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Hydronic Balancing is the process of optimising the distribution of water in a building’s heating or cooling system so it provides the intended indoor climate at optimum energy efficiency and minimal operating cost. To provide the correct power output heating or cooling devices require a certain flow known as the 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 and accurately predicting the real flow in a system is too complex. Some circuits (typically those closest to the pump) will be favoured by higher than required flows at the expense of other circuits that will have underflows. 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 a more complicated heating and cooling system 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 what flow that represents. Differential pressure controllers are usually membrane- or spring driven valves that control the differential pressures in the installation. This will simplify balancing procedures and enable the installation to be more precisely controlled. Pressure independent valves combine the balancing and control functions in one valve and work based on springs and/or membranes to precisely control the flows in the distribution network and as such need no measuring or balancing procedure. ==The reason for balancing the system and some basic information on how to do it == In a balanced system every radiator gets just enough hot water to allow it to heat up fully. Efficient balancing is done on every radiator in the house by adjusting the OUT-FLOW valve to be open only about an eighth- to a quarter- turn. Heating engineers will usually do this as part of the installation of a brand new system but they will rarely do it when replacing a component of the system, such as just the room thermostat or a part inside the boiler. They will check and adjust the balance if asked to do so but, as it can take about an hour to balance the radiators in an average sized three-bedroom house - and proportionally more or less for larger or smaller homes - many people don't want to pay for the time it takes to do the balancing properly. It is important to make sure that, when the room thermostat is calling for heat, all the radiators in the system heat up fully - to the maximum temperature possible - in sitting rooms and other daily "living" rooms but NOT in the other rooms (utility rooms, bedrooms, bathrooms, etc.) which should be kept as cool as possible. This is easy to do if you have TRVs (thermostatically-controlled radiator valves) fitted to your radiators but, if you don't have TRVs, you should be sure to open the IN-FLOW valves fully in all living rooms and turn them almost fully off in the other rooms. (Keeping them open just an eighth- to a quarter- turn usually works.) When it gets cold outside many people go round the house to open both valves on their radiators fully, in the mistaken belief that they will get more heat. But all that does is un-balance the system. The result is that the radiators nearest to the boiler take most of the flow of hot water and the other radiators get very little flow at all. If the system is unbalanced, some rooms get too hot and others never get warm enough. Often the owners of unbalanced systems imagine this is because "the boiler is too old" or "the radiators are full of silt and need flushing out" and think that the cost of getting their system repaired would be so high that they do nothing about getting it fixed! Most often their problem will disappear if they call-in someone who knows how to balance all the rads. Instead of letting your central heating system cool down completely, so that you often have to keep switching it on for a short time to give your home a big blast of heat, it is best to keep your central heating running continuously with the central wall-mounted thermostat set at the lowest temperature at which you feel comfortable. Doing this could save you money because you will not be wasting so much fuel, especially if your home is well insulated. Note: It is a sure sign that you have a faulty thermostat if you find that you continually have to turn the set temperature up by hand to get the system to start warming-up and then always have to turn that stat down again to stop the house getting too hot! You will be amazed how comfortable your home will be if you get that faulty thermostat replaced! 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydronic balancing」の詳細全文を読む スポンサード リンク
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