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EHU-700 DIAGNOSTICS
THE Series EHU-700 has built in diagnostics to detect system problems early, before they become
severe. If possible, the diagnostic routine performs corrective measures. If necessary, the unit is shut-
down and a dry contact is closed to enable a remote alarm.
The diagnostic messages that result in the unit being shutdown are displayed automatically. The other
messages are displayed when the diagnostic display mode is selected with the mode switch. If the dis-
play mode selection is left in the diagnostic mode for 10 seconds, the Input/Output circuit diagnostic
check will begin.
DIAGNOSTIC DISPLAY MESSAGES
C00 = NORMAL OPERATION
C01 = HIGH WATER
C02 = TANK NEEDS CLEANING*
C03 = INTERLOCK CIRCUIT
C04 = HIGH-LIMIT CIRCUIT
C05 = DRAIN SYSTEM FAILURE*
C06 = FILL SYSTEM FAILURE*
C07 = OVERCURRENT FAILURE*
C08 = MANUAL TANK SHUT-OFF
C09 = I/O DIAGNOSTICS
* Automatic shutdown and Alarm contact closure.
C00: NORMAL OPERATION
C01: HIGH WATER:
A high-water float switch prevents water carry-over into the duct due to too high a water level in
the tank. When the high water limit is reached the HIGH WATER light comes on and the fill
valve is blocked until some water is boiled away and the water level drops. This is not
uncommon on startup. The diagnostic display mode will indicate C01.
NOTE: the high water light goes off as soon as the high water condition is cleared but the
operation on the fill valve does not resume until after a fifteen second delay period. If C01 is
displayed and the water level is in the lower half of the steam generator, high static pressure
exists, contact the factory for assistance.
C02: TANK NEEDS CLEANING:
If the HIGH WATER lights is on continuously during normal service (i.e. after initial startup) and
the current is not increasing, the tank probably needs cleaning (refer to the maintenance
section of this manual). If this condition persists without being serviced, the display panel will
display diagnostic message C02. The unit will shutdown and the dry contact will close to
activate the remote alarm. NOTE: False C02 messages may occur if incoming water is very
pure (< 100 μMhos/cm²). Please consult factory.
C03: INTERLOCK CIRCUIT:
The fan interlock circuit may be a sail switch or (preferably) a duct pressure switch. When air
flow in the duct is not present, the interlock circuit should open and the microcontroller will
de-energize the contactor. The diagnostic mode will display the message C03 and the fill
solenoid is blocked.
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