How Does a Dehumidifier Work? Refrigerant & Desiccant Explained

Dehumidifiers use two primary technologies to extract moisture from air: refrigerant systems that cool air to condense water vapour, and desiccant systems that absorb moisture chemically. Each method suits different industrial applications depending on temperature, humidity levels, and operational requirements.

Basic Dehumidification Process

All dehumidifiers follow the same fundamental principle: they extract water vapour from air and collect it as liquid water. The process involves drawing humid air into the unit, removing moisture through either cooling or absorption, then releasing the dried air back into the room.

• Humid air enters the dehumidifier through an intake grille
• Moisture is extracted using refrigeration coils or desiccant materials
• Water vapour condenses into liquid and drains to a collection point
• Dry air is expelled back into the space through an outlet
• The cycle continues until desired humidity levels are reached

How Refrigerant Dehumidifiers Work

Refrigerant dehumidifiers use the same cooling technology found in air conditioners and refrigerators. They work by cooling incoming air below its dew point, causing water vapour to condense into liquid droplets.

The process begins when a fan draws warm, humid air over a cold evaporator coil. As the air temperature drops below the dew point, moisture condenses on the coil surface and drips into a collection tray or drain line.

1. Humid air enters through the intake and passes over the cold evaporator coil
2. Air temperature drops below the dew point, causing water vapour to condense
3. Liquid water drips from the coil into a collection system
4. Cooled, dry air passes over the warm condenser coil to return to room temperature
5. Reheated dry air is expelled back into the space
6. The refrigeration cycle continues with the compressor maintaining the temperature differential

Refrigerant dehumidifiers perform best in warm, humid conditions. Below approximately 15°C, ice can form on the evaporator coil, which reduces efficiency and may damage the unit. Browse our range of refrigerant dehumidifiers for applications above this threshold.

How Desiccant Dehumidifiers Work

Desiccant dehumidifiers remove moisture through absorption rather than condensation. They use materials like silica gel or lithium chloride that naturally attract and hold water molecules from the air.

The heart of a desiccant system is a slowly rotating wheel coated with moisture-absorbing material. As humid air passes through one section of the wheel, the desiccant absorbs water vapour, while a separate heated airstream regenerates the material by evaporating the collected moisture.

1. Humid air enters the unit and passes through the desiccant wheel
2. Desiccant material absorbs water vapour directly from the air stream
3. Dried air continues through the wheel and exits into the space
4. A separate heated air stream passes through the saturated section of the wheel
5. Heat evaporates absorbed moisture from the desiccant material
6. Moist regeneration air is expelled outside, while the wheel continues rotating

Desiccant units operate effectively across a wide temperature range, from -20°C to +50°C, making them the only viable option for cold stores, freezer rooms, and unheated warehouses where refrigerant systems fail. Explore our desiccant dehumidifier range for cold-environment applications.

Refrigerant vs Desiccant Technology Comparison

Each dehumidification technology excels under different operating conditions. Understanding these differences helps determine which type works best for specific applications and environments.

Ideal Humidity Levels for Commercial Facilities

Maintaining the correct relative humidity (RH) is critical for product integrity, occupant health, and regulatory compliance. The ASHRAE Standard 55 recommends indoor RH between 30% and 60% for occupied commercial buildings.

Different industries require tighter control within that range.

• Warehousing and logistics: 40% to 55% RH to prevent condensation on stored goods
• Pharmaceutical manufacturing: 30% to 45% RH for product stability and GMP compliance
• Food processing and cold storage: 35% to 50% RH to inhibit mould and bacterial growth
• Data centres and server rooms: 40% to 55% RH to prevent static discharge and corrosion
• Museums and archives: 45% to 55% RH for preservation of artefacts and documents

Key Dehumidifier Components Explained

Each component plays a specific role in the dehumidification process.

• Compressor: Pressurises refrigerant gas to create the temperature differential needed for condensation
• Evaporator Coil: Cold surface where water vapour condenses as humid air passes over it
• Condenser Coil: Hot surface that reheats dried air before it returns to the space
• Desiccant Wheel: Rotating drum coated with moisture-absorbing material in desiccant units
• Blower Fan: Moves air through the system and maintains consistent airflow rates
• Collection Tank: Stores condensed water or channels it to a drain connection

Humidity Sensors and Control Systems

Modern dehumidifiers use a humidistat to measure relative humidity and compare it to a desired setpoint. When humidity rises above the target level, the control system activates the unit automatically.

• Capacitive sensors measure humidity by detecting changes in electrical conductivity
• Digital displays show real-time humidity levels and allow precise setpoint adjustment
• Automatic defrost controls prevent ice formation on refrigerant coils
• Continuous drain options eliminate the need to empty collection tanks

Commercial vs Residential Dehumidifier Differences

Commercial and industrial dehumidifiers from the Moisture Cure commercial range are engineered for continuous operation and higher moisture removal rates. They incorporate robust components and advanced features not found in residential units.

These systems run 24/7 and handle much larger air volumes, with ducted installation options for whole-building control.

Factors Affecting Moisture Extraction Rates

Several environmental and operational factors influence how quickly and efficiently a dehumidifier removes moisture from air. Australian workplace health and safety guidelines from Safe Work Australia highlight thermal comfort and humidity as key factors in occupant wellbeing. Understanding these variables helps optimise performance and select appropriately sized equipment.

Temperature has the greatest impact, as warmer air holds more moisture than cooler air.

• Air Temperature: Higher temperatures increase moisture-holding capacity and extraction potential
• Relative Humidity: Greater humidity differential drives faster moisture removal
• Airflow Volume: Higher air movement rates increase the amount of moisture processed
• Air Circulation: Poor circulation creates humid pockets that reduce overall effectiveness
• Heat Sources: Equipment or processes that generate heat can increase humidity levels
• Ventilation: Outside air infiltration affects the moisture load on the dehumidifier

Ducted vs Portable Dehumidifier Configurations

Ducted dehumidifiers connect to existing HVAC systems or dedicated ductwork for whole-building humidity control. Portable units provide localised moisture removal for specific rooms or areas.

Ducted systems require professional installation but offer comprehensive coverage. Portable units provide flexibility but limited reach in large spaces.

Maintaining a Commercial Dehumidifier

Regular maintenance keeps commercial dehumidifiers at peak efficiency. Schedule service based on operating hours rather than calendar intervals, as heavy-duty applications accumulate wear faster.

• Air filters: Inspect weekly in dusty environments and replace or clean monthly to maintain airflow
• Evaporator and condenser coils: Clean quarterly with a soft brush or compressed air to prevent efficiency loss
• Condensate drains and trays: Flush monthly to prevent blockages and microbial buildup
• Desiccant wheels: Inspect for contamination every six months and replace per the manufacturer’s schedule
• Humidity sensors: Calibrate annually against a reference hygrometer to ensure accurate readings
• Electrical connections: Check for corrosion or loose terminals during each service

Choosing the Right Dehumidification Technology

Selecting between refrigerant and desiccant dehumidifiers depends on operating conditions, performance requirements, and installation constraints. Consider temperature range, target humidity levels, and energy efficiency when making this decision.

For most commercial applications with moderate temperatures and humidity levels, refrigerant technology provides cost-effective moisture removal. Desiccant systems excel in cold environments or applications requiring very low humidity levels.

Ready to find the right dehumidification solution for your facility? Our humidity control specialists can help you select the right equipment and configuration for your specific requirements. Contact Moisture Cure Commercial for expert advice and competitive pricing on professional-grade dehumidification systems.

Frequently Asked Questions

What temperature should a room be for a dehumidifier to work effectively?

Refrigerant dehumidifiers work best between 15°C and 35°C. Below 15°C, ice forms on the evaporator coil and efficiency drops sharply. For spaces that operate below 15°C, such as cold stores, freezer ante-rooms, or unheated warehouses, a desiccant dehumidifier is the appropriate choice as it operates effectively from -20°C to +50°C.

How much water should a commercial dehumidifier extract per day?

Commercial units typically extract between 50 and 500+ litres per day, depending on capacity, ambient temperature, and humidity levels. Extraction rates are always measured at standard test conditions (typically 30°C and 80% RH), so real-world output varies with actual site conditions.

Can a dehumidifier remove mould from a commercial building?

A dehumidifier prevents mould growth by keeping relative humidity below 60%, which denies mould the moisture it needs to colonise surfaces. It will not remove existing mould. Active infestations require professional remediation first, followed by ongoing humidity control to prevent recurrence.

How do you size a dehumidifier for a warehouse or factory?

Sizing requires calculating the moisture load based on room volume, ventilation rate, number of air changes per hour, ambient conditions, and any internal moisture sources such as wet processes or open water. Undersized units run continuously without reaching target humidity. Contact a specialist for a site-specific sizing assessment rather than relying on generic room-size calculators.

Should a commercial dehumidifier run continuously?

Most commercial dehumidifiers are designed for continuous 24/7 operation and will cycle on and off automatically via the built-in humidistat. Running in auto mode is more energy-efficient than manual on/off switching, as the unit only operates when humidity exceeds the setpoint.

Refrigerant and Desiccant Dehumidifiers from Moisture Cure Commercial

Moisture Cure Commercial stocks both refrigerant and desiccant dehumidifiers to suit different applications, operating conditions, and humidity targets.

• FRAL FDW62
• FRAL FD360
• FRAL FD520
• FRAL FD750
• FRAL FD980
• Full commercial dehumidifier range

Talk to Moisture Cure Commercial

Moisture Cure Commercial has supplied dehumidifiers and humidifiers to Australian businesses for over 20 years. Whether you need help selecting the right unit, sizing a system for your facility, or troubleshooting an existing setup, our team can help.

Call us on (02) 6584 2511 or browse our commercial dehumidifier range to find the right solution for your operation.