Issue
Excessive LON network traffic can overload communication capacity, leading to LON communication delays or errors.
Product Line
TAC IA Series, EcoStruxure Building Operation
Environment
- I/A Series MNL‑800 controllers
- Building Operation Automation Server / ASP
- LON networks
- I/A Series R2, AX, and N4 JACE LON networks
Cause
Output (NVO) SNVT values are transmitted too frequently, often more frequently than operationally required.
Improper configuration of NCI timing objects (Send Heartbeat, Receive Heartbeat, Minimum Out Time, Minimum Propagation Time) can also lead to excessive traffic.
Improper configuration of NCI timing objects (Send Heartbeat, Receive Heartbeat, Minimum Out Time, Minimum Propagation Time) can also lead to excessive traffic.
Resolution
Several NCI (configuration) objects control how the controller sends and receives LON data. Correct tuning prevents network saturation.
1. Send Heartbeat NCIs (nciSndHeartBeatA/B/C/D)
- Each NVO is assigned to one Send Heartbeat group.
- This value determines the periodic transmission interval for each bound output.
2. Receive Heartbeat NCIs (nciRcvHeartBeatA/B/C/D)
- Each NVI is assigned to one Receive Heartbeat group.
- If an NVI does not receive a value before the timeout, it reverts to its default value.
3. Minimum Output Time (nciMinOutTime)
- Regulates how frequently consecutive NVO values are sent.
- Critical rule:
The number of bound NVOs × nciMinOutTime must be less than the shortest Send Heartbeat value.
Example:- If Heartbeat = 120 seconds
- NVOs bound = 60
→ nciMinOutTime must be < 2 seconds
- Recommended guideline:
nciMinOutTime = (Shortest Send Heartbeat) / (2 × Number of bound NVOs)
4. Minimum Propagation Time (nciMinPropTm)
- Prevents rapidly changing NVOs (e.g., temperatures) from flooding the network.
- Typical setting: 1–5 seconds
Additional Reference
More detail is available in WorkPlace Tech Tool 4.0 Engineering Guide (F‑27254), Chapter 6 (installed with Workplace Tech and also available in the WorkPlace Tech Software Package on mySchneider.)
