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BACnet Tuning Tips: Small Changes, Major Performance Gains

bas bacnet n4 niagara networking
Purple Flower Fine-tuning your BACnet network can dramatically boost communication speed, reliability, and performance.

Below are the key areas to optimize.

Key Moves


  • Tuning Policies: Control COV vs. polling, write behavior, and timing.
  • Queue Settings: Avoid overflows with smarter sizing + throttling.
  • Timeouts: Adjust APDU settings to reduce abandoned transactions.
  • MS/TP: Optimize baud rates + wiring for speed and reliability.
  • Worker Threads: Scale concurrent work with worker pools.

Tuning Policies: Optimize point-level communication

  • COV: Use for static values. For fast-changing points, reduce/disable ? use RPM if available.

  • Polling: Adjust poll rates (fast / normal / slow) in your Tuning Policy.

  • Writes: Control with Write_On_Start / Up / Enabled.

Queue Full Exceptions (QFE): “Error writing BACnet point” = write queue overflow

  • Reduce load: Disable Write-on-Start for select points.

  • Increase size: writeWorker.maxQueueSize = 1.5 × writable points.

  • Throttle: Increase Min/Max Write Time in Tuning Policies.

Abandoned Transactions: Device response timeout = “Transaction abandoned!”

  • Increase: APDU Timeout.

  • Decrease: APDU Retries (e.g., set to 1) to reduce load + speed up failure detection.
Network Misconfiguration: Router loop detected

  • Check Plan: Verify network map for router loops.

  • Settings: network.maintainRoutingEnabled = True to prevent routing from auto-disabling.
MS/TP Performance & Reliability

  • High CPU? Drop baud rate below 76.8k (N4.12+ JACE-8000 uses a co-processor).

  • Reliability: Ensure proper RS-485 termination & biasing. Use a handheld oscilloscope to verify signal strength.
Worker Threads

  • Manage concurrency (N3.8+)

  • Add a Worker Pool to worker or writeWorker to adjust thread count and improve throughput.

Bottom Line: BACnet tuning isn’t a massive overhaul. It’s smart, surgical changes that boost network performance fast.


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