Operating Characteristics; Introduction; Overview; Power Down / Power Up - Honeywell HC900 Installation And User Manual

Operating Characteristics - Introduction

Introduction

This section applies to all controllers, that is, non-redundant and redundant. For operating characteristics
unique to redundant controllers, see Redundant Operating Characteristics on page 155.
This section provides insights into system functioning that are useful in configuration, in installation
/commissioning tasks, and also in normal and abnormal operation. For related information regarding
diagnostic indications, how they should be interpreted, and determining appropriate actions, refer to the
Diagnostics section in this user manual.

Overview

The HC900 Controller components begin operation as soon as power is applied, and continue until power is
removed. The operation of the system varies according to the following interacting factors:
•
Power transitions: Power DOWN / Power UP
Power DOWN transitions are usually planned and controlled, but in some cases such as power outages,
are unintended. To ensure proper operation in either case, the HC900 Controller includes software that
controls operation at power restoration. The controller handles a Power-UP transition as one of two
types: Cold Start or Warm Start
•
Operating Modes: Program (Locked), Program, Offline, Run, and Run (Locked)
Operating Modes are selected:
−
by positioning the (Operating) Mode switch on the Controller Module or RSM,
−
by selecting parameters on displays (operator interface, Designer Software).
In some cases, mode transitions also restart (Cold Start or Warm Start) controller operation.
•
Results of diagnostics: in case of system hardware or software fault, the controller automatically alters
operation as appropriate for the diagnosed conditions.

Power Down / Power Up

The HC900 Controller is designed to facilitate restoration of process operation after a power outage. The
active control configuration is maintained in battery-backed RAM, and the last configuration update
performed in the program mode is also stored in Flash memory on the Controller Module. When power is
restored, the system automatically enters a diagnostic procedure that checks the integrity of hardware,
software, and the control database. Depending on the results of the diagnostic, the controller will execute
either a Warm Start or a Cold Start.
Warm Start
A Warm Start is a restart of the control strategy using dynamic data that is stored in battery backed RAM to
allow control action to resume exactly as it was before the restart. In the Warm Start procedure
(flowcharted in the main flow of Figure 79), diagnostic testing proves the integrity of the hardware,
software, and configuration database resulting in an automatic Warm Start of process control. Control
action is resumed exactly as it was before the outage.
This flowchart also indicates actions that would be taken by the controller in case of fault. Notice that if
primary diagnostic testing determines that RAM or firmware is faulty, all process control functions cease,
and the Status LED (red color) strobes one blink, periodically. If RAM and firmware tests pass, but the
database in RAM is faulty, the controller initiates the Cold Start operation.
Revision 19
06/14

Operating Characteristics

HC900 Process Controller Installation and User Guide 145