Redundant Operating Characteristics; Overview; Start-Up; Modes Of Operation (Figure 83) - Honeywell HC900 Installation And User Manual

Redundant Operating Characteristics - Overview

Redundant Operating Characteristics

Overview

This section describes operating characteristics specific to redundant controllers.
In a redundant HC900 system, the Lead Controller performs all primary tasks including interfacing with
remote I/O racks, communicating with a local HMI, exchanging data with peer controllers, interfacing with
Modbus slave devices, and communicating with a Host PC application. Detection of a fault or removing
power from a Reserve Controller will initiate a diagnostic prompt in the Lead Controller, but will have no
impact on the process under control. The detection of a fault or removing power from a Lead Controller
will initiate failover, that is, transfer all primary tasks to the Reserve Controller, establishing this controller
as the new Lead. Following a failover, the new Lead Controller will remain the Lead, even if the condition
that caused the failover is corrected.

Start-Up

•
Assignment of Lead and Reserve status is determined at start-up
−
First available C75 assumes Lead
−
In case of a tie, CPU mounted in the left position of the rack will Lead
−
No user configuration or manual operations required to establish Lead / Reserve status
•
Lead Controller assumes control of I/O and all external communication interfaces.
•
Reserve Controller receives the configuration from the Lead Controller

Modes of operation (Figure 83)

The modes of operation are:
•
Run
•
Run/Program
•
Program
You can change modes with:
•
key-switch on the redundancy control module
•
HC Designer software
•
HC Utilities software
•
local 1042 or 449 operator interfaces.
•
a command from a supervisory host
Both Lead and Reserve Controllers maintain the same mode. Placing the Lead Controller into the Program
mode will also place the Reserve Controller in the Program mode.
Revision 19
06/14
HC900 Process Controller Installation and User Guide 155