Air-conditioning Glossary of Definitions, briefs comes under our specialties
- HVAC Comprehensive Glossary of Terminologies
- Typical HVAC Processes-Air handling units, fan coil units, exhaust fans
- Typical Plumbing Systems-Transfer pumps, sump pumps, water tanks
- Typical Chilled Water Systems- Chillers, Secondary pumps, HEX systems
- Field Equipment- Sensors, valves, actuators, relays, variable frequency drives
HVAC
- Heating, Ventilation, Air conditioning
- Controls temperature, humidity and air quality inside a building
- Especially important in medium to large buildings such as office/residential towers
- All preferably integrated into one system
- In warm climates usually no need for a heating system
Heating
- Central heating often used in cold climates to heat private houses and public buildings
- Heating systems usually comprise of a boiler, furnace, heat pump or district hot water to heat water, steam or air
- Piping distributes heated fluid and radiators transfer this heat to air and structures, e.g. floor heating system
Ventilation
- The process of ”changing” or replacing air in any space to control temperature or remove moisture, smoke, carbon dioxide, etc
- Ventilation includes both the exchange of air to the outside as well as circulation of air within the building
- One of the most important factors for maintaining acceptable indoor air quality in buildings
- Supply air used for ventilation is filtered and cooled and/or heated inside air handling units
Air conditioning
- Refers to the cooling and dehumidification of indoor air for thermal comfort
- Air conditioning systems are designed to stabilise the air temperature and humidity within an area
- Excess heat from the circulating air is usually removed by a cooling coil that is supplied with cold water
- To decrease relative humidity the circulating air needs to be cooled to a temperature below the dew point and then heated back to meet the requirement
Major Terms
- Air handling unit (AHU) – a central unit consisting of a blower, heating and cooling elements, filters, etc. that are in direct contact with the airflow
- Chiller – a device that removes heat from a liquid.
The cooled liquid flows through pipes and passes through coils in air handling units, FCUs, etc
- Coil – equipment that performs heat transfer inside an AHU etc.
- Damper – a plate or gate placed in a duct to control airflow
- Fan coil unit (FCU) – a small terminal unit that is often composed of only a blower and a cooling coil
- Variable air volume (VAV) – an HVAC system that has a stable supply air temperature and varies the airflow rate with dampers and adjusting fan speeds to meet the temperature requirements
- Air handling units are used for circulating air inside a building or a part of a building
- Typically consists of two fans (exhaust and supply), filters, a heat recovery unit, and one or more coils for heating/cooling
- To improve air quality circulating air is mixed with fresh air
- Usually equipped with a heat recovery unit for energy saving purposes
- Supply air temperature kept constant so that temperature can be adjusted locally with thermostats
- Fresh air handling units are used for supplying fresh air inside a building or part of a building
- Indoor air quality is improved as the serving area is treated with 100% fresh air
- Usually takes more energy to heat/cool fresh air to target temperature
- Usually equipped with a heat recovery unit for energy saving purposes
- Can also be used for supplying precooled air for FCUs
- Used for extracting air from the building or part of a building
- Ventilated areas are usually toilets, kitchens and other areas where fumes should be extracted directly outside
- Parking areas are usually equipped with exhaust fans that are controlled according to carbon monoxide measurements or time schedules
- Fan coil units are used for cooling purposes in small areas
- Consist of a blower and a cooling coil
- Can either circulate the air inside the serving area or are supplied with precooled air from an air-handling unit
- Controlled with a Lonix room module and a thermostat for local setpoint adjustment
- Variable air volume systems are used for controlling the air flow of constant temperature in different parts of the buildings
- Dampers inside ducts regulate the flow of air to different serving areas
- Pressure difference measurements accross supply and exhaust fans are used for maintaining a constant pressure inside ducts
- Thermostats inside serving areas are used for local setpoint adjustments that affect the air flow through dampers
- Transfer pumps are used for pumping liquid from one place to another
- In residential and office buildings they are typically used for maintaining adequate supply of water in water tanks
- Usually On/Off controlled according to liquid level switches
- Booster pumps are used in applications where the normal system pressure is low and needs to be increased
- Typical in high rise buildings where domestic water pipeline pressure needs to be high to better serve tenants in the upper floors
- Pipeline usually divided into a high and low pressure zone (lower and higher floors)
- Either PRV or VSD controlled
- Sump pumps are used to remove water that has accumulated in a sump pit
- Sump pumps are usually controlled with two level switches: higher switch for indicating when the pump should start and a lower switch for indicating when the pump should stop
- Pump should not be let run dry so the lower level switch should be above the pump, upper level switch should be located near the top
- Water tanks are used for storing e.g. domestic water in high rise buildings
- High and low level switches are used for alarming and controlling transfer pumps
- More accurate level indication can be obtained with a pressure difference transducer
- Chillers transfer heat from a liquid to the surrounding air
- Consist of a primary pump and a heat exchanger
- Chilled fluid is used by air handling units and FCUs to cool supply air temperature
- Usually more than one chiller is used so that some of them are on standby and are taken into use when more cooling power is needed.
- Usually controlled according to return temperature
- Secondary pumps maintain adequate system pressure in a chilled water system
- Usually a pump set that consists of several pumps equipped with variable frequency drives are used
- As with chillers, when the cooling power (pressure) needed is very low only one pump should be running and the others on standby
- When more cooling is needed more pumps should be started
- Controlled according to the pressure difference between the return and supply headers
– Active 0-10V transducer
– (0/4 – 20 mA transducer)
- Active 0-10V transducers or pressure switches
- Typically for measuring gases (ventilation) or liquids (plumbing processes)
- Sensor measures the difference between two pressures introduced as inputs to the sensing unit, for example, measuring the pressure drop across a filter in an AHU
- When selecting an appropriate transducer it is important to know the measured range
- Active 0-10V transducers
- Usually includes temperature measurement as most relative humidity sensors use temperature compensation to reach more accurate results
- In HVAC mostly used to monitor/control relative serving area humidity (measured either locally in the serving area or in the return air duct)
- Typically carbon monoxide (CO) or carbon dioxide (CO2) concentrations are measured
- Active 0-10V transducers
- Carbon dioxide is a good measure of indoor air quality (if concentration exceeds 700 ppm more ventilation is needed)
- Carbon monoxide measurements are usually used in parking areas for controlling exhaust fans. In areas where people stay longer periods a limit of 25 ppm is recommended
- An electrical switch that is used for controlling electrical circuits with other circuits
- Usually a hard current circuit is controlled with a weak current circuit e.g. a 230Vac circuit can be controlled with 24Vdc
- Used for controlling devices that need to be powered off completely e.g. light groups, pumps, VFDs etc
- Valves are used to control the flow of fluids in pipes
- Valve drives are used to open and close valves with an electrical input command (digital, 0-10V)
- Valve selection can be difficult and usually valve types need to be approved by the designer
- Valve drives are purchased from the valve manufacturer
- Variable frequency drive is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor
- In automation perspective, the speed of the electric motor can be controlled with a 0-10Vdc control signal
- In BMS, variable frequency drives are mostly used for controlling fans and pumps
- variable-frequency motors on e.g. fans save energy by allowing the volume of air moved to match the system demand
- Most motors (fans, pumps) are controlled through starter panels
- Connections: modules -> starter panel -> motor
- Starter panels usually include –Run status indication
– Trip alarm indication (and reset)
– H-0-A indication
– On/Off control (power)
– VFD control signal and feedback
- Describes all the needed I/O points and field devices for BMS
- Very important for a project as some other documents and especially the bill of quantity (BoQ) are based on it
- Should always be kept up to date
HVAC Design & Project Management Glossary of Terminologies Elaborated which comes under our super specialties
- Temperature
- Humidity
- Air movement
- Fresh air
- Clean air
- Noise levels
- Lighting
- Furniture and work surfaces
Comfort Requirements directly proportional to :
- Dry-bulb temperature
- Humidity
- Air movement
- Fresh air
- Cleanliness of the air
- Noise levels
- The Five System Loops
- Airside
- Chilled water
- Refrigeration
- Heat rejection
- Controls
- Supply Fan and Filter
- Cooling Coil
- Chilled-Water Cooling Coil
- Constant-Volume System
- Constant supply-air quantity
- Variable supply-air temperature
- Variable supply-air quantity
- Constant supply-air temperature
- cooling coil
- supply fan
- return-air inlet
- supply-air outlet
- filter
- supply-air outlet
- return-air dampers
- outdoor-air dampers
- cooling coil
- supply fan
- filters
- Central air handler
- Sheet-metal supply duct
- VAV terminal
- Flexible sheet-metal supply duct
- Diffuser
- Outdoor-air inlet
- Shell-and-Tube Evaporator
- Pump and Control Valve
- Compressor
- Condenser
- Expansion Device
- Coil with two-way control valve
- Coil with three-way control valve
- Water Chiller
- Pump
- Cooling Coil
- Control Valve
- compressor
- condenser
- Condenser water
- Evaporator
- Liquid Refrigerant
- Airflow
- Refrigerant Vapor
- Cooling coil (evaporator).
- Expansion Device
- Air-cooled Condenser
- Compressor
- Propeller-type condenser fans
- Compressors
- Supply Fan
- Filters
- Exhaust Fan
- Cooling coil (evaporator)
- Air-cooled condenser
- Shell-and-Tube Evaporator
- Pump and Control Valve
- Compressor
- Condenser
- Expansion Device
- Cooling Tower
- Propeller Fan
- Sprayers
- Fill
- Outdoor Air
- Sump
- Cooling Tower
- Pump
- Bypass Pipe
- Control Valve
- Water-cooled Condenser
- Propeller-type Condenser Fans
- Air-cooled Compressor Condenser
- Evaporator
- Compressor
- Packaged Rooftop Air Conditioner
- VAV terminals
- System-level controller
- Dedicated outdoor-air unit
- Fan-coil units
- Exhaust fan
- System-level Controller
- Air-cooled chiller
- Hot-water boiler
- Pumps
- Airflow
- Evaporator
- Refrigerant Vapor
- Liquid Refrigerant
- Expansion Valve
- Cooling Coil (evaporator)
- Expansion device
- Compressor
- Air-cooled condenser
- Air-cooled condenser
- Cooling coil (evaporator)
- Exhaust fan
- Filters
- Supply fan
- Propeller-type condenser fans
- Compressors
- Air-cooled condenser
- Compressors
- Cooling coil (evaporator)
- Supply fan
- Refrigerant piping
- Water-cooled
- Air-cooled
- Air-cooled condensing unit
- Refrigerant piping
- Remote evaporator
- Installed cost
- Energy consumption
- Space requirements
- Freeze prevention
- Building height, size, shape
- System capacity
- Centralized maintenance
- Stability of control
- Individual tenant billing
- System Categories
- Single zone constant volume
- Single zone variable volume
- Multiple zone constant volume
- Multiple zone variable volume
- Air volume delivered by supply fan
- Single Thermostat
- Single zone, constant volume Packaged Terminal Air Conditioner
- Single zone, constant volume Packaged DX Rooftop System
- Air-cooled condenser
- Compressors
- Cooling coil (evaporator)
- Supply fan
- Refrigerant piping
- Chilled-Water Terminal System
- Four-Pipe Versus Two-Pipe System
- Dedicated Outdoor-Air System
- Single zone, constant volume Water-Source Heat Pump
- Single zone, constant volume Water-Source Heat-Pump System
- Single zone, constant volume Ground-Source Heat-Pump System
- Single Zone, Variable Volume
- Single zone constant volume
- Single zone variable volume
- Multiple zone constant volume
- Multiple zone variable volume
- Multiple Zones, Constant Volume
- Multiple zones, constant volume Multi-zone Air Handler
- Multiple zones, constant volume Changeover–Bypass System
- Multiple Zones, Variable Volume
- Multiple zones, variable volume VAV Terminal Units
- Multiple zones, variable volume DX Rooftop VAV System
- Multiple zones, variable volume Self-Contained DX VAV System
- Multiple zones, variable volume Central Chilled-Water VAV System
- Multiple zones, variable volume Two-Fan, Dual-Duct VAV System
- Multiple zones, variable volume Dual-Duct VAV Terminal Unit
- Preference of Building Owner
- Available Construction Budget
- Size and Shape of Building
Comfort requirements
- Temperature
- Humidity
- Air movement
- Fresh air
- Clean air
- Noise levels
- Number of tenants
- After-hours usage
- Extra Low Voltage Design and Project Management