.Buildings.Fluid.HydronicConfigurations.ActiveNetworks.InjectionTwoWayCheckValve .Buildings.Fluid.HydronicConfigurations.ActiveNetworks.InjectionTwoWayCheckValveThis configuration (see schematic hereunder) is nearly similar to Buildings.Fluid.HydronicConfigurations.ActiveNetworks.InjectionTwoWay except for the check valve that is added into the bypass. If used in DHC systems and if the control valve is not properly sized to maintain the set point at all loads, the check valve prevents recirculation in the service line which degrades the ΔT in the distribution system. If used to connect a heating coil, the check valve reduces the risk of freezing in case of secondary pump failure.
See the documentation of Buildings.Fluid.HydronicConfigurations.ActiveNetworks.InjectionTwoWay for a summary table of the main characteristics of this configuration. In addition, the following non-recommended applications should be mentioned, and the control valve authority is reduced by the check valve pressure drop.
| Non-recommended applications |
Radiant systems due to the risk of overheating or condensation in case
of secondary pump failure Constant flow consumer circuits due to the risk of elevated secondary pressure when the check valve is closed and the primary and secondary pumps are in series |
|
Control valve authority (See the nomenclature in the schematic.) |
β = ΔpA-B /
(Δp1 + ΔpA-J) |
With this configuration, if the check valve is closed, the primary pressure differential is transmitted to the consumer circuit, lowering the authority of the terminal control valves. Therefore this configuration is rather recommended in conjunction with a variable flow consumer circuit where the circulation pump speed is modulated to track a differential pressure set point. Hence, when the primary and secondary pumps are in series, the secondary pump is operated at a lower speed.
The check valve is configured with a default pressure drop
res3.dpValve_nominal=5e3 Pa
for a mass flow rate equal to the maximum value of
m2_flow_nominal and the check valve fully open.
Note that with a variable flow consumer circuit the bypass
line may be sized with a lower design flow rate.
Hence the parameter res3.m_flow_nominal is not
assigned a final value and may be overwritten.
The pressure drop through the check valve is compensated by the secondary pump,
while the pressure drop through the control valve is compensated by the
primary pump.