Variable water ﬂow system (VWF)
Variable water ﬂow is a hydronic control function package that permits control of the water ﬂow rate. The VWF not only ensures control at full load, a speciﬁc Carrier algorithm linked to an electronic frequency converter also continuously modulates the ﬂow rate to minimise pump consumption at full load as well as part load. The hydronic module includes pressure transducers that permit intelligent measurement of the water ﬂow rate and real-time display on the Touch Pilot Junior interface. All adjust-ments can be made directly on the interface, speeding up start-up and maintenance. As VWF acts directly on the pump, the system no longer requires the control valve at the unit outlet. However, for applications with two-way valves a bypass system must be kept to guarantee the minimum ﬂow rate. Operating mode at part load Touch Pilot Junior includes two part-load operating modes: - Constant outlet pressure control - Constant delta T control. 1 – Constant unit outlet pressure control The control continuously acts on the pump speed to ensure a constant outlet pressure. This solution is suitable for installations with two-way valves. When these close, the water speed will accelerate in the system branches that are still open. For a ﬁxed-speed pump this results in an unnecessary increase of the pressure at the pump outlet. The outlet pressure control mode ensures that each circuit branch always has a uniform supply, without unnecessary energy waste. In industrial processes such as plastic injection moulding, this solution ensures that each terminal unit has the correct pressure supply. 2 – Constant delta T control The VWF algorithm maintains a constant delta T no matter what the unit load, reducing the ﬂow rate to the minimum. This solution can be used for systems with two-way or threeway valves and achieves higher energy savings than the “Constant unit outlet pressure control” mode. It is suitable for the majority of comfort applications.
Full-load set point The ﬂow rate control at full load uses the Touch Pilot Junior interface, reducing the pump speed. This ﬁrst control saves energy that would normally be dissipated in the control valve. For example, if the pressure supplied by the pump is reduced by 20% the power consumption of the pump is reduced by the same ratio, compared to a traditional installation.