Safety Considerations Guide, Tricon v9.0 - Tuv-fs.com

40 Types of FaultsTypes of FaultsExternal FaultsA controller is subject to external faults and internal faults, which are reported bythe:• Status indicators on a module’s front panels• Diagnostic Panel in TriStation• System attributes on the Control Panel in TriStationA controller may experience the following types of external faults:• Logic power faults• Field power faults• Load or fuse faultsWhen an external fault occurs, the controller asserts an alarms. How the alarm iscommunicated is module-specific. In some cases, a yellow alarm indicator isprovided on the module. For example, a Load/Fuse alarm is provided on digitaloutput modules. In most cases, the System alarm is asserted, and the System alarmindicators on the Main Chassis Power Modules are lit. The Diagnostic Panel inTriStation identifies the faulting module by displaying a red frame around it. Forinstructions on responding to specific alarm conditions, see the Tricon Planningand Installation Guide.Internal FaultsInternal faults are usually isolated to one of the controller’s three channels (A, B orC). When an internal fault occurs on one of the three channels, the remaining twohealthy channels maintain full control. Depending on the type of fault, thecontroller either remains in TMR mode or degrades to dual mode for the systemcomponent that is affected by the fault. For more information of on operatingmodes, see “Operating Modes” on page 41.When an internal fault occurs, the controller lights the red Fault indicator on thefaulting module and the System alarm on the Main Chassis Power Modules to alertthe operator to replace the faulting module.Tricon Safety Considerations Guide