In this module, we look at the control functions … for a variable-speed controlled … primary pump in a Grundfos … Distributed Pumping system. Primary pumps are built in parallel for optimizing primary pump speed together with Control MPC. This is done, as required, by detecting and equalizing the differential temperature between the primary pumps and the distributed pumps, measured over the bypass pipe.
The main priority for the Control MPC is to protect chillers, ensuring a minimum flow over the active chillers. The next priority is to avoid primary pumps over-pumping, by aligning primary side flow with secondary side flow. This equates with no flow over the bypass pipe. The main benefit is to identify and avoid or minimize the ‘low’ delta T syndrome, thereby saving energy, which is a typical issue in cooling systems.

The number of chillers and primary pumps varies depending on building and system size. To ensure minimum flow over each chiller, a differential sensor or flow meter must be installed at each chiller. A signal from an isolation valve or the building management system – a pre-start signal - tells the controller which chiller is in operation. This enables the controller to validate each active chiller, potentially increasing the primary pump flow if any chiller flow is below limit.

If you have an existing Building Management System or control system, please contact your Grundfos sales office. With a Grundfos Distributed Pump system, you get the right flow at all times and can configure the system using the control functions of the Control MPC.