AC Disconnect
A service disconnect located near outdoor HVAC equipment that provides a local means of disconnecting electrical power.
Access Panel
A removable equipment panel used to reach serviceable components inside a furnace, air handler, condenser or package unit.
Accumulator
A vessel typically installed in the suction line to help prevent liquid refrigerant from reaching the compressor.
Actuator
An electric or electronic device that moves a damper, valve or other controlled component.
Air Handler
An indoor HVAC assembly that normally contains a blower and coil and may also contain electric heat, filters or controls.
Air Scoop
A hydronic fitting designed to help separate entrained air from circulating water.
Air Separator
A hydronic component that removes entrained or dissolved air from a hot-water heating system.
Air Vent
A manual or automatic device used to release trapped air from hydronic piping or terminal units.
Airflow Switch
A switch used to prove that air is moving before or during operation of certain HVAC equipment.
Anemometer
An instrument used to measure air velocity and, with appropriate methods, estimate airflow.
Anti-Short-Cycle Timer
A time-delay control that helps prevent a compressor or other equipment from restarting too soon after shutdown.
Aquastat
A temperature-sensing control commonly used on boilers and hydronic systems to start, stop or limit equipment based on water temperature.
Backdraft Damper
A damper designed to allow airflow in one direction while limiting reverse airflow.
Balancing Damper
A manual or automatic damper used to adjust airflow through a duct branch.
Ball Valve
A quarter-turn shutoff valve that uses a drilled ball to open or close fluid flow.
Barometric Damper
A draft-regulating device used on some combustion vent systems to help maintain proper draft.
Belt Drive
A motor-and-pulley drive arrangement that turns a blower wheel through a belt.
Blower Door Switch
A switch that interrupts equipment operation when a furnace or air-handler access panel is removed.
Blower Housing
The enclosure around a centrifugal blower wheel that directs air into the supply path.
Blower Motor
The motor that drives the indoor blower wheel.
Blower Wheel
A centrifugal fan wheel, often called a squirrel-cage wheel, that moves air through the indoor equipment.
Boiler
Heating equipment that transfers heat into water for distribution through radiators, baseboard, radiant tubing or other hydronic terminals.
Boiler Drain
A drain valve used to drain water from boilers, piping or hydronic components.
Breaker
An overcurrent protective device that opens an electrical circuit when current exceeds its rating or a fault occurs.
Burner
A device that mixes fuel and air and supports controlled combustion in a furnace or boiler.
Burner Orifice
A precisely sized opening that meters gas flow into a burner.
Burner Rack
The assembly that supports and aligns multiple furnace burners.
Bypass Damper
A damper used in some zoning systems to relieve excess supply pressure by routing air around part of the distribution system.
Bypass Humidifier
A humidifier that uses a duct bypass and furnace airflow to move air across a wetted evaporative pad.
Capacitor
An electrical component that stores energy and is commonly used with single-phase motors and compressors for starting or running.
Capillary Tube
A fixed-bore refrigerant metering device made from small-diameter tubing.
Catch-All Dryer
A trade term often used for a filter-drier installed in a refrigeration system to remove moisture, acid and debris.
Check Valve
A valve that allows flow in one direction and restricts reverse flow.
Circuit Board
An electronic control board that receives inputs and sends outputs to operate HVAC components.
Circulator Pump
A pump used to move heated water through a hydronic heating system.
Coil Cleaner
A chemical cleaning product formulated for evaporator or condenser coil surfaces. Product selection must match the coil and manufacturer guidance.
Combustion Analyzer
An instrument used to measure combustion gases and evaluate appliance combustion performance.
Compressor
The component that circulates refrigerant vapor and raises its pressure and temperature.
Compressor Crankcase Heater
A heater used on some compressors to help prevent refrigerant migration and dilution of compressor oil during off cycles.
Condensate Drain
Piping that carries condensate away from an evaporator coil, air handler, furnace or dehumidifier.
Condensate Pan
A pan that collects water beneath an evaporator coil or other condensing component.
Condensate Pump
A small pump used to lift condensate to a suitable drain point when gravity drainage is not practical.
Condenser Coil
The coil surface in the condenser where refrigerant rejects heat.
Condenser Fan
The outdoor fan that moves air across a condenser or outdoor heat-pump coil.
Condenser Fan Motor
The motor that drives the outdoor fan blade.
Contactor
An electrically controlled switch used to apply line voltage to compressors, fan motors and other loads.
Control Transformer
A transformer that commonly reduces line voltage to 24 VAC for HVAC control circuits.
Copper Fitting
A fitting used with copper tubing, including elbows, couplings, reducers and tees.
Core Removal Tool
A tool used to remove or replace Schrader valve cores, often while maintaining system access.
Crankcase Heater
A heater attached to or installed in a compressor sump to keep compressor oil warm during off periods.
Curb Adapter
A fabricated transition used to mount replacement rooftop equipment to an existing roof curb.
Cut-In Pressure
The pressure at which a pressure control closes or initiates operation.
Cut-Out Pressure
The pressure at which a pressure control opens or stops operation.
Damper
A plate or blade installed in ductwork to regulate or shut off airflow.
Defrost Board
An electronic control used on heat pumps to manage outdoor-coil defrost operation.
Diffuser
A supply-air outlet designed to distribute air in a specific pattern.
Digital Manifold
An electronic manifold instrument used to measure refrigerant pressures, temperatures and calculated refrigeration values.
Disconnect
A local switching means used to isolate equipment from electrical power.
Draft Inducer
A motor-driven fan that establishes airflow through a furnace heat exchanger and vent system before ignition.
Drain Trap
A shaped section of condensate piping used where required to allow proper drainage under positive or negative air pressure.
Duct Board
Rigid fiberglass board used to fabricate certain duct systems or plenums.
Duct Collar
A round or rectangular fitting used to connect a branch duct to a trunk, plenum or air device.
Duct Liner
Insulation installed on the inside surface of metal ductwork for thermal or acoustic control.
Duct Sealant
Mastic or approved sealant used to seal duct joints and leakage points.
Ductless Mini-Split
A split-system heat pump or air conditioner using one or more indoor units without conventional central ductwork.
ECM Motor
Electronically commutated motor used in many modern blowers and fans for efficient, electronically controlled operation.
Economizer
A control and damper arrangement that can use outdoor air for cooling when conditions are suitable.
Electronic Expansion Valve
An electronically controlled refrigerant metering device that adjusts flow through commands from a controller.
Emergency Heat
A thermostat mode that disables normal heat-pump compressor heating and uses the configured backup heat source.
End Switch
An auxiliary switch that proves a damper, valve or actuator has reached a commanded position.
Energy Recovery Ventilator
A ventilation device that exchanges heat and some moisture between exhaust and incoming outdoor air streams.
Evaporator Coil
The heat exchanger where refrigerant absorbs heat and evaporates. In standard cooling operation, this is normally the indoor coil.
Expansion Tank
A tank that accommodates thermal expansion of water in a closed hydronic heating system.
Fan Blade
A propeller-style blade used on condenser fans, heat pumps, exhaust fans and other axial-airflow applications.
Fan Center
A packaged transformer and relay assembly commonly used in older or simple HVAC control systems.
Fan Coil
An indoor unit containing a fan and coil used to heat or cool air.
Fan Limit Control
A control used on some furnaces to manage blower operation and high-temperature limit protection.
Filter Grille
A return-air grille designed to hold an air filter.
Filter-Drier
A sealed refrigerant-line component containing desiccant and filtration media to remove moisture, acid and debris.
Flame Rollout Switch
A safety switch designed to open if flame or excessive heat is detected outside the normal burner/heat-exchanger area.
Flame Sensor
A device used by many gas furnaces to prove that burner flame is present.
Flare Fitting
A mechanical tubing connection using a flared tube end and matching nut/fitting, common on mini-splits and some refrigeration systems.
Flex Connector
A flexible connection used to reduce vibration transmission in duct, gas or piping applications.
Flex Duct
Flexible insulated duct consisting of an inner liner, reinforcing helix, insulation and outer jacket.
Float Switch
A condensate safety control that opens a control circuit when water rises to an abnormal level.
Foam Tape
Adhesive-backed foam used for gasketing, vibration isolation, sealing and cabinet interfaces.
Furnace
Heating equipment that warms air and distributes it through ductwork.
Fuse
A sacrificial overcurrent protective device that opens a circuit when current exceeds its rating.
Fusible Link
A heat-sensitive link designed to release or open at a specified temperature in certain safety applications.
Gas Cock
A manual shutoff valve installed in a gas piping system.
Gas Flex Connector
A listed flexible connector used between fixed gas piping and an appliance where permitted.
Gas Valve
An electrically controlled valve that regulates fuel gas flow to burners.
Gauge Manifold
A service instrument used to connect to refrigeration systems and read high- and low-side pressures.
Grille
An air inlet or outlet device with fixed openings and no adjustable damper.
Grommet
A protective insert used where wires, tubing or piping pass through sheet metal or other sharp openings.
Heat Anticipator
An adjustable resistance element in older mechanical thermostats used to influence heating cycle timing.
Heat Exchanger
A furnace component that transfers heat from combustion gases to the circulating indoor air without mixing the two.
Heat Pump
Refrigeration equipment that can provide both cooling and heating by reversing the direction of heat transfer.
Heat Recovery Ventilator
A ventilation device that transfers sensible heat between outgoing and incoming air streams.
Heat Strip
An electric resistance heating element or assembly installed in an air handler or package unit.
High-Limit Switch
A temperature safety control that interrupts burner operation if furnace temperature rises above its allowable range.
High-Pressure Switch
A pressure safety control that opens or signals a fault when high-side refrigerant pressure exceeds a set limit.
Hot-Surface Igniter
An electrically heated ignition element used to ignite gas burners.
Humidifier Pad
A replaceable evaporative media panel used in many bypass and powered humidifiers.
Humidistat
A control that senses humidity and operates humidification or dehumidification equipment.
Ignition Control Module
An electronic control that manages ignition sequencing and flame proving on combustion equipment.
Inducer Motor
The motor that drives a draft inducer fan.
Inverter Compressor
A compressor driven by variable-frequency electronics so capacity can modulate over a range.
Isolation Relay
A relay used to electrically separate one control circuit or device from another.
Isolation Valve
A shutoff valve installed to isolate a component for service.
Junction Box
An enclosure used to contain electrical splices and wiring connections.
Leak Detector
An instrument or solution used to detect refrigerant or gas leaks, depending on the detector type.
Limit Switch
A temperature, pressure or position switch that stops or permits operation based on a defined condition.
Line Set
The pair of refrigerant tubes connecting indoor and outdoor sections of a split system.
Liquid Line
The smaller refrigerant line that normally carries high-pressure liquid refrigerant toward the metering device during cooling.
Liquid-Line Solenoid
An electrically operated valve installed in a liquid refrigerant line to control refrigerant flow.
Low-Pressure Switch
A pressure control that opens or signals a fault when low-side pressure falls outside a defined range.
Mastic
A thick sealant commonly used to seal duct joints and seams.
Metering Device
A device such as a TXV, piston or electronic expansion valve that controls refrigerant flow into the evaporator.
Micron Gauge
An instrument used to measure deep vacuum during refrigeration-system evacuation.
Mini-Split
A ductless or limited-duct split system using one or more indoor units connected to outdoor equipment.
Motor Module
The electronic control portion of certain ECM motors.
Motor Pulley
A pulley mounted on a motor shaft in a belt-driven blower system.
Multi-Tap Motor
A motor with multiple speed taps used to select different operating speeds.
Multi-Zone System
An HVAC system serving multiple independently controlled zones or indoor units.
Needle Valve
A fine-control valve used to regulate small fluid or gas flows in service equipment and specialty applications.
Nitrogen Regulator
A pressure regulator used with nitrogen cylinders for pressure testing, purging or brazing support.
Oil Separator
A device used in some refrigeration systems to separate compressor oil from discharge gas and return oil to the compressor.
Orifice
A fixed refrigerant metering opening, often installed in a piston-style distributor assembly.
Overload
A protective device that opens when a motor or compressor experiences excessive current or temperature.
Oxidation
Chemical reaction with oxygen that can contribute to corrosion of metals and electrical contacts.
P-Trap
A U-shaped drain trap used in condensate piping where required by equipment pressure conditions.
Package Unit
A self-contained HVAC unit that houses major heating and/or cooling components in one cabinet.
Pancake Condensate Pump
A low-profile condensate pump used where space is limited.
Panel
A removable cabinet section or electrical enclosure used to access or protect components.
Piston
A fixed-orifice refrigerant metering component used in some HVAC systems.
Plenum
A large supply or return air chamber attached to HVAC equipment.
Pressure Switch
A switch that changes state when sensed pressure reaches a defined threshold.
Primary Drain
The normal condensate drain connection intended to carry water away from an evaporator pan.
Programmable Thermostat
A thermostat that changes temperature setpoints according to a programmed schedule.
Puller
A mechanical tool used to remove pulleys, wheels or other press-fit components from shafts.
Quick Disconnect
A fitting or connector designed for rapid connection and disconnection in approved service applications.
Recovery Cylinder
A refillable cylinder specifically rated and identified for storing recovered refrigerant.
Recovery Machine
Equipment used to remove refrigerant from a system and transfer it into an approved recovery cylinder.
Register
A grille-like air outlet or inlet that includes an adjustable damper.
Relay
An electrically operated switch used to control another circuit.
Return Drop
A vertical or horizontal duct section that connects the return system to the equipment.
Reversing Valve
A valve that changes refrigerant-flow direction so a heat pump can switch between heating and cooling.
Rollout Switch
A safety device that opens if flame or excessive heat appears outside the intended combustion path.
Run Capacitor
A capacitor designed to remain in a motor or compressor circuit during operation.
Safety Pan
A secondary pan installed beneath equipment or a coil to help contain water if the primary drainage system fails.
Schrader Core
A spring-loaded valve core used in many refrigerant service ports.
Scroll Compressor
A compressor design that uses orbiting and stationary scroll elements to compress refrigerant vapor.
Secondary Drain
An auxiliary condensate drain or overflow connection intended to provide warning or backup drainage.
Service Port
A connection point used by qualified technicians to access refrigerant-system pressure.
Service Valve
A valve on outdoor equipment used to isolate or access refrigerant piping.
Sheet Metal Screw
A self-tapping or self-drilling screw commonly used to assemble HVAC sheet-metal components.
Sight Glass
A viewing device used in some systems to observe fluid condition, flow or moisture indication.
Slinger Ring
A ring or feature on some fan assemblies that helps distribute condensate or water.
Solenoid Valve
An electrically operated valve used to start or stop fluid or refrigerant flow.
Spade Connector
A flat-blade electrical terminal used for quick wire connections.
Split System
An HVAC system with major components located in separate indoor and outdoor cabinets.
Start Capacitor
A capacitor used briefly during motor or compressor startup to provide additional starting torque.
Suction Accumulator
An accumulator installed in the suction line to reduce the risk of liquid refrigerant reaching the compressor.
Suction Line
The larger refrigerant line that normally carries low-pressure vapor from the evaporator toward the compressor in cooling mode.
Supply Boot
A sheet-metal fitting that connects a branch duct to a register or grille opening.
Supply Plenum
The main chamber attached to the discharge side of a furnace or air handler.
Thermocouple
A heat-responsive device used on older standing-pilot systems to prove pilot flame.
Thermostat
The device that senses indoor conditions and requests heating, cooling or fan operation.
Thermostatic Expansion Valve
A refrigerant metering device that modulates flow into the evaporator based on sensed operating conditions.
Transformer
An electrical device used to change voltage, commonly reducing line voltage to 24 VAC for controls.
Trap Primer
A device used to maintain water in a plumbing trap where evaporation could allow the trap to dry.
TXV
Thermostatic expansion valve, a common modulating refrigerant metering device.
Union
A fitting that allows a piping connection to be separated without cutting the pipe.
Unit Heater
A self-contained heating appliance that discharges heated air directly into a space.
UV-C Lamp
An ultraviolet germicidal lamp used in some HVAC applications, commonly aimed at coil or drain-pan surfaces.
Vacuum Pump
A pump used to evacuate air and moisture from a sealed refrigeration system.
Vacuum-Rated Hose
A hose designed for low-restriction evacuation work and deep-vacuum service.
Variable Capacity
HVAC equipment capable of modulating output over a range instead of operating only at fixed stages.
Variable-Speed Blower
A blower system that can adjust airflow for different modes, capacities or control strategies.
Vent Connector
The portion of a venting system that connects an appliance to a chimney or common vent.
Vent Damper
A motorized or automatic damper used in some vent systems to reduce standby losses or control vent flow.
Vibration Isolator
A rubber, spring or composite mount used to reduce transmission of equipment vibration.
Whip
A flexible electrical conduit assembly commonly used between a disconnect and outdoor HVAC equipment.
Wire Nut
A twist-on insulated connector used to join electrical conductors where appropriate.
Zone Damper
A motorized damper that opens or closes to control airflow to a zone.
Zone Panel
A control panel that coordinates multiple thermostats and zone dampers with HVAC equipment.
Zone System
An HVAC arrangement that independently controls different areas using dampers, multiple indoor units or other zoning methods.