Stulz DRH User manual

DRH
Direct Room Humidier
Installation, Operation and Maintenance Manual
Ultrasonic Humidication
DRH Series
GEN2
Energy Efficient Ultrasonic Humidifier
Models: DRH 04, 06, 08, 16
Installation, Operation and Maintenance Manual

IOM
Notice
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owner of the equipment for which this manual is written may photocopy the contents of this
manual for internal use only. No part of this document may be photocopied, reproduced, or
translated into another language for use by anyone other than the owner of the equipment for
which this manual is written without the prior written consent of STULZ Air Technology
Systems, Inc. (STULZ).
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Systems, Inc. Distributing or photocopying this document for external distribution is in direct
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Unpublished — rights reserved under the copyright laws of the United States and of other
countries. Other brands and tradenames are trademarks of their respective owners.
Copyright 2019 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
https://www.stulz-usa.com/en/
®

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
Table of Contents
Introduction ......................................................................................................................................................................... 6
Safety ...........................................................................................................................................................................................6
Safety Summary ..................................................................................................................................................... 6
Specifications ..................................................................................................................................................................................8
General Design................................................................................................................................................................................9
Main Parts .........................................................................................................................................................................................9
Ultrasonic Nebulizer Unit .................................................................................................................................... 9
Mist Guide................................................................................................................................................................. 9
High Water Float Switch...................................................................................................................................... 9
Low Water Float Switch....................................................................................................................................... 9
Fan ..................................................................................................................................................................... 9
Air Filter ..................................................................................................................................................................... 9
Water Fill Valve Solenoid.................................................................................................................................. 10
Water Supply Valve............................................................................................................................................. 10
Water Supply Tubing.......................................................................................................................................... 10
Drain and Overflow Assembly ........................................................................................................................ 10
Temperature Sensor.......................................................................................................................................... 10
Solid State Relay ................................................................................................................................................. 10
Level Controller.................................................................................................................................................... 10
Installation......................................................................................................................................................................... 12
Receiving the Equipment ..........................................................................................................................................................12
Site Preparation............................................................................................................................................................................13
Mounting/Placement .................................................................................................................................................................14
Supply and Drain Piping.............................................................................................................................................................14
Main Power and Control Wiring..............................................................................................................................................16
Wire Sizing Control Box to Humidifiers..................................................................................................................................17
Connecting Humidifier(s) to ControlBox....................................................................................................... 17
Single Humidifier................................................................................................................................................. 17
Multiple Humidifiers (Grouped)...................................................................................................................... 18
Operation........................................................................................................................................................................... 19
Purge the Water Line ..................................................................................................................................................................19
Initial Operation Checklist .........................................................................................................................................................19
Procedure for Operation............................................................................................................................................................19
Precautions....................................................................................................................................................................................20
Steps for Long Term Shutdown ...............................................................................................................................................20
Maintenance/Repairs................................................................................................................................................... 21
Periodic General Maintenance.................................................................................................................................................21
Air Filter .................................................................................................................................................................. 23
Water Supply Strainer/Flow Regulator ...................................................................................................... 23
Float Switches...................................................................................................................................................... 24
Water Tank............................................................................................................................................................. 25
Mist Guides............................................................................................................................................................ 25
Troubleshooting and Repair .....................................................................................................................................................26

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Common Repairs/Parts Replacement ..................................................................................................................................28
Preparation for Repairs (Removal of Water Tank)................................................................................... 28
Reassembling....................................................................................................................................................... 28
Replacing the Temperature Sensor ............................................................................................................. 29
Temperature Sensor on Water Tank ............................................................................................................ 29
Replacing a Transducer .............................................................................................................................................................30
Replacing a Nebulizer Print Plate ................................................................................................................. 31
Water Solenoid Valves, Float Switches and Level..............................................................................................................31
Control Board ....................................................................................................................................................... 31
Fill Solenoid Valve............................................................................................................................................... 31
Float Switch .......................................................................................................................................................... 32
Level Control Board ........................................................................................................................................... 32
Drain Solenoid Valve .......................................................................................................................................... 32
Product Support ............................................................................................................................................................. 33
Technical Support........................................................................................................................................................................33
Obtaining Warranty Parts ..........................................................................................................................................................33
Obtaining Spare/Replacement Parts ..................................................................................................................... 34
Drawings............................................................................................................................................................................ 35
Layout Drawing of Humidifier (Covers Removed to Show Parts) ..................................................................................35
Electrical Circuit Diagrams........................................................................................................................................................36
Typical Wiring Diagram for Modbus Version............................................................................................. 36
Typical Wiring Diagram for Stand-Alone Version.................................................................................... 37
Figures
Figure 1. Ultrasonic Humidifier- Model DRH-06.......................................................................................................... 8
Figure 2. Installation of Humidifier.................................................................................................................................. 13
Figure 3. Locating the Humidifier.................................................................................................................................... 14
Figure 4. Piping Connections............................................................................................................................................ 15
Figure 5. Water Inlet Connector....................................................................................................................................... 16
Figure 6. Electrical Connections...................................................................................................................................... 17

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Nomenclature
DRH-04-S
DRH DAH S 04
Ducted Air
Humidifier
Ducted Air
Humidifier
Stand
Alone
Number of
Transducers

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
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Introduction
DRH Ultrasonic Humidifiers are designed and manufactured with the highest quality
craftsmanship using the finest materials available in the industry.It will provide years of
trouble free service if installed and maintained in accordance with this manual.
Spare parts are available from STULZ to ensure continuous operation. Using substitute
parts or bypassing electrical components in order to continue operation is not
recommended and will VOID THE WARRANTY. Damage to the unit from improper
installation, operation or maintenance is not covered by thewarranty.
Due to technological advancements, components are subject to change without notice.
Each unit is designed as a stand-alone direct room humidifier. Any use beyond this is
deemed to be not intended. STULZ is not liable for any damage resulting from improper
use. The system is designed to be installed indoors unless otherwise noted on the
equipment nameplate.
Safety
We use NOTES along with CAUTION and WARNING symbols throughout this manual to
draw your attention to important operational and safety information.
A bold text NOTE marks a short message in the information to alert you to an important
detail.
A bold text CAUTION safety alert appears with information that is important for
protecting your equipment and performance. Be especially careful to read and follow all
cautions that apply to your application.
A bold text WARNING safety alert appears with information that is important for
protecting you from harm and the equipment from damage. Pay very close attention to all
warnings that apply to your ap- plication.
A safety alert symbol accompanies a general WARNING or CAUTION safety
statement. A safety alert symbol accompanies an electrical shock hazard WARNING
or CAUTION safety statement.
Safety Summary
The following statements are general safety guidelines. They are followed by warnings
and cautions. Prior to performing any installation, operation, maintenance or
troubleshooting procedure read and understand all instructions, recommendations and
guidelines in this manual.
WARNING
High voltage is used in the operation of this equipment. Death on contact may result if
personnel fail to observe safety precautions.

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
7
CAUTIONS
This unit must be installed according to local and national electric codes. All maintenance and
repairs must be per- formed by a qualified technician. All person networking on or near
equipment should be familiar with hazards associated with electrical maintenance.
Always turn off the main power and unplug the unit before beginning work on the equipment.
NOTES
Wiring terminations may become loose during transit of the equipment therefore, so verify all
wiring terminations are secure prior to operation. Do not attempt to make repairs without the
proper tools. STULZ offers no warranty protection on humidification systems using controls
that are not provided by STULZ.
CAUTIONS
It is essential that Deionized (DI) or Reverse Osmosis (RO) water be used as the supply water
source to maintain full warranty cover- age. The use of untreated water will VOID THE
WARRANTY.
Use only non-corrosive stainless steel or poly tubing rated for use with DI water to supply the
humidifier.
Provide a drain with an air gap per local and national plumbing codes.
Never block the mist outlet or the opening of the air inlet. The humidifier may be filled with the
condensed mist and electrical shorts may result.
Never attempt to remove the mist guide cover and/or the mist blow tubes while the humidifier
is operating, or electrical shorts may result.
If there is a risk of supply water freezing, pipe insulation should be provided.
Never apply power when the humidifier is overturned or upside down. Damage to the
ultrasonic nebulizer unit or transducer may result.
Never drop the humidifier or apply hard shock to it. It may damage internal parts.
Drain the water in the tank for sanitary reasons when humidifier is turned is off for more than 3
days.
Observe the unit for water leakage. A short circuit could occur if the humidifier is splashed
with water while operating.

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Figure 1. Ultrasonic Humidifier- Model DRH-06
Specifications
Type
DRH Series Ultrasonic Humidifier
Model
DRH-04
DRH-06
DRH-08
DRH-16
Nebulizing capacity (lb/h) 4.4 6.6 8.8 17.6
Qty. of Ultrasonic nebulizers/unit 4 6 8 16
Power source 48VDC
Rated power consumption (W) 134 195 256 505
Weight (lb) 19.8 24.3 30.9 50.7
Electrical Characteristics
Allowable voltage range 47-51VDC
Insulation resistance 100 M.Ohms or more (excluding solid-state components).
Dielectric voltage withstand Operational when 1500VACisapplied for1 minute (excluding solid-state components).
Operating Conditions
Ambient working conditions 34 to 122°F; 90%RH or less.
Water supply quality DI or RO water. Water conductance <5 microsiemens purity.
Water supply pressure 30 to 75 psi
Water supply temperature 40°F to 104°F
These parts must be provided by the user:
DI or RO supply water, Water supply valve, Water supply tubing (1/4”
stainless steel or poly tubing rated for DI water), power supply wiring and control wiring to the control box.
1. Calcium, magnesium or other agents that may be contained in the supply water are atomized into
the air together with the mist and may form white powders after the water has evaporated. To avoid
this, always use DI or RO supply water.
2. The nebulizing capacity of the transducer in the ultrasonic nebulizer unit decreases gradually with

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use. It should usually be exchanged after about 10,000 to 15,000 hours of operation, (depending
on water quality and suitable voltage), although the unit may continue to run as long as its effective
capacity meets the particular requirements.
3. To ensure full warranty coverage, the input voltage to the humidifier must not exceed 51VDC. If the
input voltage exceeds 51VDC, damage to the transducers and print plates will result.
General Design
The DRH Ultrasonic Humidifier directly atomizes water, producing a fine mist. The humidifier
incorporates high frequency nebulizers to produce ultrasonic waves, a fan to propel the mist
out, and an automatic water supply mechanism to maintain the supply water at a constant
level. When conducting routine maintenance, it is important to clean the air filter and water
tank because it significantly affects the humidifying capacity and life of the ultrasonic
nebulizers.
Main Parts
Ultrasonic Nebulizer Unit
This consists of a modular assembly located in the bottom of the water tank incorporating a
1.6 Mhz power oscillator on and a piezoelectric transducer. The transducer vibrates at that
frequency,developing ultrasonic columnar waves in the water and producing a fine mist
above that column.
Mist Guide
The mist guide carries the mist off the top of the columnar wave and directs it up and out of
the humidifier.
High Water Float Switch
For maximum atomization, it is essential the water level in the tank be constantly maintained.
The High Water Float Switch is an input to the Level Controller. It is open when the water level
is below the optimal level and is closed when the water level reaches the maximum level.
Low Water Float Switch
Operating the humidifier when the water level is below the top of the transducers will damage
the Ultrasonic Nebulizer Unit. The Low Water Float Switch is an input to the Level Controller. It
is open when the water level is near an unsafe level and is closed when the water level is at a
minimal level.
Fan
The 24VDC fan or fans both lightly pressurizes the air above the water to provide a path for
the mist to pass through the Mist Tubes and provides a sheet of air to carry the mist away from
the humidifier into the room. The fan is controlled by the Level Controller.
Air Filter
The Air Filter removes coarse dust from the air and prevents the humidifier water tank from

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becoming dirty which would affect the mist output.
Water Fill Valve Solenoid
The Water Fill Valve Solenoid is a 24VDC solenoid that allows water from the water supply to
enter into the tank when energized by the Level Controller. There is an orifice to restrict the
flow of water.
Water Supply Valve
NOTE: The user must provide the water supply valve.
A valve must be installed upstream from the humidifier for service and maintenance. The valve
must be rated for use with DI water.
Water Supply Tubing
NOTE: The user must provide the water supply tubing.
Water supply tubing must be provided to connect the water supply to the water strainer/flow
regulator on the end of the unit. The strainer/flow regulator is equipped with a 90° swiveling,
¼” push-to-connect fitting. Use ¼” stainless steel or poly tubing rated for use with DI water.
Drain and Overflow Assembly
The Drain and Overflow Assembly contains a 24VDC drain solenoid valve, an overflow pipe
and a drain outlet. The drain valve solenoid is controlled by the Level Controller to drain water
from the tank via the drain outlet.
If the water level in the tank exceeds the height of the overflow pipe, the excess water is di-
verted to the drain outlet. The drain outlet pipe is 1/8” MPT and ships with a stainless steel
cap.
Temperature Sensor
The temperature sensor monitors the temperature of the tank and is read by the Level
Controller which prevents overheating and freeze protection. Indication is read at the Level
Controller in the humidifier.
Solid State Relay
The 48VDC operating voltage for the Ultrasonic Nebulizer Units is switched on and off by a
solid state DC relay controlled by the Level Controller.
Level Controller
The Level Controller is a microprocessor based device located in the electric box that receives
inputs from sensors and other inputs and in turn controls the valves, fan and Ultrasonic
Nebulizer Units.
It consists of a DC-DC power supply to convert the 48VDC to 24VDC for the fans and
solenoids and a further reduction to 5VDC for the microprocessor, sensors, power switches
and either a Modbus interface to communicate with the Ultra-Series Control box or a simple
standalone input interface depending on which model humidifier was purchased. The 48VDC

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must be present at all times to allow the Level Controller microprocessor to monitor the inputs
and control the outputs.
The microprocessor monitors the on/off command from either the Modbus or the input dry
contact (depending on which model was purchased). If commanded on, the microprocessor
checks the Low Water Float Switch and the High Water Float Switch. If the water is too low,
the microprocessor turns on the Water Fill Valve Solenoid and monitors the Float Switches.
When the water level is above the low water level, the fan is turned on. When the water level is
above the high water level, the Water Fill Valve Solenoid is turned off and the Solid State Relay
is turned on. When the water level falls below the high water level, the microprocessor turns
the Water Fill Valve Solenoid on again to maintain optimal water level.
When the on/off command is removed, the Solid State Relay is turned off and, after a few
seconds time delay to eliminate the remaining mist from the humidifier, the Fan is turned off.
Proportional control is accomplished by the microprocessor monitoring the proportional
signal from the Modbus or proportional input (depending on which model was purchased).
When the proportional signal is greater than 10% of the maximum input, the microprocessor
will turn the Solid State Relay on and off in a pulse-width modulation control.
The period of the pulse width is 1 second. For 10% control, the Solid State Relay is turned on
for 0.1 second and off for 0.9 second. The on time increases as the input approaches 100%.
At 100%, the Solid State Relay is on continuously.
Safety control is built into the microprocessor. The voltage applied to the transducer affects
the amount of mist produced.
WARNING
Too high or too low a voltage can cause damage to the transducer prevents mist from being
formed. The microprocessor monitors the 48VDC to be within a range of voltages. If the
voltage is out of range, the microprocessor will not energize the Solid State Relay. If the
temperature of the tank rises too high, the microprocessor turns off the Solid State Relay.
If the temperature approaches freezing, the microprocessor turns off the Solid State Relay
and the fan, and then drains the tank to prevent damage from freezing water. When the
temperature returns to a safe level, normal operation is resumed.
A low level alarm is annunciated when the microprocessor sees the Low Level Float Switch
indicate low water after the tank has been filled. A fill alarm is annunciated when the High
Water Float Switch does not indicate the water level has been achieved after a predetermined
amount of time.
A transducer alarm is annunciated if the transducers have been energized and no water is
used in a predetermined time (indicating no transducer is functioning). For the Modbus
version of the Level Controller, failure to receive commands on the Modbus within a

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predetermined amount of time will annunciate a communications alarm.
The Level Controller has an LED that displays, by blinking, any alarm condition that occurred
after power up. Each alarm is associated with a number of blinks, followed by a pause, and
then the next alarm is displayed. To view the LED, the Mist Guide Cover and electrical access
cover must be removed. The LED blink pattern for each alarm displays by number with a
corresponding alarm condition as shown in the table below.
Installation
Receiving the Equipment
Your Ultrasonic Humidifier has been tested and inspected prior to shipment. To ensure that
your equipment has been received in excellent condition, make a visual inspection of the
equipment immediately upon delivery.
Carefully remove the shipping container and all protective packaging. Open the box and
thoroughly inspect the unit for any signs of transit-incurred damage. If there is shipping
damage, it must be noted on the freight carrier’s delivery forms BEFORE signing for the
equipment.
Any freight claims MUST be done through the freight carrier. STULZ ships all equipment FOB
factory. STULZ is not liable for any equipment damage while in transit. STULZ can assist in the
claim filing process with the freight carrier. Should any such damage be present, notify
Product Support prior to attempting any repairs contact STULZ Product Support at (888) 529-
1266 or email [e-mail]..
Check the equipment against the packing slip to see if the shipment is complete. Report all
Number
of Blinks
Alarm
Condition
1
Low Voltage
2
High Voltage
3 Freeze
4 High Temperature
5
Low Water
6
Fill Alarm
7
Communications
8 Transducer

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discrepancies to the appropriate authority.
Contents of the package:
1. Humidifier
2. Six foot long power cable with moisture-proof, twist-lock connector on one end
3. Installation, Operation and Maintenance manual
Avoid dropping or jarring the unit to prevent damage to the internal parts. Always store the
unit in a dry location prior to installation.
A Data Package has been sent with your unit. It contains this manual, system drawings,
applicable Manufacturer Safety Data Sheets (MSDS) and other applicable instructions based
on the configuration and options selected for your unit. The data package has been placed in
your unit in a clear plastic bag. For future reference, keep these documents with the unit.
Site Preparation
Ultrasonic humidifiers are designed for easy service access. Install the unit in a secure
location where it cannot be tampered with and the power switch cannot be inadvertently
turned off. Allow access to the unit for routine operation, servicing and for necessary
maintenance. Position the humidifier in such a way that the unit can be easily removed for
future inspection and maintenance. Refer to the installation drawing provided with your unit
for the dimensions of the humidifier.
NOTE: Working clearance requirements need to be established prior to mounting the unit.
Refer to local and national electrical codes before installing the unit.
When selecting the installation location, attention should be paid to the air flow in the room so
that the atomized mist can be uniformly diffused throughout the room. If any obstacle exists in
front of the atomized mist outlet, the mist will be condensed on the obstacle to form water
droplets.
Figure 2. Installation of Humidifier

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The unit must be installed horizontally and level to prevent the float switches from giving a
false reading. Prepare hanging bolts for installing from the ceiling or brackets for wall
mounting (see Figure 1). The distance from the humidifier to the ceiling should be a minimum
of 18” and the distance to the wall must be 3” or more. For the installation mounting base
dimensions, see the installation drawing provided with your unit.
Figure 3. Locating the Humidifier
NOTE: Humidity control can only be achieved in a sealed room or if the room has vapor
barriers installed. It is recommended that walls, ceilings and floors be sealed to prevent
migration of humidity.
Mounting/Placement
These ultrasonic humidifiers are designed for mounting to a flat surface. Ensure the base is
capable of supporting the weight of the unit. Weight estimates can be found on the
installation drawing provided with your unit. Secure the unit with fasteners (field supplied by
others), so that it will not move during operation. Ensure the front edge of the humidifier is not
hanging over the edge of the support bracket.
Supply and Drain Piping
The humidifier will require a field installed water supply line and drain line. Refer to the piping
diagram provided with your unit for details. For the water supply, use DI or RO water. The water
supply to the humidifier cannot be taken directly from the public water service. Untreated
supply water will leave a residue in the conditioned space where white powder is produced
after evaporation from the calcium or magnesium which is dissolved in the water.
In cases where water quality, especially residue from evaporation, pH, total hardness and

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
15
water conductivity exceeds or is outside the range of standard, routine maintenance intervals
to ensure continuous operation will be more frequent than usual. Also, the operating life of the
transducers and print plates will be significantly reduced.
CAUTION
It is essential that DI or RO water be used as the supply water source to maintain warranty
coverage. The use of untreated water will VOID THE WARRANTY.
NOTE: The water supply piping must be non-corrosive stainless steel or poly tubing rated for
use with deionized water.
Prepare the water supply piping. The water supply piping should be equipped with a water
supply valve for maintenance purposes (user provided) at a place as close as possible to the
humidifier. The valve must be rated for use with DI water. After the water supply valve is
installed, flushing should be done by supplying water (see Section 3.1, Purge the Water Line).
This is a necessary step to prevent chips and oil in the piping from entering the humidifier.
The strainer/flow regulator is equipped with a 90° swivel, ¼” push-to-connect, fitting (see
Figure 4). Connect the water supply piping to the humidifier by means of a 1/4” stainless steel
or poly tubing (user provided). If there is a risk that the water supply piping could freeze, wrap the
piping with insulating material.
Figure 4. Piping Connections

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Figure 5. Water Inlet Connector
A drain line rated for use with DI water must be provided from the I/8” MPT water tank drain
stub in the side of the unit. Connect the drain line to the stub so that overflowing water can be
directed into a drain pan or an appropriate place such as an open building drain with an air
gap per local and national plumbing codes. The drain line must meet local and national
plumbing codes, be sloped downward and away from the humidifier, include an air gap, and
the end must not be obstructed.
Main Power and Control Wiring
NOTE: For wiring, refer to the electrical drawing supplied with your unit to determine the total
number of interconnecting conductors required for your system and for the proper wire
terminations. For internal wiring of the humidifier, see the Electrical Circuit Diagrams at the
end of this manual.
CAUTIONS
Wiring terminations may become loose during transit of the equipment, therefore, verify all
wiring terminations are secure prior to operation.
Verify that the main power supply to the control box coincides with the voltage, phase and
frequency information specified on the nameplate. The nameplate also provides the full load
amps (FLA), the current that the unit will draw under full design load, the minimum circuit
ampacity (MCA) for wire sizing, and the maximum fuse size (MFS) for circuit protection.
For safety, the power source must be provided with a circuit breaker. Ensure a ground is
connected to the unit. The humidifier is rated to operate with a nominal input of 48VDC. To
maintain warranty coverage, never allow the humidifier input voltage to exceed 51 volts as

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damage will occur to the transducers and print plates.
Wire Sizing Control Box to Humidifiers
The table below indicates the correct electrical wire sizing from the control box to the
humidifier power cable for three different distances. All wire sizes listed are for stranded,
THHN or NTW wire only. Do not use solid conductor wire. For distances over 75 feet consult
the factory.
In addition to the above power wires, humidifiers controlled by the Ultra-Series control box
use RJ45/ CAT5 data communication cables, daisy chained from the humidifier(s) to the
control box.
The data communication cable is not to exceed 1000 feet total length from the control box to
the last humidifier. A termination resister must be installed on the last humidifier as shown in
the electrical drawing provided with your unit.
CAUTIONS
The termination resistor is to be placed only on the last unit in the data communication string.
The power supply provided with the equipment is sized and selected based upon the
expected load. Do not connect anyadditionalloads to thecontrol power supply.
Power Cable With Twist Lock Connector
Data Communications Cable Connection
For Single Humidifier
Data Communications Daisy Chain
Connection For Grouped Humidifiers
Figure 6. Electrical Connections
Connecting Humidifier(s) to ControlBox
As a standard, STULZ GEN2 Ultrasonic humidifiers are equipped with a twist lock power
connector and (2) RJ45 ports for data communication. The Ultrasonic Control box will also be
equipped with an RJ45 port for data communication. The DRH Series Ultrasonic Humidifiers
are designed for stand-alone direct room applications. A 6 foot power cable with a moisture-
proof, twist-lock connector on one end is provided with each humidifier.
Single Humidifier
Once the humidifier and control box are installed, the total 48VDC wire length and wire size
(AWG) should be determined using the table below. A junction box (not provided) is necessary

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
18
to make the connection between the field-installed 48VDC power wiring and the factory
provided humidifier power cable.
RJ45/CAT5 cable (not included) should be used in required length(s) to make the data
communications connection between the humidifier and the control box. The factory provided
end-of-line termination resistor should be installed in the second RJ45 port.
Multiple Humidifiers (Grouped)
Once the humidifiers and control box are installed, the total 48VDC wire length and wire size
(AWG) should be determined using the table below for each humidifier. A junction box (not
provided) is necessary to make the connection between the field-installed 48VDC power
wiring and the factory provided humidifier power cable.in the group. The factory provided
end-of-line termination resistor should be installed in the second RJ45 port of the last
humidifier.
RJ45/CAT5 cable (not included) should be used in required length(s) to make the data
communications connection between the humidifier and the control box. Additional RJ45
cables (not included) should be used in required lengths to make the data communications
connections between humidifiers
48VDC Wire Sizing from Control Box to Humidifiers
MODEL CURRENT
(AMPS)
WIRE SIZE (AWG) # OF
WIRES
(Includes 1
Ground)
25 Ft 50 Ft 75 Ft
DRH-04 2.8 16 16 14 3
DRH-06 4.0 16 16 14 3
DRH-08
5.3
16
14
12
3
DRH-16 10.5 16 14 12 3
NOTE
: Table reflects correct electrical wire sizing from the control box to
the humidifiers.
Do not exceed 75 foot maximum distance.

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Operation
Purge the Water Line
Before operating the unit, metal shavings or debris that may form during the installation
process must be flushed from the water supply piping. Perform the following steps before
allowing water to flow into the humidifier:
1. Ensure the main disconnect switch from the control box is set to Off for safety.
2. With the water supply valve closed, disconnect the supply tubing from the filter strainer in the side of
the unit.
3. Open the supply valve and flush the tubing into a bucket or building drain for about 30 seconds.
4. After the water line is purged, close the valve and reconnect the supply line to the inlet
strainer/flow regulator.
Initial Operation Checklist
For new installations, ensure the unit is ready to operate by going through the following
checklist prior to start-up.
• The humidifier is installed horizontally and level.
• No obstacle is within 15 feet in front of the atomizing direction.
• The electrical wiring is correctly connected.
• De-ionized or reverse osmosis water supply is used.
• The water supply piping and overflow piping are correctly connected and secured.
• All parts are correctly installed.
• After these items have been verified, begin operation.
Procedure for Operation
1. Turn the main power source switch on the control box to the “On” position.
2. Open the water supply valve allowing water to flow to the humidifier.
3. Perform a manual drain cycle to flush any particulates from the tank utilizing the system controller
(see STULZ Ultra-Series controller IOM manual #OUU0078, Section 5.5.1.2).
4. Set the humidity setpoint to the desired humidity level.
5. When power is supplied to the humidifier and there is a demand for humidification, water flows into
the unit. When the water in the tank reaches the required level, the ultrasonic nebulizers will start
producing mist.
6. If the unit does not start operating, increase the humidity setpoint to create a demand for
humidification.

DRH Series GEN2 Ultrasonic Humidifier IOM Manual
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7. During operation, the humidifier starts and stops by means of a signal from the control box.
8. The water level in the water tank is maintained by the level controller.
9. If the water level in the tank falls below the safety level for any reason during operation, power to
the ultrasonic nebulizers is cut off by the level controller.
After starting operation, check the following items on a regular basis:
1. Atomized mist is visible through all the mist blow tubes.
2. Verify the humidifier parts, overflow pipe and other piping for signs of leaking water.
3. Change the humidity setpoint to ensure the control box is interconnected properly and that it
controls the operation of the humidifier.
4. Verify that the mist diffusion is good and that objects in the room or any obstacle are not directly
exposed to the mist.
Precautions
Take the following operating precautions.
1. Do not remove the air filter at the bottom of the humidifier during operation.
2. Do not block the outlet of the mist blow tubes; component failure could occur.
3. Drain the water from the water tank for sanitary reasons if the unit is turned off for more than 3
days.
Steps for Long Term Shutdown
If the humidifier is not signaled to turn On for a period of three days, the level control board
will automatically signal the humidifier to operate a drain cycle.
When operation is stopped for a long time (one week or longer), the following steps may be
performed. Also, refer to Section 4.1, Periodic General Maintenance.
1. Close the water supply valve.
2. Drain the water tank.
3. Turn the main switch on the control box to Off.
4. Inspect and clean the water tank interior and the air filter.
5. To restart operation after a long-term shutdown, see the previous section Procedure for Operation.