumes incremental accumulation immediately following reset.

Limitations and Operational Precautions

Operational Precautions and Audit Trail Considerations:
- Resetting operating hours on running machinery may disrupt maintenance scheduling; restrict reset authorization to maintenance supervisors via SIMATIC Logon user permissions.
- Do not permanently leave ResetLi high (1), as this continuously forces TotalTim to zero, preventing all future runtime tracking.

Engineer FAQ

Why is there no Reset button on the standard CountOh faceplate?

Siemens intentionally omitted a direct reset button to protect critical historical maintenance data from accidental operator erasure.

What is the easiest way to reset CountOh without editing pictures?

Enter 0 for days, hours, and minutes in the Preset value fields and click the 'Preset' button on the standard faceplate.

What does Feature.Bit30 do on CountOh?

Feature.Bit30 determines whether the Reset parameter evaluates operator input (ResetOp when LiOP=0) or interconnected logic (ResetLi when LiOP=1).

Can I trigger a reset automatically from an SFC sequence?

Yes, connect an SFC step output or pulse block to the ResetLi input pin of CountOh with LiOP = 1.

Does CountOh track motor start cycles as well as running hours?

Yes, CountOh tracks both operating hours (TotalTim) and the number of start-stop cycles (TotalAct).

Technical References

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Resetting Pump Operating Hours on CountOh via WinCC Faceplate - Preset Workaround and Logic Triggers