R-22, commonly known as Freon, is a hydrochlorofluorocarbon (HCFC) refrigerant that was widely used in air conditioning systems before being phased out due to ozone depletion concerns. Production ceased in 2020, making repairs increasingly expensive.

R-410A, marketed as Puron, is a hydrofluorocarbon (HFC) refrigerant that replaced R-22 in modern air conditioning systems. It operates at higher pressures but doesn't deplete the ozone layer, though it still contributes to global warming.

R-32 is a next-generation refrigerant with lower global warming potential (GWP) than R-410A. It offers higher energy efficiency and is increasingly adopted in new HVAC systems as part of environmental sustainability efforts.

A refrigerant leak occurs when the chemical coolant used in air conditioning systems escapes through cracks, corrosion, or damaged connections in the refrigeration cycle. This reduces cooling efficiency and can damage the compressor.

Refrigerant charge refers to the specific amount of refrigerant required for optimal system performance. Undercharging or overcharging reduces efficiency and can cause equipment damage. Proper charging requires precision measurement.

The compressor is the heart of an air conditioning system. It pressurizes refrigerant gas and circulates it through the system, enabling heat transfer from inside to outside. Compressor failure is one of the most expensive AC repairs.

A scroll compressor uses two spiral-shaped scrolls to compress refrigerant. One scroll remains stationary while the other orbits, creating compression pockets. Scroll compressors are quieter and more efficient than reciprocating models.

A reciprocating compressor uses pistons driven by a crankshaft to compress refrigerant gas. Common in older and smaller AC units, they're reliable but noisier and less efficient than modern scroll compressors.

A variable speed compressor adjusts its operating speed to match cooling demand, rather than cycling on and off. This provides superior comfort, humidity control, and energy efficiency compared to single-stage compressors.

The evaporator coil is an indoor component that absorbs heat from your home's air. As refrigerant flows through the coil, it evaporates and removes heat and humidity, delivering cooled air into your living space.

The condenser coil is the outdoor component where refrigerant releases absorbed heat to the outside air. It works in conjunction with the condenser fan to dissipate heat collected from your home.

An air handler is the indoor unit containing the blower fan, evaporator coil, and air filter. It circulates conditioned air throughout your home via ductwork and works with the outdoor condenser unit.

The blower motor powers the fan that circulates air through your ductwork and into your home. A failing blower motor may produce unusual noises or reduced airflow.

An Electronically Commutated Motor (ECM) is a variable-speed blower motor that uses DC power and electronic controls. ECM motors are significantly more energy-efficient than traditional PSC motors and provide better airflow control.

A Permanent Split Capacitor (PSC) motor is a traditional single-speed blower motor. Less efficient than ECM motors, PSC motors are less expensive but consume more electricity and provide limited speed control.

A capacitor is an electrical component that stores and releases energy to start motors and keep them running. AC capacitors commonly fail in hot climates and cause system shutdown.

A start capacitor provides the initial electrical boost needed to start a compressor or motor. It disconnects once the motor reaches operating speed. Failure prevents the system from starting.

A run capacitor remains in the circuit while the motor operates, improving efficiency and torque. Bulging, leaking, or failed run capacitors cause reduced performance or system failure.

A contactor is an electrical relay that controls high-voltage power to the compressor and condenser fan. When the thermostat calls for cooling, the contactor closes to energize these components.

The transformer reduces standard 120V or 240V power to 24V for thermostat and control circuit operation. Transformer failure prevents the entire HVAC system from functioning.

The control board is the electronic brain of an HVAC system, managing system operation, safety controls, and communication between components. Modern boards feature diagnostics and fault codes.

HVAC stands for Heating, Ventilation, and Air Conditioning. An HVAC system is the complete comfort system that regulates temperature, humidity, and air quality in buildings.

A split system is the most common HVAC configuration, with separate indoor and outdoor units connected by refrigerant lines. The outdoor unit contains the compressor and condenser; the indoor unit has the evaporator and air handler.

A package unit combines all HVAC components (compressor, condenser, evaporator, blower) in a single outdoor cabinet. Common in commercial applications and homes without indoor space for equipment.

A heat pump is a dual-purpose system that provides both heating and cooling by transferring heat rather than generating it. In summer it removes heat from inside; in winter it extracts heat from outside air and brings it indoors.

A dual fuel system combines an electric heat pump with a gas furnace. The heat pump provides efficient heating in moderate weather; the furnace activates in extreme cold for cost-effective operation year-round.

A furnace is a heating system that generates warm air by burning fuel (gas, oil, or propane) or using electric resistance. The heated air is distributed through ductwork to warm your home.

A boiler heats water or produces steam for hydronic heating systems. Heated water circulates through radiators, baseboard heaters, or radiant floor systems to warm the building.

A mini-split (ductless) system provides heating and cooling without ductwork. One outdoor unit serves multiple indoor air handlers, offering zone control and energy efficiency for room additions or older homes.

A geothermal heat pump uses the stable temperature of the earth or groundwater for highly efficient heating and cooling. Though expensive to install, geothermal systems offer the lowest operating costs.

A thermostat is the control device that monitors indoor temperature and signals your HVAC system when to heat or cool. Modern programmable and smart thermostats can significantly reduce energy costs.

A smart thermostat connects to Wi-Fi for remote control, learning algorithms, and energy reports. Features include geofencing, voice control, and integration with home automation systems.

A programmable thermostat allows scheduling temperature setbacks for different times of day and days of the week. Proper programming can reduce energy costs by 10-30% without sacrificing comfort.

A zoning system divides a home into separate temperature zones with individual thermostats and motorized dampers. This provides personalized comfort and reduces energy waste by conditioning only occupied areas.

A zone damper is a motorized gate installed in ductwork that opens and closes to control airflow to specific zones. Dampers work with the zoning control panel and zone thermostats.

A humidistat monitors and controls indoor humidity levels. It works with humidifiers or dehumidifiers to maintain optimal moisture levels for comfort and health, typically 30-50% relative humidity.

SEER (Seasonal Energy Efficiency Ratio) is a measurement of air conditioning cooling efficiency. It represents the total cooling output during a typical cooling season divided by total electric energy input. Higher SEER ratings indicate more efficient systems. Minimum standards range from 13-15 depending on region.

SEER2 is the updated efficiency measurement standard introduced in 2023, using more realistic testing conditions than SEER. SEER2 ratings are typically 4-5% lower than equivalent SEER ratings.

HSPF (Heating Seasonal Performance Factor) measures heat pump heating efficiency. It represents total heating output divided by electricity consumed during a typical heating season. Higher HSPF indicates better efficiency.

AFUE (Annual Fuel Utilization Efficiency) measures furnace and boiler efficiency as a percentage. A 95% AFUE furnace converts 95% of fuel to heat, with 5% lost through exhaust. Modern furnaces range from 80-98% AFUE.

EER (Energy Efficiency Ratio) measures cooling efficiency at a specific outdoor temperature (95°F). While SEER measures seasonal average, EER indicates performance during peak cooling conditions.

BTU (British Thermal Unit) measures heating and cooling capacity. One BTU is the energy needed to raise one pound of water by one degree Fahrenheit. In HVAC, higher BTU ratings indicate greater heating or cooling power.

Tonnage refers to an air conditioner's cooling capacity. One ton equals 12,000 BTU per hour of cooling. Residential systems typically range from 1.5 to 5 tons. Proper tonnage sizing is critical for efficiency and comfort.

CFM (Cubic Feet per Minute) measures airflow volume. HVAC systems typically require 400 CFM per ton of cooling capacity. Proper CFM ensures adequate air circulation and system performance.

Static pressure measures resistance to airflow in ductwork, expressed in inches of water column. High static pressure indicates restricted airflow from undersized ducts, dirty filters, or closed dampers, reducing system efficiency.

Superheat is the temperature increase of refrigerant vapor above its boiling point. Technicians measure superheat to verify proper refrigerant charge. Typical superheat ranges from 8-12°F for fixed orifice systems.

Subcooling is the temperature decrease of liquid refrigerant below its condensation point. Measured at the condenser outlet, subcooling indicates refrigerant charge level. Typical subcooling ranges from 8-12°F.

An air filter removes dust, pollen, and airborne particles from circulating air. Regular filter replacement (every 1-3 months) is essential for system efficiency, indoor air quality, and preventing equipment damage.

MERV (Minimum Efficiency Reporting Value) measures air filter effectiveness on a scale of 1-16. Higher ratings capture smaller particles. Most residential systems use MERV 8-13 filters. Higher MERV filters may reduce airflow.

HEPA (High Efficiency Particulate Air) filters capture 99.97% of particles 0.3 microns or larger. True HEPA filters exceed MERV 16 and require specialized equipment due to high airflow resistance.

An HVAC tune-up is preventive maintenance performed annually to clean components, check refrigerant levels, test safety controls, and ensure optimal performance. Regular tune-ups extend equipment life and prevent breakdowns.

Coil cleaning removes dirt, debris, and biological growth from evaporator and condenser coils. Dirty coils reduce heat transfer efficiency by up to 30% and should be cleaned during annual maintenance.

Refrigerant recovery is the EPA-required process of removing refrigerant from a system before service or disposal. Certified technicians use recovery machines to capture refrigerant for reuse or proper disposal.

A frozen evaporator coil occurs when ice forms on the indoor coil, blocking airflow and cooling. Common causes include restricted airflow from dirty filters, low refrigerant, or blower motor failure.

Short cycling is when an HVAC system turns on and off too frequently without completing full heating or cooling cycles. This reduces efficiency, increases wear, and often indicates oversized equipment or thermostat issues.

Compressor failure is a catastrophic problem often requiring complete AC replacement. Common causes include electrical issues, refrigerant flooding, contamination, overheating, or age. Prevention involves regular maintenance.

Water leakage from indoor HVAC units typically results from clogged condensate drains, frozen evaporator coils, or cracked drain pans. Left unaddressed, leaks cause water damage and mold growth.

No cooling can result from thermostat issues, tripped breakers, failed capacitors, refrigerant leaks, or compressor failure. Diagnosis requires systematic testing of electrical and mechanical components.

Hot spots are areas of a building that don't cool properly compared to other rooms. Causes include insufficient insulation, duct leaks, improper duct sizing, solar heat gain, or need for zoning.

High indoor humidity despite AC operation indicates oversized equipment, insufficient runtime, low airflow, refrigerant issues, or need for dedicated dehumidification. Ideal indoor humidity is 30-50%.

Ductwork is the network of metal or flexible tubes that distributes heated or cooled air throughout your home. Leaky or poorly insulated ducts can reduce HVAC efficiency by up to 30%.

Duct sealing uses mastic or specialized tape to close leaks in ductwork. Properly sealed ducts improve efficiency, comfort, and indoor air quality. Duct tape is ironically not recommended for ducts.

Flexible ductwork consists of a wire coil covered with insulation and plastic. Less expensive than rigid metal ducts but more prone to restrictions from kinks, compressions, or sagging that reduce airflow.

Supply ducts carry conditioned air from the HVAC unit to rooms throughout the building. Supply registers (vents) deliver air at ceiling or floor level based on system design.

Return ducts pull air back to the HVAC unit for conditioning. Adequate return air is critical for system performance. Undersized return ducts cause high static pressure and reduced efficiency.

Ventilation is the process of exchanging indoor air with fresh outdoor air. Proper ventilation removes pollutants, controls humidity, and maintains healthy indoor air quality. ASHRAE standards specify minimum ventilation rates.

An Energy Recovery Ventilator (ERV) exchanges heat and moisture between incoming and outgoing air. ERVs provide fresh air ventilation while minimizing energy loss, ideal for humid climates.

A Heat Recovery Ventilator (HRV) transfers heat between incoming and outgoing air without exchanging moisture. HRVs are ideal for cold, dry climates where humidity control is less critical.

Indoor Air Quality refers to the air quality within buildings as it relates to health and comfort. Poor IAQ results from inadequate ventilation, pollutants, humidity issues, or biological contaminants.

Volatile Organic Compounds (VOCs) are chemicals that evaporate at room temperature from products like paints, cleaners, and building materials. Some VOCs cause health issues. HVAC filtration and ventilation reduce VOC levels.

UV (Ultraviolet) lights installed in HVAC systems kill mold, bacteria, and viruses on coils and in airstreams. UV-C wavelength is most effective for germicidal applications, improving air quality and coil cleanliness.

An air purifier removes pollutants, allergens, and contaminants from indoor air. Technologies include HEPA filtration, activated carbon, UV lights, ionization, and photocatalytic oxidation.

A humidifier adds moisture to dry indoor air, typically needed in winter. Whole-house humidifiers integrate with HVAC systems. Proper humidity (30-50%) prevents dry skin, static, and respiratory irritation.

A dehumidifier removes excess moisture from indoor air. Whole-house dehumidifiers work with HVAC systems to maintain optimal humidity. Essential in humid climates to prevent mold and improve comfort.

A rooftop unit is a packaged HVAC system installed on commercial building roofs. RTUs contain all components in a single weatherproof cabinet and are the most common commercial AC configuration.

A chiller is a central cooling system that produces chilled water circulated to air handlers throughout large buildings. Chillers offer efficient cooling for commercial and industrial applications.

A cooling tower removes heat from chiller systems by evaporating water. Warm water from the chiller sprays over fill material while fans draw air through, cooling the water for return to the chiller.

A Variable Air Volume (VAV) system adjusts airflow to different building zones based on demand. VAV boxes contain dampers and controls, providing energy-efficient comfort control in commercial buildings.

An economizer uses cool outdoor air for free cooling when outside temperatures allow. Common in commercial systems, economizers significantly reduce compressor runtime and energy costs during mild weather.

Variable Refrigerant Flow (VRF) systems use refrigerant as the cooling and heating medium, allowing simultaneous heating and cooling in different zones. VRF offers superior efficiency and zone control.

Energy Star is an EPA certification program identifying high-efficiency products that meet strict energy performance criteria. Energy Star HVAC equipment uses significantly less energy than standard models.

Inverter technology varies compressor speed electronically to match cooling demand precisely. Inverter AC units are significantly more efficient than fixed-speed models and provide better temperature control.

Two-stage cooling provides low and high capacity operation. The system runs in low stage most of the time for efficiency and comfort, switching to high stage only during peak demand.

A load calculation (Manual J) determines the proper HVAC system size for a home based on square footage, insulation, windows, climate, and other factors. Proper sizing is critical for efficiency and comfort.

Manual D is the industry standard for residential duct design. It specifies duct sizing, layout, and airflow requirements to ensure proper air distribution and system performance.