ZEKS Eclipse
TM
90-5,000ZPB Desiccant Dryers
www.zeks.com
15
7.1 MOISTURE INDICATOR
The Blue Moisture Indicator (BMI) analyzes a sample of the
control air supply that is taken from the dryer outlet. If dryer
performance deteriorates, the BMI provides a visual indication of
compromised dew point. Under normal operating conditions, the
beaded media in the BMI appears blue in color. In the event of a
dryer malfunction or prolonged dryer shut down, it will turn gray
in the presence of moisture.
The dryer sequence will not start if the tower pressures are below
80 PSI at time of dryer startup. For dryers equipped with the
Fail-To-Shift and NEMA 4 options, the valves will not operate
if the line pressure is less than 75 PSIG. For dryers equipped
with the Moisture Load Control option, the Dew Point Transmitter
must not be installed until the dryer has continuously operated
for 24 hours and the Blue Moisture Indicator (BMI) appears blue
in color.
NOTE: The MLC function must be turned o
ff
during
this period to avoid unnecessary alarms.
NEMA 1 CONFIGURATION ALARMS AND INDICATORS
7.2 HIGH HUMIDITY ALARM (Optional)
The purpose of the High Humidity Alarm is to provide the
operator an indication if the equipment fails to supply air at
its designed dew point. This is accomplished by passing a
sample of dried air from the control line across a sensing
element. If the sensing element is exposed to air with a dew
point of -10°F or higher (for -40°F dryers), the sensor sends
a signal to the humidistat. Power is then supplied to the red
alarm light on the NEMA 1 enclosure. This light will remain
illuminated until the problem is corrected and the sensing
element has dried out.
7.3 FAILURE-TO-SHIFT ALARM (Optional)
The Failure-to-Shift Alarm provides an indication of valve
switching failure that could occur when the towers transition
between the drying and regeneration steps. Pressure
transducers are utilized to constantly monitor the pressure of
the towers during the drying and regeneration steps to ensure
that the correct pressure values are maintained.
NEMA 4 CONFIGURATION ALARMS AND INDICATORS
7.4 FAIL-TO-SHIFT AND TOWER PRESSURE ALARM
MONITORING (with NEMA 4/Digital Controller option)
The optional Fail-To-Shift alarm provides an indication of
a valve failure that could occur when the towers transition
between the drying and regeneration steps. Pressure
transducers are utilized to constantly monitor the pressure
of the towers during the drying and regeneration steps to
ensure correct tower pressure values are maintained during
each step.
The tower designated for regeneration should be under 7 PSI
during this step while the other tower should be maintained
at line pressure. When the mu
ffl
ers are properly serviced
and maintained, regenerating tower pressure will typically be
under 3 PSI. An alarm will be triggered under the following
conditions:
1.
De-pressurization Fault: The tower designated for
regeneration does not de-pressurize below 7 PSI within a
designated time period immediately after the designated
purge valve is energized AND/OR...
2. Pressurization Fault: The previously regenerated tower
that switches to drying does not pressurize above a high
pressure set-point within a designated time period.
The Fail-To-Shift option can be de-activated by accessing
SCREEN 10 in TECHNICIAN MODE. The function can be
turned o
ff
if a fault occurs with a pressure transducer.
During normal dryer operation, the Controller will also monitor
the tower pressure value of the Drying tower to ensure the
system is operating properly. The dryer must be equipped
with the Fail-To-Shift control option for this to operate
properly. TABLE 7.6 ALARM STATES details a list of Alarms
& Controller actions that occur if an irregular pressure value is
detected during normal ZPB dryer operation.
7.5 MOISTURE LOAD CONTROL (with NEMA 4/Digital
Controller option)
The Moisture Load Control (MLC) feature is designed to
minimize the use of purge air during low
fl
ow or low water
loading conditions. On -40°F units, a sensor samples the
moisture content from the online tower and provides a signal
to the Controller. This function utilizes a Dew Point Transmitter
to monitor the dew point of the air exiting the dryer. Note that
the Dew Point Transmitter must not be installed on a new
start-up and not until the dryer has continuously operated for
a minimum of 24 hours and the BMI appears blue in color.
When the MLC function is activated, a 30 minute delay will be
initiated to allow the dryer to regenerate. If the MLC set-point is
satis
fi
ed for more than eight continuous hours, the Controller
will revert to a
fi
xed cycle for a period of 60 minutes in order to
prevent the desiccant beds from becoming overloaded during
rapid changes in compressed air demand.
See TABLE 7.6 ALARM STATES for a list of Alarms, Causes and
Recommended Actions.
7.0 ALARMS AND INDICATORS
!
NOTICE
Do not restrict purge exhaust
fl
ow in any way. Keep Purge
Mu
ffl
ers clean. If exhaust
fl
ow must be piped away from the
dryer, consult factory for correct pipe sizing and con
fi
guration
guidance.
