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Translation from original instructions
7.3.3 Flowzer VDE
The “VDE” function is used to set the speed of the pump to such level that the pressure difference between the unit inlet
and outlet is kept constant and the water flow rate is consequently kept constant.
The speed of the pump is set automatically to preserve the desired flow through the heat exchanger in the unit.
This function is useful when the head of the pump aboard the unit is greater than the system requires, which would result
in a higher water flow circulating.
The result of flow rate reduction is energy consumption saving.
The value corresponding to the difference between the input and the output pressure needs to be monitored to ensure the
correct water flow.
In heat pump units the controller is designed to offer the opportunity to set two pressure difference values: one for cooling
and one for heating.
Please find below the hydraulic diagram of a system where the unit can be installed.
Vmin.
U2
U1
Un
Y2V
Y2V
Y3V
VP
A2
UL
UE
BT2
BT1
ΔPex
BP41
The abbreviations present in the diagram indicate:
- A2 = cooling unit controller
- BT1 = unit input temperature sensor
- BT2 = unit output temperature sensor
- EU = heat exchanger in cooling unit
-
BP41= differential pressure sensor;
-
ΔPex = pressure difference at the ends of the unit;
-
VP = variable flow pump
-
ΔPp = pressure difference at the ends of the system
-
U1, U2 .. Un = points of use present in the system/plant
- Y2V = 2-way valve servo controls
- Y3V = 3-way valve servo controls
-
Vmin = minimum water volume in the system/plant
- UL = limit of the supply.
This type of system requires that the min. water flow rate is also guaranteed when there is no load. This is made possible
through the installation of 3-way valves on the user points.
The installation of 3-way valves on the furthest user points also provides for greater thermal flywheel, which enables limiting
the capacity of the buffer tank.
Parameters relating to the pressure difference in the evaporator are set up at the factory.
If they need editing, check that the water flow rate through the heat exchanger in the unit is within the opera
-
ting limits admitted in the technical catalogue.
