JCI MSEA: How to Switch Modes Using Heartbeats

The following article shows rough steps needed to create the points and logic to detect heartbeat signals coming from Events2HVAC and to automatically switch your controlled points to backup HVAC schedules when the heartbeat signals stop coming in.  Lack of heartbeat can be caused by several things:  network outage, controller offline, ADX offline, Events2HVAC server shutdown, inability to login to ADX, etc.  Adding failover 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 failover to backup schedules.

1. Create Target Heartbeat Objects

Create a binary value object that will receive heartbeat signals from the Events2HVAC (E2H) server.  E2H can be configured to send a toggle value (0/1) or a ping (single value 1) every 5 minutes.  This example uses the toggle method.

HB-1 (Binary Value) Heartbeat Target receives 0/1 toggle from Events2HVAC server every 5 mins.

2. Create Scheduling Mode Object

This will be a binary value that will indicate the scheduling mode.  For this example, 0=OFF (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 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.


4. Create Logic for Stale Heartbeats

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

Below LCT logic diagram will detect if the HB-1 heartbeat signal stops toggling.  If toggle is not detected after 6 mins, the 15 min failover delay is activated.  Once the 15 min delay timer completes it will force E2H-MODE to OFF.  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 mode after heartbeat returns.

You can test the logic by overriding the HB-1 BV point to either OFF or ON and waiting 16 minutes.

When the heartbeat comes back, 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. Create Heartbeat Targets in Events2HVAC

Create a separate heartbeat target in Events2HVAC for each heartbeat point that your created above.  Ideally you would create a target on each NAE controller and create the same logic so if a single building loses communication, only the affected zones in the building will be switched to backup schedules.

See Help:  MSEA Heartbeat Tab

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