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HVAC GLOSSARY

Robinsons Facilities Services team of HVAC engineers has assembled a glossary of HVAC terms to help our clients understand our work and to help explain the work we complete on your boilers and HVAC systems.

HVAC Glossary

Robinsons Facilities Services team of HVAC engineers has assembled a glossary of HVAC terms to help our clients understand our work and to help explain the work we complete on your boilers and HVAC systems.

Absolute pressure
The combination of atmospheric pressure and gauge pressure

Accumulator
The storage tank that prevents liquid refrigerant from flowing into the compressor.

AC
Alternating current

ACRIB
The Air Conditioning and Refrigeration Industry Board

Air conditioner
The system that controls temperature, air quality and humidity within a building.

Air handling unit
Air handling units (AHUs) are the central unit of an HVAC system which moves the air around the ductwork to provide extraction and ventilation.

Air source heat pump
Air source heat pumps (ASHP) absorb heat from the outside air to heat your commercial property and hot water system.

Ambient
Atmospheric conditions of temperature & pressure.

Biomass boiler
Biomass boiler systems burn wood chips, pellets, or logs to power central heating and hot water boilers.

Blend
A mixture of refrigerants that can be separated by distillation.

BTU
The British thermal unit (BTU) is the energy required to raise one pound of water by one degree Fahrenheit and is often used in the HVAC industry.

Bubble point
The pressure point at which a refrigerant liquid starts to vaporise.

CUE
The Carbon Usage Effectiveness measurement is calculated by dividing the energy consumption by the IT energy consumption to measure the ratio of the total CO2 emissions.

Cascade system
A system with multiple refrigerant circuits working in series to provide the designated level of cooling.

Centrifugal compressor
The unit which compresses gas using centrifugal force.

CFC
Chlorofluorocarbon which consists of high ozone depleting and global warming gases which was banned from use in 2000.

CIBSE
The Chartered Institution of Building Services Engineers.

CITB
The Construction Industry Training Board.

Chlorine levels
In England and Wales, chlorine levels in water are maintained by individual water companies, but typically the level of residual disinfectant in the form of free or combined chlorine is 0.5mg/l or less.

Coil
A component that provides heat transfer to air when mounted inside an air handling unit.

Commercial LPG Boiler
Liquefied Petroleum Gas (LPG) is a combination of gaseous hydrocarbons produced from natural gas, oil extraction and oil refining. LPG boilers burn fuel to produce hot water to heat radiators and water supplies.

Commercial Steam Boiler
Steam boilers utilise vaporised fluid to power processes such as water heating, central heating and power generation.

Compressor
The part of the refrigeration system that raises the pressure to increase the temperature of the refrigerant and circulates it though the closed loop system.

Condensate
The moisture that is removed from the air during the dehumidification process in air conditioning.

Condenser
The coil or vessel that removes the superheat of compression, condensing the refrigerant gas into a high-pressure liquid.

Conduction
The process involving the vibration of molecules or the movement of electrons that creates a transfer of heat.

ConstructionLine
Robinsons Facilities Services are a Gold Member of the ConstructionLine platform, which means local businesses in the construction sector can use ConstructionLine to select suppliers they know are verified, approved and accredited, and see us as an existing member. ConstructionLine undertake verification checks to vet all suppliers on their platform, the main one being the completion of a PAS91 questionnaire, a standard pre-qualification document which covers the common minimum standard for construction procurement.

Convection
The process involving changing in density of a fluid that creates a transfer of heat.

COP
The coefficient of performance is the ratio of the total capacity of the refrigerant effect versus the work by the compressor over a unit of time which measures the efficiency of the system.

CWR
Chilled water return.

CWS
Chilled water supply to a cooling unit.

Cyber Essentials Accreditation
Robinsons Facilities Services have been accredited with the Cyber Essentials, which proves that we have put systems and controls in place to guard against the most common cyber threats and to demonstrate our commitment to cyber security, which includes customer records and data.

Damper
The modulating device that controls airflow rates through ductwork or air handling equipment.

Decanter
The storage cylinders used for safely storing refrigerant during maintenance.

Dehumidification
Removing moisture from the air to reduce the humidity level of a building or area.

Dew Point
The temperature and pressure at which refrigerant gas starts changing from vapour to liquid.

Duct
The components of HVAC systems that transfer air.

Ductless HVAC system
Usually these comprise of individual wall-mounted units in each room, linked to an outside compressor. A ductless system can be used in individual rooms, but also as a supplement to an existing split system.

Economiser
A mechanical device that helps reduce energy consumption by recycling energy within an HVAC system.

EER
The Energy Efficiency Ratio (EER) is calculated by dividing the cooling capacity in kW by the power input to measure a system’s efficiency.

ECA Scheme
The Enhanced Capital Allowance (ECA) Scheme is a tax relief scheme that provides investment for energy-saving equipment for businesses.

Evaporator coil
An evaporator coil helps to evaporate refrigerant within a duct system.

Evaporating temperature
The temperature in an evaporator at which the refrigerant vaporises.

Expansion valve
Expansion valves regulate the amount of refrigerant flowing from the liquid line into the evaporator.

FCU
The fan coil unit (FCU) is part of an HVAC system that heats or cools the system.

F-gas
Fluorinated gases are types of man-made gas that were created to help eliminate ozone depleting gases, and include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6).

Fluorocarbon
Most refrigerants are classed as fluorocarbon, which is a type of chemical that contains fluorine and carbon.

GAS SAFE register
GAS SAFE is the official list of gas engineers who are qualified to work legally on gas appliances. RFS is GAS SAFE registered.

Gas recovery
By removing used gas from a refrigeration system and safely storing it during maintenance, we avoid releasing the gas into the environment.

Heat reclaim
Heat reclaim units transfer heat that would otherwise be lost into incoming airflow to heat your building and deliver filtered, fresh air while extracting stale, stagnant air.

ISO9001
International quality management systems. RFS has been accredited with ISO9001.

IWFM
The Institute of Workplace and Facilities Management (IWFM) is the pioneering body for workplace and facilities management professionals. In 2019, Robinsons Facilities Services became a corporate member of the IWFM.

Legionalla
The legionella bacteria can multiply under certain conditions and temperatures within water systems. Being exposed to legionella from your water system is potentially fatal and as it is carried in airborne water droplets it is important that you monitor and control this exposure.

MUA
Make up air (MUA) units are air handler units that only use outdoor air.

Mindful employer
Robinsons Facilities Services provides its employees with access to professional workplace mental health training, information and advice, and this has empowered us to support the mental wellbeing of our staff.

NAPIT
The National Association of Professional Inspectors and Testers, of which Robinsons Facilities Services is an accredited member.

OFTEC
Oil and Renewable Heating Technologies is a trade association that represents training providers and liquid fuel heating equipment manufacturers, promoting high standards and supporting the development of sustainable low carbon heating. Robinsons Facilities Services have been accredited by OFTEC.

Oil separator
A device that separates oil from refrigerant.

Packed HVAC system
All the components of this system are stored together in one unit, which is located outside.

PAT Testing
Portable Appliance Testing (PAT Testing) involves the examination of electrical appliances and equipment to ensure they are safe to use.

Planned maintenance
Planned maintenance is work that is scheduled and agreed upon to be carried out on equipment over a specific period, for example, quarterly or annually.

Pressure and strength HVAC tests
Tests to prove the integrity of an HVAC system prior to evacuation and addition of refrigerant.

Prompt Payment Code Accreditation
The Prompt Payment Code is administered by the Chartered Institute of Credit Management and covers prompt payment, as well as wider payment procedures, such as giving clear guidance, help and communication to suppliers and encouraging good practice throughout the supply chain. Robinsons Facilities Services has been awarded this accreditation.

Reactive HVAC maintenance
Reactive maintenance or breakdown maintenance when businesses only attend to issues with their HVAC systems when they occur. Reactive maintenance can be costly and while unforeseen problems can always happen with equipment, even under a planned maintenance programme, it is always better to do everything you can to prevent known problems that are likely to occur.

Recycled refrigerant
Recovery of refrigerant to reuse it that involves cleaning the refrigerant by oil separation and distillation to help remove acidity, moisture, and particulate matter from the refrigerant.

REFCOM
Robinsons Facilities Services are F-Gas certified by the Register of Companies Competent to Manage Refrigerants (REFCOM). REFCOM carry out random surveillance and audits to enforce the F-Gas regulations and an organisation’s continuing certification. They also work closely with the Environment Agency and Defra to monitor compliance.

Refrigerant
The fluid that is used in HVAC systems to transfer heat throughout a refrigeration system. Refrigerants are working compounds that can safely absorb heat at a low temperature.

Refrigerant charge
The measure of refrigerant within an HVAC system.

Spare HVAC parts
Spare parts are the consumable or replaceable items that are critical to a machine’s operation which can be sourced and replaced quickly.

Split HVAC system
A split system effectively means you have a unit inside and a unit outside, with air being circulated then by a system of ducting and vents. Split systems typically carry lower operating costs and are energy efficient.

Sub cooling
Sub cooling is when refrigerant changes from a liquid to a gas due to the refrigerant becoming colder than the saturation temperature.

Super heating
Super heating, which usually occurs in the evaporator, refers to the number of degrees a vapor is above its boiling point/saturation temperature at a specific pressure.

Thermostatic expansion valve (TEV)
A thermostatic expansion valve (TEV) is a device that creates a constant evaporator temperature by regulation of refrigerant flow through an HVAC system.

TM44
TM44 is the guidance created as part of the Energy Performance of Buildings Directive. A TM44 inspection must be carried out on an air conditioning system every five years to assess the performance of the air conditioning system with a particular focus on energy efficiency.

VRV air conditioning system
Variable Refrigerant Volume (VRV) Air Conditioning Systems are a split AC system for multiple rooms in a building, so there is one external unit and several indoor units feeding off it.

Water chlorination
Water chlorination is a specialist hygiene and legionella monitoring method that should be done to any new water system and as an ongoing treatment to existing water systems. Water chlorination treatments prevent diseases and disinfect and descale water systems.

Water Safety Risk Assessments
Commercial businesses are required by law to assess their water systems for legionella bacteria risks and to protect people from exposure to these risks. Employers should carry out surveys of their plant, systems and equipment and act on recommendations for remedial work that is found to be necessary. Regular reviews of water safety risk assessments are also required.

Zoning
The process of dividing a space into separate areas to help improve efficiency of HVAC systems and to harness better control of the temperature.

Accreditations See our full list of accreditations Accreditations

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