Hydronic Balancing
Encyclopedia
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 underflow
s.
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 radiator
s.
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.
required. Control valves may temporarily help by gradually reducing the flow in favoured circuits, thus allowing unfavoured 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.
Balancing limits the flow in favoured circuits, forcing water through unfavoured 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 (saves on 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.
s and blocked filters. These flaws are exposed while they can still be cheaply fixed. That is, before control equipment is commissioned, before ceilings are mounted, and most important, before tenants move in.
After several years use even the best-designed and best-built plants can suffer operational problems. A problem can have many causes: filters or valves may be clogged, terminal units and heat exchanger
s may have been replaced, a pipe may have been damaged during renovation
s, or a child's mischievous fingers may have left a shutoff valve half open. Balancing valves allow the measurement of differential pressure and temperature thereby pinpointing the cause of many such operational problems.
Heating system
A heating system is a mechanism for maintaining temperatures at an acceptable level; by using thermal energy within a home, office, or other dwelling. Often part of an HVAC system. A heating system may be centralized or distributed.-See also:...
or cooling system so it provides the intended indoor climate at optimum energy efficiency
Efficient energy use
Efficient energy use, sometimes simply called energy efficiency, is the goal of efforts to reduce the amount of energy required to provide products and services. For example, insulating a home allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature...
and minimal operating cost
Operating cost
Operating costs can be described as the expenses which are related to the operation of a business, or to the operation of a device, component, piece of equipment or facility.-Business operating costs:...
.
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 underflow
Underflow
Underflow may refer to:* Buffer underflow, in computer science, a condition in which an attempt is made to read an empty buffer* Arithmetic underflow, in floating point arithmetic, a condition in which an intermediate result is strictly between zero and the smallest normalized number in the...
s.
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 radiator
Radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...
s.
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.
Problems caused by improper balance
In an unbalanced system there will always be favoured circuits that receive more water than they require. These favoured circuits steal flow from unfavoured circuits which will not then be able to provide the heating or coolingCooling
Cooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to:-Techniques:* Air conditioning* Air cooling* Computer cooling* Cryogenics* Conduction * Infrared solar cells* Laser cooling...
required. Control valves may temporarily help by gradually reducing the flow in favoured circuits, thus allowing unfavoured 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.
Balancing limits the flow in favoured circuits, forcing water through unfavoured circuits. As a result the required design flows are available to all circuits and the system can provide the required Indoor Air Quality
Indoor air quality
Indoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants....
. 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 (saves on 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.
Methods
Balancing an installation is a complicated and involved procedure because closing or throttling a valve will increase the flow in other parts of the installation. That is why a very structured procedure must be followed. The two most used methods are Compensated balancing and Proportional balancing. Both use an iterative methodology that will result in properly distributed flow in full load situation. The complicated nature of these balancing procedure is the reason that automatic solutions are gaining traction because it reduces or eliminates the need for complicated balancing procedures. Because of that differential pressure controllers and pressure independent valves are getting more and more popular.Troubleshooting
The act of balancing can reveal common glitches such as wrongly mounted terminal units, damaged pipes, back-to-front check valveCheck valve
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....
s and blocked filters. These flaws are exposed while they can still be cheaply fixed. That is, before control equipment is commissioned, before ceilings are mounted, and most important, before tenants move in.
After several years use even the best-designed and best-built plants can suffer operational problems. A problem can have many causes: filters or valves may be clogged, terminal units and heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s may have been replaced, a pipe may have been damaged during renovation
Renovation
Renovation is the process of improving a structure. Two prominent types of renovations are commercial and residential.-Process:The process of a renovation, however complex, can usually be broken down into several processes...
s, or a child's mischievous fingers may have left a shutoff valve half open. Balancing valves allow the measurement of differential pressure and temperature thereby pinpointing the cause of many such operational problems.