Issue
I/A Series R2 Optimum Start Stop program object may improperly calculate start time when outdoor air temperature compensation is used.
Environment
I/A Series R2 (all versions)
Cause
Optimum start / stop compensation is performed through the use of a program object. The object could calculate a negative start lead time when outdoor air temperature compensation was used.
Resolution
A check was added to the program object to prevent a calculated negative start leadTime due to outdoor air temperature compensation. The revised object is available for download from The Exchange Download Center. Download the file >> OSS for Niagara 08_03_11.zip
In addition, the object includes the following change history.
10-Nov-00 Moved the parameter reset control to an external stimulus
16-Aug-01 Changed reset input from BooleanPriority to DateTime
20-Dec-02 Added check for command time > next event time to account for a large leadtime calculation that results in a start time prior to midnight
14-Sep-05 Added safety check to prevent dynamically adjusted runtime factors from becoming too large
25-Apr-06 Corrected the following stop-time issues:
1) stop-time calculation when earliestStopTime is after schedule stop time
2) stop-time calculation when start/stop times span midnight
3) determining when to perform stop-time analysis
05-Nov-08 Added changes from 2002 and 2003
Added prestart (maxStartLimits) and comfortLimit inputs 18 Nov 02
Added the ability to use OA temperature for OSS calculation 24 Feb 03
12-Dec-08 Added OA temperature to message strings. Added output for calculated command time.
19-Feb-09 Corrected issues with stop-time analysis:
1) lastStartTime was being used for stop-time calculation
2) analysis for heating was adjusting drift time for cooling
3) analysis for cooling was adjusting drift time for heating
Corrected issues with stop time calculation:
1) heating mode failed to drift when > upper comfort limit
2) cooling mode failed to drift when < lower comfort limit
3) stop mode calculation always reflected the next event time
15-Oct-09 Added properties and check to prevent dynamically adjusted drift time factors from exceeding a specified maximum value.
03-Aug-11 Added check to prevent calculated negative start leadTime due to outdoor air temperature compensation.
