Stulz DESICAiR 500 Series Installation and operation manual

DESICAiR®Series 500
Engineering Manual
Desiccant Dehumidification

Notice
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(STULZ).
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Other brands and trade names are trademarks of their respective owners.
Copyright 2017 by Stulz Air Technology Systems, Inc.
Printed in the United States of America.
All rights reserved.
Stulz Air Technology Systems, Inc.
1572 Tilco Drive
Frederick, MD 21704
USA

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) i
Table of Contents
1.0GENERAL INFORMATION..................1
1.1Forward........................................................1
1.2Safety Summary..........................................1
1.3Warnings & Cautions...................................1
1.4General Theory of Operation.......................3
1.5Construction.................................................4
1.5.1Design Features ..........................................4
1.5.2Cabinet.........................................................4
1.5.3Inlets and Outlets.........................................4
1.5.4Dehumidifier Identification Number .............4
1.5.5Dehumidifier Identification Number (DIN)
Sheet............................................................5
2.0INSTALLATION ...................................6
2.1Receipt of the Unit.......................................6
2.2System Location and Clearance..................6
2.3Connecting Ductwork...................................6
2.4Utility Connections.......................................7
2.4.1Power Hookup.............................................7
2.5Installing a Humidistat or Control Sensor....7
3.0OPERATION ........................................8
3.1Installation Checks.......................................8
3.2Start-Up........................................................8
3.3Controller .....................................................9
3.4Automated Capacity Control........................9
3.4.1D-Stat I.........................................................9
3.4.2D-Stat II........................................................9
3.5Reactivation.................................................9
3.6Control Panel...............................................9
3.6.1Mode Selector Switch..................................9
3.6.2Control Panel Lights ..................................10
3.6.3High/Low Power Selector Switch...............10
3.6.4Hour Meter.................................................10
3.6.5Sample Nameplate....................................10
4.0UNIT FEATURES...............................11
4.1Standard Features.....................................11
4.1.1Control Sensor Terminals..........................11
4.1.2Dampers ....................................................11
4.1.3Monitoring Unit Performance.....................11
4.2Optional Features......................................11
4.2.1Portable Construction................................11
4.2.2Customer Interface Terminals ...................11
4.2.3Electrical Disconnect .................................12
5.0PREVENTIVE MAINTENANCE .........13
5.1Monthly ......................................................13
5.2Yearly.........................................................13
5.3Desiccant Rotor Drive Motor Maintenance13
5.4Blower Motor Maintenance........................13
5.4.1General Inspection.....................................13
6.0TROUBLESHOOTING.......................14
7.0REPAIR PROCEDURES....................16
7.1Desiccant Rotor Drive Belt Tension ..........16
7.2Rotor Cleaning and Replacement.............16
7.2.1Preparation................................................16
7.2.2Cleaning ....................................................17
7.3General Rotor Handling Guidelines...........17
7.4Rotor Repair..............................................18
8.0STULZ PRODUCT SUPPORT...........19
8.1Technical Support......................................19
8.2Obtaining Warranty Parts..........................19
8.3Obtaining Spare/Replacement Parts.........19

DRY Series 500 Installation, Operation and Maintenance Manual
ii (April 2017)
List of Figures
Figure 1 - General Theory of Operation ...................3
Figure 2 - Locating Wall-Mounted Humidistat/Control
Sensor ......................................................7
Figure 3 - Control Panel............................................9
Figure 4 - Sample Nameplate.................................10
Figure 5 - Differential Pressure Gauges.................11
Figure 6 - Portable Construction Features .............11
Figure 7 - Cabinet Interior- Top View .....................14
Figure 8 - Rotor Drive Belt Tension........................16
Figure 9 - Rotor Scratch Repair..............................18
Appendices
Appendix A, Forms
Installation Checklist ..........................................A1
Maintenance & Service Checklist.......................A2
Appendix B
Glossary...............................................................B

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) 1
1.0 GENERAL INFORMATION
1.1 Forward
Congratulations, theDESICAiR® DRY Series 500
dehumidification system covered by this manual
is designed and manufactured by Stulz Air
Technology Systems, Inc. Recognized as a world
leader, Stulz Air Technology Systems, Inc.
(STULZ) provides dehumidification systems
manufactured with the highest quality
craftsmanship using the finest materials available
in the industry. The unit will provide years of
trouble free service if it is installed, operated and
maintained in accordance with this manual.
Damage to the unit from improper installation,
operation or maintenance is not covered by the
warranty.
STUDY the instructions contained in this manual.
They must be followed to avoid difficulties. Spare
parts are available from Stulz Air Technology
Systems to ensure continuous operation. Using
substitute parts or bypassing electrical or
refrigeration components in order to continue
operation is not recommended and will VOID
THE WARRANTY.
1.2 Safety Summary
Read and understand all instructions,
recommendations, and guidelines in this manual
regarding the installation, maintenance, and
operation of this unit prior to installation and start-
up. All maintenance and repairs should be
conducted by personnel thoroughly trained in the
operation and maintenance of this or like
equipment.
The input power supply to the equipment must be
shut off before beginning work on the equipment.
Take extreme care to ensure every capacitor
likely to hold electrical charge has been
grounded. Always remove all rings, watches, and
other jewelry when working on electrical
equipment. Some of the equipment used may
present the hazard of Electrostatic Discharge
(ESD). When working inside the equipment,
always ground all parts before touching. When
possible, use a wrist grounding strap while
working on or near ESD sensitive components.
Never operate the unit with any cover, screen,
guard, panel, etc., removed unless the
instructions specifically state to do so, and then,
do so with extreme caution to avoid personal
injury. Never attempt to lift any component in
excess of 35 pounds without additional help.
Placards and/or stickers have been placed in
various locations on or in the unit. These
placards/stickers are intended to call attention
to personal safety and equipment damage
hazards.
Certain maintenance and cleaning procedures
may either recommend or specify the use of
solvents, chemicals, or cleansers. Always refer
to the Manufacturers Material Safety Data
Sheet (MSDS) prior to the handling of any of
these solvents, chemicals, or cleansers.
1.3 Warnings & Cautions
The following is a condensed list of
WARNINGS and CAUTIONS that are noted
throughout this manual. All personnel who
operate, maintain or service this euipment
should read and understand these WARNINGS
and CAUTIONS. All WARNINGS indicate a
potential threat to personnel and all CAUTIONS
indicate a potential threat of equipment
damage.
Voltages used with this unit
can be deadly. Be careful not to come in
contact with high AC input voltage connections
when installing or operating this equipment.
Use the services of a qualified electrician
and/or technician to make the electrical power
connections and perform maintenance.
DISCONNECT THE MAIN
POWER TO THE UNIT PRIOR TO
PERFORMING ANY MAINTENANCE OR
SERVICE. Turning the “On-Off-Auto” mode
selector switch to the OFF position DOES NOT
disconnect power to controls or the unit itself.
Whenever the nature of the
operation permits, keep one hand away from
the equipment to reduce the hazard of current
flowing through vital organs of the body.

DRY Series 500 Installation, Operation and Maintenance Manual
2 (April 2017)
Never work on electrical
equipment unless there is someone nearby who
is familiar with the operation and hazards of the
equipment and is competent in administering first
aid. When operators aid the technician, the
technician must warn them about dangerous
areas.
Do not be misled by the term
"low voltage" which may appear either within this
manual or on enclosed drawings or documents.
Electrical voltages as low as 50 volts may cause
death under certain conditions.
DO NOT TOUCH the hot
system components. The design reactivation
temperature range is 250° F to 300° F. The
components of the reactivation system may be
extremely hot during operation. Be absolutely
certain the unit and/or reactivation components
are cool before attempting to work on any
components.
!
CAUTION
Air intake and discharge
openings must be free of obstructions. Ensure
filters are clean and access panels are on and
properly secured.
!
CAUTION
Do not operate the unit
without filters. It is better to operate the unit
with dirty filters than with no filters. Operating
the unit with no filters may void the warranty.
Blower motors may start
unexpectedly when the unit is running due to
an automatic resetting of the internal overload
device.
Do not allow anyone under
the equipment while it’s suspended from a
lifting device.
Do not allow the unit to swing
while suspended from a lifting device. Failure to
observe this warning may result in injury to
personnel and damage to the equipment.

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) 3
1.4 General Theory of Operation
This unit is designed to dehumidify a user-defined
space or process to humidity levels that are
below those attainable with a refrigeration-based
system. Moisture is removed from the air through
an adsorption process using a dry desiccant
material that is impregnated to the desiccant
rotor's fluted surface area. Air to be dehumidified
(process air) is filtered, dehumidified, and
supplied to the conditioned space at a lower
relative humidity and a slightly higher dry bulb
temperature than its inlet condition.
Simultaneously a second air stream (reactivation
air) is filtered, heated by the reactivation heater
system and passed through a separate segment
of the rotor. The heated air removes the
previously adsorbed moisture from the desiccant
in the rotor and exhausts it to an area other than
that being conditioned.
During operation, the desiccant rotor
continuously rotates at a constant speed
through the process and reactivation sections
of the dehumidifier. The two air streams are
separated by face and peripheral seals, and by
the internal fluting of the rotor. Process and
reactivation airflows are counterflow to each
other to maximize the efficiency of the
adsorption process and to help prevent the
rotor's flutes from fouling.
The reactivation heater is designed to raise the
reactivation air temperature approximately
180º F above ambient. The energy from the
heated air is used to desorb the moisture.
Reactivation discharge air temperature is
approximately 130º F to 150° F and moist.
Controls are included in the unit to vary the
amount of reactivation heat based upon the
amount of moisture adsorbed from the process
air stream.
Figure 1 - General Theory of Operation
Reactivation
25% of Rotor
Surface
Process
75% of
Rotor
Surface
Desiccant
Rotor
Process
Air Inlet
Reactivation
Air Outlet
Process
Air Filter
Reactivation
Air Blower
Process
Air Blower
Reactivation
Air Filter
Process
Air Outlet
Reactivation
Heater(s)

DRY Series 500 Installation, Operation and Maintenance Manual
4 (April 1017)
1.5 Construction
This DRY Series 500 rotary desiccant
dehumidification system has passed extensive
Quality Control checks, including a complete
functional test. Every effort has been made to
ensure the dehumidification system will perform
satisfactorily for many years.
1.5.1 Design Features
• Rugged All-Aluminum Cabinet
• Optional Portable Design with
Wheels and Lift Handle(s)
• Continuous or Automatic Operation
• 120 Volt Control Circuit
• Inert, Stable Silica Gel Desiccant
• Non-toxic, Non-corrosive Desiccant
• Capable of withstanding 100% RH
without adverse affect
• Counterflow Process and
Reactivation Air Patterns
• Overheat Safety Protection
• Process and Reactivation Inlet Air
Filters
• Two Stage Electric Reactivation Heat
• High/Low Heater Selector Switch
• Easy Access to Internal Components
• Low Operating Cost, Energy Efficient
Dehumidification
For a comprehensive list of the features included,
refer to the DIN Sheet provided specifically for your
unit. The DIN sheet is a listing of all the features
that are included (see Section 1.5.4). For particular
detail of the features, refer to the drawings
provided with this unit.
1.5.2 Cabinet
This unit is self-contained in an aluminum cabinet
and is rated for indoor or outdoor use (See unit
nameplate). The exterior of the cabinet is finished
with a durable, protective finish to protect it against
corrosion. A removable access panel is provided
on top for easy access to all major components for
maintenance and/or service.
The operator controls are conveniently located on
the electric box panel at the end of the unit (see
the Installation drawing provided). The cabinet
houses the desiccant rotor assembly and drive
system, process and reactivation air blowers, a
reactivation heater system and electrical controls.
1.5.3 Inlets and Outlets
Inlet and outlet openings include round duct
connections for flexible or hard duct. The openings
are furnished with screens to prevent birds and
small animals from nesting in the inlets and outlets.
For specific detail, refer to the installation drawing
provided with the unit.
The dehumidification system is equipped with
manually adjusted process and reactivation dampers
for setting airflows to achieve the required pressure
drops across the rotor (See 4.1.3 Monitoring Unit
Performance).
Filtration is accomplished through the use of 30%
pleated filters located in the process and reactivation
air inlets, as shown in the installation drawing.
1.5.4 Dehumidifier Identification Number
The Dehumidifier Identification Number (DIN)
defines the specific features provided with your unit
(see Section 1.5.5). The DIN Sheet for this unit is
included for reference in a Technical Data Package.
The Technical Data Package also contains a
Technical Data Sheet, a Test Report (showing
performance information), Drawings and this
manual. A manual for the system controller is also
provided. These documents should be stored in a
safe place on or near the unit for reference.
A “Warranty Registration and Start-up
Checklist” is also included with the Data
Package. This form must be completed during
installation and returned to STULZ Product
Support to activate your warranty.

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) 5
1.5.5 Dehumidifier Identification Number (DIN) Sheet
The DIN starts with the model number. The model number includes the process cfm followed by the desiccant rotor
diameter combination (ex. DRY-700-35). The first 15 digits after the model number (represented by the uppercase letters
A-N below) pertain to the cabinet construction, rotor, and process and reactivation accessories or options.
Process CFM Rotor Diameter in Centimeters
DRY - XXX - XX - A A - B C D E F G H - I J K- L M N
Model Number Reactivation Cabinet Construction Process Reactivation
Type and Rotor Assembly Assembly
The last 15 numbers (represented by lowercase letters a-m) pertain to the electrical system, unit controls, the power
supply, control scheme, and the control panel.
a a b c - d d e - f g h i j k l m
Power and Capacity Optional
Wiring Control Features
The following is a sample DIN Sheet for a DESICAiR DRY Series 500 Desiccant Dehumidifier.

DRY Series 500 Installation, Operation and Maintenance Manual
6 (April 2017)
2.0 INSTALLATION
2.1 Receipt of the Unit
Upon receiving the DESICAiR desiccant
dehumidification unit, immediately inspect the
unit for damage which may have occurred
during shipment. Carefully remove the shipping
cover and protective packaging. Remove the top
access panel. If any damage is found, report it to
the carrier immediately. Any obvious damage
incurred during shipping must be noted on
the freight carrier’s delivery forms BEFORE
signing for the equipment. Freight claims
must be done through the freight carrier.
Generally, all equipment ships “F.O.B. Factory”.
STULZ can assist in the claim filing process with
the freight company.
Remove any loose parts, and check the
equipment against the packing list to see if the
shipment is complete. Report all discrepancies
to the appropriate authority.
2.2 System Location and Clearance
The dehumidifier is designed to be operated in a
level position. Choose a location convenient to
the area to be dehumidified. Allow enough room
around the dehumidification system to access
controls, gauges, dampers, stowage area, etc.
Recommended minimum clearances on all sides
of the unit are 1x the full width of the cabinet.
The reactivation discharge air
can be very warm and humid. Keep items that
may be damaged by excessive heat and
humidity away from the reactivation air outlet.
The “process” and “reactivation” inlet and outlet
openings are located on the ends of the unit as
shown on the Installation drawing.
To judge the clearance requirements, consider
that all the components are housed inside the
DESICAiR dehumidifier cabinet. The rotor is
typically the largest of the components that may
need removal. Blower assemblies, while
somewhat smaller, also require sufficient
clearance for removal.
Position the unit in the desired location. Make
sure the mounting surface is able to support the
weight of the equipment and keep it level. The
following general requirements should also be
considered:
1) The power source should be located as near
as possible to the installed location of the
equipment.
2) The power source wiring should include a
main power disconnect switch. If the unit is
purchased from STULZ without an optional
power disconnect switch, one should be
provided by the installer. Provisions should
be made to ensure power is not accidentally
disconnected during normal operation and
the main disconnect switch is not used
instead of the mode selector switch to turn
the system off for normal shut-down.
3) If possible, avoid locations where the air
intakes will be laden with dust, dirt, soot,
smoke, or other debris.
4) DO NOT operate the unit in or near
flammable or corrosive environments or
allow flammable or corrosive air into the unit.
5) Refer to the wiring diagram provided with
your unit for the proper electrical
connections.
2.3 Connecting Ductwork
Ducting should be sized for the appropriate air
quantity and pressure drop. The clearance
required for the duct connections depends on
whether the unit is to be ducted for process air,
reactivation air, or both.
When installing a unit outside the conditioned
space, the process inlet and outlet must be
ducted to and from the conditioned space to
prevent humid air from entering the process air
stream.
The reactivation air temperature at the outlet will
be warm (approximately 130º F) and humid.
When installing a unit in the conditioned space,
the reactivation inlet and outlet must be ducted
to and from another area to prevent the warm,
moist air from being returned to the conditioned
space. If duct work is connected to the
reactivation outlet, it should be insulated and
sloped down and away from the unit. This will
prevent condensed moisture from accumulating
at the reactivation outlet.
Refer to the Installation drawing provided with
your unit for the duct connection sizes and
locations.

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) 7
All ducting must be air-tight or the
dehumidification system will not perform to its
maximum capability. Even small leaks can have
a dramatic effect on system performance.
Flow regulation dampers are provided with this
unit. After ductwork is installed, refer to Section
4.1.3, Monitoring Unit Performance for
information concerning setting the correct
airflows. If air volumes are not set correctly, the
unit’s performance may be affected.
Ensure the inlets and outlets are free of
obstructions and the filters are kept clean.
2.4 Utility Connections
2.4.1 Power Hookup
HIGH VOLTAGE IS USED IN
THE OPERATION OF THIS UNIT. Use the
services of a QUALIFIED ELECTRICIAN ONLY
to make the electrical power connections.
1. Refer to the electrical drawing for the main
power connections and see the unit
nameplate for the minimum circuit ampacity
(MCA) and maximum fuse size (MFS).
2. If your unit was purchased with the optional
portable design features (Section 4.2.1), a
15 foot power cable is stowed in the lower
storage compartment. The cable is pre-
terminated in the dehumidifier control box.
Extend the cable from the storage
compartment and connect it to the power
source. A power plug may be customer
supplied if needed. Ensure it is appropriate
for the power requirements of the
dehumidifier per the unit nameplate.
3. If your unit was not purchased with a power
cable, connect power to TB1 or to the
optional main disconnect switch per the
electrical drawing provided with the unit.
4. Branch circuit protection is required by
National Electric Codes.
2.5 Installing a Humidistat or Control Sensor
A terminal block is provided for the connection of a humidistat or On/Off control sensor. Interconnecting field
wiring must be installed in accordance with NFPA 70 of the National Electrical Code (N.E.C.).
Wire the humidistat or control sensor per the electrical drawing. Wall-mounted control sensors should
typically be mounted 4-5 feet up from the floor in the conditioned space (see the diagram below).
Locate the sensor according to the application. To control the conditions in a space, a wall mounted sensor
may be used in the space or a duct mounted sensor may be located in the return air inlet duct if the air is re-
circulated. To control the air supplying a process, a duct mounted sensor may be located in the supply air
duct near the process. Duct mounted sensors cannot be used for D-Stat control but can be used if the unit
is configured for control schemes where the process blower runs continuously such as D-Stat II (See
Section 3.4 Automated Capacity Control).
Figure 2 - Locating Wall-Mounted Humidistat/Control Sensor
4-5 ft.
Mount the sensor in the center of the room
where air circulation is good.

DRY Series 500 Installation, Operation and Maintenance Manual
8 (April 2017)
3.0 OPERATION
The following information provides an overview of
the operating procedures and sequences. Before
operating the unit, go through the checklist below
to ensure all electrical and utility connections are
correct and the unit is ready for operation.
NOTE: A Warranty Registration and Start-Up
Checklist is provided in the data package supplied
with your unit. It should be completed during
installation and a copy should be sent to STULZ
Product Support. It will assist if service or
troubleshooting support is needed.
3.1 Installation Checks
Recommended tools for performing the pre-
operation checkout include a voltage meter with
temperature probe, a flashlight, a Phillips and
flathead screwdriver, and a digital amp meter.
1. Verify the main power per the unit nameplate.
ONLY USE POWER THAT’S RATED FOR
THIS UNIT PER THE NAMEPLATE.
INCORRECT POWER MAY DAMAGE THE
UNIT AND CAUSE DAMAGE TO PROPERTY
OR INJURY OR DEATH TO PERSONNEL.
2. With the mode selector switch (S15) and the
optional disconnect switch (S16) in the OFF
position, recheck that all utility connections
have been properly made.
WARNING If the unit is not equipped
with a disconnect switch (optional), the
unit will have power when the electrical
connections to TB1 are made. Use caution
when servicing the unit. Refer to the
electrical drawing when performing
service.
3. Check the wiring to any remote sensors,
humidistats, start/stops, etc. Refer to the
electrical drawing for specific wiring
connections.
4. Check all electrical connections for tightness.
5. Be sure there are no loose parts or spare
parts (such as extra filters, etc.) located inside
the unit.
6. Be sure the access panel on top is closed
tightly. Small air leaks can significantly reduce
unit performance.
3.2 Start-Up
1. Apply power to the unit. The white “Power On”
light (DS1) should illuminate.
2. Turn the mode selector switch to “ON”. Ensure
the rotation of all motors, (process,
reactivation, and rotor drive motor), are as
indicated by the arrow labels.
3. Set the airflows to the required rotor pressure
drop versus the airflow required for this
application. Airflow is indicated by rotor
pressure drop values as viewed on the
differential pressure gauges mounted on the
unit. The Technical Data Sheet shows the
optimum “Reactivation Side” and “Process
Side” pressure drops (Rot. Press. Drop, in.
w.c.). Process and reactivation airflows are set
using airflow dampers located on the air inlets.
For a detailed description of setting and
monitoring airflows, refer to Section 4.1.3,
Monitoring Unit Performance.
4. Verify that amp draws of each component are
within ±10% of the ratings shown on the unit
nameplate.
5. Verify the operation of all switches and
safeties.
6. The green “Unit On” and red “Fault Indication”
lights are equipped with “press-to-test”
capability. This feature can be used to test
operation of the lamp element when main
power is on. If a “press-to-test” light does not
illuminate when pressed, it may be burned out
or the electrical connections may be faulty.
7. Set the humidity to the desired setting.
8. Verify the grain depression across the system
(in the process air stream) is correct per the
Technical Data Sheet.
NOTE: During basic unit operation, process air will
enter one side of the unit cool and humid and
leave the other side of the unit warm and dry.
Reactivation air will enter one side of the unit cool
and will leave the other side very warm and moist.

DRY Series 500 Installation, Operation and Maintenance Manual
(April 2017) 9
3.3 Controller
This unit is equipped with a solid state
microprocessor based controller mounted inside the
cabinet. Generally, this device is used to control the
reactivation heater to maintain a reactivation
discharge air temperature setpoint. The controller is
shipped from the factory pre-programmed. The
source manufacturer’s operating manual for the
controller is provided under separate cover. Refer
to the source manufacturer’s instructions for
detailed information on operating the controller and
adjusting parameters.
3.4 Automated Capacity Control
3.4.1 D-Stat I
What it Does:
This control method cycles the dehumidifier on
and off to maintain the relative humidity
setting.
Requires:
A wall-mounted humidistat or dry contact to
enable remote start/stop.
How it Works:
The dehumidifier responds to a control signal
from a humidistat or a customer supplied dry
contact, which cycles the unit on and off to
maintain the relative humidity setting. The unit
mode selector switch (S15) must be set to
AUTO.
Conditions:
Sensor control range: 15 to 90% RH
Ambient range: 40 to 125º F
Space control accuracy: +/-7% RH
3.4.2 D-Stat II
How it Works:
This control method functions similar to D-Stat I
except the process blower runs continually. The
reactivation heater and blower cycle on and off
in response to a humidistat (optionally provided
by STULZ) or a customer-supplied dry contact.
As an option, the process blower may cycle on
and off based upon a separate, customer-
supplied Remote Start/Stop contact.
Sensor control range: 15 to 90% RH
Ambient range: 40 to 125º F
Space control accuracy: +/-7% RH
NOTE: D-Stat I and D-Stat II will not work without
a humidistat or a customer supplied dry contact
closure.
3.5 Reactivation
Electric heat is generated by an SSR (solid state
relay) controlled heater. The SSR cycles the
heater on and off based upon a signal from the
system controller to maintain the reactivation
discharge air temperature setpoint.
The temperature of the reactivation air entering
the rotor is about 180° F above ambient
(depending upon the moisture load in the
reactivation air, and/or the flow of the reactivation
air). Refer to the electrical drawing for more detail
on the heater circuit.
3.6 Control Panel
Figure 3 - Control Panel
3.6.1 Mode Selector Switch
The DRY Series 500 unit is equipped with a three
(3) position mode selector switch (On/Off/Auto)
located on the control panel. Refer to the table
below for the basic modes of operation:
Mode Status of Unit
OFF
Unit is off, power is still live if main
disconnect switch is ON; white
“Power On” indicator light is
illuminated.
ON Unit is on and runs continuously; green “Unit On” indicator light is
illuminated
AUTO
Unit cycles on and off in response to
a humidistat or Remote Start/Stop
contact; green “Unit On” indicator light
is illuminated when unit is running
Control Panel
Lights- 3.6.2
Mode Selector
Switch- 3.6.1
High/Low Power
Selector- 3.6.3
Run Hour
Meter- 3.6.4
Controller- 3.3
Power
Disconnect- 4.2.3

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NOTE: The unit will not operate in the AUTO mode
unless a humidistat is installed (and the contact is
open) or the appropriate jumper connection is not
made on the unit terminal block to enable Remote
Start/Stop control of the dehumidifier. Refer to the
electrical diagram for specific wiring connections.
3.6.2 Control Panel Lights
Each unit is equipped with visual indication lights to
notify the operator of the current status of the unit. The
green “Unit On” and red fault indicator lights are
equipped with “Press to Test” capability. This should
be used to test operation of the lamp element. If a light
does not illuminate when pressed, it may be burned
out or the electrical connections may be faulty.
Certain status indicator lights may operate together
with optional customer interface terminals (See
Optional Features). For specific information regarding
troubleshooting fault lights, refer to the
Troubleshooting section of this manual.
The "light" next to the following indicator light
name specifies its color.
W = White
R = Red
G = Green
Standard Indication Lights
POWER ON
This illuminates white when main power is
supplied to the unit.
UNIT ON
This illuminates green when main power is
supplied to the unit and the unit is running.
HIGH REACTIVATION TEMPERATURE
This illuminates red and the heater shuts off when:
a. The reactivation air entering the rotor is above
the high temperature setpoint of 340° F. A manual
reset of Overheat Safety Switch (S4-2) is
necessary
b. The air leaving the rotor is above 175° F. A
manual reset of Overheat Safety Switch (S4-1) is
necessary.
c. There is insufficient reactivation airflow across
the air proving switch (S14).
d. A fusible link (FL1-1 or FL1-2) opened. This
requires replacement.
3.6.3 High/Low Power Selector Switch
A two-(2) position selector switch, located on the
control panel, may be used to select the power
consumption of the reactivation heater. The
normal switch position is “High”, which allows the
reactivation heater to operate at its full rated 9 KW
output. When the switch is set to “Low”, the
reactivation heater output is reduced to 3 KW and
drying capacity is significantly reduced.
3.6.4 Hour Meter
An hour meter, located on the control panel, gives
the elapsed run time for purposes of scheduling
maintenance.
3.6.5 Sample Nameplate
For information about operating voltage for this
unit, refer to the nameplate located near the
electrical control box. A sample nameplate is
shown in Figure 4. The unit nameplate provides
technical operating information along with the
model number, serial number and specific Stulz
Air Technology Systems job number. This
information will be required if it is necessary to
contact STULZ for additional information, warranty
information, or spare parts.
Figure 4 - Sample Nameplate
W
R
G

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4.0UNIT FEATURES
4.1 Standard Features
4.1.1 Control Sensor Terminals
This unit is equipped with terminal positions for the
connection of a customer installed control device,
such as a humidistat, for operating the capacity
control scheme (see Section 3.4, Automated
Capacity Control).
In general, the control device provides an on/off
switching signal, turning the dehumidification unit
on and off to maintain space relative humidity to
the setting on the device. The control scheme
manages the reactivation heater. Refer to the
electrical drawing for details on interfacing the
control sensor with the equipment.
4.1.2 Dampers
This unit is equipped with manually adjustable air
dampers for the process air stream and
reactivation air stream. The dampers are
slide/locking style, and are located in the duct
connections. The dampers are used to adjust the
process and reactivation air flows to meet design
conditions for optimal unit performance. The
dampers are to be readjusted after installation of
the ductwork is complete. Refer to 4.1.3,
Monitoring Unit Performance.
4.1.3 Monitoring Unit Performance
Two (2) differential pressure gauges are provided
to indicate the pressure drops across the rotor
(see Figure 5). Rotor pressure drop (static
pressure) correlates directly to airflow. In order to
maintain optimum performance, process and
reactivation airflows should be set to the
recommended rotor pressure drops. Refer to the
Technical Data Sheet included with the unit to
determine the appropriate values for the rotor
pressure drops (inches w.c.).
Figure 5 - Differential Pressure Gauges
After all ductwork is installed during initial
installation, the airflows may need to be adjusted
to re-establish rotor pressure drops to the values
indicated on the unit Technical Data Sheet.
Set the airflows by adjusting the process and
reactivation air dampers while the unit is still cold.
The air dampers are generally located in the
process and reactivation air inlets.
Afterward, if the differential pressure gauges show
readings that are significantly lower than the initial
factory settings, there may be an obstruction or
the filters may need to be changed. Operating the
unit with dirty filters will reduce unit performance.
Never operate the unit without filters as this may
damage the desiccant rotor.
4.2 Optional Features
This unit may be equipped with one or more of the
following optional features. For a detailed list of
the features purchased with this unit, refer to the
Dehumidifier Identification Number (DIN) sheet
provided with the unit. The DIN number for this
unit can be found on the DIN sheet.
4.2.1 Portable Construction
The dehumidifier may be equipped with optional
portable design features to allow for easy moving
and positioning of the unit. Rubberized wheels are
mounted beneath the cabinet base and a lift handle
is conveniently located at the end of the unit to raise
the unit on the wheels. A 15 foot long electric power
cable is included with this option. The power cable is
pre-terminated inside the electric control enclosure.
A storage compartment is furnished beneath the
cabinet for stowing the electric power cable (see
Figure 6).
Figure 6 - Portable Construction Features
4.2.2 Customer Interface Terminals
This unit is equipped with customer interface
terminals located on terminal blocks in the electrical
enclosure. The terminals can be used for a control
device to manage dehumidification. Refer to the unit
DIN sheet to determine which type control device is
to be used.
NOTE: Refer to the electrical drawing for specific
ratings of the control device and for wiring details.
Lift Handle
Wheels (2)
Power Cable Storage

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REMOTE START STOP CONTROL
Terminal positions are provided to connect a
remotely operated “Start/Stop” control device (i.e
humidistat). It may be used to start and stop the
unit when the mode selector switch is in the “Auto”
position. When the circuit is closed the unit will
operate; when the circuit is opened the unit will
stop (after the purge cycle). Refer to the Electrical
drawing to determine the correct wiring for the
control device.
NOTE: The unit will not start if space humidity is
below the setting on the humidistat.
4.2.3 Electrical Disconnect
This unit may be equipped with an optional non-
fused, rotary main power disconnect switch (S16)
located on the control panel. The disconnect
switch allows power to be removed during
maintenance or service functions. The handle of
the switch is equipped with a lockout feature to
prevent unauthorized actuation during periods of
service or maintenance. If not furnished by
STULZ, a disconnect switch is recommended and
may be required by national electrical codes. If a
disconnect switch is NOT provided, the unit will
have power when the electrical connections to the
main power terminal block (TB1) are made. Use
caution when servicing the unit. For wiring details,
refer to the electrical drawing provided with the
unit.
WARNING
Even with the optional Power Disconnect Switch
(S16) in the “Off” position, incoming power may
still be “live” between the switch and the main
power source. Power must be disconnected from
the main source before servicing.
WARNING
Components may still be energized with the
“On/Off/Auto” mode selector switch (S15) in the
“Off” position. Power must be disconnected from
the main source before servicing the unit.

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5.0PREVENTIVE MAINTENANCE
Minimal periodic Preventive Maintenance Checks
and Services (PMCS) are recommended to ensure
utmost performance of the DRY Series 500
dehumidification unit. Routine maintenance can
correct deficiencies before they cause serious
damage to the equipment and helps ensure the
unit is ready for operation at all times.
A schedule for preventive maintenance inspection
and service should be established immediately after
installation of the unit. A system should be
established to record any problems, defects, and
deficiencies noted by operators and discovered
during maintenance inspections, together with the
corrective actions taken. Use copies of the Periodic
General Maintenance Checklist in Appendix A to
record maintenance inspections. For assistance,
contact STULZ Product Support.
The following lists the preventive maintenance
checks and services that should be performed and
the recommended intervals. When operating
under extreme or unusual conditions, such as a
very dusty or sandy environment, it may be
necessary to reduce the maintenance intervals
indicated. The schedule below assumes your
system operates continuously.
Disconnect all power before
performing any service or maintenance function.
Turning the unit “On/Off/Auto” selector switch
(S15) to the “Off” position DOES NOT disconnect
power.
5.1 Monthly
• Check all electrical connections to ensure they
are tight and not shorted to ground.
• Ensure the control panel lights are functional and
not burned out (Use the “Press to Test” feature).
• Remove, clean, and/or replace the filters to
ensure proper airflow through the unit. If your
environment is exceptionally dusty or sandy,
this may be required on a more frequent basis.
• Check the rotor seals for wear and ensure they
evenly contact the rotor face and rotor flange.
• Check the rotor drive belt for signs of
abnormal wear.
• Lubricate motor bearings if necessary.
• Ensure shaft key, pulley and bearing
lockdowns are tight.
5.2 Yearly
• Thoroughly clean the unit inside and out,
making sure to remove any dust from fan
blades and dirt buildup in the ductwork (if
applicable).
5.3 Desiccant Rotor Drive Motor
Maintenance
A speed reducing gearmotor is used to rotate the
desiccant rotor. The gearmotor bearings are pre-
lubricated and do not require re-lubrication.
Periodically inspect around the gearmotor for
accumulated dirt and remove by vacuuming. Dirt
accumulation can cause motor heating and a fire
hazard. Also observe the motor while operating for
high motor current, unusual noises or vibration,
overheating, worn or loose couplings and belts or
loose mounting bolts.
5.4 Blower Motor Maintenance
5.4.1 General Inspection
Inspect the blower motors at regular intervals
(approximately every 550 hours of operation or
every 3 months). Keep the motors clean and
make sure the ventilation openings are clear. The
steps listed below should be performed at each
inspection.
Voltages used with this unit can
be deadly. Use the services of a qualified
electrician and/or technician to make the electrical
power connections and perform maintenance.
1. Ensure the motor is clean. Check to make
sure the interior and exterior of the motor are
free of dirt, oil, grease, water, etc. because
these things can accumulate and block motor
ventilation. If the motor is not properly
ventilated, overheating can occur and cause
early motor failure.
2. Use a “Megger” periodically to verify the
integrity of the winding insulation, and record
the readings. If there is a significant drop in
insulation resistance, immediately investigate.
3. Ensure all electrical connections are tight.

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6.0TROUBLESHOOTING
The DESICAiR dehumidifier is designed for
continuous and dependable operation. In the
event that a high reactivation temperature is
encountered, a lamp on the control panel
illuminates red to provide an alarm indication.
The following guidelines are included to assist you
in troubleshooting the dehumidifier due to
operational or performance problems. Refer to the
electrical and installation drawings provided with
your unit for the location of the system
components and their relationship to each other. If
the problem can’t be resolved using the guidelines
below, contact STULZ Product Support for
assistance (see Section 8.0).
NOTE: The High Reactivation Temperature safety
could trip if the main power is disconnected from
the unit while it is running. Before disconnecting
main power, turn the dehumidifier mode selector
switch to the OFF position and wait five (5)
minutes until the reactivation time delay shuts off
the reactivation blower.
Problem: Unit Does Not Run
If the dehumidifier is controlled by a remote device
such as a humidistat, check this device before you
check the dehumidifier itself.
In the AUTO mode:
1. Check remote humidistat or control device.
2. If this check-out does not solve the problem,
set the mode selector switch to the ON
position. If the unit operates, the problem is
related to the remote controller or the wiring
between the controller and the dehumidifier.
In the ON mode:
1. Check power supply for correct voltage and
phase.
2. Check wiring connections. Refer to the
electrical diagram provided with the unit.
3. Check circuit breakers and reset if necessary.
4. Check the motor thermal overloads or circuit
controllers.
Problem: “High Reactivation
Temperature" Light is Illuminated
A High Reactivation Temperature Fault can
indicate a number of fault conditions. Allow at
least 10 seconds for the blowers to cool the unit
and then check the Overheat Safety Switches,
(S4-1) & (S4-2). If one of the switches is tripped,
turn the unit selector switch OFF and disconnect
main power. Reset the tripped safety switch.
See Figure 7 for the location of the overheat
switches.
Figure 7 - Cabinet Interior- Top View
Check the fusible links (FL1-1) & (FL1-2). If a
fusible link has opened, a replacement is
necessary. See Figure 7 for the location of the
fusible links.
To prevent this problem from recurring, verify
that reactivation air volume is sufficient. Refer to
Section 4.1.3, Monitoring Unit Performance for
information on setting and verifying the correct
airflow. Ensure the filters are clean, the rotor
flutes are not dirty (clogged), the reactivation
damper is in the proper position and the
ductwork is not obstructed or damaged.
S4-1 S4-2 Fusible
Links
FL1-1, 2
Overheat
Safety Switch
Reset Button

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Problem: Process Blower Does Not
Turn, Yet “Unit On” Lamp is
Illuminated
1. Check the motor thermal overload and circuit
controller (CT3) for the process blower.
a. Reset if necessary.
b. Identify and correct the cause of the overload
condition.
In this case, amp draw of the motor exceeded the
design condition. With main power off, ensure the
blower turns freely. Also, ensure all wire
connections are tight and no shorts are present.
c. Ensure the overload current setting on CT3
matches the motor data plate FLA for the
rated voltage. Adjust CT3 if necessary.
Problem: Reactivation Blower Does
Not Turn, Yet "Unit On" Lamp is
Illuminated
1. Check the motor thermal overload and circuit
controller (CT2) for the reactivation blower.
a. Reset if necessary.
b. Identify and correct the cause of the overload
condition.
In this case, amp draw of the motor exceeded the
design condition. With main power off, ensure the
blower turns freely. Also, ensure all wire
connections are tight and no shorts are present.
c. Ensure the overload current setting on CT2
matches the motor data plate FLA for the
rated voltage. Adjust CT2 if necessary.
NOTE: With D-Stat II capacity control, the
reactivation blower and desiccant rotor do not run
if humidity conditions are satisfied.
Problem: Desiccant Rotor Does Not
Turn
1. Ensure the belt and tensioner are properly
positioned. Realign the belt or reset the
tensioner if necessary. See Section 7.1
2. Check the power supply to the rotor drive
motor.
a. Ensure all wire terminations are tight and no
shorts are present.
b. Check the transformer circuit breakers.
3. Check the seals for wear. If the surface is
worn through, then increased drag will occur.
This may cause increased power draw or too
much torque for the motor.
Problem: Dehumidifier Performance
is Reduced
This condition could indicate a problem with the
dehumidifier or a change in moisture loads
within the space which is being conditioned. See
the Technical Data Sheets provided with your
unit to verify the performance conditions are as
stated.
It is important that the power supply voltage be
correct and that the airflow rate be adjusted to
the correct values.
1. To check the dehumidifier performance, take
dry bulb and wet bulb temperature
measurements upstream and downstream
of the dehumidifier rotor in the process air
stream. Convert the readings to dry bulb
temperature and grains per pound. Compare
the results to those indicated by the
Technical Data Sheets provided. If the
results are comparable, the problem is not
with the unit. In this case, analysis of the
entire “system” of duct work and space,
including any changes in moisture loads
(occupancy etc.), is required.
2. Ensure the fans are rotating in the correct
direction. If they are reversed, turn the unit
off then disconnect main power. Check the
motor wiring against the diagrams shown on
the motor nameplate to ensure it matches
the phase and voltage shown on the
dehumidifier nameplate (Figure 4). If the unit
is 3 phase, simply switch any two power
supply leads at the power distribution block.
If the unit is single phase, reconnect the
wires according to the motor nameplate
diagram.
3. Check the process and reactivation airflows.
See Section 4.1.3, Monitoring Unit
Performance.
The desiccant itself is designed for a ten year
life with little degradation over time (<10% over
10 years). However, improperly filtered air or oil-
contaminated air can affect the capacity of the
desiccant. If this is the case, performance may
be restored by cleaning the rotor as described in
Section 7.2, Rotor Cleaning and Replacement.
If the result of following the above
troubleshooting steps doesn’t solve the problem,
contact DESICAiR Product Support.

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7.0 REPAIR PROCEDURES
Under normal operating conditions and with the
proper preventive maintenance, the unit should
provide excellent service for many years. If
necessary, the unit may be returned to the
manufacturer or a suitably qualified depot for
major overhaul and refurbishment. All work must
be performed by qualified technicians and should
include replacement of rotor, seals, motors,
starters, contactors, bearings and other
accessories as necessary.
7.1 Desiccant Rotor Drive Belt
Tension
The rotor drive belt is used to turn the rotor. The
belt is placed over the rotor, the drive pulley and
the tension idler pulley (refer to Figure 8 below).
The rotor drive belt is designed to last a long time,
as long as the belt alignment and tension are
correct. Over a period of time, the rotor drive belt
may stretch causing slippage and therefore
require tension adjustment.
Figure 8 - Rotor Drive Belt Tension
The rotor drive belt may be adjusted using the
following steps:
De-energize the unit and remove the access
cover.
Loosen the nut on the tension idler pulley.
Slide the tension idler pulley in the slot inward
toward the rotor until the rotor drive belt grips
the outside surface of the rotor firmly.
Tighten the nut snugly on the tension idler
pulley.
Energize the unit and let the rotor make
several revolutions, carefully checking that the
rotor is rotating smoothly and continuously.
Replace the cover on the unit.
7.2 Rotor Cleaning and
Replacement
The DESICAiR silica gel rotor is washable. Over
time, dirt may accumulate on the surface of the
rotor, blocking the openings of the flutes. The
rotor may require periodic cleaning to maintain
peak performance. Accumulated dirt can be
removed from the surface of the rotor using a
vacuum cleaner. Heavier accumulations may be
removed by washing the rotor with clean water.
If the desiccant wheel is continuously exposed
to air containing oil laden vapors, it may be
necessary to wash the rotor with a solution of
water mixed with a light, non-alkaline detergent.
The following procedure describes the steps
required to clean the rotor. Required materials
include:
Dry vacuum
Wet vacuum
Hand-held spraying device (found at
most hardware stores)
Water/solution supply
7.2.1 Preparation
To wash the rotor it is recommended that it first
be removed from the dehumidifier. Operate the
unit with the reactivation blower ON, the
reactivation heater OFF, and the process blower
OFF for two hours, or until the entering and
leaving reactivation air temperature is the same.
Pre-cooling the air stream is not necessary.
1. Disconnect the power (turning the mode
selector switch to the OFF position DOES
NOT disconnect the power).
2. Remove the top cover from the unit to allow
access to the rotor cassette.
3. Loosen the drive belt tensioner and allow
the belt to drop free from the drive system.
Carefully remove the rotor. Be careful not to
damage the surface. If damage does occur,
repairs may be made by applying RTV silicone to
the damaged area (see Section 7.4, Rotor Repair).