When using FX-PC 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, N30, Companion, Facilitator, and FX Supervisory Controllers. N2-configured FX-PC 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 NAEs, Project Builder for N30s, and FX Workbench for FX Supervisory Controllers.
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. At CCT Release 10.1, an N2 Mapping feature was added, allowing you to configure this information to resemble that of the legacy N2 controller being replaced.
- N2 Device Type: With the CCT N2
Mapping feature, you can define the FX-PC 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 the FX-PC controller to have a UNT N2 device
type to match the N2 supervisor's definition. Note: DX and FX-PCV 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 FX-PC 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 FX-PC 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 FX-PC 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 FX-PC controllers. Therefore, the N2 supervisor reports these points as offline unless they are unmapped (deleted) from the N2 supervisor's database.
Also, some legacy N2 controller application points may be defined differently in FX-PC controllers, which would require remapping the FX-PC 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-configured FX-PC 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 FX-PC controllers is their actual, discrete values.
- N2 Open Override command to an FX-PC controller object value does not persist after power cycle.
- Commands to a Default Value attribute do not persist after a power cycle.
- Writing to a point in the FX-PC controller through the N2 network integration changes the present value of the attribute but does not write the value to non-volatile memory. This means that the new value is not persisted following a power cycle of the FX-PC controller. The workaround is to use the Setpoint command to update the value in non-volatile memory.
Be sure to introduce the changes to your customer and the system operators accordingly.