Hoja de Referencia del Examen · Referencia Rápida
South Carolina - Air Conditioning
South Carolina · PSI Services Contractor
Verificado, no estimado. Cada cifra a continuación proviene de la estructura oficial del examen que mantenemos: número de preguntas, puntaje de aprobación y ponderación de temas. Las preguntas de práctica están fundamentadas en la ley fuente con citas de estatutos. Omitimos cualquier cifra que no podamos verificar en lugar de adivinarla.
Total de preguntas
80
Puntaje de aprobación
70%
Tiempo del examen
240 min
Administrado por
PSI Services Contractor
Formato
Se permiten materiales de referencia
Porción Estatal de South Carolina 80 preguntas
Tuberías en General
1 Q · 1%
Gas piping system sizing methods and sizing tables (longest length, branch length, hybrid pressure)Approved piping and tubing materials for fuel gas systems (steel, copper, CSST, polyethylene, aluminum)Piping joints, fittings, and connection methods (threaded, brazed, welded, press-connect, flared)Pressure testing, leak detection, and purging of gas piping systemsPiping support intervals and protection against physical damageShutoff valves and pressure regulators in gas piping systemsHydronic piping materials, joints, and testing requirementsRefrigerant tubing types, cutting, bending, flaring, brazing, and soldering proceduresGas Piping Installations
Tubería General
1 Q · 1%
ACR copper tubing types and specifications (soft vs. hard-drawn, Type K and L wall thickness, sizing by OD)Cutting tubing procedures and tools (tubing cutter, hacksaw blade selection, squaring, reaming, and deburring)Bending tubing methods and minimum bend radius (bending springs, lever-type benders, kinking prevention)Flared connections and fittings (single and double flares, flaring procedure, SAE vs. JIC angles, flare nut sizing)Soldering and brazing procedures (flame types, filler metals, flux application, capillary action, purging with nitrogen)Swaged connections (swaging tools, overlap length, preparation for soldered or brazed joints)Non-refrigerant tubing and pipe types (copper water tubing, ABS/PVC/CPVC plastic pipe, steel pipe, joining methods)Specialized tube couplings and dissimilar metal connections (mechanical and compression fittings for aluminum-to-copper joints)Working with Tubing and Piping
Ensamblaje de Tuberías
1 Q · 1%
Types of refrigerant and non-refrigerant tubing and pipe (ACR copper, plastic, steel)Cutting, reaming, and bending tubing techniques and toolsFlared connections: single and double flare procedures and fittingsSoldering and brazing procedures, equipment, and filler materialsSwaged connections and specialized tube couplingsGas piping materials, joints, and fittings per SC Fuel Gas CodeGas pipe sizing methods, pressure drop, and allowable operating pressureHydronic piping materials, joint types, and installation requirements per SC Mechanical CodeGas Piping Installations
Sistemas de Tuberías
4 Q · 5%
Gas piping sizing methods and pressure drop calculationsApproved piping and tubing materials for gas, refrigerant, and hydronic systemsPiping joints and connection types (brazed, soldered, flared, threaded, mechanical)Refrigerant line components (filter-driers, sight glasses, liquid receivers, check valves, solenoid valves)Hydronic piping system designs and installation requirementsFuel oil piping materials, joints, and installation requirementsPiping system testing and pressure requirementsTubing cutting, bending, and fabrication techniquesGas Piping InstallationsHydronic Heating FundamentalsRefrigerant Flow ComponentsWorking with Tubing and Piping
Tuberías de Drenaje
1 Q · 1%
Condensate drain pan requirements and placement relative to cooling coilsCondensation prevention on duct exteriorsSlope requirements for drainage in underground duct installationsPlastic piping and tubing in plenums (flame spread and smoke-developed index requirements)Plumbing and mechanical products in plenums listing and labeling requirementsDuct Systems
Válvulas
1 Q · 1%
Refrigerant flow control valves: shutoff, check, and solenoid valve types and operationService valve positions and procedures: back seated, front seated, mid-position, and cracked openPressure-regulating valves: crankcase pressure regulators (CPRs) and evaporator pressure regulators (EPRs)Relief valves and safety pressure devices for refrigerant systems and cylindersMetering devices as valves: thermostatic expansion valves (TXVs), automatic expansion valves (AXVs), and electronic expansion valves (EEVs)Hydronic system valves: mixing valves, balancing valves, pressure-reducing valves, flow-control valves, backflow preventers, and zone valvesShutoff valve placement requirements in hydronic piping systems per SC Mechanical CodeGas piping valve and regulator requirements per SC Fuel Gas CodeGas Piping Installations
Especialidades de Tuberías
1 Q · 1%
Refrigerant flow control valves (shutoff, check, solenoid, and service valves)Filter-driers and sight glasses/moisture indicators for refrigerant systemsPressure-regulating valves (crankcase pressure regulators, evaporator pressure regulators, relief valves)Gas piping materials, fittings, and joint types (SC Fuel Gas Code Chapter 4)Gas piping sizing methods and pressure drop requirementsGas piping shutoff valves and appliance connectionsHydronic piping materials, fittings, and joint types (SC Mechanical Code Chapter 12)Tubing cutting, bending, flaring, brazing, and swaging techniquesGas Piping Installations
Bombas
2 Q · 2%
Circulating pump types and components (wet-rotor centrifugal pumps, impellers)Pump placement relative to expansion tankCavitation causes and effects on circulating pumpsWater circulation troubleshooting (air-bound systems, bleeding and purging procedures)Pump operation sequences in hydronic system controlsHydronic system pressure testing requirements (100 psi minimum, 15-minute duration)Shutoff valve requirements at pumps and system equipment per SC Mechanical CodeHydronic Heating Fundamentals
Aislamiento de Tuberías
1 Q · 1%
Insulation flame spread and smoke-developed index requirements (ASTM E84/UL 723)Required insulation thickness per International Energy Conservation CodeInsulation characteristics for air plenum installationsHeat loss factors for bare vs. insulated hot water and steam piping (Btuh/foot)Heat gain factors for chilled water piping insulation by pipe size and R-valueEffect of pipe location (conditioned vs. unconditioned space) on piping loadPipe heat loss calculation using temperature difference, pipe length, and insulation factorRadiant floor system insulation and thermal break requirements
Colgadores y Soportes (General)
1 Q · 1%
Duct support requirements per SMACNA standardsHanger and support spacing intervals for hydronic piping per Section 305Flexible duct and factory-made duct support per manufacturer instructionsPipe support requirements for ground-source heat pump loop systemsProtection of supported ducts from mechanical damage and weatherStructural integrity requirements for duct bracing and reinforcementDuct Systems
Control Mecánico de Sonido, Vibración y Sísmico
1 Q · 1%
Vibration isolator selection and installation for HVAC equipmentFlexible duct and pipe connections for vibration attenuationSeismic restraint requirements for mechanical equipmentSound transmission control and STC ratings in HVAC systemsNoise criteria (NC) levels for occupied spacesAcoustic duct lining and sound attenuator applicationsEquipment placement and mounting to minimize structure-borne noiseGeneral Regulations
Tratamiento de Agua para Sistemas Mecánicos
1 Q · 1%
Glycol additives and freeze protection (propylene vs. ethylene glycol, mixture ratios)Scale formation and impurity limits in boiler waterCorrosion causes and prevention (chemical scavengers, corrosion inhibitors, deaeration)Water pH requirements and embrittlement preventionInitial system preparation and boiling-out procedures (trisodium phosphate treatment)Air removal and its role in corrosion control (dissolved, free, and entrained air)Transfer fluid compatibility and flash point requirements per SC Mechanical CodeChemical compatibility of antifreeze with piping materials in ground-source heat pump systemsHydronic Heating Fundamentals
Principios de Calefacción y Enfriamiento
2 Q · 2%
Heat transfer modes (conduction, convection, radiation)Sensible heat and latent heat distinctionsThermal resistance values (R-value, U-value, K-value, C-value)Indoor and outdoor design temperatures (HTD and CTD)Heating loads: envelope conduction, infiltration, and ventilation sourcesCooling loads: solar gain, internal gains, and fenestration componentsHeat pump operating principles (heating mode and cooling mode)Compression refrigeration cycle fundamentalsHeating and Cooling Loads
Refrigerantes
1 Q · 1%
Refrigerant classification (CFC, HCFC, HFC, HFO, HC, inorganic)Ozone depletion potential (ODP) and global warming potential (GWP)Refrigerant numbering system and cylinder color codesRefrigerant toxicity and flammability classifications (ASHRAE Standard 34 safety groups)Pressure-temperature (P/T) charts and pressure-enthalpy diagramsRefrigerant phaseout schedules and EPA Section 608 requirementsRefrigerant recovery, recycling, and reclaiming procedures and equipmentSC Mechanical Code refrigerant quantity limits, machinery room requirements, and system classificationEquipment and Instruments for Refrigerant Handling and Service
Cálculos de Carga
7 Q · 9%
Heating and cooling temperature difference (HTD and CTD) calculationsThermal resistance, conductance, and U-values for building assembliesFenestration load procedures using Heat Transfer Multipliers (HTM)Opaque panel heating and cooling loads (walls, ceilings, floors, doors)Infiltration load estimation methods (ACH table, component leakage area, blower door)Duct load factors for heating, sensible cooling, and latent coolingInternal loads (occupants, appliances, lighting)Engineered ventilation sensible and latent load calculationsHeating and Cooling Loads
Equipos de Calefacción y Enfriamiento
1 Q · 1%
Heating and cooling load calculations (Manual J methodology)Thermal resistance, conductance, and transmittance values (R-, C-, U-, K-values)Indoor and outdoor design temperatures for heating and coolingGas-fired furnace components, ignition systems, and combustion efficiencyHeat pump types, components, and operating modes (air-source and ground-source)Hydronic heating system components, boiler types, and controlsOil-fired heating system operation, combustion testing, and fuel deliveryElectric heating systems, element types, and equipment sizingHydronic Heating Fundamentals
Compresores de Aire
1 Q · 1%
Compressor drive configurations (open-drive, semi-hermetic, and fully hermetic)Reciprocating compressor components and operation (pistons, crankshaft, connecting rods, valves, valve plates)Rotary compressor types (rotating-vane and stationary-blade operation)Scroll compressor operation and applicationsScrew compressor operation and capacity controlCentrifugal compressor components and operationCompressor lubrication systems (splash vs. pressure systems)Crankcase heaters and compressor cooling systemsCompressors
Pruebas, Ajuste y Balanceo (TAB)
2 Q · 2%
Airflow measurement instruments and techniques (flow hoods, anemometers, pitot tubes, manometers)Balancing damper adjustment procedures for achieving design CFM at each outletDuct leakage testing methods (duct blaster/calibrated airflow matching system) and maximum allowable leakage limitsBlower door testing procedures and ACH50 calculations for building envelope airtightnessMaximum air velocity limits for trunk ducts, branch ducts, supply outlets, and return grilles (Table N3-1)System operating point determination using blower performance curves and duct system resistance curvesDuct noise identification and correction (noise sources, carriers, and amplifiers)Duct system cleaning procedures, tools, and IAQ considerationsVentilation System Service
Fundamentos de Control HVACR
1 Q · 1%
Thermostat types and sensing elements (bimetal, thermistor, mercury switch, hydraulic)Low-voltage, line-voltage, and millivolt thermostat operation and wiringHeat anticipators and cooling anticipatorsProgrammable and digital thermostat features, programming, and Wi-Fi/smart controlsControl system fundamentals: set point, cut-in, cut-out, range, and differential adjustmentPressure motor controls (high-pressure, low-pressure, oil pressure safety controls)Motor starting relays (current relay, potential relay, solid-state relay, PTC relay) and contactorsElectrical test instruments and procedures (voltmeter, ohmmeter, ammeter, multimeter, megohmmeter)Thermostats
Esquemas de Control y Diagramas de Cableado
1 Q · 1%
Pictorial diagrams vs. ladder diagramsSchematic symbols for HVACR electrical componentsControl system fundamentals: cut-in, cut-out, range, and differential adjustmentsTemperature motor controls: sensing bulbs, bimetal devices, and electronic sensorsPressure motor controls: high-pressure, low-pressure, and oil pressure controlsMotor starting relays: current, potential, solid-state, and PTC relaysMotor protection devices: fuses, circuit breakers, and bimetal/thermistor overload protectorsDirect digital control (DDC) systems: open-loop vs. closed-loop control, sensors, controllers, and actuatorsElectrical Control Systems
Sistemas de Control HVACR
1 Q · 1%
Thermostat types and sensing elements (line-voltage, low-voltage, millivolt, bimetal, thermistor)Thermostat wiring terminals and circuit diagrams (ladder and pictorial diagrams)Heat and cooling anticipators (system lag, system overshoot, temperature swing)Programmable and digital thermostats (Wi-Fi, learning, scheduling, DIP switches)Pressure motor controls (high-pressure, low-pressure, oil pressure safety controls)Motor starting relays (current, potential, solid-state, PTC relays)Motor protection devices (fuses, circuit breakers, overload protection)Zoned systems and free cooling (dampers, economizers, zone control)Thermostats
Sala de Máquinas
1 Q · 1%
Machinery room design and construction requirements (Section 1105 general requirements)Machinery room ventilation requirements (normal and emergency airflow rates)Refrigerant detector requirements and emergency system activationMeans of egress requirements for machinery rooms over 1,000 square feetFuel-burning appliance restrictions in machinery roomsSpecial requirements for flammable refrigerant machinery rooms (Groups A2, A3, B2, B3)Special requirements for Group A2L refrigerant machinery roomsRemote controls and emergency shutoff switches for machinery room equipmentRefrigeration
Sistemas de Aire Acondicionado
3 Q · 4%
Compression refrigeration cycle components and operationResidential central air-conditioning system types (unitary vs. field-erected, split systems)Ductless and self-contained air-conditioning systems (room units, PTAC, mini-splits)Commercial air-conditioning systems (rooftop units, chillers, cooling towers)Heat pump operation, types, and components (air-source, ground-source, reversing valve)Metering devices (capillary tubes, TXV, EEV, fixed-orifice)Heating and cooling load calculations (Manual J, heat transfer values, design temperatures)Thermostat types, wiring, and controls for cooling systemsThermostats
Bombas de Calor
4 Q · 5%
Heat pump operating modes (heating and cooling cycle refrigerant flow)Types of heat pumps (air-source vs. ground-source)Reversing valve operation and connectionsHeat pump system components (accumulator, compressor, metering devices, coils)Defrost methods and controls (reverse cycle and electric heat defrost)Auxiliary heat and balance pointHeat pump efficiency ratings (EER, SEER, HSPF, COP)Heat pump installation, maintenance, and troubleshootingHeat PumpsResidential Central Air-Conditioning Systems
Hornos (Equipos de Calefacción de Aire Caliente)
2 Q · 2%
Gas furnace combustion principles and fuel types (natural gas vs. LP gas)Gas ignition systems (standing-pilot, intermittent-pilot, DSI, and HSI)Gas furnace safety controls (high-limit switch, rollout switch, pressure switch)Gas furnace efficiency ratings and categories (AFUE, Category I–IV venting)Oil furnace components and operation (gun burner, fuel unit, primary control unit, cad cell relay)Electric furnace heating elements and sequencer controlsCombustion venting systems and vent connector requirements (SC Fuel Gas Code)Heat pump auxiliary heat, defrost controls, and reversing valve operationOil-Fired Heating Systems
Calentadores Especializados
2 Q · 2%
Electric heating element types (open wire, open ribbon, tubular cased wire)Electric furnace and duct heater controls (sequencers, contactors, airflow switches)Electric baseboard heating unit installation and controlsElectric radiant heating systems (direct and indirect infrared, radiant floor and ceiling panels)Safety controls for electric heating systems (high-limit switches, fusible links, overcurrent protection)Gas-fired specialized heaters (vented/unvented room heaters, wall furnaces, floor furnaces, unit heaters, infrared radiant heaters)Sauna heater installation requirements (guards, temperature/timer controls, ventilation, warning notices)Pool and spa heater installation requirementsElectric Heating Systems
Chimeneas, Conductos de Humo, Ventilaciones y Conectores de Ventilación
3 Q · 4%
Appliance venting categories (Category I, II, III, IV) and vent type selectionVent and chimney termination height and location requirementsSizing of venting systems using code tables for Category I appliancesVent connector materials, clearances, slope, and installation requirementsMasonry chimney construction, flue lining systems, and cleanout requirementsDraft hoods, draft controls, and barometric draft regulatorsDirect-vent, mechanical draft, and power exhauster systemsCondensate drainage requirements for Category II and IV appliancesOil-Fired Heating SystemsChimneys and VentsGas-Fired Heating Systems
Aire de Combustión
2 Q · 2%
Indoor combustion air requirements (volume and standard method calculations)Outdoor combustion air provisions (two-opening and one-opening methods)Combustion air opening sizing, location, and minimum dimensionsCombustion air ducts (materials, termination, and installation requirements)Louvers, grilles, and screens for combustion air openingsMechanical combustion air supply and appliance interlock requirementsCombustion air requirements for oil-fired appliances (NFPA 31)Dampered combustion air openings and interlock with firing cycleGas Piping Installations
Conocimientos Generales de Combustibles
1 Q · 1%
Combustion process and chemistry (stoichiometric, complete, and incomplete combustion)Properties and characteristics of natural gas and LP/propane gasGas piping materials, sizing, and pressure requirementsFuel oil grades, properties, and storage systemsCombustion air requirements for gas-fired and oil-fired appliancesVenting and chimney systems for fuel-burning appliancesIgnition systems and gas valve controls for gas-fired equipmentCombustion efficiency testing (CO2, stack temperature, draft, and smoke tests)Gas Piping Installations
Gas Natural
2 Q · 2%
Gas piping materials and fittings (steel, copper, CSST, polyethylene)Gas piping sizing methods and pressure drop calculationsAllowable operating pressures and pressure testing requirementsCombustion air requirements for gas-fired appliancesVenting system types and appliance categories (Category I–IV)Vent and chimney sizing, termination, and clearance requirementsGas furnace components, ignition systems, and safety controlsCombustion efficiency, flue gas analysis, and AFUE ratingsGas Piping Installations
LP Gas
2 Q · 2%
LP gas piping system design and sizing (pressure drop, pipe sizing tables, and methods)Approved piping materials and fittings for LP gas systems (steel, copper, CSST, polyethylene)LP gas storage tank installation requirements and NFPA 58 complianceTwo-stage regulator systems for LP gas (first-stage and second-stage pressure regulation)LP gas system pressure testing, leak checks, and purging proceduresCombustion characteristics of LP gas (specific gravity, BTU content, flammability limits, air-fuel ratios)Venting requirements for LP gas appliances (categories, vent types, termination clearances)LP gas appliance installation requirements (clearances, ignition source elevation, prohibited locations)Gas Piping Installations
Conocimientos y Principios Generales de Sistemas de Ductos
4 Q · 5%
Pressure units and blower performance curves (IWC, ESP, CFM relationships)Available static pressure calculation and component pressure lossesTotal effective length and friction rate determinationFitting equivalent lengths and duct run resistanceAir velocity limits for supply and return ductsDuct system types and configurations (radial, extended plenum, reducing trunk, perimeter loop)Duct materials, construction standards, and insulation requirementsDuct leakage, sealing methods, and system efficiencyAir DistributionDuct Systems
Conversiones/Equivalencias de Ductos
4 Q · 5%
Round-to-rectangular duct conversion using equal friction rate equivalency tablesRound-to-oval duct conversion using equal friction rate equivalency tablesFriction chart use to determine round duct diameter from CFM and friction rateFriction rate calculation from available static pressure and total effective lengthDuct sizing slide rule equations for round duct diameter by material typeFitting equivalent length concept and conversion to pressure dropRoughness factors and friction chart corrections for different duct materialsEquivalent length adjustment for non-default velocity and friction rate conditionsDuct Sizing CalculationsBasic Duct Sizing Principles
Dispositivos/Sistemas Mecánicos de Lámina Metálica
2 Q · 2%
Duct system types and configurations (radial, extended plenum, reducing trunk, perimeter loop)Duct sizing procedure using ACCA Manual D (friction rate, available static pressure, total effective length)Sheet metal duct construction materials, gauges, and fabrication standardsDuct joints, seams, and sealing methods (mastic, UL 181 tapes, mechanical fasteners)Fitting equivalent lengths and their effect on critical circulation pathFire and smoke dampers: ratings, actuation, and installation requirementsDuct insulation requirements, vapor retarders, and R-value standardsDuct leakage testing, sealing requirements, and system efficiency impactsAir Distribution
Componentes del Sistema de Ductos
5 Q · 6%
Duct system configurations (radial, extended plenum, reducing trunk, perimeter loop)Supply and return air fitting equivalent lengths and pressure lossesAvailable static pressure calculation and component pressure drop deductionsDuct materials (sheet metal, fibrous glass duct board, flexible wire helix)Registers, diffusers, grilles, and supply outlet selectionDamper types and functions (balancing, fire, smoke, zone)Duct insulation requirements and vapor retardersDuct sealing requirements and leakage testing (duct blaster, mastic, tape)Air Distribution
Ductos Metálicos
3 Q · 4%
Metal duct sheet metal thickness requirements by duct size and static pressure classificationDuct classification by operating pressure and SMACNA construction standardsJoints, seams, and connections in metallic ducts — fastening and sealing methodsRound-to-rectangular equivalent duct sizing and aspect ratio considerationsAir velocity limits in metal supply and return trunk and branch ductsFitting equivalent lengths for elbows, takeoffs, boots, and transitionsDuct leakage effects on system performance and required sealing practicesFire and smoke damper requirements for metallic ducts penetrating rated assembliesAir Distribution
Ductos de Fibra de Vidrio
1 Q · 1%
Fibrous glass duct construction standards and code compliance (NAIMA, SMACNA, UL 181)EI pressure rating classifications for fiberglass duct board (475, 800, 1400)Seams, joints, and closure systems for fibrous glass ductwork (UL 181A-P, 181A-M, 181A-H tapes and mastics)Reinforcement, hangers, and supports for fiberglass duct systemsRecommended installation locations for rigid fiberglass duct boardDuct board friction rate and airway sizing using duct slide rule (vs. sheet metal equivalents)Leakage class characteristics of fibrous glass duct systems and sealing requirementsTemperature limitations for nonmetallic fiberglass ductwork (250°F maximum per SC Mechanical Code)Duct Systems
Sistemas de Filtración
1 Q · 1%
Types of air filters (disposable, washable, electrostatic, carbon, HEPA)MERV ratings and filter efficiency standardsAir filter testing and measurement methods (atmospheric dust spot efficiency, synthetic dust weight arrestance, fractional efficiency, DOP HEPA method)Electronic air cleaner operation and maintenanceUltraviolet (UVG) germicidal light systems installation and maintenanceIonizing air purifiers and ozone considerationsFilter pressure drop measurement and replacement intervalsHeat recovery ventilators (HRV) and energy recovery ventilators (ERV)Air Distribution
Equipos y Dispositivos de Ventilación
1 Q · 1%
Minimum outdoor airflow rates and ventilation rate calculations by occupancy typeMechanical vs. natural ventilation requirements and intake opening location/protection rulesExhaust system requirements by occupancy and contaminant type (cooking, dryers, hazardous materials, garages)Duct construction, materials, sizing, sealing, and insulation requirementsRegisters, diffusers, grilles, dampers, and airflow balancingFire and smoke dampers: installation, ratings, and actuation requirementsAirflow measurement instruments and testing methods (blower door, duct blaster, flow hoods, anemometers)Ventilation load calculations for heating and cooling (sensible and latent) including heat recovery equipmentExhaust Systems
Sistemas de Extracción
2 Q · 2%
Exhaust discharge location requirements and minimum separation distancesCommercial kitchen Type I and Type II hood systemsClothes dryer exhaust duct installation and length limitationsHazardous exhaust systems for flammable vapors, dusts, and toxic materialsSmoke control system design and equipment requirementsMakeup air requirements for exhaust systemsVentilation system balancing, airflow measurement, and duct testingEnergy recovery ventilation systems and prohibited applicationsExhaust SystemsAir Distribution
Seguridad
2 Q · 2%
Lockout/tagout (LOTO) procedures for electrical, hydraulic, pneumatic, and mechanical systemsPersonal protective equipment (PPE) selection and requirements — head, eye, hearing, respiratory, and foot protectionFire hazards and fire extinguisher classes, types, and PASS techniqueFall protection systems — guardrail systems, personal fall arrest systems, and safety netsConfined space entry requirements — permit spaces, atmospheric testing, and attendant dutiesElectrical safety — grounding, GFCI protection, working clearances, and overcurrent protectionHazard communication — safety data sheets (SDS), GHS pictograms, and chemical/refrigerant hazardsSafe work practices — ladder and scaffold safety, proper lifting, and first aid proceduresSubpart D-Occupational Health and Environmental Controls
Distinciones Clave
Compresor de tornillo únicovsCompresor de doble tornillo
Un compresor de tornillo simple utiliza un rotor principal que engrana con dos rotores en forma de estrella accionados por el rotor principal, mientras que los principios básicos de funcionamiento son los mismos que los de otros compresores de tornillo.
Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.2.4 — Single Screw CompressorTerminal de salida de gases tipo B-WvsTerminal de salida de gases tipo B o L
Un conducto de desagüe de gases de tipo B-W deberá terminar a una altura vertical de al menos 12 pies por encima de la parte inferior de la caldera de pared, mientras que los conductos de desagüe de gases de tipo B o L deberán terminar a una altura de al menos 5 pies por encima de la campana de extracción o el collarín de chimenea del aparato conectado más alto.
SC Fuel Gas Code 2021, Chapter 5 Chimneys and Vents, Section 503.6.6Válvula de cierre de los electrodomésticos en la misma estancia (409.5.1)vsVálvula de cierre de un electrodoméstico en un colector (409.5.3)
La opción de instalación en la misma estancia aplica el límite de 6 pies, mientras que deberá ubicarse una válvula colectora, fácilmente accesible y identificada de forma permanente, a una distancia máxima de 50 pies del aparato al que da servicio (siendo la tubería que va desde la válvula colectora hasta una distancia máxima de 6 pies del aparato diseñada, dimensionada e instalada conforme a las secciones 401 a 408).
SC Fuel Gas Code 2021, Chapter 4 — Section 409.5.3 Located at ManifoldDoble abocardadovsUna sola llamarada
Los abocardados dobles se fabrican con un doble grosor de tubo metálico y son más resistentes, pero solo se recomiendan para tubos con un diámetro exterior de 5/16" o superior, ya que no se pueden conformar fácilmente en tubos más pequeños (los tubos de 1/4" tienen un abocardado simple).
Modern Refrigeration and Air Conditioning (20th ed.), Page 148Presión de servicio de las tuberías de plástico — gas naturalvsPresión de servicio de las tuberías de plástico — Gas LP
Las tuberías de plástico instaladas exclusivamente en el exterior y bajo tierra no deben funcionar a presiones superiores a 100 psig en el caso del gas natural ni a 30 psig en el caso del gas licuado de petróleo (GLP).
SC Fuel Gas Code 2021, Chapter 4 — Section 404.17.1 LimitationsThimble, 4 pulgadas más grande (aparato de campana extractora homologado, recorrido corto y abierto)vsSombrero de 2 pulgadas más grande (aparato de extracción homologado, recorrido abierto de al menos 6 pies)
En el caso de los aparatos homologados con campanas de tiro y de los aparatos homologados para conductos de gas de tipo B, el casquillo de ventilación deberá tener un diámetro no inferior a 4 pulgadas mayor que el del tubo metálico de pared simple, aunque se permite que sea como mínimo 2 pulgadas mayor cuando haya un tramo de tubería al aire libre de al menos 6 pies entre la salida de la campana de tiro y el manguito; la diferencia de 6 pulgadas se aplica a los aparatos no homologados con campanas de tiro y la de 12 pulgadas a los aparatos residenciales y de baja potencia.
SC Fuel Gas Code 2021, Chapter 5 — Section 503.7.7 (Single-Wall Penetrations of Combustible Walls)Pérdida de calor HTMvsAporte térmico HTM
Un HTM de pérdida de calor es el valor U del componente multiplicado por la diferencia de temperatura (IDT – ODT), mientras que un HTM de ganancia de calor ajusta esa misma diferencia en función de factores como la exposición solar y el almacenamiento de calor, y normalmente se consulta en una tabla en lugar de calcularse.
Modern Refrigeration and Air Conditioning (20th ed.), Page 992Terminal O del termostatovsTerminal B del termostato
O activa la válvula de inversión para el modo de refrigeración y B la activa para el modo de calefacción (se muestra como un terminal combinado O/B); L es la luz de control del sistema/servicio y W2 es la etapa 2 de calefacción o calefacción auxiliar, y los termostatos deben conectarse según la letra del terminal, no según el color del cable.
Modern Refrigeration and Air Conditioning (20th ed.), Page 1102 — Section 40.5.1 Temperature ControlsVentilación de aparatos de gas de categoría I y categoría IIvsVentilación de aparatos de gas de categoría III / categoría IV
La categoría I es de presión negativa sin condensación (tubo de ventilación de clase B) y la categoría II es de presión negativa con condensación (material especial para el tubo de ventilación especificado por el fabricante), mientras que la categoría III es de presión positiva sin condensación (acero inoxidable) y la categoría IV es de presión positiva con condensación (PVC).
Modern Refrigeration and Air Conditioning (20th ed.), Page 1134Sistema de lubricación a presiónvsSistema de lubricación por salpicadura
La lubricación a presión suministra aceite a presión a todas las superficies de los cojinetes, por lo que el compresor funciona de forma más silenciosa incluso con holguras mayores en los cojinetes, ya que el aceite a presión amortigua los cojinetes.
Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.3.4 — Pressure LubricationActivación del control termostático del ventiladorvsDispositivo de desconexión termostática del ventilador
Un control termostático del ventilador cierra sus contactos para poner en marcha el ventilador cuando la temperatura de la cámara de distribución alcanza unos 140 °F (60 °C) y abre sus contactos cuando la cámara de distribución se enfría hasta unos 90 °F (32 °C) tras la parada del quemador.
Modern Refrigeration and Air Conditioning (20th ed.), Page 1029Mayor diferencia de temperatura del termostato (por ejemplo, activación a 26 °F / desactivación a 14 °F)vsDiferencial del termostato más reducido (por ejemplo, activación a 24 °F / desactivación a 16 °F)
Si se modifican el inicio y el fin del ciclo en la misma medida y en direcciones opuestas, la temperatura media de la caja se mantiene constante; al aumentar la diferencia, se alarga la duración del ciclo y se amplía el intervalo entre ciclos, mientras que al reducirla se obtienen ciclos más cortos y frecuentes.
Modern Refrigeration and Air Conditioning (20th ed.), Pages 355–357 (Section 16.2.2 Differential Adjustment)Quemador de alta potenciavsQuemadores de gas atmosféricos (de cinta, ranurados, de inyección)
Un quemador de alta potencia utiliza un soplador para impulsar tanto el aire primario como el secundario hacia el tubo del quemador y es necesario para el fuelóleo, mientras que los quemadores de gas atmosféricos se basan en el efecto de sifón o venturi que se produce cuando el gas fluye a través de un orificio y se utilizan con gas combustible.
Modern Refrigeration and Air Conditioning (20th ed.), Page 1124Fuga predeterminada en conductos sellados según el Manual J — lado de suministrovsFuga predeterminada en conductos sellados según el Manual J — lado de retorno
La tasa de fuga predeterminada para el caso base en los sistemas de conductos sellados es de 0,12 Cfm/pie cuadrado de superficie de conducto en el lado de suministro y de 0,24 Cfm/pie cuadrado en el lado de retorno (el valor predeterminado para el suministro sin sellar es 0,35).
Manual J, Section 1-8 and Section 23-1Términos Clave
Persona competente (29 CFR 1926.32(f)) OSHA 1926 CFR 29, Page 31
Persona capaz de identificar los riesgos existentes y previsibles en el entorno o en las condiciones de trabajo que resulten insalubres, peligrosas o que supongan un riesgo para los empleados, y que esté autorizada a adoptar medidas correctivas inmediatas para eliminarlos (no se requiere ningún título, experiencia ni certificado específico).
Circuito de clase 2 Modern Refrigeration and Air Conditioning (20th ed.), Page 296 (Section 13.2.2 Electrical Codes)
Un circuito de control remoto, como el cableado de un termostato, alimentado por una fuente de alimentación cuya tensión de salida no supere los 30 V y cuya potencia no supere los 1000 VA, que el personal especializado en climatización y refrigeración está autorizado a instalar (pero no los conductores de derivación, de alimentación ni de servicio que alimentan el equipo).
Espacio libre (compresor alternativo) Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.2.1 — Clearance Space
El pequeño volumen que queda entre el pistón en el punto muerto superior y la placa de válvulas, de aproximadamente 0,010″ a 0,020″ (0,254 mm a 0,508 mm).
Conexión prensada Modern Refrigeration and Air Conditioning (20th ed.), Pages 160–161
Una unión realizada ensanchando un extremo del tubo para poder insertar y soldar con soldadura fuerte otro tubo del mismo tamaño, siendo la longitud de solapamiento igual al diámetro exterior del tubo (un tubo ACR de 3/4" requiere un solapamiento de 3/4").
Holgura en la unión de soldadura fuerte Modern Refrigeration and Air Conditioning (20th ed.), Page 158
El espacio de entre 0,001" y 0,005" entre el tubo y el casquillo del racor, que garantiza la máxima resistencia y solidez de la unión; un ajuste a presión demasiado apretado impide la penetración capilar, mientras que un holgura excesiva puede provocar grietas bajo tensión o vibración.
Bomba de circulación de rotor húmedo Modern Refrigeration and Air Conditioning (20th ed.), Page 1039
Una bomba hidrónica centrífuga cuyos cojinetes se lubrican con el agua del sistema de circulación, lo que elimina la necesidad de un retén de eje y reduce el ruido y el mantenimiento.
Equipos de recuperación (pasivos) dependientes del sistema Modern Refrigeration and Air Conditioning (20th ed.), Appendix G — Type II (high- or very high-pressure appliances), Recovery Requirements, Page 1570
Equipos de recuperación que dependen del propio sistema; su uso está prohibido en cualquier sistema que contenga más de 15 libras de refrigerante (5 libras definen un electrodoméstico pequeño, 50 libras es el umbral de carga para la reparación de fugas y 200 libras modifican los niveles de vacío de evacuación requeridos).
Multiplicador de transferencia de calor (HTM) Modern Refrigeration and Air Conditioning (20th ed.), Page 992
El valor U de un elemento constructivo multiplicado por una diferencia de temperatura, introducido para cada elemento en una hoja de cálculo de cargas.
Activación del sensor del extractor de cocina tipo I SC Mechanical Code 2021, Chapter 5, Section 507.1.1 (Operation)
Cuando uno o varios sensores de temperatura o de energía radiante activen el extractor de campana de tipo I, este deberá ponerse en marcha en un plazo máximo de 15 minutos tras el encendido del primer electrodoméstico al que da servicio dicha campana.
Aire de combustión a través de los espacios entre montantes y vigas (Código Mecánico de Carolina del Sur 304.11, excepción del punto 1) South Carolina Mechanical Code, Chapter 3 (General Regulations), Section 304.11, Item 1 Exception
Se permite que los espacios libres entre montantes y viguetas dentro de las viviendas sirvan para el paso del aire de combustión, siempre que no se retire más de un bloque cortafuegos obligatorio.
Capacidad nominal por hora de la compuerta cortafuegos Modern Refrigeration and Air Conditioning (20th ed.), Page 767
La resistencia al fuego de las compuertas cortafuegos debe ser del 75 % de la resistencia al fuego de la pared, el suelo o la tabique que atraviesan; por lo tanto, una barrera de 2 horas requiere una compuerta de 1,5 horas.
Aparato de gas de categoría II Modern Refrigeration and Air Conditioning (20th ed.), Page 1134
Un aparato cuya salida de humos funciona a presión negativa y cuyos gases de combustión salen a una temperatura inferior a su punto de rocío, por lo que se forma condensado, lo que requiere el uso de un material especial para la salida de humos especificado por el fabricante.
Depósito compensador de carga Modern Refrigeration and Air Conditioning (20th ed.), Page 1089
Un depósito de bomba de calor que almacena el exceso de refrigerante líquido; la tubería de gas lo atraviesa sin desembocar en su interior, mientras que la tubería de líquido, de menor diámetro, se conecta al depósito y lo llena durante el modo de calefacción.
Inyección de aceite (compresor de tornillo) Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.2.4 — Oil Injection
El aceite inyectado sella el espacio libre entre los rotores y el cilindro para evitar fugas de refrigerante y ayuda a refrigerar el compresor, lo que contribuye a una alta eficiencia.
Construcción del compresor totalmente hermética Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.1.2 — Fully Hermetic Compressors, Construction
El compresor y el motor suelen estar montados sobre resortes en el interior de la cúpula hermética (algunos utilizan resortes de montaje externos) y cuentan con conductos internos flexibles de descarga y aspiración, por lo que la mayor parte de la vibración no se percibe fuera de la cúpula.
Valor de diseño del 99 % según ASHRAE ACCA Manual J (8th ed.), Section 18-1, Page 18-2 (PDF Page 164)
La base de la temperatura de bulbo seco exterior para las cargas de calefacción residencial, lo que significa que la temperatura exterior será inferior al valor de diseño aproximadamente el 1 % del total de horas de los meses fríos (entre 85 y 90 horas al año).
Temperatura de desconexión del desescarche (desescarche con termistor) Modern Refrigeration and Air Conditioning (20th ed.), Page 524 — Section 21.1.9 Evaporator Defrost Controls
La temperatura del serpentín del evaporador, de unos 40 °F, a la que el termistor indica al control de descongelación que finalice el proceso y se reanude la refrigeración normal.
Límite de ruido impulsivo o de impacto (29 CFR 1926.52(e)) OSHA 29 CFR 1926, §1926.52(e)
La exposición de los trabajadores al ruido impulsivo o de impacto no debe superar los 140 dB de nivel de presión acústica máximo, un límite independiente de los niveles continuos basados en la duración que figuran en la tabla D-2 (por ejemplo, 90 dBA durante 8 horas).
Fórmulas que Debes Saber
Multiplicador de transferencia de calor de calefacción para un componente
HTM (Btu/pie cuadrado) = valor U del conjunto × HTD; p. ej., 0,07 × 50 = 3,50, 0,07 × 75 = 5,25, 0,10 × 60 = 6,00Carga térmica de un componente (Q = U × superficie × diferencia de temperatura)
Carga (Btuh) = HTM × superficie de carga; p. ej., pared: 136 pies cuadrados × 3,50 = 476 Btuh; cristal: 60 pies cuadrados × (0,30 × 50 = 15,00) = 900 Btuh; techo: 140 pies cuadrados × (0,03 × 50 = 1,50) = 210 Btuh; puerta: 20 pies cuadrados × (0,50 × 70 = 35,00) = 700 Btuh (el área de carga de las ventanas es el área de la abertura en bruto)Superficie neta de pared expuesta
Superficie neta de la pared = (longitud de la pared visible × altura de la pared) − superficie de las ventanas − superficie de las puertas; p. ej., 24 pies × 9 pies = 216 pies cuadrados − (2 × 30 de cristal + 20 de puerta) = 136 pies cuadradosFlujo de aire por infiltración derivado de los recambios de aire
CFM = (renovaciones de aire por hora × volumen de la estancia) ÷ 60; p. ej., 0,6 × (16 × 14 × 10 = 2.240 pies cúbicos) ÷ 60 = 22,4 cfmCarga térmica por infiltración
Btuh = 1,1 × ACF × CFM × HTD; p. ej., 1,1 × 1,00 × 22,4 × 70 = 1.725 Btuh; 1,1 × 1,00 × 15,4 × 60 = 1.014 BtuhReajuste de la carga térmica total para una temperatura exterior de diseño más baja
Nuevo total = antiguo total × (nuevo HTD ÷ antiguo HTD), ya que cada componente es proporcional al HTD; p. ej., 4.820 × (80 ÷ 70) = 5.509 Btuh; 2.958 × (70 ÷ 60) = 3.451 BtuhCarga térmica total de la estancia
Total = pared + cristal + puerta + techo + infiltración; p. ej., 770 + 1.155 + 700 + 470 + 1.725 = 4.820 Btuh; y 1.008 + 504 + 432 + 1.014 = 2.958 BtuhLongitud equivalente total de un tramo de conducto
TEL = suma de las longitudes medidas en línea recta + las holguras equivalentes a los codos; p. ej., (28 + 22 + 15 = 65 pies) + (2 codos × 25 pies = 50 pies) = 115 piesPérdida por fricción en un tramo de conducto
Pérdida por fricción = (longitud equivalente total ÷ 100) × coeficiente de fricción; p. ej., (115 ÷ 100) × 0,10 pulgadas WC = 0,115 pulgadas WCTemperatura del aire mezclado y porcentaje de aire exterior
T_mix = (CFM de retorno × temperatura de retorno + CFM exterior × temperatura exterior) ÷ CFM total, y OA% = CFM exterior ÷ CFM total; p. ej., (3.000 × 60 + 1.000 × 92) ÷ 4.000 = 68,0 °F y 1.000 ÷ 4.000 = 25 %Carga adicional de refrigerante para un conjunto de tuberías largo (según los datos del conjunto de tuberías que figuran en la ilustración)
Pies añadidos = longitud total del conjunto de tuberías − la longitud cubierta por la carga de fábrica; carga añadida = pies añadidos × la tasa indicada en onzas por pie (dividida entre 16 onzas/libra para las libras); por ejemplo, con la cobertura de fábrica de 15 pies de la figura y 0,6 onzas por pie: 65 − 15 = 50 pies × 0,6 = 30,0 onzas ≈ 1,9 libras