Control modes
In addition to constant pressure control, VASCO – VAriable Speed COntroller allows other control modes such as fixed frequency, constant flow, constant temperature.
Constant pressure.
It controls the pump speed to maintain constant pressure at a set point independent of the water demand in the system.
In a hydraulic system equipped with the device, the standard pressure tank is replaced by a smaller tank which functions to maintain the set pressure in the system when the pump is stopped.
Constant pressure 2 values.
By selecting the constant pressure 2 values control mode, in irrigation systems, only one pump can serve two zones with different pressure sets. It is possible to switch the two values by acting on a digit input contact.
Fixed frequency 2 values.
If it is not necessary to operate at constant pressure but is required to select 2 different pump speeds, by selecting fixed frequency 2 values control mode it is possible to switch the 2 values by acting on a digit input contact.
Constant temperature.
The control method at constant temperature is used to maintain the temperature of the pumped fluid to vary the thermal load. This control system is used in air conditioning or refrigeration and cooling towers. In this latter case, for example, the temperature measured by a sensor in the return water is kept constant.
External frequency.
In some application, it is chosen to change the frequency of the pump by using an external signal coming from a trimmer or a PLC. In this case, after selecting the External Frequency control mode, it is enough to connect an input signal 4-20 mA or 0-10V, proportional to the desired frequency, to the AN4 analogue contact.
Constant flow.
By selecting the constant flow control mode and using a flow transducer, it is possible to control the flow of the pumped liquid to vary the system condition.
This control mode is used, for example, in a system for filtering the pumped fluid in which the obstruction of the filter would lead to a progressive reduction of the flow rate if it is not compensated by an increasing of the pump speed.