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11. TROUBLESHOOTING
SYMPTOM
POSSIBLE CAUSE(S)
CORRECTIVE ACTION
11.1 Indicator lights not
illuminated
No power to unit.
Check voltage at terminal board.
Off/On switch turned off.
Turn on.
Blown fuse.
Replace fuse.
Off/on switch or board malfunction.
Replace board.
11.2 Moisture indica-
tor turns yellow
(elevated outlet
dew point)
Design conditions exceeded.
Refer to Sections 4 & 9 to determine if dryer is being outside of design
limitations.
Spent desiccant (useful service life has ended).
Replace desiccant.
Contaminated desiccant (e.g. with oil)
Take corrective action. Refer to Section 4.1 to determine proper prefiltra-
tion before changing desiccant.
Saturated desiccant (saturated with water)
Refer to 11.3 for corrective action. Operation at reduced flow may reacti-
vate desiccant beds until desired outlet dew point is achieved.
11.3 Premature satura-
tion of desiccant
Insufficient purge flow - Purge pressure too low
Refer to Section 9 to determine correct Purge Pressure Indicator setting.
Incomplete tower depressurization (tower pressure
greater than 2 psig) - clogged mufflers
Replace muffler inserts.
Incomplete tower depressurization -
Purge/repressurization valve fails to open
Verify voltage to pilot solenoid valve. Check pilot air pressure (60-120 psig
required). Verify proper actuator operation.
Insufficient purge time - Incorrect controller settings
Refer to Section 7 or 8 to determine correct controller cycle settings.
Insufficient purge time - Faulty controller
Refer to Section 7 or 8 to verify proper time sequence. Replace controller
board as required.
11.4 Tower fails to
repressurize to line
pressure
Purge/repressurization valve fails to close (air loss
from mufflers during tower repressurization portion
of cycle)
Verify removal of voltage to pilot solenoid valve. Verify proper actuator
operation. This is a spring-assisted, normally closed valve. Check valve for
obstruction or seat damage.
Insufficient purge flow - Purge pressure too low
Refer to Section 9 to determine correct Purge Pressure Indicator setting .
Purge Pressure Adjustment Valve should never be completely closed.
11.5 Excessive purge is
discharged during
purge cycle
Excessive purge flow - Purge pressure too high
Refer to Section 9 to determine correct Purge Pressure Indicator setting .
Inlet switching valve fails to close.
Verify voltage to pilot solenoid valve. Check pilot air pressure (60-120 psig
required.) Verify proper actuator operation. Check valve for obstruction or
seat damage.
(Models 40 through 3000) Shuttle Valve; or (Models
4100 through 5400) same tower Outlet Check or
opposite tower Purge Check Valves fail to close
Repair or replace valve(s) as needed.
11.6 Excessive desic-
cant dust down-
stream
Fluidization of desiccant bed - design conditions for
maximum rated flow exceeded
Refer to Section 4 or 9 to determine if dryer is being operated outside of
design limitations.
Fluidization of desiccant bed -
Rapid repressurization of offstream tower due to:
Faulty timer
Insufficient purge flow - purge pressure too low
Refer to Section 7 or 8 to verify proper time sequence.
Refer to Section 9 to determine correct Purge Pressure Indicator setting .
11.7 Switching Failure
Alarm
(Level 1 & Level 2
Controllers only)
Faulty pressure switches or control board
Replace components
Offstream tower did not de-pressurize in time and/or
below 10 psig
Check mufflers, check or shuttle valve(s), inlet switching and purge/
repressurization valves, purge pressure adjustment, and controller set-
tings.
Offstream tower did not re-pressurize in time and/or
above 10 psig
Check air supply to dryer, purge/repressurization valve, purge pressure
adjustment, and controller settings.
