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Hydronic balancing, also called hydraulic balancing, is the process of optimizing the distribution of water in a building's hydronic heating or cooling system by equalizing the system pressure. In a balanced system every radiator is set to receive the proper amount of fluid in order to provide the intended indoor climate at optimum energy efficiency and minimal operating cost.
To provide the correct power output, heating or cooling devices require a "design flow." Theoretically, it is possible to design plants that deliver the design flow at each terminal unit (heating or cooling device). In reality, this is not possible because pipes and valves only come in certain sizes. Moreover, predicting the real flow in a system is prohibitively complex. Some circuits (typically those closest to the pump) will be favored by higher than required flows at the expense of other circuits that will have underflows.
Control valves may temporarily help by gradually reducing the flow in favoured circuits, thus allowing unfavored circuits to achieve the correct flow. This will however cause long delays in reaching the set temperature in the building after night setback and will make the installation very inefficient.[ citation needed ]
Balancing limits the flow in favoured circuits, forcing water through unfavored circuits. As a result, the required design flows are available to all circuits and the system can provide the required indoor air quality. Avoiding overflows means the pump is not doing unnecessary work which saves energy, reduces operating cost and can reduce the size of the pump required (saving on the initial pump investment). Balancing also saves energy and operating costs by reducing the amount of time between starting a plant and reaching the required indoor climate. For example, after every set back unbalanced plants must start earlier and run at maximum capacity for longer than balanced plants thereby using more energy.[ citation needed ]
In small heating systems (e.g. domestic systems), balancing is quite easy because of the small number of terminal units and relatively simple distribution network. Balancing can normally be achieved by simply pre-setting the flow through the radiators.
Larger buildings, such as offices or hospitals, have more complicated heating and cooling systems and require a more accurate balancing technique. To obtain a plant with the correct design flows, consultants design systems to include balancing valves, differential pressure controllers or pressure independent control valves.
Balancing valves allow the measurement of differential pressures which can be used to calculate a flow. There are various balancing methods, but all involve measuring differential pressures and adjusting them to the correct value by calculating the flow which each one represents.
Differential pressure controllers are usually membrane- or spring-driven valves that control the differential pressures in the installation. This simplifies balancing procedures and enables the installation to be more precisely controlled.
Pressure independent valves combine the balancing and control functions in one valve and use springs and/or membranes to precisely control the flows in the distribution network. As such they need no measuring or balancing procedure.
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid to flow through it in only one direction.
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning systems, which can both cool and warm interior spaces.
Hydronics is the use of liquid water or gaseous water (steam) or a water solution as a heat-transfer medium in heating and cooling systems. The name differentiates such systems from oil and refrigerant systems.
A forced-air central heating system is one which uses air as its heat transfer medium. These systems rely on ductwork, vents, and plenums as means of air distribution, separate from the actual heating and air conditioning systems. The return plenum carries the air from several large return grills (vents) to a central air handler for re-heating. The supply plenum directs air from the central unit to the rooms which the system is designed to heat. Regardless of type, all air handlers consist of an air filter, blower, heat exchanger/element/coil, and various controls. Like any other kind of central heating system, thermostats are used to control forced air heating systems.
A circulator pump or circulating pump is a specific type of pump used to circulate gases, liquids, or slurries in a closed circuit. They are commonly found circulating water in a hydronic heating or cooling system. Because they only circulate liquid within a closed circuit, they only need to overcome the friction of a piping system.
A zone valve is a specific type of valve used to control the flow of water or steam in a hydronic heating or cooling system.
Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and convection. Use of underfloor heating dates back to the Neoglacial and Neolithic periods.
The wax thermostatic element was invented in 1934 by Sergius Vernet (1899–1968). Its principal application is in automotive thermostats used in the engine cooling system. The first applications in the plumbing and heating industries were in Sweden (1970) and in Switzerland (1971).
In heating, ventilation, and air conditioning (HVAC), testing, adjusting and balancing (TAB) are the three major steps used to achieve proper operation of heating, ventilation, and air conditioning systems. TAB usually refers to commercial building construction and the specialized contractors who employ personnel that perform this service.
Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plants or any similar use of such an engine.
Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating.
HVAC is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many of which are summarized in this glossary.
Instrumentation is used to monitor and control the process plant in the oil, gas and petrochemical industries. Instrumentation ensures that the plant operates within defined parameters to produce materials of consistent quality and within the required specifications. It also ensures that the plant is operated safely and acts to correct out of tolerance operation and to automatically shut down the plant to prevent hazardous conditions from occurring. Instrumentation comprises sensor elements, signal transmitters, controllers, indicators and alarms, actuated valves, logic circuits and operator interfaces.
Automatic balancing valves are utilised in central heating and cooling systems that rely on flow of water through the system. They use the latest flow technology to ensure that the design flow rate is achieved at all times irrespective of any pressure changes within the system.
Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented by Daikin Industries, Ltd. in 1982. Similar to ductless mini-split systems, VRFs use refrigerant as the primary cooling and heating medium, and is usually less complex than conventional chiller-based systems. This refrigerant is conditioned by one or more condensing units, and is circulated within the building to multiple indoor units. VRF systems, unlike conventional chiller-based systems, allow for varying degrees of cooling in more specific areas, may supply hot water in a heat recovery configuration without affecting efficiency, and switch to heating mode during winter without additional equipment, all of which may allow for reduced energy consumption. Also, air handlers and large ducts are not used which can reduce the height above a dropped ceiling as well as structural impact as VRF uses smaller penetrations for refrigerant pipes instead of ducts.
The Uniform Mechanical Code (UMC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation, inspection and maintenance of HVAC and refrigeration systems. It is designated as an American National Standard.
Radiant heating and cooling is a category of HVAC technologies that exchange heat by both convection and radiation with the environments they are designed to heat or cool. There are many subcategories of radiant heating and cooling, including: "radiant ceiling panels", "embedded surface systems", "thermally active building systems", and infrared heaters. According to some definitions, a technology is only included in this category if radiation comprises more than 50% of its heat exchange with the environment; therefore technologies such as radiators and chilled beams are usually not considered radiant heating or cooling. Within this category, it is practical to distinguish between high temperature radiant heating, and radiant heating or cooling with more moderate source temperatures. This article mainly addresses radiant heating and cooling with moderate source temperatures, used to heat or cool indoor environments. Moderate temperature radiant heating and cooling is usually composed of relatively large surfaces that are internally heated or cooled using hydronic or electrical sources. For high temperature indoor or outdoor radiant heating, see: Infrared heater. For snow melt applications see: Snowmelt system.
The Glossary of Geothermal Heating and Cooling provides definitions of many terms used within the Geothermal heat pump industry. The terms in this glossary may be used by industry professionals, for education materials, and by the general public.