Armstrong World Industries EHU-703, EHU-701 manual C04 High Limit Circuit, C05 Drain System Failure

C04: HIGH LIMIT CIRCUIT:

When the humidity in the duct reaches the high limit stat set-point, the circuit will open and the microcontroller will de-energize the contactor. The diagnostic mode will display the message C04 and the fill solenoid is blocked.

C05: DRAIN SYSTEM FAILURE:

This routine checks for a failure to reduce current if the drain valve is energized for more than five seconds. If the actual current does not decrease when the microcontroller demands a drain cycle, the unit will go into a diagnostic routine. This routine will try twice to correct the drain system failure by cycling the drain valve rapidly. If the failure is not corrected, the unit will shut down. The tank off indicator will light, the numerical display will show C05 (the drain valve failure message), and the dry contact will close to activate the remote alarm.

Drain system failure can be due to a plugged drain valve, drain valve solenoid failure, scale buildup in the tank, or drain piping problems. Refer to the maintenance section of this manual for resolution of these problems.

C06: FILL SYSTEM FAILURE:

After start-up, if the fill valve is on and has been on for more than four minutes, the diagnostic routine will check the fill valve operation. If the actual amp signal is less than the current when the fill valve was opened, the unit will go into a diagnostic routine. If the problem cannot be corrected, a fill system failure will be triggered and the unit shut down. The three digit display will show C06 to indicate this condition, and the dry contact will close to activate the remote alarm.

Fill system failure can be due to excessive or insufficient inlet water pressure, a failed fill valve solenoid, a plugged fill valve failed open, or a backflow preventer. Refer to the maintenance section of this manual for resolution of these problems.

C07: OVERCURRENT FAILURE:

The overcurrent limit (OCL) is 20% above the nominal amp rating of the unit. When the actual current reaches the OCL, the microcontroller will de-energize the contactor and energize the drain valve for 15 seconds. Then the contactor will be re-energized to see if the drain valve has corrected the overcurrent condition. This procedure is repeated 5 times.

If the overcurrent still exists, an overcurrent failure indication of C07 is displayed, the unit is shut down, and the dry contact will close to activate the remote alarm. The unit will have to be manually reset and the overcurrent condition addressed by the maintenance personnel.

An overcurrent failure can result from the cold startup of a tank that was previously running at a high load, resulting in the tank water becoming too conductive for start-up. If this is suspected, manually drain the tank for 15-30 seconds, then try to restart the system. If the overcurrent failure repeats, the drain system could be partially plugged, or the tank may be in need of cleaning. Refer to the maintenance section of this manual for resolutions to these problems.

C08: MANUAL TANK SHUT-OFF:

The tank on/off button will de-energize the tank contactor. The tank off light and the diagnostics indicator will be on and the display will show the message C08. The unit will stay in this condition until the button is pressed again. In the tank off mode, the manual drain button is still active, but the mode select button is not.

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