Armstrong World Industries EHU-703 - Manual (Page 22)

C09: I/O DIAGNOSTICS
If the display mode selection is left in the diagnostic mode for 10 seconds, the Input/Output
circuit diagnostic check will begin. The display will show the message C09, the tank will be off,
and the diagnostics mode light will remain on.
Output Circuits: The diagnostics will first check all the output circuits: fill valve, drain valve,
and tank contactor to make sure they are working. When a light comes on, you will hear the
corresponding valve or contactor circuit energize for about 2 seconds. Each circuit is checked
twice before proceeding to the next circuit.
Input Circuits: Next the microcontroller checks the status of all input circuits, beginning with
the control stat. the 3 digit display will show 0% Demand, then the actual stat demand. It will do
this twice. The input diagnostics continues by checking the fan interlock switch, high limit duct
humidistat, and high water switch. The display will now show C09 followed by any additional
messages that indicate problems with the input circuits.
When the I/O diagnostic check is finished, the demand mode light will be on, the display will
show the control stat demand and the unit will return to normal operation. The complete I/O
diagnostic check lasts less than 2 minutes.
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