This configuration (see schematic below) is used for variable flow primary circuits and either constant flow or variable flow secondary circuits that have a design supply temperature identical to the primary circuit but a varying set point during operation.
 
The following table presents the main characteristics of this configuration.
| Primary circuit | Variable flow | 
| Secondary (consumer) circuit | Constant or variable flow | 
| Typical applications | Widely used in heating applications as it is very simple to achieve. | 
| Non-recommended applications | Low-temperature systems that would require the control valve to be operated on a limited opening range: use Buildings.Fluid.HydronicConfigurations.PassiveNetworks.DualMixing instead. | 
| Built-in valve control options | Supply temperature | 
| Control valve selection (See the nomenclature in the schematic.) | β = ΔpA-AB /
(Δp1 + ΔpA-AB) The control valve is sized with a pressure drop equal to the maximum of Δp1 and 3e3 Pa. | 
| Balancing requirement | In most cases the bypass balancing valve is not needed. However, it may be needed to counter negative back pressure created by other served circuits, see Buildings.Fluid.HydronicConfigurations.PassiveNetworks.Examples.SingleMixingOpenLoop. | 
| Lumped flow resistance includes (With the setting use_lumFloRes=true.) | Control valve valand primary balancing valveres1 | 
The parameter dp1_nominal stands for the potential
primary back pressure and must be provided as an absolute value.
By default the secondary pump is parameterized with
a design pressure rise equal to
dp2_nominal + dpBal2_nominal +
max({val.dpValve_nominal + dp1_nominal, val.dp3Valve_nominal + dpBal3_nominal}.