JCI MSEA: How to Switch Modes Using BACnet Status

The following article shows rough steps needed to create the points and logic to monitor the scheduling status coming from Events2HVAC and to automatically switch your controlled points to backup HVAC schedules when the status point shows OFF or OFFLINE.  No status can be caused by several things:  network outage, controller offline, Events2HVAC server shutdown, Events2HVAC schedules disabled, etc.  Adding fail-over logic similar to the next steps will minimize the operator interaction that would need to take place to switch to fixed building schedule due to an outage.

It is assumed that each controlled zone object has a schedule object that is commanded at priority 15. E2H commands its scheduled state to the same zone objects at priority 14.

There are other ways to do this, so please consult your JCI technician on what the best way to accomplish fail-over to backup schedules.

1. Discover the Events2HVAC BACnet Status Point

Follow these steps to discover the E2H-S binary point to be used to switch scheduling modes.  Discover Events2HVAC Client Device

2. Create Scheduling Mode Object

This will be a binary value that will indicate the scheduling mode.  For this example, 0=Manual (backup schedules), 1=E2H Auto (E2H generated schedules).  This can also be overridden by the operator to force to backup schedules if needed.

E2H_MODE (Binary Value) for the commanded scheduling mode

3. Create an Interlock To Release Priorities

Create an interlock to trigger when E2H-MODE = OFF.  The action tables will release priority 14 on all the points that are being controlled by E2H so that they can revert to priority 15 default schedules.  Note:  This example shows only one point to be released (BV1).  This would typically release all of the zones that E2H is commanding in this NAE controller.


4. Create LCT Logic for Monitoring the BACnet Status E2H-S

Create a control system object for detection of stale heartbeat conditions.

Below LCT logic diagram will detect if the Events2HVAC E2H-S signal goes OFF (0) or OFFLINE.  If E2H-S = OFF (0) of OFFLINE, the 15 min failover delay is activated.  Once the 15 min delay timer completes it will force E2H-MODE to Manual (0).  This will in-turn trigger the interlock to release all priority 14 commands from E2H.  This also shows a 15 min delay when switching back to Auto (1) mode after E2H-S = ON (1).

You can test the logic by overriding the E2H-S BV point to either OFF or ON and waiting 15 minutes.  You test the OFFLINE condition by shutting down the Events2HVAC Windows service process.

When the E2H-S points comes back online and ON (1), the E2H_MODE switch will return to AUTO (after 15 min).  However, the commands to each controlled point won't change until E2H commands a new state to each zone at priority 14.

5. Enable BACnet Events2HVAC Scheduler Status Point

To enable the Events2HVAC BACnet device to start broadcasting its status point, go to the Devices menu - BACnet - BACnet options.  Select the Heartbeat tab and check the "Enable Local Scheduler Status BV-1".

See Help:  BACnet Heartbeat Tab

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