DRH Direct Room Humidification

DRH - Direct Room Humidifiers

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Stand-alone Ultrasonic Humidifiers

STULZ Direct Room Humidifiers (DRH) are designed for stand-alone room applications. DRH are typically mounted on the perimeter wall serving mission critical applications, or any environment where tight humidity control is required. 

Data Center
Data Center
Our units are designed for highest requirements and maximum reliability
Small, medium & large rooms
Small, medium & large rooms
Precision air conditioning units for low to high heat loads
Medical technology
Medical technology
Reliable and noise-optimized cooling of your equipment
Libraries and Museums
Libraries and Museums
High Tech Manufacturing
High Tech Manufacturing

Product Overview

At a glance


  • Data Centers
  • Libraries and Museums
  • High tech Manufacturing
  • Printing and Duplication
  • Food and Beverage
  • Grow Room & Vertical Farming 
  • Health Care Facilities
  • Laboratories
  • Commercial Offices
  • Tobacco/Humidors

Key Features:

  • Only needs 7% of the power required by an electric steam humidifier
  • 90% smaller droplet than nozzles
  • 100% of the demineralized water in the humidifier is utilized and does not require a flush cycle
  • Does not require a flush cycle
  • Energy efficient
  • Improves efficiency of high sensible heat applications
  • Mixed bed deionization water treatment systems
  • Low operational expense equates to very short ROI
  • Meets California's Title 24 requirements
  • Only needs 7% of the power required by an electric steam humidifier
  • 90% smaller droplet than nozzles
  • 100% of the demineralized water in the humidifier is utilized and does not require a flush cycle
  • Mounts below the ceiling in a conditioned space
  • On wall or column with factory furnished mounts
  • Suspended from above in open space
  • Integral blower and washable filter
  • Absorption distance determined by RH of room
  • Made in USA
Technical Data


Technical date is subject to change without notice.


Why is humidification important in data centers?

Why humidify your mission critical facility?

Today's high tech environment requires meticulous control of humidity to eliminate static electricity, ensure quality manufacturing processes, preserve precious documents and works of art, and provide comfort while adhering to Indoor Air Quality standards. The specific reasons to humidify are as numerous as the applications, but the purpose is common across the board: to eliminate problems that can damage products, ruin buildings, or jeopardize health.

Ultrasonic Humidification

When RH reaches levels below 35%, static electricity may develop on surfaces and materials. Static electricity is not only annoying; it can wreak havoc on computers by burning microchips, and wiping out memory cards. Elimination of static electricity also greatly reduces the risk of solvent fires in the printing industry - commercial presses develop extraordinary amounts of electricity at the roller and ignite solvents in the ink wells. And if you ever wiped your finger across your television screen you know that static electricity attracts dust, a real problem in the plastics and films manufacturing process where dust can ruin a product or in the healthcare industry where dust can kill.

Indoor Air Quality affects man and machine and both operate best at optimum environmental conditions and IAQ and IEC standards are forcing manufacturers and building owners to adjust their management of air quality control. If a building's main HVAC system does not have the capacity to maintain RH levels within a comfort zone of 50% to 60%, then proper humidification can help reduce adverse effects of occupant discomfort, bacteria growth, viruses, fungi, mites, allergic reactions, respiratory infections, chemical interactions and ozone production.

Adiabatic vs. Isothermal Humidification in Mission Critical Environments

Adiabatic vs. Isothermal Humidification in Mission Critical Environments

The type of humidification used can make a significant dent in operating expenses and maintenance costs.  Learn about Adiabatic/Evaporative vs. Isothermal/Steam Humidification below.


Isothermal/Steam Humidification

Isothermal/Steam humidification systems use electricity or gas as an external heat source to change water to steam.  Energy consumed from an external energy source is approximately 1,000 BTU/LB of moisture.

  • Electrode canister
  • Infrared
  • Electric resistance
  • Direct steam injection (building steam)
  • Steam-to-steam
  • Gas-fired

Adiabatic/Evaporative Humidification

Adiabatic/Evaporative humidification systems use mechanical energy to generate water particles and/or evaporate water to/from media.  Energy extracted from air stream is approximately 1,000 BTU/LB of moisture.

  • Ultrasonic - piezoelectric transducer
  • High pressure water nozzle
  • Compressed air nozzle
  • Centrifugal atomizing (sling type)
  • Evaporative pad
How Ultrasonic Works

Ultrasonic humidifiers are one of the most environmentally friendly products that can be used in data centers

A piezoelectric transducer immersed in a water bed, converts a high frequency, electronic signal into a high frequency mechanical oscillation.  As the oscillation speed is increased to a level where the water particles can no longer follow the oscillating surface, a momentary vacuum and strong compression occur, leading to the explosive formation of air bubbles (cavitation).  At cavitation, broken capillary waves are generated, and tiny (1 micron diameter) droplets break the surface tension of the water and are quickly dissipated into the air, taking vapor form and absorbed into the air stream.

The principle of ultrasonic humidification is based on the superimposition of two effects:

1. Cavitation bubble implosion

The change in amplitude of the oscillator gives rise to powerful water hammers that release tiny cavitation bubbles. The implosion of the bubbles on the surface emits tiny water aerosols into the ambient air.

2. Capillary wave theory

The ultrasonic oscillators generate regularly formed Rayleigh surface waves in the water tank. Minute water aerosols are also emitted into the ambient air on the crests of these waves.

By superimposing these two effects, the use of ultrasonic humidifiers enables a homogeneous aerosol mist to be produced with minimal energy consumption.


***Fig. 1: The humidifier is switched on. The oscillator amplitude is positive.***

***Fig. 2: The oscillator amplitude is negative. The inertia of the water creates a vacuum. ***

***Fig. 3: After approx. 10 amplitudes, the ultrasonic humidifier reaches 100 % of its output.***

STULZ E² Control and Monitoring

STULZ E² Control and Monitoring

  • Engineered for single or multiple humidifier systems
  • Utilizes STULZ E2 Microprocessor Controller for integrated operation of up to 16 humidifiers per zone
  • Ultra-Series control boxes enclose up to eight power supplies each, providing power and control distribution
  • Proportional analog output from microprocessor converted to Pulse Width Modulation at humidifiers
  • Monitors and communicates various system functions and alarms including water quality via integrated control and/or optional BMS
Water Treatment

Mixed Bed Deionization (DI) provides high purity water quality specified for STULZ Ultrasonic Humidification Systems

Portable exchange Deionizers (PEDI) and total water systems serviced by 700+ Culligan dealerships throughout North America.  Culligan assures third party certification of industry standards and complete end-to-end solutions from a single source.


STULZ Demi-Cabinet enclosures for unitary RO and/or DI applied to small capacity and light commercial humidifier applications

Demi cabinets are used when the volume of water processed is relatively small. A demi cabinet should not be used on any water treatment opportunity which requires greater than 50 gallons per day on a design day. The advantage of demi cabinet is that it uses 100% of the supply water not wasting any water through the demineralization process. 


Reverse osmosis (RO) is used for moderate flow applications normally between 40 and 200 gallons per day. The RO system allows for higher volume of water to be treated than DI bottles alone, and will substantially reduce the maintenance requirement of changing DI bottles.  The disadvantage of the RO cabinet is that the system does not have an RO pump and as such the RO design recovery is only about 30%. This means that there will be a high volume of waste water. RO design recovery is the amount of process water made from the RO plant. The higher the pressure applied to the water source the higher the RO design recovery percentage.

  • Culligan high purity reverse osmosis (RO) plant preconditioner for large capacity humidifier applications

  • CHP-250 to 8000 GPD RO/DI packages include prefilteration, storage, reressurization, UV sterilization, monitoring and start-u

Mixed Bed Deionization

STULZ Demi-Cabinet mixed bed deionization (DI) systems are used for the removal of ionized organic and inorganic minerals and salts from water, using a concurrent ion exchange procedure.  The positively charged ions are removed by cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions.  The negatively charged ions are removed by anion exchange for a chemically equivalent amount of hydroxide ions.  The hydrogen and hydroxide ions introduced in this process unite to form deionized water molecules.  The mixed bed DI resin is housed in plastic bottles and has a nominal mineral removal capacity of 10,000 grains.
A complete system consists of two DI Bottles connected in series and housed in a steel cabinet with a lockable hinged door.  Within the cabinet, a water shut-off valve is provided in the supply side piping.  A conductivity sensor with a 10 ft. long cable is provided in the DI water outlet side for connection to the STULZ Ultrasonic control panel for monitoring the purity of the DI water being dispensed.  Water inlet and outlet connections are accessible from outside the cabinet.

Water Treatment Application Guide

Understanding water treatment is essential in being able to properly apply a water treatment solution for STULZ Ultrasonic Humidifier Systems. Ultrasonic Humidifiers require water treatment to prolong the life of the transducers and to prevent mineral deposits in the water from being introduced into the air stream.

In the STULZ Water Treatment paper, you will find details on:

  • Understanding water chemistry

  • Water treatment solutions

  • Water treatment components

  • A sample water quality report with definitions and cost calculations

  • Unit conversions

  • STULZ Water Treatment System details

Energy Analysis

A STULZ Ultrasonic Humidifier needs only 7% of the power required by an electric steam humidifier. Assuming a humidification requirement or 20 lbs/ hr., a DAH-16 has a power requirement of 0.495 kW at 21.1 lbs/hr. Using a comparable capacity steam type humidifier, the power requirement is 6.8 kW at 20 lbs/hr, which is an energy premium of approximately 93%.

In a typical application, the yearly humidification requirement is approximately 2500-3000 hrs. ROI is typically 1-2 years verses Steam or Infrared.

At a $0.08 per kWh Utility Rate:
Ultrasonic yearly power requirement3,000 hrs x 0.495 kW
1,485 kWh
Yearly electrical energy cost1,485 x $0.08 kWh
Steam electrode yearly power requirement3,000 hrs x 6.8 kW
20,400 kWh
Yearly electrical energy cost20,400 kWh x $0.08/kWh
Yearly electrical energy savings$1,513.20


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