Issue
The local time inside a Xenta programmable unit is dependent upon server time, time zone, and daylight savings time settings. Incorrect DST settings result in incorrect times in the controller which causes problems from incorrect start times on HVAC equipment, to incorrect alarm time stamps in alarm queues.
Product Line
TAC Vista
Environment
Xenta Programmables version prior to 3.74
Xenta 280, 281, 282, 283, 300, 301, 302, 401, 401:B
Cause
In 2007, most of the United States and Canada changed when DST is observed to the second Sunday in March to the first Sunday in November. Because it had never changed prior to that, programmable controllers retained the old settings (first Sunday in April to last Sunday in October).
Resolution
The issue was resolved with the release of firmware MOT version 3.74. Upgrading your controllers to 3.74 is a viable solution, however not always cost effective. There are two ways to work around the issue.
Note: For information on how to download firmware to Xenta programmable devices using the Download Wizard please see Download an .MOT file into a Xenta Programmable controller.
Configure TAC Xenta Central DST Settings
Refer to the TAC Vista Technical Manual Chapter 19.6
In the folders pane, right-click the folder where you want to place the time event object.
Point to New, point to Object, and then click Time Event – Object.
Type the name.
Open the time event object.
On the General tab, type a description.
On the Time Event Settings tab, set a suitable repeat interval, for example, first Monday in each week.
Click OK.
In the folders pane, right-click the folder where you want to place the Central Daylight Settings – Xenta object.
Point to New, point to Object, and then click Central Daylight Settings – Xenta.
Type the name.
Open the Central Daylight Settings – Xenta object. Two options are available. You can use Windows start and end times for the daylight saving time or specify your own start and end times. If you want to specify your own start and end times:
Clear the Use Windows settings check box.
In the Daylight saving starts box, set the start time for the daylight saving time.
In the Daylight saving ends box, set the end time for the daylight saving time.
In the Update schedule box, browse to the time event object that triggers the push to the TAC Xenta devices.
Click Select.
Click OK.
Note: You must select Manual DST Mode and Central DST for each controller in the system for a global change to take effect.
Manually set DST Settings for each controller
The DST Xenta object is not available in all versions of Vista. If that is not an option, DST settings on each controller can be manually set for the start day and stop day. Unfortunately, time settings do not allow for designations of "first Sunday" or "last Sunday," only calendar dates. So each controller will have to be edited each year to maintain correct time settings.
In order to facilitate this, this utility: ODXentaTimezoneChanger was created. It must be used each year to update the settings, but it will allow you to change all time settings on all controllers in a Vista database simultaneously, greatly reducing the time it takes to correct a system.
NOTE: If the Lonworks network has not been properly commissioned & downloaded the tree will not properly communicate with the Vista Server. Check your network tree for asterisks to see if any downloads are required.
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