Air Conditioning & Heat Pump Inspection Glossary of Terms and Conditions

A-coil - An evaporator coil shaped like the letter A, commonly installed inside an air handler or furnace plenum.

Air conditioning - A system that cools indoor air by removing heat and transferring it outdoors. Many systems also dehumidify the air.

Air gap - An open physical separation between a water outlet and the flood-level rim of a receiving fixture. It helps prevent contaminated water from flowing backward into the potable water supply.

Attic venting - Openings or systems that allow air to circulate through an attic, helping manage heat and moisture.

Backdrafting - The reversal of normal exhaust flow, allowing combustion gases to spill back into a building rather than vent outdoors.

Backflow preventer - A device designed to prevent water from flowing backward into a potable water supply.

Belt drive - A motor arrangement that uses a belt and pulleys to drive a fan or blower.

Capillary tube - A narrow, fixed-length tube that acts as a refrigerant metering device by restricting refrigerant flow into the evaporator.

Central thermostat - A temperature-control device that monitors indoor conditions and signals the heating or cooling system to operate.

Clothes dryer or water heater vent - An exhaust passage intended to carry moisture, lint, or combustion gases outdoors. It should not be connected to an air-conditioning condensate drain or used as a substitute for an approved ventilation system.

Combustion appliances - Appliances that burn fuel, such as natural gas, propane, or oil, to produce heat. They require appropriate combustion air and safe exhaust venting.

Compressor - The component of a refrigeration system that compresses refrigerant vapor and circulates it through the system.

Compressor life - The expected service life of an air-conditioning or heat-pump compressor. Actual lifespan depends on operating conditions, maintenance, installation, and equipment quality.

Compressor warranty - The manufacturer's warranty covering the compressor for a specified period, subject to its terms and conditions.

Condensate collection - The gathering of water produced when humid air passes over a cold evaporator coil and moisture condenses out of the air.

Condensate drain pan - A tray beneath an evaporator coil that collects condensation and directs it toward a drain.

Condensate pump - A small pump used to move collected condensate to a suitable drainage location when gravity drainage is not practical.

Condenser coil - The heat-exchange coil where hot refrigerant releases heat and condenses from vapor into liquid. In cooling mode, this is generally the outdoor coil.

Condenser fan - A fan that moves air across the condenser coil to help release heat into the outdoor environment.

Crankcase heater - An electric heating element that keeps refrigerant from migrating into and diluting compressor oil during periods when the compressor is not operating.

Dehumidification - The removal of moisture from indoor air, commonly accomplished as warm humid air passes over a cold evaporator coil.

Direct drive - A fan or blower arrangement in which the motor is directly connected to the fan wheel, without a belt and pulley system.

Duct insulation - Insulation applied to heating and cooling ducts to reduce unwanted heat transfer and help prevent condensation.

Ductwork capacity - The amount of air that a duct system can deliver or return while maintaining suitable airflow and pressure. Capacity depends on duct dimensions, layout, resistance, and equipment requirements.

Evaporative coolers - Cooling devices that lower air temperature by evaporating water into an airstream. They work best in hot, dry climates and add moisture to the air.

Evaporator coil - The heat-exchange coil where liquid refrigerant absorbs heat and evaporates into a gas. In cooling mode, it is generally located indoors.

Evaporator fan - A fan that moves indoor air across the evaporator coil to transfer heat from the air to the refrigerant.

Excess current - Electrical current drawn by equipment beyond its expected operating range, potentially indicating a mechanical, electrical, or equipment problem.

Expansion device - A component that controls the flow of refrigerant into the evaporator while reducing its pressure. Examples include capillary tubes, fixed orifices, and thermostatic expansion valves.

Filter/dryer - A refrigerant-system component that removes moisture, contaminants, and particles from the refrigerant.

Fixed orifice (accurator) - A fixed-size opening that meters refrigerant flow into the evaporator. An accurator is a type of fixed-orifice metering device.

Flex duct - Flexible ductwork, usually consisting of a wire-supported inner liner, insulation, and an outer vapour barrier, used to distribute conditioned air.

Full Load Amperage (FLA) - The current a motor is designed to draw when operating at its rated full load under specified conditions. It is a nameplate rating, not necessarily the actual current drawn at all times.

Ground-cooled systems - Cooling systems that use the relatively stable temperature of the ground as a heat sink or heat source. Ground-source heat pumps are a common example.

High returns - Return-air openings located high on walls or near ceilings, where they draw warmer air from the upper part of a room.

Humidifier duct damper - A damper used to control airflow through ductwork serving a whole-house humidifier.

Inadequate cooling - A condition in which an air-conditioning system fails to maintain the desired indoor temperature or provide sufficient cooling under expected operating conditions.

Inoperative - Not functioning or failing to operate as intended.

Latent heat - Heat absorbed or released during a change of state, such as water evaporating or refrigerant condensing, without a corresponding change in temperature during the phase change.

Latent heat of vaporization - The amount of heat required to convert a liquid into a gas without changing its temperature during the phase change.

Liquid line - The refrigerant line that carries high-pressure liquid refrigerant from the condenser toward the expansion device.

Louvers - Angled slats or blades installed in an opening to direct airflow while helping limit the entry of rain, debris, or unwanted air.

Low returns - Return-air openings located near floor level, where they draw cooler air from the lower part of a room.

Noise/vibration - Unusual sound or physical movement produced by HVAC equipment. Possible causes include loose components, unbalanced fans, worn bearings, compressor problems, or improper installation.

N-coil - An evaporator coil arranged in an N-shaped configuration, often used in air handlers or furnace installations.

No electrical disconnect - A condition in which the required local electrical disconnecting means is missing or not readily accessible near the HVAC equipment.

One ton - A unit of cooling capacity equal to 12,000 British thermal units per hour (BTU/h). It originated from the approximate amount of heat required to melt one ton of ice in 24 hours.

Out of level - Equipment that is not installed level. Depending on the equipment design, this can affect drainage, operation, vibration, or service life.

Oversized - Equipment with a capacity greater than needed for the space or building. Oversized air conditioners may cool quickly but run for shorter cycles, potentially reducing humidity control and efficiency.

Rated Load Amperage (RLA) - A compressor electrical rating used by manufacturers to identify an expected operating-current value under specified conditions. It is not necessarily the same as the measured running current.

Receiver - A storage vessel in a refrigeration system that holds liquid refrigerant leaving the condenser before it flows toward the metering device.

Refrigerant - A fluid that circulates through a refrigeration or heat-pump system, absorbing heat in one part of the system and releasing it in another.

Return ducts - Ducts that carry indoor air back to the heating or cooling equipment to be filtered, heated, cooled, or otherwise conditioned.

Rotary, spray and drip - Types of evaporative-cooling arrangements. They use different methods of exposing water to moving air to promote evaporation and cooling.

Rust - Iron oxide corrosion that can develop on metal components exposed to moisture and oxygen. It may affect equipment cabinets, coils, supports, and other metal parts.

Short cycling - Frequent starting and stopping of heating or cooling equipment over short periods. It can result from oversized equipment, thermostat problems, restricted airflow, or equipment faults.

Sight glass - A transparent viewing window in a refrigerant line, often used to observe refrigerant condition or moisture indicators where the system design includes one.

Single pass - An evaporative-cooling arrangement in which air passes through the cooling medium once before being discharged into the building or space.

Sludge - Thick deposits of oil, dirt, moisture-related contaminants, or degraded material that can accumulate in refrigeration equipment and interfere with operation.

Slugging - A compressor condition in which liquid refrigerant or oil enters the compressor cylinders or compression chamber. Because liquids do not compress like gases, slugging can cause severe mechanical damage.

Suction line - The refrigerant line that carries low-pressure refrigerant vapor from the evaporator back to the compressor.

Supply ducts - Ducts that deliver heated or cooled air from the HVAC equipment to rooms throughout a building.

Swamp coolers - Another name for evaporative coolers, which cool air by evaporating water.

Temperature drop - The difference in air temperature measured between the return-air and supply-air sides of an operating cooling system. It can help assess system performance, although the expected range depends on operating conditions.

Thermostatic expansion valve - A refrigerant metering device that regulates refrigerant flow into the evaporator based on the refrigerant's superheat, helping maintain appropriate evaporator operation.

Trap - A curved section of drain piping that retains water to prevent air or gases from passing through. In condensate drainage, traps may be required depending on the equipment's pressure conditions.

Undersized - Equipment or components with insufficient capacity for the intended application. Undersized HVAC equipment may struggle to maintain the desired indoor temperature.

Undersized wire - Electrical wiring with a conductor size inadequate for the equipment's current requirements, circuit length, or applicable electrical code.

Water-cooled systems - Cooling systems that transfer heat to water rather than directly to outdoor air.

Water-cooled condenser coil - A heat exchanger that transfers heat from refrigerant to circulating water, allowing the refrigerant to condense.

Whole-house fan - A large fan that draws outdoor air through open windows and exhausts indoor air into the attic, typically helping cool a house when outdoor temperatures are lower than indoor temperatures.

Whole-house fans - Fans designed to ventilate a home by drawing cooler outdoor air through living spaces and exhausting warmer indoor air into the attic or outdoors.

Wrong breakers - Circuit breakers that are incorrectly sized or unsuitable for the HVAC equipment, potentially compromising electrical protection and safe operation. Breaker selection must follow equipment specifications and applicable electrical requirements.