Schedule Fail-over Strategies

During the integration of Events2HVAC (E2H) with your existing HVAC system, it is important to include either a manual or automatic schedule fail-over logic so that when the E2H server loses communication with your HVAC controllers you can revert to your default zone/building schedules during the disruption.  Things that can cause disruptions between E2H server and your building controllers are:

  • E2H Server Maintenance (Windows updates, server reboots, etc)
  • E2H Server Failures (Hard drive failure, or other extended disruption to server)
  • Network Communications failure between E2H and controllers.
  • Power outage at individual buildings
  • Controller Offline (power disruption, downloads, network disruption, failure, etc)
  • Inability to login to HVAC system (e.g. MSEA JCI password expires)

Without a fail-over strategy, your zones will remain at the last commanded state until normal communication is returned between the E2H server.  This time can be a short time frame (controller offline) or an extended time frame (server down).  You probably don't want your zones holding the last command for more than a few hours.

Starting at v1.5, you now have more options to design in an automatic switch-over strategy for schedules during these situations.  These options for switch-over will require additional programming on your HVAC system by your HVAC technician.

BACnet Status Point

If you are using the Events2HVAC BACnet/IP interface to communicate to your HVAC controls, there is a new binary point within Events2HVAC that your controllers will be able to read across the network. This BACnet status point indicates three possible conditions to the controller:

  1. (1) ON – schedules are available and flowing through Events2HVAC as normal
  2. (0) OFF – no schedules are available
  3. OFFLINE – communication with the server hosting Events2HVAC has been lost

To take advantage of this feature, logic must be added to your controller(s) to switch to backup HVAC schedules if the status is either OFF or OFFLINE for a specified period of time. Logic must also be added to return to using schedules from Events2HVAC when the status returns to ON.

The new BACnet status point is not enabled by default, so you will need to turn it on to enable this new feature.  Learn how here: BACnet Heartbeat

This is the preferred method to automate backup schedules with Events2HVAC if you are using BACnet-enabled HVAC controls. But if your controller cannot read the status point for some reason, you can also use the heartbeat method described below.

Heartbeat

If you are using the Events2HVAC Johnson Controls Metasys (MSEA) interface, you can use the new heartbeat feature to automate switching to backup schedules in the event of loss of communication from the server hosting Events2HVAC. (Note: This can also be used with the BACnet/IP interface if your controller cannot read the BACnet Status Point described in the previous section.)

The heartbeat sends a status from Events2HVAC to the MSEA controller(s) every 5 minutes, indicating that the Events2HVAC service is still alive and sending schedules. There are two types of heartbeat signals that can be sent:

  1. Ping: Sends a single command every 5 minutes. (Binary 1, Analog 100). For this type of signal, the controller logic must reset its own point value back to zero once the signal is received.
  2. Toggle Value: Sends alternating commands every 5 minutes. (Binary 0/1, Analog 0/100)

The heartbeat target points can be of type binary value, binary output, analog value, or analog output.

To take advantage of this feature, logic and target points must be added to the MSEA controller(s) to switch to backup schedules if the heartbeat signal has not been received for a defined delay period (15 minutes or more). When the signal comes back (after a delay), the logic should switch back to Events2HVAC schedules.

To enable heartbeats in E2H refer to MSEA Heartbeat section of the help documents.  For a complete example on this logic see Heartbeat Logic for JCI MSEA

 

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