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On the <I> Mark V Speedtronic, we received the following intermittent Diagnostic alarm:

Droop Description
0282 IOMA CPD input hardware problem

Also we notice that, the Compressor Discharge Pressure (CPD) indication on <I> is fluctuating intermittently.
For the moment, the machine is still running and on the <I> we locked this alarm.

Can any one suggest, what is the reason for this alarm?

From a very old <Q> Diagnostic Alarm "Help" file:

0282 ;IOMA CPD INPUT HARDWARE PROBLEM

CAUSE The CPD input does not pass internal diagnostic checks.

EFFECT Bad I/O data, particularly for the CPD input.

ACTION Try replacing the DCC/SDCC card.


Is the panel a SIMPLEX or a TMR panel? Which processor is this Diagnostic Alarm being generated for?

It's either an intermittent transmitter or transmitter wiring (easier to check/resolve and should be done *before* replacing the DCC/SDCC card) or it could be a cable problem (follow the signal using the Signal Flow Diagrams in Appendix D of the Mark V Application Manual, GEH-6195), it could be a card connector problem (corrosion, as has been reported several times on control.com).

Thanks for your reply,

The panel is TMR. The diagnostic alarm is being generated intermittently for all processors R, S & T but, not at the same time, sometimes on R only, sometimes on S only and sometimes on T only.

Now, the machine is running, we will wait until the next Shut-Down to check the wirings, the transmitter and maybe to replace the card.

Look at the Mark V Application Manual, GEH-6195, Appendix D, the page "<Q> Core - Compressor Discharge Pressure Inputs on TBQB" for details on the CPD input(s). A TMR Mark V requires three CPD inputs, and some turbines only have one, so the TBQB can be configured to "fan" one input to all three control processors. NOTE: If this is done, and the CPD transducer is a 4-20mA transducer, only *one* dropping resistor must be IN.

If the alarm is happening on all three processors, it's likely something that is common to all three processors--like a single transducer, or an intermittent connection in the circuit of a single transducer, or the TBQB card.

Or, corrosion on the cable connectors of the cables between the TBQB and the TCQCs, or the TCQCs to the DCCs/SDCCs.