Issue
How can a BACnet system be customized to maximize data throughput? The site has a Niagara R2 Enterprise Server and a UNC with a variety of MSTP controllers connected to the UNC.
Environment
- Niagara R2 Enterprise
- UNC
- MSTP controllers
Cause
Improper configurations won't achieve optimum performance.
Resolution
This can be a relatively complicated question, however, there are a number of basic steps that can be taken in terms of best practices to enhance performance.
Within the UNC station, any BACnet objects that are not needed are to be deleted. During the learn of a BACnet controller, many objects are learned that are not used.
All BACnet objects when learned into a station are placed in Poll-Always containers. All but the most critical objects, schedules and trended objects are to be moved to Poll-on-Demand containers.
All controllers on the MSTP bus should be consecutively addressed. Gaps in addressing add delay in communications.
The MaxMaster setting in all controllers, including the UNC, is to be set to a numeric value two greater than the highest MSTP controller address on the network. To leave MaxMaster at 127 but only have 20 controllers on the network will also add delays in communications looking for the other non-existent 107 controllers.
The MaxInfoFrames setting in the UNC or MNB-1000 is to be set to a number higher than 5 but no more than 20. This setting determines how many pieces of information can be requested each time the UNC or MNB-1000 receives the token on the MSTP bus. The default value is 1 and if left at this value the system will be sluggish with updating values on graphic screens. The range of 5 to 20 is given as a starting point for experimenting and each system will be different depending on the number of controllers and what data is being requested. Lab tests have shown there is a performance curve with an optimum point. Starting at a value of 5, performance increases as the value increases. Performance will then peak and any further increase to the setting will result in a performance reduction. As a result, stay above 5 but less than 20.
Refer to the document titled "I/A Series MicroNet BACnet Wiring, Networking, and Best Practices Guide" (F-27360) for additional information.
