Introduction to Residential Air Conditioning (Theory)

Explore the Montreal Protocol and how CFC phase-out protects the ozone layer from ultraviolet radiation, enabling the ozone to heal and supporting safer residential air conditioning.

Learn how temperature expresses the hotness of a substance, measured with a thermometer on Celsius, Fahrenheit, and Kelvin scales, and how atomic vibration explains why water feels hot and cold.

Explore temperature conversion across Celsius, Kelvin, and Fahrenheit, including freezing and boiling points and absolute zero. Learn conversion formulas from Fahrenheit to Celsius and Kelvin to Celsius with practical examples.

Compare small vs large contact areas to see how pressure changes; pressure equals perpendicular force over area (Newton per square meter, Pascal), explaining why a sharp nail penetrates a table.

Explain how atmospheric pressure arises from gravity and surrounding air, how it increases with depth, decreases with altitude, and is defined at sea level.

Gauge pressure uses atmospheric pressure as the reference; zero equals atmospheric pressure, so readings like 20 pascals are above atmosphere. Calibrate to zero at different altitudes using a refrigeration manometer.

Explore absolute pressure and vacuum pressure, and learn how a vacuum pump creates zero pressure; apply the formula absolute pressure equals gauge pressure plus atmospheric pressure to compute values.

Explore how heat flows from a hot object to a cold one until both reach the same temperature, achieving equilibrium via energy transfer between fast and slow particles.

Explores the solid state of water and contrasts it with the liquid and gas states, noting ice's fixed particle positions, definite shape, and volume from strong attractions.

Explore how heating a solid causes melting into a liquid with a definite volume, whose weak attractions let it adopt the container's shape and allow particle movement.

Gas particles have more energy than liquids, with weak attractions that let them move freely in random directions, have no fixed size or shape, fill any container, and are compressible.

Explore the three heat transfer methods, focusing on conduction, heat transfer by direct contact. See how a heated candle warms a metal rod until thermal equilibrium.

Understand convection as heat transfer by the movement of a fluid. A flame heats the fluid, making it rise and cooler fluid sinks, forming a rising and sinking cycle.

Explore radiation as heat transfer without contact, illustrated by campfire warmth and sunlight, and note that hotter objects emit more radiation, including humans detectable by infrared sensors.

Explore specific heat capacity and how heat, measured in joules, raises the temperature of a one-kilogram material by one degree. Compare water and glass, noting joules per degree and watts.

Define heat quantity as the heat energy needed to change temperature. Apply Q = m c ΔT using mass, specific heat, and temperature difference with a worked example.

Explore the two types of heat energy, latent and sensible heat, with sensible heat raising temperature without changing state. Use sensible heat formula q = m cp (Tf - Ti).

Explore latent heat, the energy to change state without temperature change, from solid to liquid (fusion) and liquid to gas (vaporization). Use Q = m × L_f (joules per kilogram).

Define and apply protective personal equipment (PPE) to minimize exposure to workplace hazards. Review examples such as safety gloves, glasses, vest, shoes, helmet, breathing apparatus, earmuffs, clothing, and safety harness.

Identify safety practices for air conditioning maintenance by disconnecting power before servicing, avoiding live wires with bare hands, using PPE when handling refrigerant, using right tools, and grounding metal pots.

Discuss power tool safety tips, including not using electric tools in wet conditions unless approved, grounding tools, maintaining a clean workspace, and keeping tools connected to their power source.

Learn safe handling and storage of refrigerants by securing cylinders during transport, reading product labels and safety data sheets, and storing them in ventilated, dedicated spaces with warning signs.

Explore two copper tubing types: soft copper, coils for bending but not structurally sound; hard copper, used in refrigeration, comes in straight lengths and can be bent when heated.

Identify the advantages of copper tubing: economy, light weight, handling, formability, and elimination of elbows to prevent leakage. Note the disadvantage: ammonia corrodes copper and cannot be used with ammonia.

Explore a sample hvac copper tube catalog, contrast hard copper in straight lengths with soft copper in coils, and note outer diameters and soft sizes like 1/4 and 3/8 inch.

Learn to cut copper tubes using a tube cutter, preferred for soft copper, with a brief look at hacksaws for hard copper; future lessons expand on tube cutters.

learn to use a tube cutter to cut soft copper tubing, including placing the copper, tightening the knob, and revolving and tightening until the cut, while avoiding excessive pressure.

Remove burrs from copper tubes after cutting to prevent turbulence and potential damage to air conditioning devices. Use a tube cutter or a deburring tool for easy, effective reaming.

Unroll copper tubes from rolls onto a flat surface, extend to the desired length, cut with a tube cutter, and cap ends to prevent debris and protect air conditioning system.

Explore joining copper tubes in residential air conditioning by contrasting pipe and tube wall thickness, and outline joining methods such as brazing and flaring, with swaging performed before flaring.

Learn how to flare copper tubes to create leakproof joints using a flaring tool, flare nut, and union, including tube sizing, 1-2 mm extrusion, and correct assembly.

Learn brazing to join copper tubes with a filler metal of lower melting point, above 427°C, using oxyacetylene, and inspect for leaks after cleaning and cooling.

Swaging joins two copper tubes of the same diameter by expanding one end to fit over the other, bracing the joint before brazing using a punch-type tool and hammer.

Learn to bend copper tubing using a level type bender, achieving up to 180 degrees by placing the tube between the jaws and pulling to form precise 90-degree angles.

Define refrigerant ton as the cooling capacity unit and relate it to latent heat of fusion for ice to water, with 12,000 BTU per ton and 3.52 to kilowatts.

Explore how a refrigeration system removes heat from an enclosed space using a working fluid, and learn about its four components: compressor, condenser, evaporator, and expansion valve.

The evaporator in a fan coil absorbs heat as hot air passes through the cooling coil, turning liquid refrigerant into vapor by the expansion valve lowering pressure and temperature.

Explore the expansion valve, a metering device that regulates refrigerant entering the evaporator by reducing pressure and temperature while maintaining constant superheat.

Explore how the outdoor unit's compressor draws in low-pressure vapor refrigerant in vapor state through the suction line, compresses it to high pressure and temperature, and discharges it.

Explain how the condenser rejects heat to the outdoors, condensing vapor to liquid, and directing refrigerant through the cycle from evaporator to compressor, condenser, receiver, and expansion valve.

Explore the refrigeration cycle, including expansion, evaporation, compression, and condensation, and learn how expansion valve lowers pressure, evaporator absorbs heat, compressor raises pressure, and condenser liquefies the refrigerant.

Explore how residential air conditioning condenser units use air to cool refrigerant by absorbing heat, and compare natural convection condensers with forced convection condensers.

Discover natural convection condensers that rely on ambient air flow with no fans, and examine fin static, wire static, and blade static types and their trade-offs.

Learn how forced convection condensers cool coils with a fan, compare draw-through and blow-through designs, and examine advantages like compact space and disadvantages such as fan noise and blocked intake.

Explore how expansion valves regulate refrigerant into the evaporator by lowering pressure and boiling point, and compare capillary tube, thermo static expansion valve, and electronic expansion valve.

Explore the capillary tube, a copper pipe expansion valve with no moving parts, whose capacity depends on length and diameter and cannot adjust to load changes, requiring proper charging.

The thermostatic expansion valve maintains superheat by regulating refrigerant flow to the evaporator, adjusting for varying cooling loads using bulb pressure, evaporator pressure, and spring pressure.

Compare internal and external equalized TXVs. Explain why the internal equalized TXV suits low evaporator pressure drop, and describe sensing bulb, inlet, outlet, evaporator pressure, and spring pressure.

External equalized TXVs tap evaporator outlet pressure via a dedicated line, unlike internal equalized TXVs that tap evaporator inlet pressure, a setup suitable for large pressure drops across the evaporator.

Explore advantages and disadvantages of a thermostatic expansion valve (TXV). It regulates refrigerant flow into evaporator to handle varying loads and maintain superheat, but requires a receiver to store refrigerant.

Define superheat as the difference between the evaporator outlet temperature and the refrigerant's saturated temperature, and show how TXV adjustments to 3–6°C regulate flow and system performance.

Place the thermostatic expansion valve bulb at the evaporator exit, preferably at the 2:00 or 10:00 position, and horizontally on the suction line, not vertically.

Explore how an electronic expansion valve uses a stepper motor, a controller, and pressure and temperature sensors to regulate refrigerant flow in the evaporator based on sensor feedback.

Analyze the electronic expansion valve’s advantages, including reliable, high-accuracy control and lower maintenance, against its disadvantages—higher cost and multiple components, with refrigerant bleeding issues.

Explore additional air conditioning devices that improve system performance, protect components, and simplify maintenance for smoother operation.

Explain how a check valve uses a ball and spring to allow flow in one direction and block reverse flow. Position it at the evaporator outlet for multi-evaporator systems.

Installed between the evaporator and compressor, the suction line accumulator prevents liquid refrigerant from entering the compressor by letting only vapor pass through a metering bottom orifice.

Learn how the filter dryer traps water and dirt before the expansion valve, with sight glass, and replace it whenever the system is opened or every two years per manufacturer.

The sight glass lets you observe moisture in the system before the expansion valve and after the filter dryer, with color changes (green for dry, yellow for moist).