ENCLOSURE COOLING Glossary
Contents INTRODUCTION... 3 TYPES OF COOLING EQUIPMENT... 4 COOLING EQUIPMENT COMPONENTS... 5 ESSENTIAL COOLING S... 8 COOLING EQUIPMENT ACCESSORIES... 13 EQUIPMENT THAT NEEDS COOLING... 16 IMPORTANT STANDARDS... 17 DOCUMENTATION AND CALCULATIONS... 19 NEXT STEPS... 20
Introduction: About This Glossary This glossary explains some of the terms that are specifically related to enclosure cooling. Its purpose is to extend and enhance your knowledge and understanding of enclosure cooling systems. Hopefully this glossary will remove some of the mystery associated with the subject and enhance interaction between the users and enclosure cooling manufacturers. The glossary is broken up into seven sections, starting with a short section about the types of enclosure cooling equipment and followed by a section covering cooling system components. This leads to a long section that explains cooling terms and cooling accessories. The last two sections deal with engineering standards and documentation. In order to avoid confusion, items are only defined once, even though they may logically be included in more than one section. 3
Types of Cooling Equipment These are the most common types of enclosure cooling equipment. Air conditioner Refrigeration-based cooling system that uses the thermodynamic properties of a refrigerant in order to extract heat from an enclosure. Key components of an air conditioner are a compressor, expansion valve, condenser, and evaporator. Air conditioners can cool enclosures to temperatures that are below ambient temperature. The thermal capacity of standard air conditioners varies between 1,000 BTU/H and 20,000 BTU/H. Typical power sources include 110, 230, and 480 volts AC and 48 volts DC. Enclosure air conditioners operate on a closed-loop cooling cycle. Air to air heat exchanger This is an enclosure cooler that works by circulating hot air from the enclosure over a heat-conductive heat pipe. This in turn discharges the heat to the outside air. A heat exchanger uses no external power for the cooling process and is extremely efficient. The heat exchanger relies on a thermal gradient, so its only limitation is that it cannot cool below ambient air temperature. An air to air heat exchanger operates on a closed-loop cooling cycle. Enclosure and air conditioner package An electrical enclosure supplied as a kit with an enclosure air conditioner. The enclosure features cutouts required for a designated air conditioner model. Filtered fan package An enclosure cooling fan designed to remove heat from an electrical enclosure. The package supplied includes a fan with inlet filter and an exhaust vent with filter. Fans remove heat; they do not cool an enclosure. They draw outside air into the bottom of the enclosure and discharge it at the top. Fans operate on an open-loop cooling cycle. 4
Cooling Equipment Components This section describes the major components that are used in enclosure cooling equipment and how they work. Air filter A device manufactured from a porous material designed to trap dust, debris and oil in the air while causing minimal airflow restriction. Blower A mechanical device for moving air, consisting of a motor that is fitted with rotating impellers in a squirrel-cage configuration. Compressor protection system Comprehensive compressor safeguards, including high- and low-pressure cutouts and short-cycle protection. Condensate Water that condenses from the air as it is chilled by the air conditioner s evaporator coil. Condensate must be collected and removed. Condensate evaporation system A method of removing the condensate collected by the air conditioner evaporator. It uses the heat from the compressor s hot gas line in order to evaporate the water, which is then discharged as vapor to the ambient air. Condensate evaporation avoids the need for messy condensate drains and has the added benefit of reducing the hot gas s temperature, increasing system efficiency. This method is unique to Thermal Edge enclosure air conditioners. Condenser coil An air-cooled device that is used in order to concentrate hot, pressurized refrigerant gas into a liquid. As the gas cools, it gives off heat to the ambient air. 5
Cooling Equipment Components (cont.) Compressor A rotary, positive displacement pump used in order to compress refrigerant gas so that it can be condensed into refrigerant liquid. Modern refrigerant compressors incorporate many design features that increase the overall efficiency of air conditioners. Digital temperature controller An electronic mechanism fitted to an enclosure air conditioner and used in order to control the enclosure temperature around a user-defined set point. The controller has several additional functions that include high-temperature alarms, high- and low-pressure alarms, and compressor anti-short cycle function. It is able to communicate with remote-control and monitoring devices using various protocols. Evaporator coil A device inside the air conditioner through which a mixture of refrigerant liquid and expanding refrigerant vapor passes. As the liquid vaporizes, it absorbs heat, and this cools the evaporator coil, and cooling the air going into the enclosure. Heat pipe This is the heart of the air to air heat exchanger. It is a vertical tube fitted with aluminum fins in order to aid heat transfer. It is partially evacuated and filled with a suitable refrigerant. The refrigerant is chosen so that it boils when hot air from the enclosure is passed over it. As the refrigerant boils, it absorbs heat from the enclosure. The refrigerant vapor rises to the top of the pipe, where it is cooled by ambient air that is blown over the tube. This vapor condenses back into liquid, giving up its heat to the ambient air. Hightemperature alarm An adjustable alert mechanism connected to a set of dry contacts actuated by the digital controller that provides a warning if the enclosure temperature goes too high. Mounting options Enclosure air conditioners and air to air heat exchangers are primarily designed to be mounted on either side of an electrical enclosure. Optionally, they can be mounted on the enclosure door, provided it is strong enough and the enclosure is anchored down. Air conditioners are also available to mount on the top of an electrical enclosure. 6
Cooling Equipment Components (cont.) Power cord Power supply wiring connected to enclosure coolers and fans that is fitted with a suitable plug. Power switch An on/off power control fitted to enclosure coolers to energize the unit. Refrigerant: A substance that absorbs heat in order to form a vapor. When compressed, it condenses and gives up that heat. Rigid chassis Air conditioners and air to air heat exchangers with a rigid chassis provide the ability to be serviced without being removed from an electrical enclosure. Sloped top The top surface of air conditioner shrouds is sloped in order to allow easy water runoff. Thermal expansion valve A special flow controller that regulates the circulation of refrigerant liquid to the air conditioner evaporator. It operates by sensing the temperature of the refrigerant as it expands, and this allows it to control the flow of refrigerant in order to suit the heat load. A thermal expansion valve is the most efficient method of controlling the expansion of a refrigerant and can tolerate a wide heat load range. 7
Essential Cooling Terms This list comprises commonly used terms related to enclosure cooling. AC Alternating electric current. Ambient temperature The temperature of the outside air around an enclosure. Backup power Battery-operated backup power often used to provide power to telecommunications equipment during power outages. BTU/H A unit of measurement of thermal energy known as British Thermal Units per Hour. One BTU/H is equivalent to 0.29 watts. Capillary tube A long, small-diameter copper pipe used in order to control the expansion of a refrigerant. It performs the same function as a thermal expansion valve, although it is calibrated for only one temperature. It s commonly used on domestic refrigerators. CFM An abbreviation for Cubic Feet per Minute; it s used as a measure of the flow of air. Closed-loop cooling A term used in order to describe a cooling solution in which the enclosure is completely sealed, preventing the entry of outside air. This stops contaminants from entering the enclosure and is the only practical method for cooling enclosures by enclosure air conditioning, because it avoids the uncontrolled flow of hot outside air into the enclosure. 8
Essential Cooling Terms (cont.) Compressor protection A self-resetting thermal overload switch mounted to a refrigeration compressor. Conduction The transfer of heat through a solid object. Convection The transfer of heat energy using a fluid such as air or water. Cooling capacity The thermal cooling ability of an enclosure cooler measured in BTU/H or in watts. DC Direct electric current. Dehumidification The removal of water vapor from the air, usually achieved by cooling the air to a temperature below the dew point, causing the moisture to condense. Dew point The temperature at which water vapor in the air will condense. The dew-point temperature is directly related to the relative humidity of the air. Dirt and dust Small particles in the air composed of earth, soil, or waste matter. Efficiency The ratio between the input power to a machine or electronic device and the usable output power. Electrical enclosure A special cabinet that has been designed for the installation of electrical control gear and that complies with certain safety standards. 9
Essential Cooling Terms (cont.) Enclosure temperature The measure of warmth or coldness of the air inside an enclosure. Environmental factors The condition of the air around an enclosure, including its temperature and relative humidity as well as the amount of dirt and dust particles in the air. The term also encompasses exposure to the sun and the presence of corrosive substances, rain, and snow. Fan-cooled Equipment cooled by the forced circulation of air using a fan. Heat load The amount of heat generated by the equipment inside an enclosure. Heat transfer The exchange of thermal energy between physical systems. High altitude The effectiveness of an air conditioner decreases with altitude in direct proportion to the density of air. At 3,000 feet, the capacity of an air conditioner is reduced by 10 percent. Hot gas line The refrigerant tubing that carries hot, compressed gas away from the compressor. Hot spots Areas within an electrical enclosure that are hotter than others due to poor airflow or local sources of heat. Insulated enclosure An enclosure fitted with thermal lining material that reduces heat transfer through the walls on the enclosure. Latent heat The energy required in order to change the state of a substance, such as the energy required to convert water at 212 F into steam without changing its temperature. 10
Essential Cooling Terms (cont.) Maximum ambient temperature The highest temperature that has been recorded for a particular location. Minimum ambient temperature The lowest temperature that has been recorded for a particular location. Natural ventilation The natural flow of air through an enclosure, aided by the natural tendency of hot air to rise. Open-loop cooling A cooling solution that draws cooler outside air into an enclosure in order to cool equipment. It is the opposite of closed-loop cooling. Power The rate at which energy is released or used. It is measured in horsepower or watts. One horsepower is equal to 746 watts. Radiation The transfer of heat energy through electromagnetic rays. The heating effect of the sun is an example of radiation. Refrigeration cycle A closed cycle of the evaporation, compression, and condensation of a refrigerant that transfers heat from one place to another. Relative humidity The amount of water vapor present in the air compared to the maximum amount of water that the air can hold at that temperature. Solar heat load The heating effect of the sun s radiation on an enclosure. 11
Essential Cooling Terms (cont.) Telecom enclosure A special cabinet that houses telecommunications equipment. Temperature The measurement of heat energy in a body or substance. It is usually measured in degrees Fahrenheit, although the metric measures of centigrade and Celsius are also common. Temperature control The use of a controller in order to regulate the temperature of an enclosure around a set temperature. Thermostat A device used in order to regulate temperature by opening or closing a switch as the temperature around the sensor changes. Ventilated Equipment that is cooled by the flow of external air through the enclosure. Watts per F A measure of the cooling capacity of an air to air heat exchanger that provides information on the amount of heat in watts that will be removed for each degree Fahrenheit of difference between the enclosure temperature and the outside ambient temperature. This term can also be stated as watts per C. 12
Cooling Equipment Accessories This section covers those items that are generally available as optional accessories. Alarm and Controlling Web server A Web server that provides the facility to monitor and control enclosure air conditioners remotely using the Internet or an intranet. Can also be used with PLCs. Corrosiveenvironment packages A range of packages providing differing levels of corrosion protection to air conditioner coils and piping through the use of protective epoxy coatings. Dry contact alarm An optional set of contacts for providing a high-temperature alarm. Filter, 2-inch A heavy-duty, high-capacity, washable filter fitted in a 2-inch-deep frame for very dusty conditions. Hazardous location Air conditioners and air to air heat exchangers can be supplied for use with enclosures installed in the presence of explosive materials. The most common rating is for Class 1, Division 2, Groups B, C, and D hazardous locations. Heater package An optional integrated heater package can be specified with air conditioners in order to prevent the enclosure temperature dropping too low when the ambient temperature declines. 13
Cooling Equipment Accessories (cont.) High ambient option This option provides improved performance for air conditioners used in high ambient temperatures, including temperatures as high as 140 F. Louvered security cover A tamperproof filter cover. Low ambient option An option designed to assist compressor-starting in very cold weather by keeping the compressor oil warm. NEMA enclosures Air conditioners and air to air heat exchangers can be supplied for use with NEMA Type 12, 4, and 4X enclosures suited for indoor or outdoor operation in harsh conditions. Open-door kill switch This optional switch turns off the air conditioner when the enclosure doors are opened in order to prevent formation of excessive condensate. 3R shroud A NEMA Type 3R fan shroud kit designed to prevent water ingress with outdoor enclosures using filtered fan packages. Redundant system Designed for critical applications where 100 percent redundancy is required. It controls two air conditioners with provision for automatically cycling each air conditioner periodically. Remote controller An option to install the digital controller inside the electrical enclosure. Stainless steel housing All air conditioners and air to air heat exchangers can be supplied with an optional stainless steel housing with grained and polished finish. 14
Cooling Equipment Accessories (cont.) Temperature probe, adjustable A temperature probe that is attached to a 12 foot cable so it can be installed in the enclosure in order to allow the digital controller to control the temperature at any location inside the enclosure. Universal mounting plate This is used when replacing or upgrading an enclosure air conditioner that has different enclosure openings. Vibration package A vibration protection package is available for air conditioners to be mounted in locations subject to excessive vibration. 15
Equipment That Needs Cooling This section lists the most typical applications for enclosure cooling. Control cabinets Industrial and other control cabinets are often located in hot and dusty environments. These cabinets are usually sealed in order to prevent the ingress of dirt and dust. Industrial and utility electrical enclosures Most electrical enclosures will benefit from enclosure cooling, especially because of the widespread use of electronically controlled electrical equipment. PLC and SCADA systems Integrated control systems using PLCs and SCADA systems are common. In a production environment, downtime can cause widespread disruption. Although these systems are robust, their processors and memory chips should not be allowed to exceed recommended operating temperatures, and it is good practice to employ closed-loop cooling solutions. Standby batteries The service life of a standby battery system using lead acid batteries is adversely affected if ambient temperatures exceed 75 F. Standby battery installations should be cooled in order to avoid premature battery failure. Telecom equipment Telecom equipment is often installed outdoors and subject to solar radiation. Because the Telcordia GR-3108-CORE Class 1 requirements specify a maximum enclosure temperature of 104 F, most telecom cabinets need enclosure cooling. Variablefrequency drives and inverters Powerful variable-frequency drives and inverters generate a significant amount of waste heat. Additionally, these devices should not be allowed to exceed their maximum operating temperatures or they may suffer damage. In most instances, some form of enclosure cooling is recommended. 16
Important Standards Here is a brief list of some of the more important local and international standards relating to enclosure cooling systems. CE This mark specifies that equipment complies with European health and safety requirements. It is not applicable in the U.S. CSA Canadian Standard Association that is responsible for the Canadian electrical code to which enclosure cooling systems for sale in Canada must comply. IP Rating The European ingress protection code used internationally. Although similar to NEMA enclosure protection standards, it is not always directly comparable. NEC The National Electrical Code issued by the National Fire Protection Association. NEMA The National Electrical Manufacturers Association, which is responsible for the NEMA enclosure protection standards. NRTL A Nationally Recognized Testing Laboratory. OSHA The U.S. Occupational Safety and Health Administration. 17
Important Standards (cont.) Telcordia specifications Telecom standards issued by Telcordia that have wide acceptance. These include the GR-487-CORE requirements for electronic equipment cabinets and the GR- 3108-CORE equipment testing requirements. UL Previously known as Underwriters Laboratory, an NRTL laboratory that tests equipment to U.S. (UL) and Canadian (cul) standards. All Thermal Edge equipment is tested to UL standards. 18
Documentation and Calculations This section deals specifically with Thermal Edge documentation. ETM Calculator 1 An online enclosure temperature management calculator that can be used in order to calculate enclosure cooling requirements. Product sheets Data sheets providing detailed technical specifications for an individual cooling solution or for a range of cooling equipment. User and technical manual The detailed user manual supplied with each enclosure cooling product. Warranty The Thermal Edge warranty statement: All products are warrantied for one year from date of purchase. 19
NEXT STEPS The purpose of this glossary is to help designers, customers, and anyone else involved with enclosure cooling understand the various terms used and specifically to understand how these apply to Thermal Edge products. Although the glossary covers terms commonly used, it is not possible to cover everything in complete detail. All Thermal Edge products are designed with great care and built to exacting standards in order to ensure reliable operation in the field. Our Sales Team 2 and Technical Support Team 3 are always available to provide practical help and guidance to help you select the best cooling system for your application or to provide you with additional information. SOURCES 1. Thermal Edge: ETM Calculator 2. Thermal Edge: Sales Team 3. Thermal Edge: Support Team USE THE ETM CALCULATOR 2016 Thermal Edge, Inc. 888.580.0202