When using N2-capable equipment controllers to replace legacy N2 controllers, the N2 supervisor's configuration may be impacted. The legacy N2 controller families have existed through several generations of N2 supervisors. Depending on the timing of the original installation, legacy N2 controllers may be supervised by one of many types and brands of N2 supervisors, including the NCM, NAE/NCE, SNE/SNC, N30, Companion, and Facilitator. N2-capable equipment controllers should work with all Johnson Controls N2 supervisors. However, you must consider certain configuration steps to ensure the system operates as expected after the replacement.
In many instances, you can reconfigure the N2 supervisor online. However, some changes may require off-line configuration and a supervisory controller download. Therefore, you may need to have the appropriate tool such as System Configuration Tool (SCT) for NAE/NCE or SNE/SNC, and Project Builder for N30s.
A legacy N2 controller is mapped into an N2 supervisor by defining in its database the controller's N2 device type, N2 point types, and N2 point addresses. In CCT, an N2 Mapping feature allows you to configure this information to resemble that of the legacy N2 controller being replaced.
Device Type: With the CCT N2 Mapping feature, you can define the
N2-capable equipment controller's N2 device type to be a UNT, AHU, VAV, or
VND to match the legacy N2 controller being replaced. For example, consider a
situation where you are replacing a UNT controller, and it is mapped into the N2
supervisor as a UNT N2 device type. With the N2 Mapping feature, you can configure
N2-capable equipment controller to have a UNT N2 device type to match the
N2 supervisor's definition. Note: DX and VMA controllers cannot be directly mapped as before and must now be defined as VND devices.
- N2 Point Information: With the CCT N2 Mapping feature, you can define the N2-capable equipment controller's application points so that the N2 Short Name, Point Type, and Point Address match those of the legacy N2 controller being replaced. For example, consider a situation where you are replacing a legacy UNT1x1 controller, and its Zone Temperature application point is mapped into the N2 supervisor with a short name of ZN-T, and point type and address of AI-1. With the N2 Mapping feature, you can configure the N2-capable equipment controller's Zone Temperature application point to have the same ZN-T, AI-1 information to match the N2 supervisor's definition.
Even with the N2 Mapping feature, the N2 supervisor's database may still require some changes. The N2-capable equipment controller's application may not include all of the same application points as the legacy N2 controller being replaced. For example, some legacy N2 controller application points have no equivalent in N2-capable equipment controllers. Therefore, the N2 supervisor reports these points as offline unless they are unmapped from the N2 supervisor's database.
Also, some legacy N2 controller application points may be defined differently in N2-capable equipment controllers, which would require remapping the N2-capable equipment controller's N2 points in the N2 supervisor. This remapping may in turn require other configuration changes to the N2 supervisor, including changes to trend and alarm extensions, bound connections to graphics, and source and destination connections to system-wide control logic.
Although the N2-capable equipment controller is functionally similar to the legacy N2 controller it replaces, any changes to point mapping and associated changes to supervisory functionality may cause some confusion for your customers and operators. For example:
- The operator interface for adjusting the standby and unoccupied zone setpoints for VMA14xx controllers uses offset values, which are added to or subtracted from the zone setpoint; whereas the interface for adjusting the standby and unoccupied zone setpoints for CGM, CVM and FEC family controllers is their actual, discrete values.
- N2 Override command to an N2-capable equipment controller object value does not persist after you power cycle the controller.
- Commands to a Default Value attribute do not persist after you power cycle the controller.
- Writing to a point in the N2-capable equipment controller through the N2 Integration in Metasys does not cause the N2-capable equipment controller to set the point in a manner where it persists through a power cycle. In the N2 Integration the Metasys Supervisory controller is in charge of retaining the value. For example, if you change the default value of a point in an N2-capable equipment controller with the Metasys N2 Integration and the controller is reset, the supervisor writes down the last value that was commanded to it. Metasys also allows the user to setup restore command priority under the Options tab for the point such that the value or command is retained on the supervisor in the event of a power cycle to the network engine.
Be sure to introduce the changes to your customer and the system operators accordingly.
Remote Field Bus
The Remote Field Bus is a new, robust option for connecting the Metasys system to MS/TP equipment controllers and devices that are located outside the range of the local MS/TP Bus. The Remote Field Bus uses a BACnet IP to BACnet MS/TP Router as the main component. One side of the router is connected to the building IP network and the other to the remote MS/TP trunk.
You must have an IP connection to use this option. An example scenario for considering and utilizing this router in an N2 modernization plan would be an application where a DX-91xx series controller is installed on an air handling unit (AHU). By using the remote router you can convert this single remote trunk to MS/TP and gain all the benefits of this BACnet trunk. A significant benefit is that you may now look at and view logic, or do troubleshooting from a remote location.
For the Remote Field Bus feature, we recommend the JC-RTR11002-0 BACnet Router. For additional information on the JC-RTR11002-0 BACnet Router, refer to the JC-RTR11002-0 BACnet Router Catalog Page (LIT-1901208). The Remote Field Bus feature is available for use on Release 6.5 or later NxE Network Engines, and on Release 6.5.25 Open Data Server workstations.