Well-controlled cooling systems are crucial in maintaining a good indoor climate and low operation costs. Variable Primary Flow (VPF) systems are world champions in achieving this. But to avoid chiller freezing and tripping, a minimum flow through the chiller must be maintained and the system must have quick unloading capabilities. This can be achieved with a precise control system, variable capacity compressors, pumps and fans, and a well-controlled bypass line.
Substituting the traditional bypass valve with a Grundfos TPE3 pump enables you to simplify the system while maintaining minimum chiller flow. The pump is controlled in constant ΔP mode, maintaining constant pressure, and hence flow, over the chiller evaporator regardless of system load. As soon as the flow rate through the chiller is safely above minimum flow, the TPE3 pump will stop all by itself. This approach ensures the performance of the primary variable speed pumps can be reduced independently of the chiller’s minimum flow rate limitations.
On average, 30-40% of energy consumption in a commercial building comes from HVAC systems. Download our whitepaper and see how efficient chilled water systems, such as variable primary flow systems, can contribute to lower energy use as well as a reduction in pollution and CO2 emissions.
The intelligent solution: Variable flow
VPF with bypass valve
Efficiency with the added cost of complexity
VPF chilled water systems achieve their impressive efficiency and performance by adapting the cooling performance to the actual load. But decrease flow too much and too fast, there is a risk of ice forming in the evaporator. The solution very often is to fit a bypass valve in the common line, leading excess flow back to the chiller when the demands from the cooling coils are not high enough to meet the minimum flow. The result is a system where variable capacity compressors, cooling tower fans, pumps and bypass line require precise control for all components to work together.
VPF with bypass pump
The cost-effective way to maintain optimum flow through the chiller
The Grundfos bypass pump solution with constant temperature control ensures that primary pump performance is totally independent of the chiller’s minimum flow rate limitations. This avoids excess flow in the system, keeping operating costs at a minimum. Also system complexity is reduced as the only components needed for this solution is a TPE3 pump and a pressure differential sensor.