Air conditioning contractors glossary

Short, plain-English definitions of the terms you'll meet when choosing a air conditioning contractor provider in Yishun.

Fan coil unit: A fan coil unit is the indoor component of a chilled water or hot water air conditioning system. A fan pulls room air across a coil carrying water, then pushes the cooled or heated air back into the space.
Non-inverter aircon: A non-inverter aircon is an air conditioner with a fixed-speed compressor that runs at full power until the room reaches the set temperature, then switches off completely and restarts when the temperature drifts. It is the conventional design that inverter units replaced in most newer installations.
Refrigerant leak: A refrigerant leak is the escape of coolant gas from an air conditioning system's sealed circuit, which lowers cooling capacity and can damage the compressor. It usually happens at joints, flares, or coils where the copper pipework or components have worn, cracked, or loosened.
Thermostat sensor: A thermostat sensor is the small temperature probe that measures the air around it and sends that reading to the air conditioner's control board. The control board uses the reading to decide when to start and stop the compressor, which sets how often the unit cycles.
What is a BTU (British thermal unit)?: A British thermal unit (BTU) is a measure of heat energy, and in air conditioning it states how much heat a unit can remove from a room in one hour. Higher BTU ratings mean greater cooling capacity.
What is a capacitor?: A capacitor is a small electrical component in an air conditioner that stores and releases charge to help the compressor and fan motors start and keep running. It is usually a cylindrical part inside the outdoor condenser unit.
What is a chemical overhaul?: A chemical overhaul is a deep aircon cleaning in which the technician dismantles the indoor unit, or the parts of it, and washes the coil, fan, and drain components with specialist cleaning agents. It goes further than a routine service that cleans only the exposed filters and surfaces.
What is a chemical wash?: A chemical wash is an aircon cleaning procedure in which a technician applies specialist cleaning solutions to the evaporator coil, condenser coil, and other parts to dissolve dirt, grease, and biological buildup that water rinsing cannot remove. It is a targeted deep clean, distinct from the routine servicing of filters, drains, and electrical checks.
What is a compressor?: A compressor is the component in an air conditioning system that pressurises refrigerant gas and pushes it around the closed loop between the indoor and outdoor units. Without it, the refrigerant cannot absorb heat indoors or release it outside.
What is a condensate drain pan?: A condensate drain pan is a shallow tray under an air conditioner's evaporator coil that catches the water formed when warm air is cooled. It carries that water to a drain line so it does not leak into the ceiling or walls.
What is a condenser unit?: A condenser unit is the outdoor component of an air conditioning system that releases heat collected from indoors into the outside air. It houses the compressor, condenser coil and fan.
What is a drain pipe choke?: A drain pipe choke is a blockage in the condensate drain line that carries water away from an air conditioner, usually caused by algae, dust, or sludge. When the water cannot drain, it backs up and can leak from the indoor unit or the ceiling.
What is a gas top-up?: A gas top-up is the process of adding refrigerant to an air conditioning system that has lost some of its charge. Because refrigerant is sealed in a closed circuit, a system that needs topping up usually has a leak somewhere.
What is a PCB (control board) in an air conditioner?: A PCB (printed circuit board), often called the control board, is the electronic board inside an air conditioning unit that runs its logic, sensors, and fan and compressor signals. When it fails, the unit may stop, restart repeatedly, or show error codes.
What is an evaporator coil?: An evaporator coil is the indoor coil in an air conditioning system where liquid refrigerant evaporates and absorbs heat from the room air passing over it. It is the cooling half of the refrigerant cycle that sits inside the indoor unit or air handler.
What is general servicing?: General servicing is the routine, scheduled maintenance of an air conditioning system, typically covering filter cleaning, basic coil cleaning, and inspection of key components. It keeps a unit running efficiently and helps catch small faults before they become breakdowns.
What is inverter aircon?: An inverter air conditioner uses a variable-speed compressor that ramps its output up or down to match the room's cooling needs. A non-inverter (fixed-speed) unit instead runs its compressor fully on or fully off.
What is R22 refrigerant?: R22 (chlorodifluoromethane) is an older hydrochlorofluorocarbon refrigerant once common in air conditioners, now being phased out because it depletes the ozone layer. Systems that run on it need special handling and are increasingly costly to service.
What is R32 refrigerant?: R32 is a hydrofluorocarbon (HFC) refrigerant, chemically difluoromethane, used to move heat in newer air conditioning systems. It has a lower global warming potential than R410A, the refrigerant it has largely replaced in new residential units.
What is R410A refrigerant?: R410A is a hydrofluorocarbon (HFC) refrigerant blend, sold under names such as Puron, that circulates through an air conditioner to move heat from inside a room to outside. It is the standard refrigerant in many split-system and multi-split units installed in Singapore homes and offices over the past couple of decades.
What is refrigerant?: Refrigerant is the heat-carrying fluid that circulates through an air conditioner's cooling cycle, absorbing heat indoors and releasing it outdoors. It changes between liquid and gas at low temperatures, which is what makes cooling possible.
What is System 1, 2, 3 and 4 aircon?: System 1, 2, 3 and 4 aircon is the Singapore trade term for a multi-split air conditioning setup in which one outdoor condensing unit serves one, two, three or four indoor units. The number refers to how many indoor units the outdoor unit can feed.
What is the NEA energy label (ticks)?: The NEA energy label (ticks) is the tick-based rating printed on air conditioners sold in Singapore under the Mandatory Energy Labelling Scheme run by the National Environment Agency. More ticks indicate a more energy-efficient unit.
What is the Singapore Green Label?: The Singapore Green Label is an environmental certification run under the National Environment Agency's Singapore Green Label Scheme that marks air conditioners meeting set energy efficiency and environmental standards. Products that carry it are generally more energy-efficient than comparable models without the label.