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 Pro-Dialog+ interface. All adjustments 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. 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 setpoint The ﬂow rate control at full load uses the Pro-Dialog+ 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. Operating mode at part load Pro-Dialog+ includes two part-load operating modes: - Constant outlet pressure control - Constant delta T control.
Features and advantages
Reduced footprint Scroll compressors and R-410A refrigerant Variable-ﬂow pump Low-noise option (-3 dB(A)) Stacking of two units for increased capacity Several communication protocols available: JBus, BacNet, MS/TP, LON Water connection at the top or rear
The right unit for any application
The high temperature of the 61WG units makes them compatible with most heating systems, both in new and refurbished buildings and permits domestic hot water production (with a dedicated temperature setpoint). Option 153 “Built-in DHW and space heating control” allows control of both domestic hot water and space heating requirements: - Domestic hot water production: a built-in three-way valve is directed to divert the heat ﬂow from the space heating loop to the domestic hot water loop and vice versa. - Space heating control: the setpoint is adjustable, based on the daily schedule or the outside air temperature (weather compensation function). - Control of auxiliary systems: if an alarm is detected at the 61WG or if there is insufﬁcient heating capacity, a digital signal starts an auxiliary electric heater (1 to 4 stages) or boiler. - Pump control: allows control of the built-in pump as well as the pump in the secondary loop (to terminals). In 61WG units the Heating System Manager (HSM) accessory allows control of systems with several heat sources and different additional systems: electric heat, boiler or for the most complex systems district heating.
C A R R I E R 2 0 1 6 / 2 0 1 7
61WG - optimised for heating
High temperature up to +65 °C Evaporator temperature down to -5 °C Control of the three-way diverter