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The programmable controller controls the CHP, visualised in the figure below. It gives the setpoint to the external PI-controller for regulating the 3-way valve on the setpoint return temperature. Internally it will enable or disable the CHP and it will calculate the modulation based on the measured return temperature.
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The boiler is activated when the flow temperature of the system drops under 73°C, and deactivated when the flow temperature rises over 77°C. The activation also includes a check for the minimal flow rate, if the flow rate through the system is insufficient, the boiler won’t be activated. For instance, if the installation is shut down, the temperatures in the pipes will drop but the boiler won’t be activated because there is no flow through the system. During the activation of the boiler, an isolation valve at the boiler will open or close when deactivated.
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Controls
More information about the controls of the CHP can be found in Combined Heat and Power (CHP).
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