ZEKS HYDRONIX 20MPS User manual

TM MPS 20-60 V0116
TECHNICAL MANUAL
HYDRONIXTM
MPS Heatless Purge
Desiccant Compressed Air Dryer
20-60 SCFM
ZEKS Compressed Air Solutions
1302 Goshen Parkway
West Chester, PA 19380
Phone: [phone]
800-888-2323
Fax: [phone]
Web: www.zeks.com
NOTICE
Those operating the machine or performing
maintenamce should read and understand the
decals positioned on the machine and the
contents of this Technical Manual.
Ensure that this Technical Manual is not
removed permanently from the machine.

SECTION CONTENT PAGE
1. INTRODUCTION 2
2. ABBREVIATED WARRANTY 2
3. MPS HEATLESS PURGE DRYER NOMENCLATURE 3
4. RECEIVING AND INSPECTION 4
5. SAFETY AND OPERATION PRECAUTIONS 5
6. PRINCIPLES OF OPERATION 6
7. INSTALLATION/INITIAL START-UP 9
8. SCHEDULED MAINTENANCE 13
9. TROUBLESHOOTING 16
10. SPARE PARTS LIST 18
HYDRONIXTM
MPS Heatless Purge
Desiccant Compressed Air Dryer
20-60 SCFM

2
1. INTRODUCTION
ZEKS Hydronix™ Heatless Desiccant Dryers are designed to adsorb moisture from
compressed air. The dryers are constructed with two towers, each containing desiccant
beads, that alternate between online (drying) and offline (regenerating) modes, yielding a
continuous stream of dry air at the dryer’s outlet.
During normal operation, wet compressed air passes through the online tower and water
vapor present in the air is adsorbed (collected) on the desiccant beads. While air is being
adsorbed in the online tower, the moisture accumulated on the desiccant in the offline
tower is removed by a process called desorption (regeneration). After an initial rapid
depressurization, a portion of dried air from the online tower passes through the desiccant
bed, carrying the moisture off the beads and out the dryer’s exhaust.
The continuous, alternating process of adsorption and desorption is controlled using a
timer that switches the towers in a specific timed sequence. Very dry compressed air dew
points are achieved through the continuous switching and operation of this dryer. ZEKS
offers dryers to provide outlet air with either -40°F, -80°F or -100°F pressure dew point.
2. ABBREVIATED WARRANTY
ZEKS Hydronix desiccant dryers are warranted to be free from defects in material and
workmanship for a period of 12 months from the original date of shipment from the factory.
To allow the warranty to be in effect for 12 months from the date of equipment start-up,
the Warranty Registration Card must be completed and returned to ZEKS. Alternately, the
Warranty Registration Card may be completed online at www.zeks.com. The total
warranty period cannot exceed 18 months from the original date of shipment from the
factory.
Equipment must be installed and operated in accordance with ZEKS’ recommendations.
ZEKS liability is limited to repair of, refund of purchase price paid for, or replacement in
kind at ZEKS’ sole option, during the warranty time period stated above.
IN NO EVENT SHALL ZEKS BE LIABLE OR RESPONSIBLE FOR INCIDENTAL OR
CONSEQUENTIAL DAMAGES, even if the possibility of such incidental or consequential
damages has been made known to ZEKS Compressed Air Solutions. In addition, the
usual maintenance and replacement type products are not covered by this warranty.
The warranties expressed above are in lieu of and exclusive of all other warranties.
There are no other warranties, expressed or implied, except as stated herein. There are
no implied warranties of merchantability of fitness for a particular purpose, which are
specifically disclaimed.

3
3. HEATLESS DRYER NOMENCLATURE
NOMINAL
FLOW
SCFM* TYPE / DESIGN SERIES ELECTRICAL POWER OPTIONS
20 MPS = Small Pressure Swing 1= 115-1-60 (150 PSIG)
30 3 = 115-1-60 (300 PSIG)
40 A = Pneumatic (150 PSIG)
60 B = Pneumatic (300 PSIG)
0= No Options 0= NEMA 1 (-40°) 0= Standard 0= No Filter Pkg
B= F + H B= NEMA 1 (-80°) B= S + M V= Filter Pkg A
F= Fail-To-Shift L= NEMA 1 (-100°) M= Moisture Indicator 3= Filter Pkg B
H= High Humidity H= NEMA 4 (-40°) P= Adjustable Purge 6= Filter Pkg C
M= Moisture Load Control + F K= NEMA 4 (-100°) Q= P + M 7= Filter Pkg D
N= M + H D= NEMA 12 (-40°) R= Repress Line 5= Filter Pkg E
V= N.O. Inlet Valves F= NEMA 12 (-100°) S= Safety Relief Valves 4= Filter Pkg F
9= Filter Pkg A with Bypass
* Nominal Flows indicated are for 100°F inlet air temperature, 100°F ambient temperature
and 100 psig compressed air pressure.
Nomenclature shown above represents standard price sheet options. Other options are
available. Refer to nomenclature insert specific to your dryer for details.
NOTICE

4
4. RECEIVING AND INSPECTION
4.1 INSPECTION
Upon receiving your ZEKS air dryer, please inspect the unit closely. If evidence of
rough handling is detected, please note it on your delivery receipt, especially if the
dryer will not be uncrated immediately. Obtaining the delivery person’s signed
agreement to noted damages will facilitate submission of insurance claims
4.2 UNPACKING AND HANDLING
Refer to the General Arrangement drawing for the appropriate means for lifting or
moving the dryer. For those dryers that indicate lifting via the structural skid, forks
should extend all the way through the skid to reduce unnecessary forces to the
dryer during moving. When lifting the dryer, ensure that no stress is applied to the
piping or valving. Refer to Section 7.2 for locating and mounting of dryer.
Under no circumstances should any person attempt to lift heavy objects
without proper lifting equipment (i.e., crane, hoist, slings or fork truck).
Lifting any unit without proper lifting equipment, can cause serious injury.
NOTICE

5. SAFETY AND OPERATION PRECAUTIONS
Because an air dryer is pressurized and contains mechanical parts, the same precautions
should be observed as with any piece of machinery of this type where carelessness in
operation or maintenance is hazardous to personnel. In addition to the many obvious
safety rules that should be followed with this type of machinery, the safety precautions as
listed below must be observed:
1. Only qualified personnel shall be permitted to adjust,
perform maintenance or repair this air dryer.
2. Read all instructions completely before operating unit.
3. Pull main electrical disconnect switch and disconnect
any separate control lines, if used, before attempting
to work or perform maintenance on the unit.
4. Do not attempt to service any part while dryer is in an
operational mode.
5. Do not attempt to remove any parts without first
relieving the entire air system of pressure.
6. Do not operate the dryer at pressures in excess of
its rating.
7. Inspect unit daily to observe and correct any unsafe
operating conditions.
5
NOTICE
“WARNING” is used to indicate
a hazardous situation which
has some probability of death
or severe injury. Warning
should not be considered for
property damage accidents
unless personal injury risk is
present.
NOTICE
“NOTICE” is used to indicate a
statement of company policy
as the message relates directly
or indirectly to the safety of
personnel or protection of
property. Notice should not be
associated directly with a
hazard or hazardous situation
and must not be used in place
of “DANGER”, “WARNING”, or
“CAUTION”.
CAUTION
“CAUTION” is used to indicate
a hazardous situation which
may result in minor or
moderate injury.
OSHA Heading
Description
WARNING
The user of any air dryer manufactured by ZEKS Compressed Air Solutions, is hereby
warned that failure to follow the above Safety and Operation Precautions can result in
personal injuries or equipment damage. However, ZEKS Compressed Air Solutions
does not state as fact, nor does it mean to imply, that the preceding list of Safety and
Operating Precautions is all inclusive, and further, that the observance of this list will
prevent all personal injuries or equipment damage.

6
6. PRINCIPLES OF OPERATION
6.1 INTRODUCTION
As described in Section 1, water vapor is removed from compressed air by
diverting air flow alternately between two towers filled with desiccant. While one
tower processes the compressed air stream, adsorbing water vapor, the opposite
tower gets regenerated by desorbing the water vapor and venting it to atmosphere.
Refer to the Process and Instrumentation Diagram (P&ID) or the flow diagram for
visual representation of the drying and regenerating cycles.
6.2 DRYING CYCLE
Saturated compressed air enters the dryer and is diverted to the appropriate tower
by the Inlet Flow Valves. Referring to the Process and Instrumentation Diagram
(P&ID), the Left Inlet Flow Valve is actuated to a closed position to prevent air flow
from entering the regenerating tower. Simultaneously, the Right Inlet Flow Valve is
actuated to an open position, allowing air flow to the right hand tower. During this
time, the Right Tower Purge Valve is actuated to a closed position, preventing the
compressed air from venting to atmosphere. As the compressed air flows through
the desiccant bed at pressure, removal of water vapor from the air stream begins to
occur through adsorption. In the adsorption process, the desiccant beads draw
water vapor out of the compressed air and “hold” it until the right tower drying cycle
is complete. Compressed air flows out of the tower for delivery to the process use.
The Outlet Flow Check Valves provide air flow diversion to the outlet air connection
of the dryer. The Right Outlet Flow Check Valve allows air flow through to the outlet
connection of the dryer while The Left Outlet Flow Check Valve meters the purge
air to the regenerating tower.
6.3 REGENERATION CYCLE
Previously adsorbed moisture, removed from the process air stream, gets stripped
or desorbed from the desiccant material in the regeneration process. The first stage
of regeneration is tower depressurization. After the Inlet Flow Valves are switched
to divert air flow away from the regenerating tower, the appropriate Purge Valve will
be opened and the tower will be depressurized. Through rapid depressurization, a
significant portion of the previously adsorbed water vapor is stripped off of the
desiccant material and exhausted to atmosphere.
The second stage of regeneration uses a portion of the dry, compressed air,
expanded to atmospheric pressure to complete the desorption process. As shown
on the P&ID, the compressed air exits the drying tower and a portion of the air
flows through the fixed orifice located in the Outlet Check Valves. Once the air has
passed through this orifice, it expands to atmospheric pressure and continues the
regeneration process. Desorption occurs as the desiccant releases water vapor
into the regeneration air and is exhausted through the Purge Muffler.
6.4 SETTING THE REGENERATION AIR FLOW (Optional)
MPS Dryers are equipped with a fixed orifice to provide the appropriate amount of
purge air to the regenerating tower, however an adjustable purge option is
available. With this option, it is essential that the purge rate be properly set to
achieve proper dryer performance. Setting the purge flow too high will waste
compressed air and if set too low, the dryer will not achieve proper dew point
performance.

7
The purge adjustment manifold consists of the Purge Adjustment Valve, the Purge
Pressure Gauge and the Purge Orifice. When the right tower is the drying tower
(pressurized) and the left tower is depressurized (0 PSIG), manually adjust the
Purge Adjustment Valve until the gauge reading on the purge pressure gauge
matches the Purge Pressure Gauge setting listed on the laminated tag affixed to
the Orifice Plate Assembly.
6.5 TOWER REPRESSURIZATION
Upon completion of tower regeneration, and prior to the Inlet Flow Valves changing
position to switch towers, the regenerated tower must be repressurized.
Repressurization is accomplished by closing the appropriate Purge Valve. Closing
the Purge Valve allows the regeneration air to begin to pressurize the tower. In
addition to the regeneration air, the Repressurization 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. During normal tower regeneration, the Repressurization Valve is
held closed so that the only source of air for regeneration passes through the purge
adjustment assembly.
6.6 VALVES
Solenoid valves are electrically actuated valves used as the Inlet Flow Valves and
the Purge Valves for 150 psig units. These valves are normally closed valves.
When the valves are de-energized, they default to a closed position. In the de-
energized state, the Inlet Flow Valves keep the air from entering the towers and the
Purge Valves keep air from being purged from the system. For dryers rated for 300
psig, the Inlet Flow Valves and Purge Valves are replaced by actuated ball valves.
Outlet Check Valves are single-direction check valves that will allow flow in the
direction shown on the P&ID, but not allow flow in the opposite direction.
6.7 TIMER OPERATION
All timing functions are performed by the Solid State Timer (SST). The SST does
not require any adjustment. In the event of any SST malfunction consult factory.
Failure to re-pressurize prior to tower switchover will result in shocking the
desiccant material and cause premature desiccant dusting.
The right tower must be the drying tower for proper purge adjustment setting.
When the left tower is the drying tower, the Purge Adjustment Gauge will read
close to line pressure.
NOTICE
NOTICE

8
6.7.1 TIMING CYCLE FOR -40°F DEW POINT DRYERS
The standard SST timing cycle switches the Inlet Flow Valve position every five
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 30 seconds, at which time the
Purge Valve closes to initiate repressurization.
6.7.2 TIMING CYCLE FOR AND -80°F and -100°F DEW POINT DRYERS
The SST timing cycle switches the Inlet Flow Valve position every 2 minutes which
alternates the drying tower. At the same time as a tower Inlet Valve opens, the ap-
propriate 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 repressurization. The Repressurization Valve opens to assist tower
repressurization for the last 10 seconds prior to Inlet Flow Valve switching.
6.8 MOISTURE INDICATOR (Optional)
The moisture indicator senses a sample of the dried air which is taken from the
dryer outlet. The indicator provides an indication of dew point deterioration at the
outlet of the dryer. Under normal operating conditions, the indicator is blue. In the
event of a dryer malfunction or prolonged dryer shut down, it will turn gray in the
presence of moisture.
6.9 FAILURE TO SHIFT ALARM (Optional)
The Failure to Shift Alarm provides an indication of switching failure in one of the
dryer switching valves. The Fail to Shift Alarm uses a pressure switch to monitor
the pressure in each tower. The SST anticipates the appropriate open and closed
switch position based on its timing sequence. If either switch is in an incorrect
position, the Failure to Shift Alarm light will illuminate.
6.10 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 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 enclosure. This light will remain illuminated until the problem
is corrected and the sensing element has dried out.
6.11 MOISTURE LOAD CONTROL (PURGE SAVER) (Optional)
The Moisture Load Control (MLC) feature is designed to minimize the loss of purge
air during low flow or low water 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 finds that the air in each tower is dry, it will not
allow the timer 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 timer and
initiates the regeneration cycle. For -80°F and -100°F dryers, a digital dew point
monitor is used in place of the humidistat. For dryers equipped with the digital dew
point monitor, refer to the Dew Point Monitor Addendum.

9
7. INSTALLATION and START-UP
7.1 APPLICATION and CHECK ANALYSIS
To achieve the best dryer performance, you should carefully check that the design
and installation requirements outlined below are satisfied.
Operating pressure of ZEKS dryers can range from 75 -150 PSIG. Air available for
your usage will vary with operating pressure. The maximum design pressure of the
ZEKS Heatless Dryer is 150 PSIG. For units required for higher operating
pressures, consult your ZEKS representative.
The dryer must never be installed where air and/or ambient temperature exceeds
120°F or drops below +50°F. Locate dryer to avoid extremes of heat and cold from
ambient or other conditions. Avoid locating dryer outside or where it is exposed to
the elements.
7.2 LOCATING and MOUNTING
Lift the dryer only by the lifting points indicated on the General Arrangement
drawings furnished with dryer. Bolt the dryer to a suitable foundation using the bolt
holes provided in the base frame. Anchor bolts should project a minimum of two (2)
inches above the foundation. Refer to General Arrangement drawing for details.
7.3 PIPING
Pipe the compressed air lines to the inlet and outlet connections using piping and
fittings suitable for the maximum pressure rating of the system. Locate the prefilters
as close as possible to the dryer. Ensure the positioning allows for ease of
servicing. Refer to the General Arrangement drawing.
Note that the wet air inlet is at the dryer’s lower manifold, while the dry air outlet is
at the dryer’s upper manifold. In situations where air supply is required 24 hours a
day (where it is undesirable to have interrupted the airflow), a three valve by-pass
system is recommended to bypass the dryer. Use the fewest elbows necessary to
keep pressure drop at a minimum.
Once all piping has been connected, all joints including those on the dryer, should
be soap-bubble tested at line pressure to ensure no joints have been damaged in
transit and site placement.
The standard dryer is not rated for any gas other than air.
ZEKS recommends that the mufflers be removed prior to initial start up to allow
any desiccant dust generated during shipment to discharge. After running dryer
for 30 minutes, deenergize / depressurize dryer and reinstall mufflers. Note that
dryer operation will be extremely loud during this period. Proper hearing protec-
tion must be worn by all workers in the vicinity of the dryer during this procedure.
NOTICE
NOTICE

10
7.4 FILTRATION
It is important that a prefilter and an afterfilter be provided in your dryer installation.
Coalescing prefilters, located before the dryer, protect desiccant beds from contam-
ination by oil, entrained water, pipe scale, etc., thereby, extending the life of the
desiccant material. Locate prefilters as close to dryer as possible.
It is recommended that a mechanical separator be installed immediately preceding
the prefilter to remove the bulk liquid and entrained water.
Particulate afterfilters, located after the dryer, help eliminate the possibility of
desiccant dusting and carryover into the air system.
7.5 ELECTRICAL CONNECTION
Make all electrical connections to the dryer as shown on the wiring diagram. Care
must be taken in connecting the proper voltages.
Size field connection knock-out for the conduit fitting required by the NEC.
All dryers must have proper filtration. A .3 micron coalescing filter with automatic
drain & particulate after filter must be used as a minimum. Failure to provide
proper filtration for dryer will void warranty.
Dryer must be grounded with the full sized ground wire connected to an earth
ground.
Dryer must be fused according to NEC with the size fuse listed on the dryer
serial nameplate, or on specification sheet in technical manual.
NOTICE
NOTICE
NOTICE

11
7.6 START-UP
• Turn on dryer disconnect switch (supplied by customer) to apply power to the
dryer.
• With a voltmeter, check the power connections for the correct voltage shown on
the dryer serial nameplate.
• Close and secure all electrical panel covers.
• Slowly pressurize the dryer. When the dryer reaches full operating pressure,
check the system for air leaks. Soap-test all joints and fittings. To maintain desired
dew point, any leaks detected must be fixed, especially those on the outlet side of
the dryer.
• On units with Adjustable Purge, make sure that the purge adjustment valve is
open and air outlet shut off valve (if equipped) is closed.
• For dryers equipped with a Dew Point Monitor, remove the dew point monitor
sensor from the electrical enclosure and install in the sensing block that’s located
beside the enclosure and attach and secure the sensor cable to the sensor.
• On dryers equipped with the Moisture Load Control (Purge Saver) option, verify
that the Purge Saver switch is in the off position to allow standard cycling at
start-up.
• For the first 30 seconds that the dryer is energized, both purge valves will remain
closed. After 30 seconds, the left tower purge valve will be opened and depressur-
ization of the left tower will occur.
• When the dryer is energized, the Power On light and Right Tower Drying light will
be illuminated. When electrical circuit has been energized, the Solid State Timer
will start automatically. See Section 6 for logic operating sequence.
• Following depressurization, adjust purge valve as described in Section 6.4 for
dryers equipped with Adjustable Purge.
At initial start-up, check the dryer operation for one or two cycles, especially at
the time of the tower shift. Verify that all systems are operating in their proper
order and sequence. If the dryer is not functioning properly, contact distributor
or ZEKS Technical Service.
NOTICE

12
• If the dryer has been in storage or off for an extended period of time, the Blue
Moisture Indicator (BMI), if equipped, may appear gray, the High Humidity Light (if
equipped) may be illuminated and the Dew Point Monitor (if equipped) may
indicate a high dew point. Depending upon the duration of idle time, it may take
anywhere from one to twelve hours for the light to go out, the BMI to return to its
normal blue state and the dew point to drop.
• Slowly open the outlet valve to gradually pressurize the down stream piping
• On dryers equipped with Moisture Load Control, the Purge Saver switch may be
turned “ON” to save purge air as described in Section 6.11.
When opening the outlet valve, ensure drying tower gauge maintains line
pressure. Allowing pressure to drop in the dryer will result in an overflow
condition.
-80°F and -100°F dryers require flow through the dryer to lower the pressure
dew point to design levels. Failure to permit air flow through dryer (dead-
heading) will result in elevated outlet dew points. Once air is permitted to flow
through the dryer, the pressure dew point will gradually fall to design levels.
NOTICE
NOTICE

13
8. MAINTENANCE AND SYSTEM CHECK
8.1 SCHEDULED MAINTENANCE
DAILY MAINTENANCE FUNCTIONS:
•Check and record inlet pressure, temperature and flow. Verify that it is
within specifications.
•Check tower pressure gauge readings within operating tolerance.
•Check operation for proper dryer cycling, depressurization and repressurization.
•Check that the prefilter drain is operating properly and that there is no condensate
discharged from purge mufflers.
•Verify that pressure in purging tower is 10 PSIG or less. If higher, muffler replace-
ment is recommended. (Section 8.4)
•Verify that prefilter and afterfilter differential pressure is within operating limits.
Change as required. (Section 8.2)
SEMI-ANNUAL MAINTENANCE FUNCTIONS:
•Check outlet dew point.
•Blow-down relief valves.
•Replace prefilter and afterfilter elements and/or cartridges.
ANNUAL MAINTENANCE FUNCTIONS:
•Check desiccant and replace if necessary.
•Inspect and clean solenoid valves, check valves and purge lines.
•For dryers equipped with Inlet and Purge Ball Valves, inspect and clean valves.
•Test lights and switches, replace as necessary.
•Test electrical components, replace as necessary.
EVERY THREE-TO-FIVE YEARS:
•Replace desiccant.
•Replace Check Valves (Preventative)

14
8.2 Prefilters and Afterfilters
• Prefilters - The prefilter element must be changed as often as required to prevent
contamination of the dryer's desiccant bed.
The prefilter and automatic drain must be checked daily. To prolong filter element
life, it is recommended that a mechanical air/moisture separator be placed immedi-
ately before the prefilter.
• Afterfilters - The purpose of the afterfilter is to remove residual desiccant dust.
Depending upon equipment application and usage, frequency of filter element
change will vary. It is recommended that the filter element be changed every six
months at a minimum.
8.3 Solenoid Valves
If improper solenoid operation is suspected, clean all solenoid valves. Disconnect
power to the solenoid coil, depressurize unit and remove the solenoid’s coils and
plunger stems to clean. If the solenoid valves fail to operate, check the following:
• Solenoid valve leaking - Disassemble, clean and repack or replace.
• Control Circuit - Check to verify that the solenoid is receiving electric current at
appropriate times in the cycle.
• Burned out solenoid coil.
• High/low voltage - Voltage should be + 10% of nameplate readings.
8.4 Muffler Changeout Procedure
• Depressurize the dryer and turn control power off.
• Replace muffler.
• Follow Start-up procedure described in Section 7.6.
• Turn control power back on.
8.5 Outlet Check Valves
The integrity of the Outlet Check Valves are verified by visual inspection. After
depressurizing the dryer, remove the hexagonal cap located on the valve body.
Remove and inspect the seat. Replace seat as required. Note that on dryers
manufacatured without the Adjustable Purge option, the check valve seat is
provided with a specific orifice drilled into the seat. Be sure replacement seat or
complete valve is provided with the same sized orifice in the seat as the original.
Should the drying system be overloaded and/or malfunctioning, causing high
pressure drop, afterfilters will prematurely plug. This problem can be avoided by
frequent inspection and proactive replacement of elements.
To avoid injury, depressurize dryer before performing any service.
WARNING
NOTICE

15
For dryers equipped with Adjustable Purge, the Outlet Check Valves sealing can be
verified by depressurizing the dryer and applying pressure to the outlet. The Outlet
Check Valves should seal and prevent air from pressurizing the towers. If a tower
begins to pressurize, the check valve on that side requires replacement. Note that
outlet check valves for dryers with Adjustable Purge do not have an orifice provided
in the valve seat.
8.6 Desiccant Changeout Procedure
When it becomes necessary to replace the desiccant in the towers, observe the
following procedure:
• The standard units are furnished with fill and drain ports on each desiccant tower.
Remove the caps on both ports.
• To assist in getting the desiccant to flow from the tower, insert a small rod in to the
drain port as necessary. This may be required as the desiccant is packed into the
towers which may interfere with the flow of the material from the towers.
• Retainer screens, located at the inlet and outlet piping connections of the tower,
are removable on all models. It is suggested that these screens be removed and
cleaned at the time of desiccant changeout. These screens can be accessed by
disconnecting the upper and lower manifolds from the dryer towers.
• After cleaning the retainer screens, replace screens and reattach the outlet port
plug.
• With the fill port plug removed, fill the dryer tower with the appropriate grade and
size desiccant.
• Once the towers have been filled, replace the fill port plug on each tower.
• Any connections disturbed in the desiccant changeout process should be leak
tested prior to re-commissioning the dryer.
To avoid injury, depressurize dryer before performing any service.
Be sure to wear respiratory protection during the draining and filling process to
minimize inhalation of desiccant, as desiccant will produce dust during this
procedure.
CAUTION
WARNING

16
PROBLEM
Elevated dew point
Optional Blue Moisture
Indicator (BMI)
indicates high
moisture level.
Excessive pressure
drop in dryer
Failure to shift
PROBABLE CAUSE
Insufficient purge rate.
Inlet air pressure below
design condition.
Flow rate higher than design
condition.
Inlet temperature above
design condition.(120°F)
Entrained water entering
desiccant bed.
Desiccant contaminated by oil
Elevated dew point
BMI wet
Excessive flowrate.
Inlet pressure below design
condition.
No input power.
Defective solenoid valve.
Solenoid valve seal failure
CORRECTIVE ACTION
Check purge flow settings.
Check purge piping for obstruction.
Clean purge piping and muffler.
Check pressure source and system
for leakage.
Check flowrate and cause for
increased demand. Correct flowrate
condition.
Check air compressor aftercooler,
clean and service as necessary.
Check air/moisture separator, prefilter
and drains. Replace dryer desiccant if
necessary.
Install suitable prefilter. Replace dryer
desiccant.
Refer to “Elevated Dew Point” correc-
tive actions above.
Depending on degree of saturation of
the desiccant, the BMI may take a
week or more of continuous use to
switch back to its blue (dry) state.
Check flow rate and cause for
increased air demand.
Check pressure source.
Check power input.
Check solenoid valve.
Inspect and replace seals as required.
9. TROUBLESHOOTING
Refer to maintenance descriptions in Section 8 as required for trouble shooting
procedures.

17
CORRECTIVE ACTION
Check that timer circuit is not sending
a control signal.
Check Purge Valve.
Check Purge Valve. Repair and
replace if necessary.
Check that timer circuit is sending
control signal.
Purge muffler is dirty; replace.
Check Inlet Valve and Outlet Check
Valves. Verify Inlet Valve is closed to
purging tower (0 psig tower).
Reset when right tower is on line.
PROBLEM
Dryer fails to
pressurize.
Dryer fails to purge.
Excessive back
pressure in regener-
ating tower (above 5
psig)
Right tower
excessively high
pressure at the purge
gauge.
PROBABLE CAUSE
Faulty purge valve.
Purge valve does not open.
Purge valve stuck in closed
position.
Purge muffler does not pass
air.
Purge muffler passes too
much air. Air is leaking across
valve.
Improper calibration.

18
10. SPARE PARTS LIST
MODEL
DESCRIPTION 20MPS 30MPS 40MPS 60MPS
Desiccant* (698350) 22 Lbs. 44 Lbs. 44 Lbs. 66 Lbs.
Solenoid Valve∗∗ 681114 681114 681115 681115
Solenoid Valve∗∗ 681219 681219 681219 681219
Pressure Gauge 680572 680572 680572 680572
Check Valve∗∗ 681223 681223 680620 680620
Timer∗∗ 681236 681236 681236 681236
MLC/FTS Timer 681097 681097 681097 681097
MLC Humidistat 681099 681099 681099 681099
HH Humidistat 610135 610135 610135 610135
Moisture Sensor 681102 681102 681102 681102
Muffler, Purge 3/8” MPT 680938 680938 680938 680938
FTS Pressure Switch 600924 600924 600924 600924
Green Light (NEMA 1) 680999 680999 680999 680999
Yellow Light (NEMA 1) 680998 680998 680998 680998
Red Light (NEMA 1) 680997 680997 680997 680997
Pilot Light (NEMA 4) 632207 632207 632207 632207
Green Lens (NEMA 4) 632208 632208 632208 632208
Red Lens (NEMA 4) 632210 632210 632210 632210
Yellow Lens (NEMA 4) 632209 632209 632209 632209
This is a generic Parts List that is good for NEMA 1 and NEMA 4 configurations with
Moisture Load Control (MLC), Fail to Shift (FTS) and High Humidity (HH).
Do not use this Parts List for -80F, -100F applications.
* Indicates total desiccant quantity required to fill both towers.
∗∗ Denotes Parts that are recommended spares.