In Europe, the CE Marking signifies that a product complies with all European Union (EU) directives and with applicable health, safety, environmental and consumer protection standards. The mark also promotes free trade into and within the EU. The CE marking is not applied to empty enclosures because they are considered only as inactive parts of the final equipment assembly. The equipment integrator is responsible for compliance with applicable EU directives and standards. The IEC rating system uses different evaluation criteria and has more classifications than the UL and CSA standards. Because the classification ratings differ, equating IEC classifications with NEMA Type enclosures can be controversial and depends on individual interpretation of ratings. The National Electrical Manufacturers Association (NEMA) publishes ratings, but does not test or list enclosures. The NEMA enclosure designations are the standard reference for enclosures in this publication, and regardless of type, all enclosures provide protection to personnel against incidental contact with the enclosed equipment. To assist in the proper selection of an enclosure, the NEMA types are differentiated by the environmental conditions as listed below: NEMA 1 Indoor use to provide a degree of protection against falling dirt. NEMA 2 Indoor use to provide a degree of protection against falling dirt; dripping and light splashing of liquids. NEMA 3 Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust; and that will be undamaged by the external formation of ice on the enclosure. NEMA 3R Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet and snow; and that will be undamaged by the external formation of ice on the enclosure. NEMA 3S Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust; and in which the external mechanism(s) remain operable when ice laden. NEMA 4 Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water; and that will be undamaged by the external formation of ice on the enclosure. Technical Information Certifications & Standards Application The products in this catalog are designed for electrical and electronic enclosure applications in commercial or industrial locations which are classified as non-hazardous; currently Rittal does not manufacture enclosures for hazardous environments. Information on the classification of hazardous and non-hazardous locations appears later in this section. The enclosure products in this publication should be applied, installed and used only by qualified engineers, technicians or electricians knowledgeable of the standards, laws, regulations and ordinances associated with the respective application. THE INFORMATION IN THIS SECTION HAS BEEN CONDENSED FROM SEVERAL REFERENCES AND IS PROVIDED FOR GUIDANCE IN SELECTING THE APPROPRIATE ENCLOSURE FOR AN APPLICATION.THE ORIGINAL REFERENCE MUST BE CONSULTED FOR DETAILED INFORMATION. Installation Enclosures must be mounted to structures which will support the weight and sustain all other forces which the enclosure and its associated equipment may impose. Before any circuits are energized, all electrical and mechanical clearances must be checked to confirm that the equipment functions safely and properly. Assemblers and installers should consult with manufacturers and observe all regulatory procedures and practices to assure electrical and mechanical conformance in each application. Industry Standards The following information is provided with permission of the respective organizations to assist in the selection of an enclosure: Enclosure Ratings CSA, IEC, NEMA and UL use rating classifications which establish performance requirements for enclosures. CSA, NEMA and UL are the recognized organizations in North America. IEC standards fulfill a similar function in Europe and other parts of the world. Efforts to harmonize enclosure standards are underway, however several years are anticipated before the effort is complete. In North America, both UL and CSA are accredited by the Standard Council of Canada (SCC) as Certification Organizations (CO) and Testing Organizations (TO). With its SCC accreditation, UL is able to evaluate products for use in Canada. Approved products carry the cUL mark. Both UL (cUL) and CSA perform follow-up services to assure that manufacturers continue to comply with material and process specifications. Technical Information Certifications & Standards TEC 1 TECHNICAL APPENDIX
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In Europe, the CE Marking signifies that a product complieswith all European Union (EU) directives and with applicablehealth, safety, environmental and consumer protectionstandards. The mark also promotes free trade into and withinthe EU. The CE marking is not applied to empty enclosuresbecause they are considered only as inactive parts of thefinal equipment assembly. The equipment integrator isresponsible for compliance with applicable EU directives andstandards.
The IEC rating system uses different evaluation criteria andhas more classifications than the UL and CSA standards.Because the classification ratings differ, equating IECclassifications with NEMA Type enclosures can becontroversial and depends on individual interpretation of ratings.
The National Electrical Manufacturers Association (NEMA)publishes ratings, but does not test or list enclosures. TheNEMA enclosure designations are the standard reference forenclosures in this publication, and regardless of type, allenclosures provide protection to personnel against incidentalcontact with the enclosed equipment. To assist in the properselection of an enclosure, the NEMA types are differentiatedby the environmental conditions as listed below:
NEMA 1 Indoor use to provide a degree of protection against falling dirt.
NEMA 2 Indoor use to provide a degree of protection against falling dirt; dripping and light splashing of liquids.
NEMA 3 Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust; and that will be undamaged by the external formation of ice on the enclosure.
NEMA 3R Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet and snow; and that will be undamaged by the external formation of ice on the enclosure.
NEMA 3S Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust; and in which the external mechanism(s) remain operable when ice laden.
NEMA 4 Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water; and that will be undamaged by the external formation of ice on the enclosure.
Technical InformationCertifications & Standards
ApplicationThe products in this catalog are designed for electrical andelectronic enclosure applications in commercial or industriallocations which are classified as non-hazardous; currentlyRittal does not manufacture enclosures for hazardousenvironments. Information on the classification of hazardousand non-hazardous locations appears later in this section.
The enclosure products in this publication should beapplied, installed and used only by qualified engineers,technicians or electricians knowledgeable of the standards,laws, regulations and ordinances associated with therespective application.
THE INFORMATION IN THIS SECTION HAS BEENCONDENSED FROM SEVERAL REFERENCES AND ISPROVIDED FOR GUIDANCE IN SELECTING THEAPPROPRIATE ENCLOSURE FOR AN APPLICATION.THEORIGINAL REFERENCE MUST BE CONSULTED FORDETAILED INFORMATION.
InstallationEnclosures must be mounted to structures which will supportthe weight and sustain all other forces which the enclosureand its associated equipment may impose. Before anycircuits are energized, all electrical and mechanicalclearances must be checked to confirm that the equipmentfunctions safely and properly. Assemblers and installersshould consult with manufacturers and observe all regulatoryprocedures and practices to assure electrical andmechanical conformance in each application.
Industry StandardsThe following information is provided with permission of therespective organizations to assist in the selection of anenclosure:
Enclosure RatingsCSA, IEC, NEMA and UL use rating classifications whichestablish performance requirements for enclosures. CSA,NEMA and UL are the recognized organizations in NorthAmerica. IEC standards fulfill a similar function in Europe and other parts of the world. Efforts to harmonize enclosurestandards are underway, however several years areanticipated before the effort is complete.
In North America, both UL and CSA are accredited by theStandard Council of Canada (SCC) as CertificationOrganizations (CO) and Testing Organizations (TO). With itsSCC accreditation, UL is able to evaluate products for use inCanada. Approved products carry the cUL mark. Both UL(cUL) and CSA perform follow-up services to assure thatmanufacturers continue to comply with material and processspecifications.
Technical InformationCertifications & Standards
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Comparison of Enclosure Types for Non-Hazardous LocationsProvides a Degree of Protection Against the
Following Environmental Conditions TYPE OF ENCLOSURE1 2 3 3R 4 4X 5 6 6P 12 13
Incidental Contact with Enclosed Equipment X X X X X X X X X X XIndoor X X X X X X X X X X X
Outdoor X X X X X XFalling Dirt X X X X X X X X X X X
Dripping and Light Splashing Liquids X X X X X X X X X XRain, Sleet* and Snow X X X X X X
Circulating Dust, Lint, Fibers and Flyings X X X X X X XSettling Dust, Lint, Fibers and Flyings X X X X X X X X
External Ice* X X X X X XHosedown and Splashing Water X X X X
Oil and Coolant Seepage X XOil and Coolant Spraying and Splashing X
Corrosive Agents X XOccasional Temporary Submersion X XOccasional Prolonged Submersion X
* External operating mechanisms are not required to be operable when the enclosure is ice covered.
NEMA 4X Indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water andcorrosion; and that will be un-damaged by the external formation of ice on the enclosure.
NEMA 5 Indoor use to provide a degree of protection against falling dirt; settling airborne dust, lint, fibers and flyings; anddripping and light splashing of liquids.
NEMA 6 Indoor or outdoor use to provide a degree of protection against falling dirt; hose-directed water and the entry of water during occasional temporary submersion at a limited depth; and will be undamaged by the external formationof ice on the enclosure.
NEMA 6P Indoor or outdoor use to provide a degree of protection against falling dirt; hose-directed water and the entry of water during prolonged submersion at a limited depth; and will be undamaged by the external formation of ice on the enclosure.
NEMA 12 Indoor use to provide a degree of protection against falling dirt; circulating dust, lint, fibersand flyings; and dripping and light splashing of liquids.
NEMA 13 Indoor use to provide a degree of protection against falling dirt; circulating dust, lint, fibersand flyings; and spraying, splashing and seepage of water, oil and non-corrosive coolants.
Technical InformationCertifications & Standards
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Technical InformationCertifications & Standards
Reference Documents and Sources
NEMA Standards Publication 250, Enclosures for ElectricalEquipment (1000 Volts Maximum) and NEMA StandardsPublication ICS6, Enclosures for Industrial Controls andSystems
National Electrical Manufacturers Association1300 North 17th Street, Suite 1847Rosslyn, VA 22209
CSA Standard C22.2 No. 14 Industrial Control Equipment forUse in Ordinary (Non-Hazardous) Locations; CSA StandardC22.2 No. 40 Cut-Out, Junction and Pull Boxes; and CSAStandard 22.2 No. 94 Special Purpose Enclosures
Canadian Standard Association178 Rexdale BoulevardEtobicoke, Ontario, Canada M9W 1R3
UL 50 Enclosures for Electrical Equipment; UL 94 Tests forFlammability of Plastic Materials for Parts in Devices andAppliances; UL 508 Industrial Control Equipment; UL 870Wireways, Auxiliary Gutters and Associated Fittings; and UL746C Polymeric Materials - Use in Electrical EquipmentEvaluations
Underwriters Laboratories333 Pfingsten RoadNorthbrook, IL 60062-2096
Underwriters Laboratories of Canada7 Crouse RoadScarborough, Ontario M1R 3A9 Canada
IEC 529 Classification of Degrees of Protection by Enclosures; IEC 204 Electrical Equipment of IndustrialMachines
International Electrotechnical Commission1 Rue de VarembeiCH-1211Geneva 20, Switzerland
ANSI Z55.1 Grey Finishes for Industrial Apparatus andEquipment
American National Standards Institute1430 BroadwayNew York, NY 10018
Information for Comparison of IEC andCSA/NEMA/UL/cUL RatingsNEMA 250 and UL 50 specify tests for environmentalconditions such as falling dirt, ice, corrosion, oil andcoolants whereas IEC 529 does not have suchrequirements. Different rating requirements makecomparison difficult and disagreements are common.
The IEC designation consists of the letters IP followed bytwo numerals. The first number indicates the degree ofprotection provided by the enclosure with respect topersons and solid foreign objects entering the enclosure.The second number indicates the degree of protectionprovided by the enclosure with respect to the harmfulingress of water.
The data contained in the following tables are provided forinformation; however, caution is necessary when attemptingto equate IEC and NEMA enclosure ratings because anexact equivalence is not possible. The table can only beused to convert NEMA designations to IEC, it should not beused inversely. The cross reference is based on engineeringjudgement and is not approved by any standardsorganization.
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Technical InformationCertifications & Standards
Approximate Equivalence of CSA/NEMA/UL/cUL and IEC Enclosure Types*
*Comparison ratings in this table are taken from Appendix A, NEMA 250-1997. Test datamay change the equivalent rating published by the enclosure manufacturer.
Specifications for ConstructionMaterials Used in Rittal EnclosuresCold Rolled SteelA low carbon, cold finished steel, produced by passing barstock through a set of rolls. Cold rolled sheets have lessthickness variation and a better finish than hot rolled steel.
Galvanized SteelA zinc coated steel which is hot dip galvanized, metalsprayed or electroplated to provide corrosion resistance.Galvanizing provides a sacrificial coating and cathodicprotection.
Hot Rolled SteelA low carbon, hot finished steel, produced by passing barstock through a set of rolls at a temperature above the re-crystallization temperature. Hot rolled steel sheet has apoorer finish than cold rolled steel.
Pickled and Oiled Steel SheetsHot rolled steel sheets which have had the scale removedby means of a hot, weak sulfuric acid bath after which an oilfilm has been applied for corrosion resistance.
Stainless SteelA highly corrosion resistant iron alloy containing between 12%and 25% chromium. For superior corrosion resistance, Rittalfabricates enclosures from both Type 304 and 316 StainlessSteel which are non-magnetic. Type 316, a low carbonstainless steel, is harder and more corrosion resistant; it is an excellent material for marine application.
AluminumA lightweight metal which quickly forms a natural oxide layerto resist corrosion. Rittal fabricates enclosures from Type 5052aluminum, the highest strength non-heat treatable aluminumalloy recommended for marine applications.
GalvanealA hot-dip zinc coated sheet which has been heated aftercoating to allow interdiffusion of zinc and iron to form an alloycoating.
FiberglassEnclosures are molded under heat and pressure withfiberglass reinforced polyester resin to produce superiorchemical resistance in corrosive applications. The glass fiberreinforcement increases enclosure strength to withstandphysical loads such as unexpected impacts or additionaltensile loads.
NEMA Enclosure Type IEC Enclosure Type1 IP102 IP113 IP54
3R IP143S IP544 IP66
4X IP666 IP6712 IP5213 IP54
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The enclosure selection process includes the following fiveconsiderations:
1. Examination of the ApplicationIndustrial applications usually require strong mechanical enclosures which are durable. Electronic and communication applications are more diverse, but space and security are usually the more dominant considerations.
2. Environment ProtectionThe environment where the equipment will be located (i.e., outdoors, factory floor, office, laboratory, chemical plant, etc.) establishes the degree of protection required. The NEMA enclosure ratings provide the information needed to select the enclosure for your application requirements.
The application environment is a significant factor in specifying the enclosure material. For mild steel enclosures, painting is the most basic protection; stainless steel should be considered for more corrosive applications. Electromagnetic interference (EMI) and radio frequency interference (RFI) are additional environmental factors which impact enclosure material selection.
3. Space RequirementsSpace requirements include size and equipment arrangement as well as aesthetics. Accessories such as windows, back panels, swingout panels, wiring terminals,EMI/RFI shielding and climate control solutions also influence size and appearance.
4. Climate Control SolutionsEspecially in electronic enclosure applications, climate control is becoming an important issue because technology advances continue to reduce component size. Smaller components increase heat generation by placing more components in the same enclosure volume.Also in some applications, heaters are required to prevent condensation.
5. SecurityThe monetary value of equipment placed within enclosures has increased. The safety of personnel can be jeopardized by unauthorized access and operation of equipment. Enclosure security can be enhanced by the selection of hinges, latches, locks and fasteners.
The five steps in this enclosure selection process are notnew, but numerous enclosure and design options areavailable to meet a diversity of needs in each area. In addition almost any enclosure in this catalog can bemodified to meet unique application requirements in aspecific environment.
Selecting an EnclosureThe Selection Guidelines and the Enclosure Selection Guideare designed to help select a Rittal enclosure which is bestfor your application. Before using the Enclosure SelectionGuide, the first three steps in the selection process must be completed.
The application, environmental and space requirements aredependent on the sensitivity/criticality of the equipment, andits size and operation. Once these parameters areestablished, the first three steps are quickly and easilycompleted. An Enclosure Selection Checklist andsupplemental information are provided within this TechnicalSection to help select the enclosure material for theapplication environment.
Rittal offers Aluminum, Galvanized Steel, Painted Steel,Stainless Steel and Fiberglass Enclosures. The choice ofmaterial is dependent on the concentration of variouscorrosives present in the application environment and otherphysical properties necessary to meet the designspecifications. Although NEMA 4X is the only enclosurefabricated and rated for resistance to corrosive agents, otherenclosure materials and ratings offer a degree of corrosionresistance in less harsh environments.
To begin the selection process, one must consider all thecorrosive agents which can be present in an application, but determining the concentration and corroding agents maybe a complex process. Usually several corrosive elementsare present and interactions are not always well documented.
Water is the most common corrosive and is usually present to some extent in every enclosure application. Adjacentprocessing operations or other intermittent activities such ascrop dusting, industrial cleaning or road salt may expose theenclosure to a variety of corrosive agents and temperatures.Each environment is unique and all possible corrosive agentsshould be identified for the intended enclosure application.
Once the corrosive agents and concentrations are identified,information in this section can be used to select theenclosure material. Metal corrosion is influenced by surfacefinish, surface treatment such as painting or galvanizing, anduse of materials such as stainless steel, fiberglass oraluminum which are naturally corrosion resistant.
To select the best enclosure material for an application;chemical resistance, physical strength and economic dataare presented in several tables beginning on the next page.In Table 1 enclosure materials are rated on a continuum from“Recommended” to “Limited or Unacceptable” in three broadcategories of chemicals. Since the chemical resistancecategories in the table are extremely broad, some materialsmay perform well in specific corrosive environments within ageneral category and it is best to consult the detailedChemical Resistance Information provided in Table 3.
Besides the enclosure material, the corrosion resistance offeatures such as windows, gaskets, latches, etc. must also be considered. Table 4 provides the chemical resistanceinformation which can be used to select the commonly used materials for these features.
Much of the chemical resistance information in Tables 3 and 4 is based on total immersion testing in the chemical for a minimum of 30 days at 72°F. The information in thesetables is intended as a guide only. Total immersion testing is considered quite severe and the results may notnecessarily reflect the performance under actual fieldconditions. The user assumes responsibility for selection of the material based on the characteristics of the application environment.
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RELATIVEMATERIAL PHYSICAL RELATIVE APPLICATION TEMPERATURE
STRENGTH COST CONDITIONS LIMITATIONSAluminum Average Average Indoor and outdoor, marine, solvents, petrochemical None for enclosure applications
sulfates, nitrates and specific acids.Mild Steel: High Average Indoor and outdoor where the respective coating None for enclosure applicationsGalvanized Low provides acceptable protection in a mildly corrosive
Painted environment.Stainless High Average- Indoor and outdoor in highly corrosive applications. None for enclosure applications
Steel High Food and dairy processing or marine.Acrylic Average Low Enclosure windows. Weatherable, scratch resistant. -31°F (-35°C) to 180°F (82°C)
Good resistance to solvents.Poly- Average Low- Enclosure windows. Not recommended for direct -31°F (-35°C) to 248°F (120°C)
carbonate Average sunlight, exposure to organic solvents and concentrated alkalis.
Nylon Average Low Cord grip, hinges, latches. -22°F (-30°C) to 212°F (100°C)
Fiberglass Average Low- Indoor and outdoor for continuously damp and highly -40°F (C) to 250° (121°C)Average corrosive environments. Petrochem, water treatment,
food processing, coating, salts and chemicals.Gaskets:
Neoprene Low Low Oil resistance. Seams may be a problem. -40°F (C) to 225°F (107°C)Silicone Low Average Oil resistance temperature and chemical resistance. -40°F (-40°C) to 350°F (175°C)
Urethane Low Average Water and oil resistance, chemical resistance. -40°F (C) to 200°F (93°C)
Technical InformationEnclosure Materials
CONTINUUM GENERAL CATEGORY OF CHEMICALSOF USE Acids Alkalines Solvents
Detailed material strength information is beyond the scope of this catalog and should be obtained from a materials reference or Rittal; however, Table 2 provides some relativedata to help with this selection.
Table 1. Broad Categories Of Enclosure Material Chemical Resistance
Table 2. Relative Material Strength And Cost Comparison Of Commonly Used Enclosure Materials
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Fiber Steel Stainless SteelGlass Polyester Urethane Galvanized Type Type
CHEMICAL Aluminum Polyester Powder Enamel 304 316Acetyldehyde S U — — — S S
Acetic Acid (10%) L S U U U S UAcetone S L L U L S S
Aluminum Chloride (10%) U S U U U U MAluminum Sulfate (10%) L S U U U U S
Ammonia Gas L S — — — S SAmmonium Chloride U S U U U S S
Ammonium Hydroxide (10%) S L U U U S SAmmonium Nitrate (10%) M S U U U S S
Ammonium Phosphate (10%) L M S L U S MAmmonium Sulfate S S — — — S S
Aniline L U — — — S SASTM #1 Oil S S S S S S SASTM #3 Oil S S S S S S SAxle Grease S S S S S S S
Benzene S S — — S S SBoric Acid (10%) M S U U U S S
Bromine U L U U U U UButyl Acetate M L — — — S SButyric Acid U S — — — S S
Calcium Chloride (10%) L S U U U L SCalcium Hydroxide (10%) U S U U U S S
Calcium Hypochlorite (10%) L M U U U U MCalcium Sulfate M S U U U S S
Carbolic Acid (25%) M L U U U S SCarbon Disulfide S L — — — S S
Carbon Tetrachloride S M U S S U SChlorine (dry) S S — — — S S
Chlorine (water) 5-10 ppm M L S U U U —Chlorobenzene S S — — S S S
Chloroform L U — — — S SChrome Plating Solution U L U U U L L
Chromic Acid S S — — — U UCitric Acid (10%) U M U U U S SCopper Sulfate U S — — — S S
Creosote L L — — — S SCutting Fluid (5 Star) 10% S S U U U S S
Cutting Fluid (Castrol 980 H) S S S U U S SCutting Fluid (Norton 205) U S U U U S S
Cutting Fluid (Rustlick) 10% M S U U U S SCutting Oil (Dark) S S S S S S S
Diethyl Ether S S — — — S SEthyl Alcohol S S M U S S S
Ethylene Dichloride S L — — — — —Ethylene Glycol S S S S U S SFerric Chloride U S U U U S UFerric Nitrate — S — — — S SFerric Sulfate M S — — — S S
KEY :S = superior resistance /
completely unaffectedunder all conditions
Technical InformationChemical Resistance
Table 3. Specific Chemical Resistance Information Metals, Coated Metals And Fiberglass Materials
L = limited resistance / some chemical attackmay be expected over time, exposureshould be limited to fumes or occasionallight splashing
— = no data available
M = moderate resistance / superficial(aesthetic) effects only, example: some loss of surface gloss or colorchange may occur, but mechanicalproperties (strength) remain unaffected
U = unsatisfactory severe / chemicalattack in a relatively short time
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Fiber Steel Stainless SteelGlass Polyester Urethane Galvanized Type Type
CHEMICAL Aluminum Polyester Powder Enamel 304 316Fluorine S U — — — M —
Formaldehyde S S — — — L SFormic Acid U S U U U M SFuel Oil (#2) S S M S S S M
Gasoline S M — — — S SGlycerine S S — — S S S
Hydraulic Brake Fluid S S U U S S SHydraulic Oil S S S S S S S
Hydrochloric Acid (10%) U M U U U U UHydrocyanic Acid S U — — — S S
Hydrofluoric Acid (20%) U U U U U U UHydrogen Peroxide S M — — — L SHydrogen Sulfide M S — — — L SHypochlorus Acid U S — — — — —Isopropyl Alcohol S S M U S S S
Kerosene S S S S S S SLacquer Thinner S S L U S S S
Lactic Acid M S — — — L SLime M M — — — — —
Liquid Dish Soap (10%) M S U U U S MLubricating Oils S S — — — S S
Magnesium Chloride (10%) L S U U U S SMagnesium Hydroxide (10%) L S U U U S S
Mercuric Chloride (10%) U M U U U S UMethyl Ethyl Ketone S L — — — S SMethylene Chloride S S U U M S S
Milk S S — — — S SMineral Oil S S — — — S S
Mineral Spirits S S S S S S SMotor Oil (10 weight) S S S S S S S
Nickel Salts L S — — — L SNitric Acid (10%) U M U U U S S
Nitrobenzene S L — — — S SOleic Acid S S — — — L S
Perchlorethylene S S S U S S SPhosphoric Acid (25%) U L U U U S SPhosphoric Acid (50%) U U U U U S S
Pickling Solution U M U U U S MPotassium Carbonate (10%) U S S S L S SPotassium Chloride (25%) L S U U U S S
Potassium Hydroxide (25%) U U U U U M MPotassium Nitrate (10%) U S U U U S SPotassium Sulfate (10%) L S U U U S S
Soap (Igepal) 10% L S S U U S SSodium Bicarbonate (10%) L S S S U S S
Sodium Bisulfate (10%) U L U U U S SSodium Chloride (25%) L S U U U S S
Sodium Hydroxide U U U U U M M
Technical InformationChemical Resistance
Table 3. Continued
KEY :S = superior resistance /
completely unaffectedunder all conditions
L = limited resistance / some chemical attackmay be expected over time, exposureshould be limited to fumes or occasionallight splashing
— = no data available
M = moderate resistance / superficial(aesthetic) effects only, example: some loss of surface gloss or colorchange may occur, but mechanicalproperties (strength) remain unaffected
U = unsatisfactory severe / chemicalattack in a relatively short time
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Fiber Steel Stainless SteelGlass Polyester Urethane Galvanized Type Type
CHEMICAL Aluminum Polyester Powder Enamel 304 316Sodium Hypochlorite U M U U U S MSodium Nitrate (10%) M S U U U S S
Sodium Phosphate (10%) L S U U U S SSulfuric Acid (25%) U S U U U S SSulfurus Acid (10%) U U U U U S STannic Acid ((10%) L S U U U M M
Tetrahydrofuran M L U U U S SToluene S S L U S S S
Trichloroethylene S U — — — L STrisodium Phosphate L M — — — — —
Turpentine S M M U L S SVegetable Oils S S — — — S S
Vinegar M S — — — S SWater, Industrial L S L L L S S
Water, Rain L S S L L S SWater, Sea L S U U U S SWater, Tap L S S L L S S
Xylene S S L U S S SZinc Acetate S S — — — S SZinc Chloride L S S U U M SZinc Sulfate S S — — — M S
CHEMICAL PVC Nylon Rubber Rubber Urethane Acrylic carbonateAcetyldehyde U — S S — — —
Acetic Acid (10%) L U U M L S SAcetone U S U S U U U
Aluminum Chloride (10%) S U S S S S SAluminum Sulfate (10%) S L U S S S S
Ammonia Gas — S S S — S —Ammonium Chloride S U S S S S S
Ammonium Hydroxide (10%) S — L L S S UAmmonium Nitrate (10%) S U U S S S U
Ammonium Phosphate (10%) — L U S S S SAmmonium Sulfate S U S S — — —
Aniline S L U U — S —ASTM #1 Oil — — M S S S MASTM #3 Oil — — U L S S MAxle Grease — — L S S S M
Benzene U S U U — U —Boric Acid (10%) L S S S S S S
Bromine U U U U U L UButyl Acetate U S U U — U —Butyric Acid U U U — — — —
Calcium Chloride (10%) S U S S S S SCalcium Hydroxide (10%) S — U S L S S
Table 4. Specific Chemical Resistance Information
Technical InformationChemical Resistance
Table 3. Continued
KEY :S = superior resistance /
completely unaffectedunder all conditions
L = limited resistance / some chemical attackmay be expected over time, exposureshould be limited to fumes or occasionallight splashing
— = no data available
M = moderate resistance / superficial(aesthetic) effects only, example: some loss of surface gloss or colorchange may occur, but mechanicalproperties (strength) remain unaffected
U = unsatisfactory severe / chemicalattack in a relatively short time
CHEMICAL PVC Nylon Rubber Rubber Urethane Acrylic carbonateCalcium Hypochlorite (10%) S U U S U M S
Calcium Sulfate S U S S S S SCarbolic Acid (25%) — — U U U U U
Carbon Disulfide U — U — — S —Carbon Tetrachloride L S U U U S U
Chlorine (dry) L — — — — — —Chlorine (water) 5-10 ppm L — L S S S S
Chlorobenzene U S U U — L —Chloroform U U U U — U —
Chrome Plating Solution — — U U U S SChromic Acid L U U M — U —
Citric Acid (10%) S L U S U S SCopper Sulfate S L S S — U —
Creosote — U U U — — —Cutting Fluid (5 Star) 10% — — U S S S M
Cutting Fluid (Castrol 980 H) — — L S S S LCutting Fluid (Norton 205) — — S S S S S
Cutting Fluid (Rustlick) 10% — — S S S S SCutting Oil (Dark) — — U S S S S
Diethyl Ether U — — U — U —Ethyl Alcohol S — L S S U M
Ethylene Dichloride U — U U — U —Ethylene Glycol S — S S S S SFerric Chloride S U L S L S SFerric Nitrate S U S M — — —Ferric Sulfate S U S M — — —
Fluorine L — — U — — —Formaldehyde L U U M — S —Formic Acid L S U L L U SFuel Oil (#2) S — U U U S S
Gasoline S S U L — S —Glycerine S S S S — S —
Hydraulic Brake Fluid — — U S U U UHydraulic Oil — — U S S S M
Hydrochloric Acid (10%) S U L L U S SHydrocyanic Acid S — S M M — —
Hydrofluoric Acid (20%) L U U U — S MHydrogen Peroxide S U U M — S —Hydrogen Sulfide S — U M — — —Hypochlorus Acid — — — — — — —Isopropyl Alcohol — — S S S S S
Kerosene S — U U S S MLacquer Thinner — S U S L U U
Lactic Acid S L L — — L —Lime — — S M — — —
Liquid Dish Soap (10%) S — L S S S SLubricating Oils — — U U — S —
Magnesium Chloride (10%) S S S S S S S
Technical InformationChemical Resistance
Table 4. Continued
KEY :S = superior resistance /
completely unaffectedunder all conditions
L = limited resistance / some chemical attackmay be expected over time, exposureshould be limited to fumes or occasionallight splashing
— = no data available
M = moderate resistance / superficial(aesthetic) effects only, example: some loss of surface gloss or colorchange may occur, but mechanicalproperties (strength) remain unaffected
U = unsatisfactory severe / chemicalattack in a relatively short time
CHEMICAL PVC Nylon Rubber Rubber Urethane Acrylic carbonateMagnesium Hydroxide (10%) S — S S S S S
Mercuric Chloride (10%) L — U L U S SMethyl Ethyl Ketone U S S U — L —Methylene Chloride — U U S U U U
Milk S — S S — S —Mineral Oil S — L M — S —
Mineral Spirits — — U U S S MMotor Oil (10 weight) — — U U S S S
Nickel Salts S — U S — — —Nitric Acid (10%) S U U U U S L
Nitrobenzene U S U — — — —Oleic Acid S U — U — — —
Perchlorethylene — — U S U U UPhosphoric Acid (25%) S U S S U S SPhosphoric Acid (50%) S U S S U S S
Pickling Solution — — L M M S SPotassium Carbonate (10%) L S S S S S SPotassium Chloride (25%) S L S S S S S
Potassium Hydroxide (25%) S S U L M U UPotassium Nitrate (10%) S L S S S S SPotassium Sulfate (10%) SL S S S S S S
Soap (Igepal) 10% S — U S S S SSodium Bicarbonate (10%) S S S S S S S
Sodium Bisulfate (10%) S L S S L S SSodium Chloride (25%) S S S S S S S
Sodium Hydroxide S S U U M S USodium Hypochlorite S U U S U S SSodium Nitrate (10%) S S S S S S S
Sodium Phosphate (10%) S — U S S S SSulfuric Acid (25%) S U S S U S SSulfurus Acid (10%) S — U U L S STannic Acid ((10%) S U U L U S S
Tetrahydrofuran — S U U U U UToluene U S U U U U U
Trichloroethylene U U U U — U —Trisodium Phosphate S — — — — — —
Turpentine — S U L U S SVegetable Oils S — L S — S —
Vinegar — S L S — S —Water, Industrial S — S S S S S
Water, Rain S — S S S S SWater, Sea S — S S S S SWater, Tap S — S S S S S
Xylene — S U M U S UZinc Acetate — — — U — — —Zinc Chloride S U M S U S MZinc Sulfate S L S S — — —
Technical InformationChemical Resistance
Table 4. Continued
KEY :S = superior resistance /
completely unaffectedunder all conditions
L = limited resistance / some chemical attackmay be expected over time, exposureshould be limited to fumes or occasionallight splashing
— = no data available
M = moderate resistance / superficial(aesthetic) effects only, example: some loss of surface gloss or colorchange may occur, but mechanicalproperties (strength) remain unaffected
U = unsatisfactory severe / chemicalattack in a relatively short time
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CONTINUUM CHEMICAL RESISTANCE CHIP HEATOF USE Acid Alkalines Solvents Water RESISTANCE RESISTANCE
The primary function of the enclosure’spaint is to provide corrosionprotection, but benefits such asimproved appearance and addeddistinction should also be considered.The corrosive severity of theapplication conditions is the firstconsideration in selecting the finish.Once a paint has been chosen for itscorrosion protection, other factorssuch as color, gloss, texture, ease ofcleaning, retention of properties andmaintenance can be evaluated tocomplete the selection.
Table 5 rates different paint types on a continuum of use from“Recommended” to “Unacceptable”in three broad categories of chemicalcorrosives. The table also providesmoisture, heat and chip resistanceinformation. Table 6 provides arelative cost comparison of theavailable paint categories and theenclosure materials to which theymay be applied.
Technical InformationEnclosure Paint Finishes
➡➡
➡➡
➡➡
➡➡
Table 5. Broad Categories Of Paint Type Characteristics
Table 6. Relative Cost Comparison Of Paint Types
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➡
Technical InformationEnclosure Paint Finishes
Other considerations in selecting apaint type include:
• Lighter colors will dissipate heatand lower the temperature of internal equipment; darker colors will retain heat and increase the temperature of the cabinet interior. In outdoor applications lighter colors reflect sunlight and operate at lower temperatures.
• For severely corrosive applications, an inhibiting primer with an overcoat of epoxy or urethane is recommended.
• Textured finishes are generally less expensive, easier to touch-up, do not show fingerprints as readily and provide an attractive appearance; a textured paint finish is more difficult to clean.
• Some epoxy paints chalk and lose gloss.
• Safety concerns or corporate specifications may be considered in selecting a color; however, some special colors may add cost and increase lead times.
Topcoating PowdercoatedEnclosures
Rittal uses the latest electrostaticpowder coating technology todeposit a premium powder paint on enclosures; however, someapplications may require atopcoating to meet uniquespecifications such as a colorchange or material requirement. A topcoat can be applied to theexisting powdercoat using theinstructions below:
Topcoat Material Application Instructions
Air Dry Acrylic Lacquer Wipe the enclosure surfaces to be topcoated with aHi-Solid Catalyzed Acrylic clean solvent cloth. Allow the solvent to flash dry Hi-Solid Two Part Urethane for approximately 5 minutes and apply the finish asAutomotive Air Dry Acrylic directed by the paint supplier.Vinyl Air DryHi-Solid Polyester Bake Enamel
Air Dry Alkyd Lightly sand all surfaces to be topcoated with 320 Hi-Solid Polyamide Epoxy grit or finer sandpaper. Wipe all surfaces with a clean
isopropyl alcohol impregnated cloth. Allow the solvent to flash dry for 5 minutes and apply the finish asdirected by the paint supplier.
If the topcoat material does not appear in the table, consult Rittal.
Physical Properties Of Non-Metallic MaterialsTable 7 provides technical data for assistance in evaluatingnon-metallic enclosures and selecting the materials usedwith Legacy fiberglass enclosure accessories. Additionalconsiderations for inclusion in the fiberglass enclosurespecification are:• The resin system shall be pigmented grey unless
otherwise specified.• The resin system shall include a flame retardant to obtain
a flammability rating which meets UL 94-5V.• The heat distortion temperature shall be at least 350°F.
• Standard cover screws shall be stainless steel or stainlesssteel with fiberglass encapsulated heads. Other hardwareitems such as hinges and latches shall be stainless steelor fiberglass construction.
• External mounting feet shall be molded or securelyattached to the enclosures to provide a corrosion resistantsurface mounting system.
— no test data availableK = 1000N/A not applicable
all materials are UL listed
Table 7. Physical Properties Of Non-Metallic Materials
Technical InformationNon-Metallic Properties
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Technical InformationNon-Metallic Properties
Enclosure Load CapacityLarge control enclosures can support 200 lbs of equipmenton the back panel. Smaller junction and instrumentationenclosures should be limited to 75 lbs. Listed valuesassume the enclosure is vertically mounted against areasonably flat surface and are based on a minimum safety factor of two.
Maximum Temperature RatingThe deflection temperature* of polyester fiberglass rangesfrom 375-500°F. Rittal has conducted tests on enclosures atsustained temperatures of 350°F. Polyester fiberglass is ahigh temperature material compared to other polymerssuch as PVC, polycarbonate or engineered thermoplastics.In elevated temperature applications, the highesttemperature an enclosure can withstand depends on othercomponents used in the finished product. Such items asPVC air vents, and special gaskets must be consideredwhen establishing a temperature limit for both fiberglassand metal enclosures. Many times this issue is neglected orminimized when rating the product.
Sunlight (UV) ResistanceIn time, sunlight may roughen the fiberglass enclosuresurface, but its electrical and mechanical properties remainunaffected. Surface roughening caused by UV exposure isa common phenomenon encountered with virtually allfiberglass products, but it only affects surface appearance.Tests have confirmed the effect on polyester fiberglass isonly 40 to 80 microns (0.0015"-.003") in depth. Ifappearance is a concern, an outdoor acrylic paint (clear orpigmented) will provide protection for many years. Mostacrylic paints in ordinary spray cans work well.
Drilling, Sawing, Cutting and PunchingInstallers find fiberglass easy to cut or drill. Ordinary drills,hacksaws, hole saws and punches cut through fiberglasswith little effort. In large installations requiring many holes,glass abrasion may cause tools to become dull over time.Carbide tip tools work best for such applications. Formaximum accuracy, routing of openings is recommended.
Impact ResistanceRittal’s Legacy fiberglass enclosures are quite resistant todamage caused by falling tools or flying debris. Whentested in accordance with UL Standard 746C, Section 24,these fiberglass enclosures withstood an impact in excessof 216 pound/inches. The test was performed by droppinga 2" diameter solid steel ball on various areas of theenclosure from a height of 15 ft. The impact force from sucha test is comparable to dropping a large wrench from 3 or 4 ft. The durability results from randomly oriented glassreinforcing fibers incorporated in all designs.
*Deflection temperature: The temperature when a material will deflect(distort) under a flexural load of 264 psi. See ASTM D 648.
Integrity of the enclosure was not compromised
LEGACY FIBERGLASS ENCLOSUREIMPACT TEST
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Introduction Electronics, and especially micro-electronics, have made modernproduction technology more efficient.But ever smaller electronic componentsand increasingly dense packaging inenclosures have also made these complex systems more sensitive to external influences such as temperature, dust, oil, and humidity.
This can cause problems because thefailure of just one electronic componentmay lead to the complete shutdown ofan entire assembly line. Resultant costsquickly add up.
Heat especially is the number oneenemy of sensitive micro-electronics.
A rule of thumb says that the average lifespan of semi-conductors is cut in halfevery time the operating temperatureincreases 20°F (11°C) over its maximumoperating temperature. Yet, hightemperatures in enclosures can hardlybe avoided because electric equipmentsuch as transformers, power distribution components, programmable controllers,and electronic components all generateheat, also known as power loss.
Power related temperature swings in anenclosure or electronic housing can alsobe considerable. These swings causestress and premature aging of electroniccomponents which in turn lead topremature failure.
As mentioned, correct functioning ofelectronic systems and problem freeoperation of entire assembly linesdepends to a great degree on removingthe heat that is generated in enclosuresor electronic cabinets. In principle, thereare three different ways in which heatcan be dissipated: conduction, convection, and radiation.
Climate ControlHeat Removal From Enclosures
With conduction, matter itself movesheat, without itself moving, energy ispassed on from molecule to molecule.
With convection, heat is moved througha medium (another material such as agas or a liquid), the medium absorbsenergy in the form of heat and releasesenergy as heat.
With radiation, heat is transferred fromone body to another in the form ofradiation energy, without any physicalmatter in between.
Conduction and convection play animportant role in enclosures and electronic cabinets; radiation is not a big factor.
An important criterion for heat removal from enclosures is whether theenclosure is an ‘open’ (air can freelystream through) or ‘closed’ (air-tight)system. While heat naturally dissipatedfrom the inside of an ‘open’ enclosurethrough a flow of air, heat can only bedissipated from a ‘closed’ systemthrough the walls and roof.
20 30 40 50 60 70 80 900.1
1
10
100
°C
Year
s
°C = Component temperatureYears = Life span
Relationship between electronic componentlife and temperature
Integratedcircuit
Electrolyticcapacitor
Climate ControlHeat Removal From Enclosures
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Specification Fundamentals To properly determine the specifications of climate control components, a few simple calculationshave to be made. The following termsare used: • Qv [Watt]: total power loss (heat loss)
of all electric and electroniccomponents that are installed in theenclosure.
• Qs [Watt]: heat dissipation, orabsorption, through the outside surfaces of the enclosure (per VDE 0660, part 500). When the temperature inside the enclosure ishigher than the ambient temperature (Ti > Tu), heat will beradiated from the enclosure (Qs > 0).When the temperature inside theenclosure is lower than the ambienttemperature (Ti < Tu), the enclosurewill absorb heat from its environment (Qs < 0).
• Qe [Watt]: required cooling capacityof a climate control component; thisis the amount of heat a componentmust remove from the enclosure.
• QH [Watt]: required heating capacityof an enclosure heater.
• Ti [°C]: maximum allowable temperature inside the enclosure perthe electronic component manufacturer - usually between +35°C and +45°C.
• Tu [°C]: maximum ambient temperature at which all electroniccomponents inside an enclosure orelectronic cabinet should performfaultlessly.
• V [m3/h]: required air displacementfor a filter fan.
• A [m2]: exposed enclosure surfaceaccordance with DIN 57 600, part500 or VDE 0600, part 500.
• K [W/m2K]: heat transfer coefficientof an enclosure: sheet steel - 5.5 W/m2K plastic - 3.5 W/m2K
Calculation of exposed enclosure surface
Special attention should be paid to the total exposed enclosure surface because heat loss dissipated from the enclosuredepends not only on its actual value,but also on the enclosure’s location.An enclosure that stands all by itself inthe middle of a room can dissipatemore heat than an enclosure that isplaced next to a wall or in a corner. For that reason there are specialdirections on how the total exposedenclosure surface should becalculated depending on its location.These formulae for the calculation of A(see table above) are specified in DIN57 660, part 500 or VDE 0660, part500. (see table)
Inherent convection
Inherent convection is the dissipationof heat through the enclosure walls.For this to happen, the ambient temperature must be lower than thetemperature in the enclosure. Themaximum temperature increase (∆T) max that can occur as against the ambient temperature can be calculated with the following formula:
(∆T)max=Qv
Note:
When the heat loss within an enclosure is unknown, but the actualambient temperature Tu and the temperature Ti inside the enclosurecan be determined, the actual heatloss can be calculated with the following basic formula:
Qv = A.k .∆T [Watt]
This measurement must be taken withthe enclosure sealed and no fans, heatexchangers or air conditioners operating.
k.A
Climate ControlHeat Removal From Enclosures Climate ControlHeat Removal From Enclosures
■ Single enclosure,freestanding
▲Single enclosure,against a wall
✚ First/last enclosure ofa suite, freestanding
Location of enclosure per VDE 0660, part 500
◆ First/last enclosure of asuite, against a wall
♠ Enclosure within a suite,freestanding
★ Enclosure within a suite,against a wall
● Enclosure within a suite,against a wall, withcovered roof
Location per VDE 0660/500 Formula for calculation of A [m2]
■ A=1.8 x H x (W+D) + 1.4 x W x D
▲ A=1.4 x W x (H+D) + 1.8 x D x H
✚ A=1.4 x D x (H+W) + 1.8 x W x H
◆ A=1.4 x H x (W+D) + 1.4 x W x D
♠ A=1.8 x W x H + 1.4 x W x D + D x H★ A=1.4 x W x (H+D) + D x H
The Need For Climate ControlWhen the expense of electronic and electrical components and the costly implications of a system’s down time areconsidered, it is important that all reasonable steps are taken to ensure thatsteady and reliable performance of a system continues. This should, in almost allcircumstances, include climate control —cooling and/or heating.
The Purpose Of CoolingElectronic and electric equipment oftengenerate a great deal of heat during operation. Frequently located in hostileenvironments, the equipment may alsoencounter the additional problem of nothaving safe, clean air available to dissipate
unwanted heat. Such adverse conditions affect the performanceand the life expectancy of electrical/electronic system components.
Rittal cooling devices are preciselydesigned to solve the problems ofinternal heat build-up abovecomponent tolerances, excessiveambient temperatures, moisture andcontaminant laden atmospheres andcorrosive environments, which canaffect sensitive electronic equipment.A little time and effort spent early inthe design process can save a greatdeal of trouble and expense later bypreventing the need to retrofit withproper cooling devices in the fieldduring a down time situation.
To: Rittal Corporation Tel: (937) 399-0500 Date:1 Rittal Place Fax: (937) 390-8392 Page 1 of:Springfield, Ohio 45504 e-mail: [email protected] Control GroupApplications Engineer
Company Address:
Contact Name: Tel: Project Name/Number:
Title: Fax:
Application Questionnaire1. What is the maximum ambient air temperature? °F
2. What is the maximum allowable internal enclosure temperature? °F
3. What is the size and mounting style of the enclosure to be heated or cooled? H W D Mounting: (freestanding, wall, suited)
4. a: What is the measured temperature difference between the outside and inside of the enclosure with the door closed and any vents or openings sealed °F
or
b: How many Watts or BTUs of heat is given off by the equipment inside the enclosure?
5. At what voltage and frequency is the climate control device required to operate? Voltage and Hz
6. Is chilled water available for use in conjunction with an air/water heat exchanger? If no, is a chilled water cooling system a viable option?
7. Is there a specific NEMA or approval rating that the climate control equipment needs to comply with? NEMA UL CE CSA
8. Estimated project commercialization date
9. Estimated annual climate control product volume units/year
10. Special requirements or considerations
Request For Climate Control Application Information
Information NeededFor Climate ControlSelectionThe following information should beon hand to properly size cooling products: (1) Heat to be dissipated (Watts) by
the electrical components insidethe enclosure
(2) Maximum temperature expectedoutside enclosure (°F)
(3) Maximum allowable internalenclosure temperature (°F)
(4) Enclosure dimensions(5) Mounting portion of enclosure, i.e.
against wall, freestanding, in asuite of enclosures, etc.
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FIGURE 1 - Forced Convection Method
Pressurized System - pushesair through enclosure
AmbientAir
Ambient Airwith Heat Load
Fan orBlower
Cabinet
Outlet louvers
Climate ControlGeneral Selection Considerations
Three Basic Cooling MethodsWhen selecting a cooling method there are three types to consider.
(1) Passive Ventilation - If there is only a minimal heat gain in your circumstance and the ambient air is relatively cool and clean,then the use of louvers or grilles with filters can be effective. This method, however, usually provides less cooling effect than isnecessary with today’s components. The temperature rise within a sealed enclosure is seen in Figure 2.
(2) Forced Convection Air Cooling - If the installation will be in a clean, non-hazardous environment with an acceptable ambient(outside the enclosure) temperature range, a simple forced-air cooling system utilizing outside air is usually adequate.Combined with an air filter, such devices generally meet the heat removal needs of typical electronic equipment and many electrical applications (Figure 1). Examples of forced convection air cooling are filter fans, pagoda roof fans, fan trays, andblowers of various types.
Fans And Blowers Can Be Used To Pressurize (Preferred) Or Exhaust CabinetAir. The Ambient Air Should Be Filtered Before It Enters The Cabinet.(3) Closed-Loop Cooling - In harsh environments involving high temperatures, wash-down requirements, heavy particulate matter
or the presence of chemicals capable of damaging components (NEMA 4 or 12 environments), ambient air must be kept out ofthe enclosure. Closed-loop cooling consists of two separate circulation systems. One system, sealed against the ambient air,cools and recirculates the clean cool air throughout the enclosure. The second system uses ambient air or water to remove anddischarge the heat. Examples of closed-loop cooling equipment employed with electronics and process controls are heatexchangers and air conditioners. Blowers are used in higher static pressure applications (when internal equipment is denselypacked), and are at maximum efficiency when operating near their peak static pressure.
Filter Fan Airflow
Air/Air Heat Exchanger Airflow
Air ConditionerAirflow
Pagoda Roof Fan Airflow
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Climate ControlTechnical Information
This temperature graph was developedthrough empirical testing using severalenclosures of various sizes.
The temperatures represent an averageof one temperature measurement nearthe bottom of the enclosure and asecond measurement near the top.Electric heaters mounted equidistantfrom the internal surfaces of theenclosure were used as the heatsource. Because hot air rises, a significant temperature gradientoccurred from top to bottom. Typical ofan actual installation, the top was muchhotter than the bottom.
The placement of internal parts canaffect temperature and enclosuresshould be sized liberally in applicationswhere temperature rise is critical.Recall that a larger enclosure with twice the surface area reduces the temperature rise by 50%.
Exterior surface finishes significantlyinfluence temperature rise in outdoorapplications. For example, paintedsteel and fiberglass enclosures dissipate heat better than unfinishedaluminum enclosures, even though aluminum has superior thermal conductivity, because the colored surfaces of fiberglass and painted steelenclosures are more efficient thermalradiators than unfinished aluminum.Painted surfaces have an emissivity of0.96 whereas an unfinished aluminumsurface has an emissivity of 0.45. Inoutdoor applications light coloredenclosures have a high reflectancewhich minimizes solar heat gain whiledissipating internally generated heat atabout the same rate as a similar sizedark colored enclosure.
FIGURE 2. - Internal Temperature Rise vs. Internal Heat Load
GRAPH ASSUMES ENCLOSURE ISMOUNTED VERTICALLY AGAINST ACEMENT WALL SURROUNDED BY STILLAMBIENT AIR.
NOTE:TO CONVERT GRAPH TEMP TO CELSIUS MULTIPLY DEG. F BY 0.55
INTERNAL HEAT LOAD IN WATTS / SQ. FT. SURFACE AREA
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Climate ControlTechnical Information
Additional Cooling Methods
When it has been determined thatthe heat load is too large for anenclosure to dissipate by radiationand convection, the following supplemental cooling methods are available:
Louvers And Special VentilationSlots
Louvers and special ventilation slotsare designed to remove heat fromthe enclosure by allowing natural aircirculation around the heat sourceand exhausting the hot air throughslots or louvers. This method is relatively inexpensive and has nooperating cost; however, it can onlybe used to dissipate a limitedamount of heat and it is difficult topredict the temperature drop produced by a vent utilizing naturalconvection. This method should notbe used in areas where contaminantswill enter the enclosure.
Circulating Fans
In larger sealed enclosures, a fan can be used to circulate the air and reduce localized heat concentrations; however, the applications are limited because aclosed system fan only redistributesheat, it does not remove the heatgenerated by the hot spot.
Where an enclosure does not need to be sealed from the outsideenvironment, fans can be used to circulate air through an enclosureand dissipate the heat generated bypower supplies, transformers andother heat producing equipment.Fans can provide as much as 10times the heat transfer rate of naturalconvection and radiation. Once theheat input in watts/ft2 is determinedand temperature rise is establishedfrom Figure 2, the following equationcan be used to calculate the fan flow rate:
Fan Flow Rate (cfm) = 3.17 x Internal Heat Load(watts)/Temperature Rise
Example
Equipment in an E 363612 enclosure generates sufficient heat torequire a fan which will dissipate 300watts. The maximum ambienttemperature in the applicationenvironment is 115°F. If the temperature of the other contents inthe enclosure cannot exceed 125°F,what size fan is required?
The allowable temperature rise is 125°F - 115°F = 10°F. The application requires dissipation of 300 watts.
Solution
To determine the cubic feet perminute (cfm) required in a standardapplication, use the followingequation (if the air density issignificantly more than 0.075 lb. percubic foot, a non-standardapplication exists and this equationshould not be used):
Fan Flow Rate (cfm) = 3.17 x 300watts/10°F
Fan Flow Rate (cfm) = 95 cfm
This calculation is exact, but addingan additional 25% capacity to thelevel is standard to provide a safety factor.
1.25 x Fan Flow Rate (cfm) =
1.25 x 95 cfm = 119 cfm
If the air density is non-standard(significantly more than 1.075 lb. percubic foot), the following equationcan be used to calculate the fancapacity:
Fan Flow Rate (cfm) x 0.075 lb. percubic foot / Non-standard Air Density(lb. per cubic foot)
Fans can be used to draw air throughan enclosure and exhaust hot air froman enclosure or to draw cool air intoand circulate it through an enclosure.An inlet fan offers the following advantages:
• Raises the internal pressure which helps keep dust and dirt out of an unsealed or frequently open enclosure.
• More turbulent air flow improves heat transfer.
• Longer fan life in cooler incoming air.
The following considerations are important in locating a fan:
• Avoid placing transformers, power supplies or other heat generating devices in front of the fan. Although this cools the device, it increases the heat load on other devices within the enclosure. It is best to place these devices near the exhaust outlet.
• To achieve maximum cooling, the inlet and outlet should be separated by the maximum distance. If the outlet and inlet are adjacent to each other, the hot outlet air will be drawn into the inlet and cooling efficiency will be reduced. In general, the inlet should be at the bottom of the enclosure and the outlet at the top.
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• Fans should not be used or located in areas where the air flow is restricted. A plenum isrecommended to accelerate air velocity and improve fan performance. A plenum is particularly helpful when a filter is used where airborne contaminants are a problem.
• The air outlet area should at least equal the inlet area. For best results the exhaust opening should be 1.5 times the area of the fan opening.
• Air is less dense at high altitudes. For this reason air flow should be increased in high altitude applications.
• All fans used in parallel should be identical.
Heat Exchangers - Cooling
Applications requiring sealed enclosures present the greatest needfor cooling to maintain safe operatingtemperatures. Heat exchangers are agood option when precise control ofheat and humidity are not required andthe heat transfer requirements are significant. The required heat exchanger capacity can be calculated using the formula,
Heat Exchanger Capacity (watts/°C) =(Internal Heat Load T + 5.5w/m2-C xEnclosure Surface Area x ∆T) where ∆T = Temperature Rise.
Example
If the internal heat load is 1000 watts in an E 603620 freestanding steelenclosure, what is the minimum coolingcapacity for the heat exchanger unit?The maximum ambient temperature is105°F and the internal equipment willmalfunction if the internal enclosuretemperature exceeds 130°F.
Internal Heat Load = 1000 watts
Maximum Temperature Differential = Ti -To = 105°F - 130°F = -25°F = -14°C, useAbsolute Value.
Climate ControlTechnical Information
Enclosure Surface Area = 56.7 ft2 =5.3m2 from Table 1.
Heat Exchanger Capacity = (1000 - 5.5 x 5.3 x 14)/14 =42w/c
In this example, the surface areaacts to cool the enclosure and issubtracted, the AbsoluteTemperature Value is used becausethis is a temperature difference.
Air Conditioning - Cooling
Air conditioning will be required inhigh ambient temperature locationswhere precise temperature control and humidity reduction are required in a sealed enclosure.Air conditioning can also be requiredwhere neither convection, thermalradiation, louvers, slots nor acirculating fan system provideadequate cooling. Because air conditioners remove moisture fromthe enclosure, a condensate drain isgenerally required.
The four step process to size and select the air conditioner isinfluenced by the internal heat load,enclosure size and the applicationenvironment. The followinginformation is required:
Step 1. Determine the InternalHeat Load
Heat generated by all sources within the enclosure shall be addedtogether to establish the internal heatload in watts. The heat load in wattsmay be multiplied by 3.413 toconvert to BTU/hr.
Internal Heat Load ______________watts X 3.413 BTU/hr/watt =_____________ BTU/hr.
Step 2. Calculate the Surface Area of the Enclosure
The enclosure surface areacalculation is made in Table 1 usingformulas.
The surface area for an enclosurewith a height (H = 16 in); a width (W= 20 in); and a depth (D = 8 in); is:
Surface Area = [1.8(16 x 20) + 1.8(16 x 8) + 1.4 (20 x 8)]/144in2 = 7.2 ft2
= 0.67n2
Using the H, W and D dimensions,select the appropriate formula andcalculate the surface area for yourenclosure application:
H = _______
W =_______
D = _______
Surface Area = _____________n2
Step 3. Establish the Temperature Differential
The temperature differential (∆T) iscalculated by subtracting the maximum allowable temperatureinside the enclosure (Ti) from themaximum ambient temperature outside the enclosure (To).
To - Ti = ∆T = _________°C
Step 4. Calculating the RequiredAir Conditioning Capacity
The values determined in the firstthree steps are used to calculate the required capacity of the air conditioner according to the following formula,
Cooling Capacity (BTU/hr) = SurfaceArea x ∆T x K + Internal Heat Load,
whereK = 1.25 BTU/hr/ ft2 /°F (5.5w/m2-K)for sheet metal enclosures.
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Enclosure Heating
Some enclosure systems have minimum as well as maximum operating temperature limitations.When the equipment in an enclosure must be maintained above a minimum temperature at lowambients, these same equations canbe modified and used to calculatethe supplemental heat required toselect and size the heaters. The onlydifferences are that the internal heatload will help heat the enclosure andthe temperature difference, ∆T, is calculated by subtracting the minimum ambient temperature (To) outside the enclosure from therequired temperature (Ti) inside the enclosure. The minimum supplementary heat can be calculated according to one of the following equations:
∆T = Ti - To
Supplementary Heat =Surface Area x ∆T x K where K = 0.37 watts/ft2 °F
Example
If the internal heat load is 100watts in an E 162008 steel enclosure, which is wallmounted,what is the minimum heatingcapacity for the heating elements?The minimum ambient temperatureis 0°F and the internal equipmentwill malfunction if the internalenclosure temperature dropsbelow 40°F.
∆T = Ti - To = 40°F - 0°F = 40°F
=
6.27 ft2 x 40°F x 0.37 watts/ft2 °F = 93 watts
In addition to heating, supplementaryheaters are often used in enclosures tokeep the internal enclosure ambienttemperature a few degrees above the ambient temperature to preventcondensation on internal equipment.
Equipment for Climate Control
Most cooling or heating requirementscan be calculated from the data in this section and the climate controlequipment. If you have a problemdetermining your cooling or heatingrequirements or selecting the climatecontrol equipment, please contact Rittal.
Rittal’s thermal sizing software, Therm3.0 for Windows, automatically makescalculations for you.
Climate ControlTechnical Information
1. Underestimating maximum ambient temperature Undersized cooling device — system failure
2. Not considering effect of temperature on performance of Undersized cooling device — system failurean air conditioner
3. Not derating fan performance for inlet grills, filters, system Undersized cooling device — system failureimpedance, etc.
4. Not considering convective heat loss or gain Improperly sized cooling device
5. Not accurately estimating component heat loss Improperly sized cooling device
7. Placing cooling device inlets/outlets too close to Reduced performanceobstructions
8. Not specifying necessary filters & maintenance schedule for Reduced performancedirty environments
9. Not specifying corrosion protection for corrosive System failureenvironments
10. Inadequate warning system in the event of cooling failure Machine shutdown/system failure
Pitfall Effect
10 Common Pitfalls During Thermal Analysis/Design
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Energy efficient design All Rittal air conditioners come standard with thermostatic expansion valves that operate more efficiently than the expansion devices found on most competitors’ units. This can save the end user over $100 per year per air conditioner. Environmentally friendly technologyOur air conditioners come standard withR-134a refrigerant, which is not a CFC or a HCFC. We were the first to convert R-134a and is still the only company with 100% of its product line using thistechnology.Reliability/safety Our air conditionerscome standard with pressostats helpingprotect against compressor failure.Evaporator housings are insulated to maximize efficiency and minimize condensation. CE compliances also meetnew standards for products exported toEurope.Low maintenance condensor coilsRittal’s wider condensor fin spacing meansless likelihood of dirt clogging, and loss ofcooling performance.Long life fans & compressors All Rittalair conditioners come with long-life ballbearing type radial fans. Compressors arethermally protected.Advanced microprocessor controlAn advanced microprocessor controloption allows you to monitor theperformance, pinpoints maintenanceneeds, and enables remote monitoring.Installation Rittal’s air conditioners areeasily and quickly mounted. Terminalblocks offer quick and easy wiring.Availability/spare parts Rittal has fivedistribution centers across the U.S., aswell as a broad distributor network, forquick access to inventory and spare parts.Air conditioner repair and disposalRittal has a repair facility in Springfield,OH. We also offer customers refrigerantrecovery and disposal services and on-site repair service.Broad variety of voltages availableRittal offers 115V, 230V, 400V, and 460V 50 Hz and 60 Hz air conditioner models.Special features such as stainless steelhousings, environmentallly protected coils,Class 1 Div 2 explosion proof upgradesare available.Regulatory Compliance We meet globalregulatory requirements such as UL, cUL,GS, CE.
Advantages-At-A-GlanceAir Conditioners
Practical Hints Rittal air conditioners offer the rightsolution whenever optimum operatingconditions inside an enclosure arerequired. Even with high ambient temperatures is it possible to cool theenclosure’s internal temperature downto well below the ambient temperature. In terms of airflow technology the favorable arrangement of air intake and exhaust openings for the internaland external air circulation loops,ensures optimum air circulation in the enclosure. The following example shows how toquickly and accurately calculate thespecifications for an enclosure air conditioner. The fo!lowing should be taken into consideration: • Where will the enclosure be located
(dust or oil-laden air)?
• What type of location is specified perVDE 0660, part 500?
• What conditions must be anticipated(e.g. ambient temperature andhumidity)?
• What is the heat loss Qv in the
enclosure?
• What is the max. required interiortemperature Ti for the enclosure?
• Is a specific NEMA or IP (per DIN 40050) protection rating required?
• What voltage is available for air conditioner operation?
• In enclosure suites, it will benecessary to also take into accountthe heat which may have beenabsorbed from adjacent enclosures.
• Air conditioners should always be connected via door limit switches toavoid excessive condensation.
• Enclosures and air conditionersshould be located and placed sothat there is sufficient space for airintake and exhaust.
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How To Determine The Sizing For A Wallmounted AirConditioner, For The Bold Values:
▼
Enclosure dimensions:H = 2000mmW = 600mmD = 500mm
Ambient temperatureoutside the enclosure in °C
Temperature requiredinside the enclosure in °C
Heat transfer coefficientof an enclosure:sheet steel ~ 5.5 W/m2Kplastic ~ 3.5 W/m2K
Heat loss in Watts
A 4.4
Tu= +50
Ti= +35
k = 5.5
QV= 700
Calculate theeffective enclosure
surface
Calculate thetemperature differential
∆T = Ti – TU
Enter the applicable
heat transfercoefficient
Enter the
heat loss
Requiredcooling capacityQE =
Now calculate therequired cooling capacityQE = QV – k • A ∆T
A = 4.4
∆T = -15
k = 5.5
QV = 700
Watt 1063
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Advantages-At-A-GlanceAir Conditioners
• Air conditioners should be positioned such that air intakes and outlets have at least 8" of clearance from obstructions.
• The enclosure should be sealed to a NEMA 12 standard to avoid condensation.
Condensation and dehumidificationof enclosure air when air conditioners are used
When air conditioners are used, dehumidification of the internal enclosure air is an unavoidable sideeffect. During the cooling process, a part of the moisture in the air condenses at the evaporator and mustbe removed from the enclosure. Thequantity of condensate depends on therelative humidity, the air temperature atthe evaporator as well as on the volumeof air inside the enclosure.
The diagram on this page (also calledthe ‘Mollier h-x diagram’) specifies theamount of water in the air, contingenton its temperature and relative humidity.
Example:
A model 3293100 air conditioner is setat Ti = 35°C. The relative humidity of theambient air is 70%. The surfacetemperature of the evaporator isapprox. 18°C - the evaporation temperature of the refrigerant. When airof 35°C is blown over the evaporator tobe cooled down condensate will format the surface of the evaporator. The difference x = x1- x2 indicates howmuch condensate per kg air wouldaccumulate if the air were completelydehumidified. A deciding factor for theamount of condensate is how well theenclosure is sealed off from its environment.
The volume of condensate can be calculated with the following formula:
W=V · p · ∆x
where:
W= Quantity of water [g]
V= Volume of the enclosure [m3]
p= Density of air [kg/m3]
∆x= Dehumidification [g/kg dry air]per the Mollier h-x diagram
When the enclosure door is closed, only the air within the enclosure will be dehumidified and there will be considerably less condensate than withan open door.
V= H · W · D= 2m · 0.6m · 0.5m
V= 0.6 m3
W= V · p · ∆x=0.6 m3 · 1.2 kg/m3 · 11 g/kg
W= 7.92 g ≈ 8 ml
Poorly sealed cable entries, damageddoor gaskets, and unsealed installation ofdisplay screens etc. on enclosures cancause air leakage from the enclosure toincrease. If air was leaking from an enclosure at a rate of only 3 cfm, condensate would accumulate at the rate of 3 oz/h.
Conclusion
• When the air conditioner is operatingthe enclosure door should always beclosed.
• The enclosure should be sealed on allsides.
• Door switches should be used.
• Air conditioner should meet DIN andEN standards.
• Set temperature only as low as required(Typically 95°F).
Sizing For The Air ConditionerThe calculations have specified the required coolingcapacity QE = 1063 W for an ambient temperatureTU = 50°C and a required interior enclosuretemperature Ti = +35°C.
From the available Rittal air conditioners we selected wallmounted model 3298100 with a cooling capacity of 1100 Watt (see performancediagram above).
Tu= Ambient temperature (°C)Qk= Cont. refrigeration capacity (W)Ti= Internal enclosure temperature (°C)
Pd= Partial water-vapor pressure (mbar)T = Temperature of air (°C)x = Water content (g/kg dry air)
Mollier h-x diagram to determine thewater content of air
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Reliable and durable All Rittal heatexchangers are known for their durabilityand long life radial fans.
Easy maintenance They are equippedwith filterless operation for quick maintenance with the easily removablecassette.
Installation All Rittal heat exchangershave simple and clean installation, andno mounting flange is necessary.
Special features Although our heatexchangers are lightweight, they are builtwith very strong construction.
Regulatory compliance Rittal heatexchangers meet global regulatoryrequirements such as UL, cUL, VDE, CE.
Advantages-At-A-GlanceAir/Air Heat Exchangers
Practical Hints When ambient temperature is considerably lower than the temperature required inside the enclosure, air/air heat exchangers arethe climate control component ofchoice especially if the ambient aircontains dust, oil and aggressivechemicals that should not enter theenclosure.
Because of separate interior and exterior air circulation loops, outside air can not enter into the enclosure.
The following should be taken into consideration:
• What ambient temperatures Tu canbe expected?
• What is the required interior temperature Ti inside the enclosure?
• What is the total heat loss of components inside the enclosure?
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How To Determine The Sizing For An Air/Air Heat Exchanger, ForThe Bold Values:
▼
Enclosure dimensions:H = 2000mmW = 600mmD = 500mm
Ambient temperatureoutside the enclosure in °C
Temperature requiredinside the enclosure in °C
Heat transfer coefficientof an enclosure:sheet steel ~ 5.5 W/m2Kplastic ~ 3.5 W/m2K
Heat loss in Watts
A 4.4
Tu= +25
Ti= +35
k= 5.5
QV= 900
Calculate theeffective enclosure
surface
Calculate thetemperature differential
∆T = Ti – TU
Enter the applicable
heat transfercoefficient
Enter the
heat loss
Requiredcooling capacityqW=
Now calculate therequired cooling capacityqW = QV – (A • ∆T • k)
A = 4.4
∆T = +10
k = 5.5
QV = 900 W/K 65.8
Sizing For An Air/Air Heat ExchangerWhen the parameters for enclosure surface A,temperature differential ∆T, and heat loss QE havebeen calculated, the required heat exchanger canbe determined.
Air/air heat exchanger model SK 3131000 with aspecific thermal capacity of 42 W/C most closelymeets the requirements.
∆T
▲
▲
▲
3020100 30 50 60 70 80
121086420
A
30
40
50
6070
∆T
qWQV
100020003000
25 20 15 10 5 0
∆T= Temperature differential (K)Qv = Heat loss (W)qw = Specific heat output (W/K)A = Enclosure surface per VDE 0660
part 500 (m2)
Selection diagram for air/air heat exchangers
• How much heat, Qs, isradiated from the inside of theenclosure - through the walls to the environment?
• Is enough space available to install an air/air heat exchanger?
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Reliable And Durable All Rittal heatexchangers are known for their durability and long life radial fans.
Safety These air/water heat exchangers are equipped with suchsafety features as overtemperaturealarm contact, solenoid valves, waterlevel sensors, and overflow drainagepaths.
Easy Maintenance They perform wellin dirty or oily environments, without theneed to clean filters, cassettes, or coils,and require only 1-2 gal/minute ofwater.
Special Features While the exchangers offer low energy consumption, they also help maintain low capital cost.
Regulatory Compliance Rittal heatexchangers meet global regulatoryrequirements such as UL, cUL, VDE, CE.
Advantages-At-A-GlanceAir/Water Heat Exchangers
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How To Determine The Sizing For A Wallmounted Air/Water HeatExchanger, For The Bold Values:
▼
Enclosure dimensions:H = 2000mmW = 600mmD = 500mm
Ambient temperatureoutside the enclosure in °C
Temperature requiredinside the enclosure in °C
Heat transfer coefficientof an enclosure:sheet steel ~ 5.5 W/m2Kplastic ~ 3.5 W/m2K
Heat loss in Watts
A 4.4
Tu= +50
Ti= +40
k= 5.5
QV= 1300
Calculate theeffective enclosure
surface
Calculate thetemperature differential
∆T = Ti – TU
Enter the applicable
heat transfercoefficient
Enter the
heat loss
Requiredcooling capacityQE =
Now calculate therequired cooling capacityQE = QV – k • A ∆T
A = 4.4
∆T = -10
k = 5.5
QV = 1300Watt 1542
Sizing For An Air/Water HeatExchangerBecause we know that the water temperatureis + 10°C and that the water flows at a rate of200 l/h we have specified a model SK3247000 air/water heat exchanger with a cooling capacity of 1800 Watt which exceeds the required cooling capacity QE = 1542.
Vw=200l/hVw=150l/hVw=100l/h
Performance diagram SK 3247000(DIN 3168) (50/60Hz)
Tw= Water entry temperature (°C)Qx= Cooling capacity (W)Ti= Internal enclosure temperature (°C)
Tw
Qx
50°C
40°C
30°C
20°C
Practical Hints Air/water heat exchangers offer the greatest cooling performance in thesmallest available space.
• With a Rittal air/water heat exchanger, the temperature insidethe enclosure can be cooled down tobelow the ambient temperature.
• They can be used in ambient temperatures up to 158°F (70°C).
• Air/water heat exchangers areextremely practical in dirty environments.
• Water as warm as 70°F can be used. • Minimum service required because
there are no filters to exchange andthere is no direct contact with theambient air.
• They are available in wall and roofmounted versions.
Special features The air throughput inour filter fans has high cfm in a given size.
Reliability and safety NEMA 12 isachievable when using filter fans.
Installation Rittal’s filter fans are easilyand quickly mounted with the quick snap-in feature, requiring no screws or tools.
Aesthetics all of the filter fans are available with a thin louver profile.
Broad variety of voltages availableRittal offers 115V, 230V, 24V DC filter fan models to meet the spectrum ofglobal needs.
Environmentally friendly technologyRittal filter fans have a special EMC capability that is available with an off-the-shelf EMI/RFI shielded version.
Practical Hints When the ambient air is clean and theambient temperature is considerablylower than the temperature requiredinside the enclosure, Rittal filter fansshould be used to remove heat frominside the enclosure.
The design of the venting louvers ofRittal filter fans ensures unsurpassedstability of air volume as far as pressureloss is concerned; it also provides perfect contact hazard protectionagainst water.
A NEMA 12/13 (IP54) protection ratingcan be achieved when a sealing frame and fine filter are used (see accessories).
Advantages-At-A-GlanceFilter Fans
Installation tips
The way in which filter fans are installedin an enclosure, depends on the waycomponents are installed in the enclosure.
• Filter fans and exhaust filters shouldbe installed on the enclosure so thatthe air intake is at the bottom and theexhaust is at the top.
• Air flow within the enclosure isreversible: (suction or blowing).
• Since a fan’s filter will become dirty inuse, always select a larger fan thanindicated in the actual calculation.
• Use a fine filter when there are verysmall dust particles in the air.
• Install a sealing frame and fine filter when you want to increase theNEMA rating.
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How To Determine The Sizing For A Filter Fan,For The Bold Values:
Temperature requiredinside the enclosure in °C
TU = +20
Ti= +40
Calculate thetemperature differential
∆T = Ti – TU
∆T = 20
▼Heat loss in Watts QV= 800Enter the
heat lossQV = 800
Ambient temperatureoutside the enclosure in °C
▼
The following applies for thecalculation of the volume ofdisplaced air.
Sizing For A Filter Fan AndExhaust FilterWe should select a combination of a filter withan exhaust filter that can deliver an airdisplacement of at least 124 m3/h.
The performance diagram above will help usselect the proper combination of filter fan andexhaust filter.
How To Determine The Sizing For A Panel Heater,For The Bold Values:
Enclosure dimensions:H = 500mm W = 500mmD = 300mm
Ambient temperatureoutside the enclosure in °C
Temperature requiredinside the enclosure in °C
Heat transfer coefficientof an enclosure:sheet steel ~ 5.5 W/m2Kplastic ~ 3.5 W/m2K
A 3.6
Tu= +15
Ti= +20
k= 5.5
Calculate theeffective enclosure
surface
Calculate thetemperature differential
∆T = Ti – TU
Enter the applicable
heat transfercoefficient
A = 3.6
∆T = +5
k = 5.5
The required heat outputcan now be calculatedwith the followingformula:
QH = A • ∆T • k
QH = 3.6 • 5 • 5.5
Watt 99 W
Sizing For A HeaterOnce the values for the enclosure surface andtemperature differential are known, therequired heat output can be determined fromthe heater performance diagram.In this casemodel 3102000 with a heat output of 61 Watt at 10°C was selected.
High performance Utilizing PTC technology, the panel heaters operateefficiently with even heat distribution.
Reliability And Safety They have along life expectancy, while their low surface temperature ensures safe operation.
Installation All panel heaters are wiredand ready for easy snap-in or screwfastening installation.
Special Features Designed to be compact and vibration-free, panelheaters are quite powerful and sturdy.
Regulatory Compliance Rittal panelheaters meet global regulatory requirements such as UL, VDE, CE.
Practical Hints • Maximum efficiency is achieved
when enclosure heaters are installedvertically, with the cable entry at thebottom.
• A gap of 2"/50mm from the top orbottom should be allowed to develop the required convection.
• Heaters should be installed at least.4"/10mm from steel side walls and at least 1.4"/35mm from thermo-plastic materials.
• Insofar as possible, heaters shouldbe installed below the componentswhich require protection because hotair rises and will indirectly heat thosecomponents.
• In larger enclosures, even heat distribution is best achieved byinstalling several smaller heaters.
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▲
10 15 20 30 40 50 60 80 100 150 200 300 400 500
QH
30
20
15
10
∆T
7.55210
8
65
4
3
2
1.5
1
A
Heater performance diagram
QH = Required heat output (W)A = Enclosure surface area per VDE 0660, part 500 (m2)∆T= Temperature difference (K)Based on inside location, static air, heat transfer coefficient k=5.5 W/m2 K.For outdoor locations (moving air) the heat output should be doubled.
• Heaters can operate without a separate thermostat, but in order to ensure accurate air temperaturecontrol within the enclosure, installation of a thermostat is recommended.
• To avoid condensation on installedcomponents, installation of a hygrostat is also recommended.
