Absolute Zero

Absolute zero is that temperature at which molecular motion stops. It is the lowest temperature possible. There is no more heat in the substance at this point.


Annual Investment Allowance

Air Conditioner

Device used to control temperature, humidity, cleanliness, and movement of air in conditioned space.


Department for Business, Enterprise and Regulatory Reform

Boiling Temperature

Temperature at which a fluid changes from a liquid to a gas/vapour. At atmospheric pressure water boils at 100°C, refrigerant (R22) at -40.8° C.


Building Research Establishment Energy Assesssment Model


Building Schools for the Future


Type of electrical storage device used in starting and/or running circuits on many electric motors.

Carbon Filter

Air filter using activated carbon as air cleansing agent.


Climate Change Levy


Community Energy Saving Programme


Combined Heat & Power (CHP) Quality Assurance Programme


The pump of a refrigerating mechanism which draws a vacuum or low pressure on cooling side of refrigerant cycle and squeezes or compresses the gas into the high pressure or condensing side of the cycle.

Compressor, Centrifugal

A compressor, which consists of impeller and volute. The impeller rotates at aprox. 10,000 rpm. Such force changes the gaseous refrigerant into speed energy, which is converted into pressure energy for compression.

Compressor, Hermetic

Compressor in which driving motor is sealed in the same dome or housing that contains the compressor.

Compressor, Open-type

Compressor in which the crankshaft extends through the crankcase and is driven by an outside motor.

Compressor, Rotary

A compressor, which uses vanes, eccentric mechanisms, or other, rotating devices to provide pumping action.

Compressor, Screw

A compressor which consist of rotors having male and female gears and compresses by engaging one screw rotor and two gate rotors to provide pumping action.

Compressor, Scroll

A compressor which uses two scrolls, one is fixed while the other revolves in orbit to provide pumping action.


The part of refrigeration mechanism which receives hot, high pressure refrigerant gas from compressor and cools gaseous refrigerant until it returns to liquid state.

Condensing Temperature

Temperature at which a gas changes from a gas to a liquid.

Condensing Unit

That part of refrigerating mechanism which pumps vaporised refrigerant from evaporator, compresses it, liquefies it in the condenser and returns the liquid refrigerant to refrigerant control.

Cooling Tower

Device, which cools water by water evaporation in air. Water is cooled to wet bulb temperature of air.


Carbon Reduction Commitment


Refrigeration which deals with producing temperatures of 250°F below zero (-157°C) and lower.


Code for Sustainable Homes


Daikin Building Airconditioning Control System. Computer operated control/management system utilising information generated by Daikin and other equipment.


Display Energy Certificates


Department of Energy & Climate Change


Department for the Environment, Food & Rural Affairs

Defrost Cycle

Refrigerating cycle in which evaporator frost and ice accumulation is melted.


Device used to remove moisture from air in enclosed space.


Dwelling Emission Rate (relates to CSH)

Dry Bulb

An instrument with sensitive element, which measures ambient (moving) air temperature

Dry Bulb Temperature

Air temperature as indicated by ordinary thermometer.


Department of Trade & Industry


Enhanced Capital Allowance scheme

Electrostatic Filter

Type of filter, which gives particles of dust electric charge. This causes particles to be attracted to a plate so they can be removed from air stream or atmosphere.


Energy is the capacity or ability to do work.


Energy Performance in Buildings Directive


Energy Performance Certificate


Energy Saving Trust


Energy Technology List


Energy using Products directive


A term applied to the changing of a liquid to a gas. Heat is absorbed in this process.


Part of a refrigerating mechanism in which the refrigerant vaporises and absorbs heat.

Expansion Valve

A device in refrigerating system which maintains a pressure difference between the high side and low side and is operated by pressure.


Feed-in Tariff

Freezing Point

The temperatures at which a liquid will solidify upon removal of heat. The freezing temperature for water is 32°F (0°C). at atmospheric pressure.


A unit of weight and equal to one 7000th of a pound (0.064 grams). It is used to indicate the amount of moisture in the air.


Heat is a form of energy. It is related to the molecular motion or vibration.

Heat Exchanger

Device used to transfer heat from a warm or hot surface to a cold or cooler surface. Evaporators and condensers are heat exchangers.

Heat Load

Amount of heat, measured in Btu, which is removed during a period of 24 hours.

Heat Pump

A compression cycle system used to supply heat to a temperature controlled space, which can also remove heat from the same space.

Heat Reclaim Ventiliation (HRV)

Ventilation system operates on the principle of reclaiming energy from exhaust air.

Heat Transfer

Movement of heat from one body or substance to another. Heat may be transferred by radiation, conduction, convection or a combination of these three methods.


Heat & Energy Saving Strategy


A unit of power equal to 33,000 foot pounds of work per minute. One electrical horsepower equals 746 watts.


Device used to add to and control the humidity in a confined space.


Moisture; dampness. Relative humidity is ratio of quantity of vapour present in air to greatest amount possible at given temperature.

Hydrochlorofluorocarbon (HCFC)

A compound containing chlorine but since hydrogen is present, the risk of damaging the ozone layer is low.

Hydrofluorocarbon (HFC)

A compound which does not contain chlorine and does not damage the ozone layer.

Latent Heat

Heat energy absorbed in process of changing form of substance (melting, vaporisation, fusion) without change in temperature or pressure.


Low Carbon Building Programme


Microgeneration Certification Scheme


Power is the time rate of doing work.

Psychrometer or Wet Bumb Hygrometer

An instrument for measuring the relative humidity of atmospheric air.

Psychrometric Chart

A chart that shows the relationship between the temperature, pressure and moisture content of the air.


Substance used in refrigerating mechanism to absorb heat in evaporator coil by change of state from a liquid to a gas, and to release its heat in a condenser as the substance returns from the gaseous state back to a liquid state.

Relative Humidity

Ratio of amount of water vapour present in air to greatest amount possible at same temperature.

Reversing Valve

Device used to reverse direction of the refrigerant flow depending upon whether heating or cooling is desired.


Renewable Heat Incentives

SAP 2010

Standard Assessment Procedure (domestic applications)


Standard Building Energy Model (non-domestic applications)

Sensible Heat

Heat, which causes a change in temperature of a substance.

Shell and Tube Flooded Evaporator

Device, which flows water through tubes, built into cylindrical evaporator or vice-versa.

Shell Type Condenser

Cylinder or receiver, which contains condensing, waters coils or tubes.

Sky Air

Sky Air is a trade name of Daikin middle range split systems.

Soft Landings

Soft Landings means designers and constructors staying involved with buildings beyond practical completion.

Soft Landings will recognise and overcome problems beyond building handover.

Solar Heat

Heat from visible and invisible energy waves from the sun.

Specific Gravity

Weight of a liquid compared to water, which is assigned value of 1.0.

Specific Heat

Ratio of quantity of heat required to raise temperature of a body one-degree to that required to raise temperature of equal mass of water one degree.

Specific Volume

Volume per unit mass of a substance.

SPF (Seasonal Performance Factor)

The SPF takes into consideration both the energy consumption of the heat pump system as well as the consumption by peripheral equipment, such as pumps, over the entire heating season.

Split System

Refrigeration or air conditioning installation, which places condensing unit outside or remote from evaporator. Also applicable to heat pump installations.


Cooling of liquid refrigerant below its condensing temperature.

Suction Line

Tube or pipe use to carry refrigerant gas from evaporator to compressor.


Temperature of vapour above boiling temperature of its liquid at that pressure.


Degree of hotness or coldness as measured by a thermometer; measurement of speed of motion of molecules.


Target Emission Rate (relates to CSH)


Quantity of heat equivalent to 100,000Btu (105,500 kJ)


Device responsive to ambient temperature conditions.

Vacuum Pump

Special high efficiency compressor used for creating high vacuums for testing or drying purposes.

VAV (Variable Air Volume)

A central air conditioning system which works on the principle of supplying constant temperature air volume to a space, and by varying the volume, controls room temperature.

VRF (Variable Refrigerant Flow)

A direct expansion, modular central air conditioning system providing heating and cooling. Operates on the principle of varying the flow of refrigerant to a room terminal unit to achieve desired temperature.

VRV (Variable Refrigerant Volume)

Trade mark for Daikin VRF systems.

VVT (Variable Volume Variable Temperature)

Same principle as VAV, except two ducts are required, one for heating, one for cooling, with variable control dampers.

VWT (Variable Water Temperature)

Same as VWV but changing both the volume and the temperature of the water to achieve room temperature.

VWV (Variable Water Volume)

A central water based system operating on the principle of supplying constant temperature of chilled/hot water to room terminals and varying the flow to achieve room temperature.


Waste Electrical and Electronic Equipment

Wet Bulb

Device used in measurement of relative humidity. Evaporation of moisture lowers temperature of wet bulb compared to dry bulb temperature in same area.


Work is force multiplied by the distance through which it travels.