ZEKS Eclipse
TM
90-5,000ZPB Desiccant Dryers
www.zeks.com
6
Re-pressurization is accomplished when the appropriate Purge
Valve closes. Closing the Purge Valve allows the regeneration air
to begin to pressurize the tower. In addition to the regeneration
air, the Re-pressurization Valve, (standard on -80°F and -100°F
dew point and high pressure dryers; optional on -40°F dew
point dryers) opens allowing some additional air from the outlet
of the dryer to ensure adequate pressurization. This valve is
pneumatically operated.
6.6 VALVES
Control Air Solenoid Valves are used to actuate the Main Flow
Valves and Purge Valves. The Inlet Flow Valves and the optional
Re-pressurization Valve are normally-open valves, while the
Purge Valves are normally-closed valves. This arrangement
permits air to
fl
ow through the dryer in the event of power failure.
The Control Air Solenoid Valves are located below the Main
Control Box.
Outlet Check Valves are single direction check valves that will
allow
fl
ow in the direction shown on the P&ID, but not allow
fl
ow
in the opposite direction.
6.7 TIMING SEQUENCE
All timing functions on the standard NEMA 1 equipped dryers are
performed by a Solid State Timer (SST). For dryers equipped
with the NEMA 4 option, a Digital Controller controls all dryer
timing functions. Regardless of controller, the timing of ZEKS
-40°F, -80°F and -100°F dryers is outlined as follows:
6.7.1 TIMING CYCLE FOR -40°F DEW POINT DRYERS
The standard timing cycle for -40°F operation switches
the Inlet Flow Valve position every
fi
ve minutes which
alternates the drying tower. At the same time as a tower
Inlet Valve opens, the appropriate tower Purge Valve
opens to depressurize the regenerating tower. Tower
regeneration occurs for 4 minutes and 15 seconds,
at which time the Purge Valve closes to initiate re-
pressurization.
6.7.2 TIMING CYCLE FOR -80°F AND -100°F DEW POINT
DRYERS
The standard timing cycle for both -80°F and -100°F
operation switches the Inlet Flow Valve position every 2
minutes which alternates the drying tower. At the same
time a tower Inlet Valve opens, the appropriate tower
Purge Valve opens to depressurize the regenerating
tower. Tower regeneration occurs for 1 minute and 50
seconds, at which time the Purge Valve closes to initiate
re-pressurization. The Re-pressurization Valve opens to
assist tower re-pressurization for the last 10 seconds prior
to Inlet Flow Valve switching.
The re-pressurization valve is pneumatically operated by
a shuttle valve. For -100ºF applications, the timing cycle
can be adjusted from -100ºF to -40ºF or +4ºF by entering
TECHNICIAN MODE, SCREEN 6/12, when the dryer
cycle is turned o
ff
.
6.8 PURGESYNC
™
FUNCTION (with NEMA 4/Digital
Controller option)
The PurgeSync
™
function enables the dryer to reduce the timing
of the purge cycle based on compressed air demand. When this
function is activated through the TECHNICIAN MODE within
the Digital Controller, the Controller will monitor the cycle rate
of the air compressor load / unload relay. The dryer will need to
be wired to the normally-open contact of the air compressor to
allow the controller to monitor the cycle rate. The PurgeSync
™
connections are depicted on the dryer wiring diagram.
It is important to note that the PurgeSync
™
function is designed
to be operated independent of the Moisture Load Control (MLC)
option. For dryers equipped with the optional dew-point monitor,
PurgeSync
™
must be set to “OFF” in order to activate the MLC
function. Setting PurgeSync
™
to “ON” in TECHNICIAN MODE
will disable the MLC function.
For dryers equipped with the MLC option, the PurgeSync
™
function can be used as a backup method of minimizing purge
air consumption when the Dew Point Monitor is removed
for calibration or for service. It is important to note that the
performance of the dryer is based on the inlet air temperature
and pressure conditions, in addition to
fl
ow. If the temperature of
the compressed air being supplied to the dryer is above 100
o
F at
the dryer inlet, the user must exercise caution in order to prevent
the desiccant beds from becoming overloaded, possibly requiring
the PurgeSync
™
function to be de-activated. Consult factory for
higher inlet temperatures, 101
°
F - 120
°
F. Dryer sizing is a
ff
ected
by increased inlet temperatures.
When the dryer is placed into operation and the PurgeSync
™
function is activated, the Digital Controller will monitor the cycle
rate of the air compressor load / unload relay contact over a
fi
xed time period to determine the Load Time Average (LTA)
percentage. The time period can be adjusted from 30-90 minutes
by accessing SCREEN 12 in TECHNICIAN MODE. The purge
timing cycle will be adjusted by the Controller at the completion
of the initial time interval. The table below outlines the purge time
reduction based on the Load Time Average values:
NOTE:
It is important to verify that the
fi
eld wiring connections
are properly installed during commissioning of the dryer in order
to prevent operational issues. If the PurgeSync
™
wiring is not
installed, this function must be set to “OFF” within TECHNICIAN
MODE in order to prevent operational problems. In the event that
this were to occur, the dryer would operate with a reduced purge
timing cycle that will result in desiccant overloading and failure
that would void the dryer Warranty.
6.0 PRINCIPLES OF OPERATION
Purge Cycle Time Reduction
Purge
Time
Load Time Average,
Reduction
LTA %
Percentage
Greater than 90%
0%
70% - 89%
10%
50% - 69%
25%
30% - 49%
40%
0% - 29%
65%
