Supporting Legacy Supervisory Controllers

The first product that we released was the S4 Open: OPC-N2 Router. It was demonstrated in 3 of our partner booths at the AHR Expo several years ago. We received tremendous technical reviews for product capabilities and the product's ease of installation and configuration. Along with this we received many requests for smaller versions of the system for use in small building integrations. After analyzing the requests we determined that the best way to significantly drive the price down while retaining all of the core capabilities was to eliminate the Upstream N2 interface for the proposed smaller offerings. What we ended up with was versions of the OPC-N2 Router that supported 16, 32, 64, or 128 N2 devices. For special cases we could offer custom configurations that put the Upstream N2 interface back into the configuration. When we released the BACnet-N2 Router a year later we followed this same approach. We thought this was a nice offering but that it wouldn't be used very often. We evidently were wrong!


When I look back over the sales statistics it is interesting to note that we have sold at least as many custom configurations for the smaller appliances that added the Upstream N2 interface back in as we have sold standard configurations. When we defined this packaging we thought that for the smaller packages removing the Upstream N2 interface was logical because for the smaller number of N2 devices it would be relatively easier to duplicate any of the supervisory controller services in your new head end. Our integration partners have found that there is significant value in including the upstream N2 interface in these configurations and keeping the legacy supervisory controllers in place for a transition period. It turns out that there are MANY small Metasys configurations installed as part of a large building or campus instead of as the single installation in a small building.

The approach taken, especially for these larger buildings or campus environments, is:

  1. Start out by installing the BACnet-N2 Router or OPC-N2 Router with the legacy supervisory controller remaining in operation in parallel to the new head end.
  2. Develop the new user interface and graphics using it in monitor only mode.
  3. After all of the new graphics are in place come back to each supervisory controller and analyze and replace its schedules, global variables, trending, and any custom logic in the new head end or supplemental building level controllers.
  4. After you are satisfied with the results unplug the upstream N2 interface to the legacy supervisory controller and confirm that the new head end has taken over all functionality. The S4 Open appliance will automatically take over as the N2 bus master. You can keep the legacy supervisory controller available for reference as you do the final testing and commissioning of the new system.
  5. Finally unplug and remove the legacy supervisory hardware.

This provides a smooth transition strategy leading to the new head end completely managing the field gear and providing all building level services while minimizing the risk, and pressure, of having to implement a flash cut over.