Last revised: September 24, 2024
Reviewed by: Scott Orlosky, consulting engineer

Enclosure air conditioners remove the heat generated by electronic devices from the inside of cabinets or enclosures. Powerful electronic assemblies and components function within increasingly high temperatures. The heat generated is a hazard for production and functional machinery. Enclosure air conditioners are critical for the safety of production and personnel in the event of component failure. The devices typically use refrigerants and include thermostatic controls to maintain programmed environmental conditions. 

Enclosure air conditioner. Image credit: OK Solar

There are three ways to cool an enclosure: natural convection cooling, forced convection, and closed loop cooling. The first method does not require an active cooling section so we are only concerned with forced convection with an air conditioner and closed loop cooling. Natural convection is used if the ambient temperature outside the enclosure is cooler than the inside of the enclosure. The heat can be dissipated into the atmosphere by radiating it through the surface of the enclosure and through the use of grills with filters. Forced convection is best used if there is clean and cool ambient air outside of the enclosure. This may be as simple as a filter fan with the appropriate filter.

Sealed enclosure cooling is considered a closed-loop system because the seal of the housing is maintained. This prevents elements that can damage the electronics inside the enclosures. Sealed enclosures are best used in harsh conditions and when the ambient temperature is as high or higher than the desired internal temperature.

Enclosure cooling is not the same type of "comfort" cooling as found in homes and buildings. Heat-producing power and control components are typically limited to maximum enclosure air temperatures of 100° F to 110° F. The actual component surface temperatures are higher. Maintaining low enclosure temperatures often becomes problematic. Condensation may form on live electrical surfaces if their temperature falls below the dew point of the air. Subsequent corrosion or electrical safety becomes a serious issue.

Some enclosure air conditioners automatically evaporate condensate, eliminating the need for draining. Others include an air flow sensor that monitors the temperature of the condenser and ensures that blockage or contamination does not compromise cooling efficiency.

Enclosure Air Conditioner Specifications

Enclosure air conditioners use either single-phase or three-phase power and vary in terms of cooling efficiency, which is often expressed in kilowatts, tons of refrigeration, or British thermal units (BTU) per hour. Cooling capacity is the capacity of the air conditioning unit to remove heat from the room or industrial space. Physical specifications for enclosure air conditioners include mounting style, NEMA rating, and IP rating.

Phase

• Single-phase — Single-phase power is used in light commercial and residential applications.
• Three-phase — Three-phase power is typically used industrial applications. Improved efficiency and smooth running is achieved with three-phase power.

Operating Voltage

• Direct current (DC) voltages operate at 12 V DC or 24 V DC.
• Alternating current (AC) voltages operate at 115, 230, 380/400 or 460 V AC. For AC devices, frequencies include 50, 60, and 400 Hz. Typically, 400 Hz devices are used in aerospace applications.

Mounting

• Side wall mounting is used in a standard cabinet rack.
• Recessed pockets or cavities are used for mounting in tight spaces.
• Top-mount devices are used in enclosures that do not provide adequate clearance for side mounting.
• Bottom-mount devices fit the enclosure base or bottom and are usually rack-mounted.

NEMA and IP Rating

The National Electrical Manufacturers Association (NEMA), a non-profit trade organization, rates enclosures for electrical equipment. Enclosure air conditioners with NEMA 3R, NEMA 4, and NEMA 4X ratings are suitable for indoor or outdoor use and provide protection against dirt, rain, sleet, and snow. Ingress protection (IP) 34, a European standard, sets criteria for preventing the ingress of particles larger than 2.5 mm. IP 54 sets standards for protection against shock, vibration, dust, and rain. In terms of outdoor use, IP 54 is nominally equivalent to the NEMA 3 rating.

Features

Enclosure air conditioners are available with a variety of special features.

• Electrical or electronic filters — Filters on the incoming power line suppress noise caused by electromagnetic interference (EMI) or radio frequency interference (RFI).
• Interlocks, alarms, or signals — Alarms will alert users to faults or system failures.
• Short cycle detection is a feature that monitors compressor on/off cycles for length and efficiency.
• Refrigerants without chlorofluorocarbons (CFCs) — Chlorofluorocarbons are chemical compounds believed to be responsible for depleting the Earth’s ozone layer.
• Precision cooling — Designed to meet the needs of high-density computing while maintaining precise temperature levels.
• Weather resistant — The air conditioning unit is resistant to the outdoor environment and may be placed outside.
• Condensate evaporator — Products automatically evaporate condensate from the cooling operation to minimize or eliminate the necessity for draining.
• Explosion proof — Cases for explosion-proof devices are designed to prevent explosions within the air conditioner from the ignition of surrounding gases or vapors.
• Intrinsically safe — Intrinsically safe (IS) products minimize or eliminate sparking or other thermal effects that could cause ignition in the surrounding environment.
• Thermostatic control — Thermostatic control is feedback control of the cooling operation to maintain programmed environmental conditions.

Standards

Many safety agencies rate or certify enclosure air conditioners. For example, the International Engineering Consortium (IEC) publishes and maintains standards for electrical product conformity. In Europe, electrical and electronic equipment must bear the CE Mark to indicate compliance with product safety and electromagnetic compatibility directives. In North America, the Canadian Standards Association (CSA) Mark may appear alone or with indicators. Products that bear the CSA Mark alone are certified only for the Canadian market. Products that appear with the indicators "C and US" or "NRTL/C” are certified for both the U.S. and Canadian markets. Underwriters Laboratories (UL) approves both component parts and complete assemblies.

Enclosure Air Conditioner FAQs

How do enclosure air conditioners compare to other cooling methods like evaporative coolers?

When comparing enclosure air conditioners to other cooling methods like evaporative coolers, several key differences and considerations come into play:

Cooling Mechanism

Enclosure Air Conditioners: These units use refrigerant-based cooling systems to remove heat from the inside of enclosures. They are capable of maintaining temperatures below ambient levels and reducing humidity within the controlled space.

Evaporative Coolers: These coolers use the process of evaporation to cool the air. They draw warm air through water-saturated pads, causing the water to evaporate and cool the air. This method is generally less effective in high humidity environments and cannot cool below ambient temperatures.

Environmental Suitability

Enclosure Air Conditioners: Designed to operate in various challenging environments, including those with dust, dripping liquids, rain, washdown, and corrosive atmospheres. They are often built to meet specific NEMA ratings, ensuring protection against environmental hazards.

Evaporative Coolers: Best suited for dry climates where the evaporation process is more efficient. They are less effective in humid environments and are not typically designed to handle harsh industrial conditions.

Temperature Control

Enclosure Air Conditioners: Provide precise temperature control and stability, which is crucial for protecting sensitive electronic components. They can maintain a lower-than-ambient temperature, which is essential for certain applications.

Evaporative Coolers: Generally provide less precise temperature control and are limited to cooling to ambient temperatures. Their effectiveness can vary significantly with changes in ambient humidity and temperature.

Humidity Control

Enclosure Air Conditioners: Capable of reducing humidity within the enclosure, which is important for preventing moisture-related damage to electronic components.

Evaporative Coolers: Increase humidity levels as part of their cooling process, which can be detrimental in environments where moisture control is critical.

Energy Efficiency

Enclosure Air Conditioners: Typically use more energy due to the refrigeration cycle but provide reliable and consistent cooling performance.

Evaporative Coolers: Generally more energy-efficient as they rely on the natural process of evaporation, but their cooling capacity is limited compared to refrigerant-based systems.

Maintenance and Durability

Enclosure Air Conditioners: Require regular maintenance to ensure efficient operation, including checking refrigerant levels and cleaning filters. They are built to withstand industrial conditions and have long-lasting components.

Evaporative Coolers: Require maintenance of water pads and regular cleaning to prevent mold and mineral buildup. They are generally less durable in harsh industrial environments.

What are the maintenance requirements for enclosure air conditioners?

The maintenance requirements for enclosure air conditioners are crucial to ensure their efficient operation and longevity. Here are some key maintenance tasks:

Regular Inspection

Check Refrigerant Levels: Ensure that the refrigerant levels are adequate to maintain cooling efficiency. Low refrigerant levels can lead to reduced cooling capacity and potential damage to the compressor.

Inspect Electrical Components: Regularly inspect electrical components for signs of wear or damage. This includes checking connections, wiring, and control systems to prevent electrical failures.

Cleaning

Filters: Clean or replace air filters regularly to ensure proper airflow and prevent dust and debris from clogging the system. Dirty filters can reduce cooling efficiency and increase energy consumption. 

Coils: Clean the evaporator and condenser coils to remove any accumulated dirt and debris. Dirty coils can reduce heat transfer efficiency and lead to higher operating temperatures. 

Lubrication

Motors and Fans: Lubricate the motors and fans as per the manufacturer's recommendations to ensure smooth operation and reduce wear and tear.

Environmental Considerations

Corrosion Resistance: In environments subject to corrosive atmospheres, ensure that the outer cabinet and components are inspected for signs of corrosion and treated accordingly. This helps maintain the integrity of the enclosure air conditioner.

Seals and Gaskets: Check seals and gaskets for any signs of wear or damage, especially in environments with dust, dripping liquids, or washdown conditions. Replace them as needed to maintain the enclosure's protective capabilities.

Operational Checks

Temperature Control: Verify that the air conditioner is maintaining the desired temperature within the enclosure. This includes checking the thermostat settings and ensuring that the unit is cycling on and off correctly.

Humidity Control: Ensure that the air conditioner is effectively reducing humidity within the enclosure, which is critical for preventing moisture-related damage to electronic components.

Documentation and Record-Keeping

Maintenance Logs: Keep detailed records of all maintenance activities, including inspections, cleanings, and any repairs or replacements. This helps in tracking the performance and identifying any recurring issues.

By following these maintenance guidelines, you can ensure that your enclosure air conditioner operates efficiently and reliably, providing the necessary cooling and protection for your electronic components.

Enclosure air conditioners are more suitable for environments that require precise temperature and humidity control, especially in harsh industrial settings. They offer the ability to cool below ambient temperatures and are designed to handle various environmental challenges. On the other hand, evaporative coolers are more energy-efficient and cost-effective in dry climates but are limited in their cooling capacity and environmental suitability.

What are the advantages and disadvantages of thermoelectric air conditioners compared to traditional compressor-based systems?

When comparing thermoelectric air conditioners to traditional compressor-based systems, several advantages and disadvantages come into play:

Advantages of Thermoelectric Air Conditioners

Thermoelectric air conditioners do not require chemical refrigerants such as CFCs, HCFCs, or oils, which are harmful to the environment. This makes them a more environmentally friendly option.

Similar to compressor-based air conditioners, thermoelectric air conditioners have the ability to cool below the ambient temperature outside the enclosure. This is crucial for applications that require precise temperature control.

Temperature Control and Stability

Thermoelectric air conditioners offer precise temperature control and stability, which is essential for protecting sensitive electronic components.

Thermoelectric systems are generally more robust in terms of mechanical wear and tear since they have fewer moving parts compared to compressor-based systems. This can lead to lower maintenance requirements and longer operational life.

Disadvantages of Thermoelectric Air Conditioners

Thermoelectric air conditioners typically have a lower cooling capacity compared to traditional compressor-based systems. This makes them less suitable for applications requiring high cooling loads.

While thermoelectric air conditioners are environmentally friendly, they can be less energy-efficient compared to compressor-based systems, especially in applications requiring significant cooling power.

The initial cost of thermoelectric air conditioners can be higher than that of traditional compressor-based systems. This can be a consideration for budget-conscious projects.

Advantages of Traditional Compressor-Based Systems

Compressor-based systems generally offer higher cooling capacities. These systems can be more energy-efficient in applications requiring substantial cooling, as they are designed to handle larger thermal loads effectively.

Compressor-based air conditioners can be designed to operate in various challenging environments, including those with dust, dripping liquids, rain, washdown, and corrosive atmospheres. They are often built to meet specific NEMA ratings, ensuring protection against environmental hazards.

Disadvantages of Traditional Compressor-Based Systems

Traditional compressor-based systems often use chemical refrigerants that can be harmful to the environment, contributing to ozone depletion and global warming.

These systems require regular maintenance, including checking refrigerant levels, cleaning filters, and inspecting electrical components to ensure efficient operation.

Compressor-based systems may not operate efficiently at very low ambient temperatures, which can cause the units to freeze and fail.

Thermoelectric air conditioners are a more environmentally friendly option with precise temperature control and fewer maintenance requirements, but they may not be suitable for high cooling capacity needs. Traditional compressor-based systems offer higher cooling capacities and energy efficiency for substantial cooling loads but come with higher environmental impacts and maintenance requirements.

Enclosure Air Conditioner Media Gallery

Resources

GlobalSpec—Cooling Electrical Enclosures with Special-purpose Air Conditioners

GlobalSpec—Air Conditioners