Absorption Refrigeration

A refrigeration system in which cooling is achieved by the effect of a refrigerant being absorbed by a chemical substance.


Formal, third party recognition of competence to perform specific tasks.

Adiabatic Cooling

The process of reducing heat through a change in air pressure caused by volume expansion.

Air Conditioning (AC)

The process of controlling the humidity, temperature and air movement in a building or vehicle [an enclosed or occupied space], typically to maintain a cool atmosphere in warm conditions.

Air Filters

A particulate air filter is a device composed of fibrous materials which removes solid particulates from the air.

A chemical air filter consists of an absorbent or catalyst for the removal of airborne molecular contaminants such as volatile organic compounds or ozone.

Air Source Heat Pumps

See Heat Pumps

Alternating Current (AC)

Flow of electric charge that periodically reverses.

Alternative Energy

Usable energy intended to supplement or replace energy derived from fossil fuel sources.

Ambient Temperature

Temperature of a fluid or gas (usually air) which surrounds an object on all sides.

Ammonia (NH3)

A colourless gas composed of nitrogen and hydrogen with a characteristic pungent smell which dissolves in water to give a strong alkaline solution and can also be easily condensed to a liquid. Commonly used in cleaning products and as a refrigerant.

Ammonia (R717)

A refrigerant grade high purity ammonia (NH3) that has zero ODP and zero GWP. A natural refrigerant.

Ampere (Amp)

The unit of current. One ampere is the current flowing through one ohm of resistance at one volt potential.


Abbreviation for (mobile) application - an app is a piece of application software designed to run on a smart phone, tablet or other mobile device.

Automatic Expansion Valve (AEV)

An automatic expansion valve is an expansion device that meters refrigerant to an evaporator by using a pressure sensing device to maintain a constant pressure in an evaporator.

Atmospheric Pressure

The force per unit area (pressure) exerted by the weight of the air above us due to gravity.


A blend made up of two or more refrigerants with similar boiling points that act as a single fluid.

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Brazing (Silver Soldering)

Metal-jointing process whereby a filler metal is heated above its melting point and distributed between two or more close fitting parts by capillary action.

Boiling Point

The temperature at which a liquid boils and turns to vapour.

BREEAM (Building Research Establishment Environmental Assessment Method)

Environmental assessment method and rating system for buildings.

British Thermal Unit (BTU)

Traditional unit of energy. The amount of energy needed to cool or heat one pound of water by one degree Fahrenheit. The joule, the SI unit of energy, has largely replaced the BTU.

Building Management System (BMS)

A computer-based control system installed in buildings that controls and monitors the building’s mechanical and electrical equipment such as ventilation, lighting, power, fire and security systems.

Building Maintenance

See Property Maintenance


An organisation where goods (products) or services are exchanged for one another or for money. A business can be privately owned, publically owned or not for profit.

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Carbon Dioxide (CO2)

A naturally occurring chemical compound composed of two oxygen atoms covalently bonded into a single carbon atom. Primarily  produced by the combustion of fossil fuels.

Carbon Dioxide Refrigerant (R744)

A high pressure refrigerant used in both commercial and industrial applications. Non-toxic, non-flammable, non ozone-depleting, and 'environmentally friendly' with a GWP of 1.

Carbon Footprint

Total amount of greenhouse gas emissionEmission: Any substance discharged into the air, earth or water.  caused directly and indirectly by a business or activity.

Carbon Monoxide (CO)

A colourless, odourless, and tasteless gas which is slightly lighter than air. It is highly toxic to humans and animals when encountered in higher quantities.

Carbon Management

Initiatives for low carbon innovation, the reduction of carbon usage and leakage.

Carbon Trust

Independent experts on carbon reduction and resource efficiency who reinvest surpluses from group commercial activities into a mission of accelerating the move to a sustainable, low carbon economy.

Case Study

A descriptive analysis of an actual event or occurrence e.g. the application of a new technology.

Cascade System

Two or more refrigeration systems used in series. The evaporator of one system is used to cool the condenser of the other.

CFC (Chlorofluorocarbon) Refrigerant

Refrigerants comprised of Chlorine, Fluorine and Carbon which have been phased out of use because of their high ozone depletion potential (ODP)

Celsius Scale (˚C)

The standard scale used around most of the world, excluding the USA, to measure air temperature. The zero point is set to the temperature at which water freezes, and 100 degrees is the point at which water boils (at atmospheric pressure). 


The provision of written assurance (a certificate) by an independent body that a product, service or system meets specific requirements.

Certification Body

An organisation delegated by a higher governing body in a particular business sector or trade; to assess individual company compliance with the laid down standards, compliance and qualification requirements of that business sector or trade, to carry out a certification service, and keep a register of certified companies.

Chiller (Air Conditioning)

A vapour compression system designed to chill water for air conditioning systems.

Climate Change

A large-scale, long-term shift in the planet's weather patterns or average temperatures - also referred to as Global Warming.


An educational institution or a constituent part of one. A college may be a degree-awarding tertiary (post school) educational institution, a part of a collegiate university, or an institution offering vocational education.

Commercial Refrigeration

Refrigeration systems and equipment used as part of a commercial enterprise e.g. supermarket, restaurant kitchen, ice maker etc.


Checking, inspection and test running of engineering systems against set operating parameters.

Compressor (Refrigerant)

Circulates refrigerant in the vapour compression system, and increases the pressure and temperature of the refrigerant so that it can be condensed into liquid. The compressor separates the low and high sides of the system. See Reciprocating Compressors and Rotary Compressors


Waste water from the condensation formed on an evaporator in the refrigeration processes.


A heat exchanger on the ' hot side' of a refrigeration system in which refrigerant condenses and rejects heat to the cooling medium (ambient air or water).

Condensing Temperature

The temperature at which refrigerant is condensed from a vapour to a liquid.

Condensing Unit

A self contained refrigeration unit including the compressor, condenser, condenser fan motor and controls.


Reducing the use of energy by reducing waste and increasing energy efficiency.


A professional who provides professional or expert advice in a particular area.


A person or group of people who purchase products and services and are the final (end user) of those products and services in a supply chain.

Control and Monitoring System

Electronic, electromechanical or mechanical control and monitoring devices used together to maintain a desired output of any system or device.

Control of Substances Hazardous to Health (COSHH)

The law that requires employers to control substances that are hazardous to health[1].

Cooling Tower

A heat rejection device which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid.

COP (Coefficient of Performance)

A measure of the efficiency of a refrigeration system.


A large company or group of companies.

Cost Effective

When the monetary savings, primarily due to energy efficiency and the use of renewable energy, of an initiative exceed the cost of the capital and maintenance of that initiative over a period of time.

CPD (Continuing Professional Development)

Continuing Professional Development (CPD) is a way of recording the fact that you keep your skills up to date and providing recognition of the time and efforts you put into this.

Critical Pressure

The saturation pressure equivalent to the Critical Temperature.

Critical Temperature

The temperature above which gas cannot be liquefied, irrespective of pressure.


Relating to very low temperature.

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Data Centre

A facility used to house a large group of networked computer servers.

Data Centre Cooling

Air Conditioning system used to control air temperature and humidity for Data Centres.

DECC (Department of Energy and Climate Change)

The Department of Energy & Climate Change works to make sure the UK has secure, clean, affordable energy supplies and promote international action to mitigate climate change.


The removal of ice or frost build up from an evaporator, either by the use of electrical heating, system gas or periodic shut down of a refrigeration system.

Defrost Timer

An electronic timer used to initiate or terminate a defrost.

Design Services

The services of a professional refrigeration, air conditioning or heat pump design engineer, consultant or company for either RACHP system, plant or component design


Cool a liquid below its boiling point or a vapour below its saturation point.

Dew Point

The temperature at which vapour will condense or, where associated with glide, the higher or highest boiling point of the mixture.

Direct Current (DC)

Electrical current, which flows in one direction only.

Directory (Fridgehub)

Detailed listing of RACHP, energy and environmental product and service providers, education institutions, training centres, member organisations, trade associations, F-Gas certification bodies, profession institutes and certification bodies.


A business facility that purchases bulk products from a manufacturer, warehouses them, and resells them to installation, service and repair contractors or direct to end users or consumers.

Domestic Refrigerator (Fridge)

A domestic appliance used for the storage of chilled or frozen food.

Domestic RHI (Renewable Heat Incentive)

A financial incentive scheme designed to encourage uptake of renewable heating among domestic consumers. The domestic RHI is targeted at, but not limited to, homes off the gas grid. Those without mains gas have the most potential to save on fuel bills and decrease carbon emissions. The scheme covers single domestic dwellings and is open to homeowners, private landlords, social landlords and self-builders. It is not open to new build properties other than self-build.


A system for the conveyance of rainwater, wastewater or condensate. 

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For business it is the comparison of what is actually produced or performed with what can be achieved with the same consumption of resources (money, time, labour, etc.).

For RACHP systems it is the ratio of the energy delivered, or work done, by a system to the energy needed, or work required, in operating the system.

End User

The person, group of people or business who use a product or service  

Energy Efficiency

The use of less energy to provide the same service or result.

Energy Saving Trust

A social enterprise with a Charitable Foundation who through their partnerships offer impartial advice to communities and households on how to reduce carbon emissions, use water more sustainably and save money on energy bills.

Energy Management

The planning and operation of energy production and consumption for resource conservation, climate protection and cost savings, whilst ensuring users have permanent access to the energy they need.

Energy Performance Certificates (EPCs)

An EPC is required when a property is built, sold or rented and contains information about the property's energy use and typical energy costs, and with recommendations about how to reduce energy use and save money.

Energy Source

Energy is sourced from either fossil fuels (oil, coal or gas), nuclear (fission or fusion), or renewables (wind, hydro, geothermal, solar, biomass and wave)


A quantitative measure of thermal energy in a thermodynamic system or process that is not available for conversion into work.

Environmentally Friendly

Not harmful to the environment.


Discharge of a gas or refrigerant to the atmosphere.

Evaporating Temperature

The temperature at which refrigerant boils from liquid to a vapour.

Evaporative Cooling

An evaporative cooler is basically a large fan that draws warm air through water-moistened pads. As the water in the pads evaporates, the air is chilled and pushed out to the room. The temperature can be controlled by adjusting the airflow of the cooler.


A heat exchanger where heat from the refrigerated space is absorbed by the refrigerant, using latent heat of vapourisation, to maintain temperature and humidity at desired conditions.


Conferences, exhibitions, seminars and networking opportunities.

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Facilities Management (FM)

The integration of processes within an organisation to maintain and develop services which support and improve the effectiveness of its primary activities. 

Facilities Maintenance

See Property Maintenance

Fahrenheit Scale (˚F)

A scale, primarily used in the USA, to measure air temperature. The temperature at which water freezes is defined as 32 degrees, and the boiling point of water is defined to be 212 degrees (at atmospheric pressure).


A device with rotating vanes or blades that creates a current of air for cooling, heating or ventilation.

Fan Coil Unit

A device consisting of a heating or cooling coil and fan. Typically a fan coil unit is not connected to ductwork, and is used to control the temperature in the space where it is installed.

Fault Code

An automatically generated code which indicates the reason for an equipment fault.

Feed In Tariff

Payments made to households or business generating their own electricity through the use of methods which do not contribute to the depletion of natural resources, proportional to the amount of power generated.


Fluorinated greenhouse gases (F-Gases) are a group of chemicals containing fluorine. F-Gases are powerful greenhouse gases that trap heat in the atmosphere and contribute to global warming.

F-Gas Certification

From 4 July 2009 it became a legal requirement for all businesses that install, maintain or service stationary refrigeration, air-conditioning and/or heat pump equipment containing or designed to contain F-Gas refrigerants to obtain an F-Gas Company Certificate. As of July 2011 all such businesses must hold a Full Company Certificate.

To obtain a Full Company Certificate, businesses must employ sufficient numbers of personnel holding a full personnel qualification to cover expected volume of in-scope activities; and have the necessary tools and procedures for the personnel to carry out the in-scope activities that require certification.  

F-Gas Certification Body

An organisation appointed by a relevant European Member State Government Department under the Fluorinated Greenhouse Gas Regulations 2009 to carry out the certification of, and also keep a register of, companies who install, maintain or service stationary refrigeration, air-conditioning and/or heat pump equipment containing or designed to contain F-Gas refrigerants who can demonstrate they comply with the mandatory requirements of the regulations.


Fibrous, or other materials, which removes solid particulates such as dust, pollen and bacteria from the air.  


A hydrocarbon in which some or all of the hydrogen atoms have been replaced with fluorine. 

Fluorocarbon Refrigerant

A refrigerant consisting of or containing fluorocarbon.

Fossil Fuel

A natural fuel such as coal or gas formed in the geological past from the remains of living organisms.

Free Cooling

An economical method of using low external air temperatures to assist in chilling water, which can then be used for industrial process, or air conditioning systems.


Common abbreviation for a refrigerator.

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Geothermal Heat Pumps

A heat pump system that uses heat extracted directly from natural sources like hot springs, geysers and volcanic hot spots as a heat source for radiators, under-floor or warm air heating systems and hot water.

Global warming

A gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants.

Global Warming Potential (GWP)

A relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide over a specific time interval, either 20, 100 or 500 years. GWP is expressed as a factor of carbon dioxide whose GWP is standardised to 1.

Greenhouse Effect

The natural process by which the atmosphere traps some of the Sun's energy, warming the Earth enough to support life.

Greenhouse Gas

A gas that contributes to the greenhouse effect by absorbing infrared radiation.

Ground Source Heat Pumps

A heat pump system that uses heat extracted from the ground or ground water as a heat source for radiators, under-floor or warm air heating systems and hot water.

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HCFC (Hydro-chlorofluorocarbon) Refrigerant

A refrigerant comprised of Hydrogen, Chlorine, Fluorine and Carbon (e.g. R22)

Heat Exchanger

A device designed to efficiently transfer or 'exchange' heat from one substance to another, typically a condenser or evaporator.

Heat Pump

A system that transfers heat in a reversible process from one source (air, ground or ground water) and transfers it to another place (space or building).

Heat Recovery

The collection and re-use of heat arising from any process that would otherwise be lost.

HFC (Hydro-fluorocarbon) Refrigerant

A refrigerant comprised of Hydrogen, Fluorine and Carbon (e.g. R134a)

HFO (Hydrofluoro-olefin) Refrigerant

A refrigerant comprised of Hydrogen, Fluorine and Carbon but different from HFCs in that they are olefins, which mean they have very short atmospheric lifetimes of a few days, leading to distinct environmental benefits. They have a very low GWP (e.g. HFO-1234yf and HFO-1234ze)

Hire Products

RACHP equipment which can be hired on a short or long term basis e.g. mobile air conditioning or temporary catering installations for sporting events.


A common acronym for Heating, Ventilating, Air Conditioning and Refrigeration.

Hydrocarbon (HC)

A natural organic compound consisting of Hydrogen and Carbon atoms.

Hydrocarbon (HC) Refrigerants

A non toxic refrigerant with no ozone depleting properties and almost zero GWP but they are flammable (e.g. R290 propane)

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Industrial Refrigeration

Refrigeration systems and equipment used in large scale industrial applications e.g. food manufacturing and processing, breweries, chemical plants, etc.


A new or original method, idea, technology, product or service.


The action of installing an RACHP system, the state of being installed, or an RACHP system or piece of equipment installed for use.


Material that is highly resistive to conducting heat that offers reliable protection against condensation and effectively prevents energy loss.


An electrical device that converts direct current (DC) to alternating current (AC).

IOR (Institute of Refrigeration)

An independent professional body, run for refrigeration, air conditioning and heat pump professionals by its members.

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Unit of work or energy equal to one watt for one second.

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Kelvin (K)

International System (SI) unit of temperature.

Kyoto Protocol

The Kyoto Protocol is an international agreement linked to the United Nations Framework Convention on Climate Change, which commits its Parties by setting internationally binding emission reduction targets. In Doha, Qatar, on 8 December 2012, the 'Doha Amendment to the Kyoto Protocol' was adopted.

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Latent Heat

Amount of energy (heat) absorbed or released by a substance during a change in its physical state that occurs without changing its temperature. The latent heat associated with melting a solid or freezing a liquid is called the heat of fusion; that associated with vapourising a liquid or a solid or condensing a vapour is called the heat of vapourisation. The latent heat is normally expressed as the amount of heat (in units of joules or calories) per mole or unit mass of the substance undergoing a change of state.

Leak Detection

Method of finding leaks in refrigeration, air conditioning and heat pump systems.


UK, European Member State and International law.


High pressure refrigerant in its liquid state.

Low Carbon Economy

An economy which has a minimal output of greenhouse gas emissions.

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Magnetic Refrigeration

Magnetic refrigeration is based on the Magnetocaloric Effect (MCE). The MCE implies that the temperature of suitable materials (Magnetocaloric Materials, MCM) increases when exposing to a magnetic field and decreases when it stops.

The Magnetic Refrigeration System works with a controlled magnetic field that applies a series of Magnetization-Demagnetization cycles to the Magnetocaloric alloys. Each of these cycles creates a difference of temperature in the material, which being repeated, produces the final and stabilised hot and cold temperatures in the refrigerated system.


Activities required or undertaken to conserve as nearly, and as long, as possible the original condition of an asset or resource while compensating for normal wear and tear.

Managing Agent

A person, group of people or a company employed by a business owner or management company to arrange practical maintenance and general management of a building.


A person, group of people or a company which manufactures goods (products) for sale.

Marine Refrigeration

Refrigeration systems and equipment used for shipboard refrigeration of products in transit, and air conditioning for crew and passenger accommodation.

Medical Fridges

Commercial refrigerators used by the medical profession specifically for the storage of medical supplies, drugs, plasma and blood.

Member Organisation

A Member Organisation typically has a particular purpose, which involves connecting people together around a particular profession, industry, activity, interest, mission or geographical location. This might be to encourage or facilitate interaction and collaboration and may often involve promoting and enhancing the purpose itself.

Micro-generation Certification Scheme (MCS)

An internationally recognised quality assurance scheme, supported by the Department of Energy and Climate Change (DECC). MCS certifies micro-generation technologies used to produce electricity and heat from renewable sources.

MCS is also an eligibility requirement for the Government's financial incentives, which include the Feed-in Tariff and the Renewable Heat Incentive (RHI). 

Mobile Air Conditioning

Air conditioning equipment for the control of temperature and humidity in a space which can be moved from one space to another.

Montreal Protocol

The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. The treaty was opened for signature on 16th September 1987, and entered into force on 1st January 1989. Since then it has undergone several revisions.

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National Grid

An electricity and gas company that connects consumers to energy sources through its networks.

Natural Refrigerants

Naturally occurring substances such as hydrocarbons (propane), CO2, ammonia, water and air. Natural refrigerants are heat transfer mediums in RACHP systems that do not harm the ozone layer, and have little or no effect on climate change.

Nitrogen (N)

Colourless, odourless inert gas that forms about 78% of the earth's atmosphere. Liquid nitrogen (made by distilling liquid air) is used as a coolant, and for pressure testing RACHP systems prior to refrigerant charging.

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ODP (Ozone Depletion Potential)

The capacity of a refrigerant to destroy stratospheric ozone. ODP is stated relative to the ODP of CFC-11, which is taken as having an ODP of 1.

ODS (Ozone Depleting Substances)

Substances which deplete the ozone layer and widely used in refrigeration and air conditioning systems.


The Office of Gas and Electricity Markets. A non-ministerial government department and an independent National Regulatory Authority, recognised by EU Directives. Their principal objective is to protect the interests of existing and future electricity and gas consumers.

Oil (Refrigerant)

See Refrigeration Oil

Oil Filters

A filter that removes impurities from the oil used to lubricate a refrigeration system.

Oil Trap

Pipe work designed to trap refrigerant oil so that it is returned to the compressor.

Oil Separator

Separates oil from superheated discharge refrigerant vapour and returns it to the compressor crankcase.

Oil Pressure Switch

A differential pressure switch designed to protect a refrigeration compressor if the oil pressure is too low.


A person, group of people or business who operate a system either directly, or acting as a third party to the owner of a system.

Ozone (O3)

A naturally occurring gas: 10% in the troposphere (10-16 kilometres altitude) and 90% in the stratosphere (50 kilometres altitude). The large amount of ozone in the stratosphere is often referred to as the 'ozone layer'.

Ozone Layer

A layer in the stratosphere that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun.

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Photovoltaic (PV) Solar Cell

A system that changes light from the sun into electricity.


A pipe work system for the conveyance of a liquid, usually water.


The rate at which energy is converted from one form to another. The unit of measurement of power is the watt (W).

Portable Air Conditioning

Stand alone Air Conditioning units which can be moved from one area to another.

Pressure Switch

A control device which senses system pressure and open or closes at set conditions.


A person engaged, or qualified, in a profession.  

Professional Institute

A not-for-profit organisation seeking to further a particular profession, the interests of individuals engaged in that profession, and the public interest.

Property Maintenance

The upkeep and maintenance of land, property and property services. Can be a commercial venture through a property maintenance company.

The services which can be maintained are varied and include, but are not limited to, landscaping, building fabric, electrical installation, heating, ventilating, plumbing, drainage, refrigeration, air conditioning and cleaning.


The owner of a business.

Psychometrics (Hygrometry)

The science of studying the thermodynamic properties of moist air and the quantitative interdependence between temperature and humidity.

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Quality Assurance

The maintenance of a desired level of quality in a service or product, especially by means of attention to every stage of the process of delivery or production.

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Acronym for Refrigeration, Air Conditioning and Heat Pump.

Reciprocating Compressor

A compressor with pistons which glide inside a cylinder (similar to a car engine). There are three types:

  • Open - where one end of the crankshaft protrudes outside of the compressor casing to an external drive motor
  • Semi-hermetic - where the compressor and drive motor are housed inside a casing, which is designed to be opened for inspection and maintenance.
  • Hermetic - where the compressor casing is welded closed and sealed and cannot be accessed. Typically used for domestic refrigerators and freezers and medium capacity air conditioning units.

Reclaim (Refrigerant)

The recovery of refrigerant from a system into a reclaim cylinder for return to a reclaim facility for recycling.


See Refrigerated Container


The medium used for heat transfer in a RACHP system which absorbs heat on evaporating at a low temperature and a low pressure, and rejects heat on condensing at a higher temperature and higher pressure.

Refrigerant Charge

The amount (weight in kg) of refrigerant contained in a system, or the process (act) of introducing refrigerant into a system.

Refrigerant Leak Testing

See Leak Detection

Refrigerated Container

A shipping container used in freight transport that is refrigerated for the transportation of temperature sensitive cargo.


An artificial process in which work is done to move heat from one location to another.

Refrigeration Cycle

The cycle of compression, de-superheat, condensation, expansion and evaporation of the working medium (refrigerant) in a refrigeration system.

Refrigeration Oil

Oil is used in a refrigeration system to lubricate the compressor to reduce friction on metal parts, reducing wear on the compressor and prolongs the life of the system. Refrigeration oil is a special high temperature formulation designed for use in refrigeration systems.


A household or commercial appliance used for the storage of chilled or frozen food.

Registration (Fridgehub)

The provision of email contact details for individual membership of Fridgehub.


The process of reconditioning products to sound working condition.

Renewable Energy

Energy that is generated from resources which are unlimited (naturally replenished on a human timescale), including the sun, the wind, flowing water, biomass and geothermal technology.

Renewable Heat Incentive (RHI)

The world’s first long-term financial support programme for renewable heat.

The RHI pays participants of the scheme that generate and use renewable energy to heat their buildings. By increasing the generation of heat from renewable energy sources (instead of fossil fuels), the RHI helps the UK reduce greenhouse gas emissions and meet targets for reducing the effects of climate change.

There are two parts to the scheme:

Domestic - see Domestic RHI

Non-Domestic - open to commercial, industrial, public sector, not for profit and heat networks. The scheme is designed to bridge the gap between the cost of fossil fuel heat installations and renewable heat alternatives through financial support for owners.

Renewables Obligation (RO)

The main support mechanism for renewable electricity projects in the UK. Smaller scale generation is mainly supported through the Feed-In Tariff scheme - see Feed In Tariff

It places an obligation on UK electricity suppliers to source an increasing proportion of the electricity they supply from renewable sources.

Renewable Obligation Certificates (ROCs)

Green certificates issued to operators of accredited renewable generating stations for the eligible renewable electricity they generate. Operators can trade ROCs with other parties. ROCs are ultimately used by suppliers to demonstrate that they have met their obligation.

Where suppliers do not present a sufficient number of ROCs to meet their obligation, they must pay an equivalent amount into a buy-out fund. The administration cost of the scheme is recovered from the fund and the rest is distributed back to suppliers in proportion to the number of ROCs they produced in respect of their individual obligation.

Renewable Resource

A resource which can be renewed or replenished over a human time scale.

Renewable Technologies

Devices which utilise renewable energy sources e.g. solar panels or wind turbines.


Home or household.


A source or supply from which benefit is produced. Typically resources are materials, services, people, or other assets that are transformed to produce benefit.


An assessment, appraisal or testimonial.

Rotary Compressor

A compressor where the compression function is performed using mechanisms which involve either impellers, involute scrolls or screws. There are four types:

  • Scroll - this features two involute scrolls; one stationary, and one orbiting (but not rotating) around the first.
  • Stationary or rotary vane - which features vanes located inside the cylinders. The vanes may rotate on a cam in the centre of the cylinder (rotary), or be fixed to the walls of the cylinder (stationary).
  • Screw - which are based on a mechanism made up of two threaded rotors (screws) that are coupled together.
  • Centrifugal - which are made up of a rotor located inside a special chamber. The rotor is rotated at high speed, imparting high kinetic energy to the refrigerant gas.

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Saturation Point

The point at which no more of a substance can be absorbed into a vapour or dissolved into a solution.

Saturation Pressure

The pressure of a vapour which is in equilibrium with its liquid (as steam with water).

Saturation Temperature

The temperature where a substance changes between its liquid and its vapour phase.

Secondary Refrigerant

A liquid or gas used in an indirect refrigeration system that absorbs heat from the space to be refrigerated and transfers it to a heat exchanger where it is absorbed by a primary refrigerant.

Sensible Heat

The energy (heat) exchanged by a thermodynamic system that has as its sole effect a change of temperature.


A material with electrical conducting properties intermediate between that of metal and insulators.


The process of separating lubricating oil from refrigerant in a refrigeration system.


Perform routine maintenance or repair.

Sight Glass

An observation point within a refrigeration pipe work system used to indicate the condition of the refrigerant in the liquid line, the moisture content of the refrigerant, and the flow in the oil return line from the oil separator.

Social Enterprise

A business with primarily social objectives.

Solar Panel

A panel which produces either electricity or heat when light shines on it.

Solar PV (Photovoltaic)

See Photovoltaic

Solenoid Valve

An electromechanical valve controlled by an electric current through a solenoid coil.

Sole Trader

A person running their own business as an individual.

Split System

Air Conditioning systems with separate indoor fan coil units and outdoor condensing units with interconnecting pipe work and controls.


Stationary or not moving. A fixed installation.


The temperature fall beyond the condensing temperature of a refrigerant.

Subscription (Fridgehub)

Payment required to own a profile and be listed within the Fridgehub Directory, payable either quarterly or annually in advance.

Subscription Plan (Fridgehub)

The features included for either a Business, Business+ or Corporate profile within the Fridgehub Directory.    


The number of degrees a vapour is above its saturation (boiling point) temperature at a particular pressure.


Able to be maintained at a certain rate or level.

Sustainable Business

An enterprise that has minimal negative impact on the global or local environment, community, society, or economy that participates in environmentally friendly or green activities to ensure that all processes, products, and manufacturing activities adequately address current environmental concerns while maintaining a profit.

Sustainable Energy

The sustainable provision of energy that meets the needs of the present without compromising the ability of future generations to meet their needs.

Sustainable Energy Sector

Promotes security of supply over time; delivers a low carbon economy and associated environmental targets; and delivers related social objectives e.g. fuel poverty targets.

Synthetic Greenhouse Gasses

Refrigerants which are harmful to the environment that may have ozone depletion potential, global warming potential or both.

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The degree or intensity of heat present in a substance or object, especially as expressed according to a comparative scale and shown by a thermometer or perceived by touch.

Temperature Glide

The temperature difference that occurs between the vapour state and liquid state of refrigerant during evaporation or condensation at constant pressure.

T.E.W.I. (Total Equivalent Warming Impact)

The measure of the global warming impact of equipment based on the sum of the direct emissions (chemical) and indirect emissions (energy use) of greenhouse gases during the operation of the equipment and the disposal of the operating fluids at the end of life.


Using, caused by or using heat.


The study of heat (or thermal) energy and the processes by which this energy may be converted into other forms of energy.


A device which converts AC voltage and current from one value to a different value of voltage and current.

Trade Association

An association of companies in a particular business sector or trade, organised to promote their common interest. It is usually funded by companies that operate in a specific industry with a focus on collaboration between these companies. Activities include education, lobbying, publishing and standardisation. Other services such as conferences and networking events are often provided. Many associations are not-for-profit organisations governed by bylaws and directed by officers who are also members.

Training Centre

A facility for the teaching of vocational or practical knowledge, skills, and competencies. Structured courses are usually available which lead to recognised professional qualifications such as City & Guilds or cskills.

Transcritical Cycle

A thermodynamic cycle where the working fluid (refrigerant) goes through both subcritical and supercritical states. This is often the case when carbon dioxide is the refrigerant.

Transport Refrigeration

An air conditioning system for controlling the humidity, ventilation and temperature in a vehicle.


Trace and correct faults in a mechanical or electrical system.

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UK Low carbon Transition Plan

A government plan which sets out a route map for the UK's transition to a low carbon economy.

UK Renewable Energy Strategy

A government strategy to radically increase the UK's use of renewable electricity, heat and transport. It sets out the path for the UK to meet its legally binding target to ensure 15% of UK energy comes from renewable sources by 2020.


An institution of higher education and research which grants academic degrees in a variety of subjects and provides both undergraduate education and postgraduate education.

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An enclosed space entirely devoid of matter.

Vapour Compression Cycle (Refrigeration Cycle)

Uses a circulating liquid refrigerant as the medium which absorbs and removes heat from a space to be cooled and subsequently rejects that heat elsewhere.

Variable Speed Drive (VSD)

A method of controlling three phase motors by varying the supply frequency (Hz).


The process of moving or changing the air into or out of an interior space either naturally or mechanically.

Volume Flow Rate (Q)

The volume of fluid which passes through a given surface per unit of time (m3/s).

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Wall Split

Wall mounted split air conditioning system or heat pump.

Watt (w)

A unit of measure for power when energy is expended at the rate of one joule per second.

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A mixture made up of two or more refrigerants with different boiling points.


A defined area within a building that has its temperature and humidity controlled independently of other areas (zones) of the building.

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