Details on Thermostatic Valves in Basic Conditions
Information about the Thermostatic valves – Properties and dimensioning section in the Basic conditions dialog for Pipe Network Calculation Heating and for Pipe Network Calculation Cooling.
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Applies to: Heating and Cooling.
Design target
Valve authority describes the ratio between pressure loss of valve cones and the total pressure loss of the flow path or regulating section.
You can use the valve authority for the thermostatic valves to specify the test range (real valve authority) or the range in which the respective valve is to operate (dimensioning range, for setting conventional valve authority).
The best fitting thermostatic valve from the valve preselection will be selected. If only one thermostatic valve has been selected, there is no variation for dimensioning and valve authority can not be varied. If, in a particular installing installation of a valve, it is not possible to operate within the authority interval specified here, the respective setting is indicated by an exclamation mark (!) in the Results dialog.
The following steps may improve the valve authority:
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Selecting a smaller xp-value for the existing valve
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Selecting a valve with finer adjustments
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Reducing pressure losses within the flow path (velocity and R-value)
Real valve authority
Enabled: Pressure losses from the valve presetting (pre-throttling) are not added to the authority of the valve, but only to the pressure loss across the valve cone itself, i.e. the proportion that actually regulates. The pressure loss of the pre-throttling is added to the connected network (regulating section, upstream).
Conventional valve authority
Enabled: The total pressure loss of the valve including pre-throttling is used to determine the valve authority. You can either set the authority in % or set absolute pressure losses in Pa. If you activate authority and pressure loss simultaneously, the higher value is used as the limit value.
The conventional view of valve authority is, according to the more recent view, incorrect or even counterproductive. This is because the artificial increase in the flow path pressure losses by setting a minimum pressure loss across the thermostatic valve by means of the pre-throttling does not increase the controllable proportion, but only increases an additional fixed resistance, which must be added to the flow path. However, because the valve authority is defined as the ratio between the pressure difference across the regulating cross-section of the open thermostatic valve at nominal flow rate and the maximum total pressure difference of the flow-rate variable network component (pipes, resistances, throttles: for example The radiator lockshield valve or the internal throttle for valves with presetting), this measure ultimately reduces the valve authority instead of increasing it. See also the section on valve authority under: http://www.hydraulischer-abgleich.de
Define preferential:
When using radiators, it is adjustable which valves are primarily used by the program. Either the thermostatic valve, the radiator lockshield valve or the best possible combination of both valves is set as a priority.