ZEKS Eclipse 1000ZPA, Техническое руководство, Страница: 8 / 31

ZEKS Eclipse ZPA 90-5000 Desiccant Dryers
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7
7.1 MOISTURE INDICATOR
The Blue Moisture Indicator (BMI) analyzes a sample of
the control air supply which is taken from the dryer outlet.
The BMI provides an indication of dew point deterioration
at the outlet of the dryer. Under normal operating condi-
tions, the BMI appears blue. In the event of a dryer mal-
function or prolonged dryer shut down, it will turn gray in
the presence of moisture.
7.2 FAILURE-TO-SHIFT ALARM (Optional)
The Failure-to-Shift Alarm provides an indication of switch-
ing failure in one of the dryer switching valves. The Fail-
ure-to-Shift Alarm uses a pressure switch to monitor the
pressure in each tower.
At “0” PSIG the switches are normally closed which
sends a signal to the controller. When the towers pres-
surize, the switches open, thus removing the signal to
the controller. The controller anticipates the appropri-
ate open and closed switch position based on its timing
sequence. On dryers equipped with NEMA 1 electrics,
if either switch is in an incorrect position, the Failure-
to-Shift Alarm light will illuminate. The alarm light will
remain illuminated and the dryer will continue the operat-
ing sequence until the problem is corrected.
On dryers equipped with the optional NEMA 4/DPC
Package, Refer to Appendix A7, ALARMS AND INDI-
CATORS for description and explanation of alarms.
7.3 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 sen-
sor sends a signal to the humidistat. On NEMA 1 dryers,
power is then supplied to the red alarm light on the enclo-
sure. This light will remain illuminated until the problem is
corrected and the sensing element has dried out.
On dryers equipped with the optional NEMA 4/DPC
Package, Refer to Appendix A7, ALARMS AND INDI-
CATORS for description and explanation of alarms.
7.4 MOISTURE LOAD CONTROL (Optional)
The Moisture Load Control (MLC) feature is designed to
minimize the loss of purge air during low fl ow or low wa-
ter loading conditions. On -40°F units, a sensor samples
the moisture content from the online tower and provides
a signal to a humidistat. As long as the humidistat fi nds
that the air in each tower is dry, it will not allow the control-
ler to open the Purge Valves. Once the moisture content
in either tower is found to reach the threshold point, the
humidistat sends a signal to the controller and initiates the
regeneration cycle. For -80°F and -100°F dryers, a digital
dew point monitor is used in place of the humidistat.
Refer to Appendix NEMA 4 / DPC™ Package for cor-
rect operation of NEMA 4-equipped dryers with the
DPC™ Microprocessor Controller.
7.0 ALARMS AND INDICATORS