1、Page 1 of 1 2016 ASHRAE. All Rights reserved. INTERPRETATION IC 135-2016-2 OF ANSI/ASHRAE STANDARD 135-2016 BACnet - A Data Communication Protocol for Building Automation and Control Networks Approval Date: October 25, 2016 Request from: Christoph Zeller, Fr. Sauter AG, Im Surinam 55 CH 4016 Basel S
2、witzerland. Reference: This request for interpretation refers to the requirements presented in ANSI/ASHRAE Standard 135-2016, Clause 13.3.6, regarding the direct transitions. Background: There seem to be different interpretations as which transition should be taken when the optional direct transitio
3、ns are implemented. In Clause 13.3.6 the conditions for transition are defined. Specifically: (d) Optional: If pCurrentState is HIGH_LIMIT, and the LowLimitEnable flag of pLimitEnable is TRUE, and pMonitoredValue is less than pLowLimit for pTimeDelay, then indicate a transition to the LOW_LIMIT even
4、t state (e) If pCurrentState is HIGH_LIMIT, and pMonitoredValue is less than (pHighLimit pDeadband) for pTimeDelayNormal, then indicate a transition to the NORMAL event state. My Interpretation of the language is: 1) If the condition for exactly one transition is satisfied, the transition will happe
5、n immediately and independently of another transition of other (pending) transitions (e.g. due to timeouts) 2) If more than one condition is satisfied, the condition appearing first in the list of conditions will apply and a respective transition being indicated, due to its higher priority. Interpre
6、tation: Assuming pTimeDelayNormal is smaller than pTimeDelay, the current event state is HIGH_LIMIT, and pMonitoredValue is staying below both pLowLimit and (pHighLimit pDeadband) so that both conditions (d) and (e) will be satisfied once the respective time delays are elapsing. Because the condition (e) is satisfied before condition (d), due to pTimeDelay is smaller, a transition to NORMAL will be seen eventually followed up by a transition to LOW_LIMIT at a later time. Question: Is this Interpretation correct? Answer: Yes
