User Manual

White paper | Saving Energy using PICVs | June 2017
© Siemens Switzerland Ltd, 2017 2
Dynamic-Balancing Against Pressure Differences
Pressure-independent combi valves (PICVs) ensure that the
flow of hot or cold water is solely dependent on valve travel.
Within their range of operation, they are not affected by
pressure fluctuations in the building’s hydronic system. This
is called dynamic-balancing or auto-balancing.
This basic functionality is achieved by an internal
differential pressure regulator (Figure 1, #3) working in
series to the main flow control valve (#1) and regulating the
pressure differential of the flow control valve using a
pressure inlet and membrane. Hence the flow across the
entire device is independent of the pressure changes in the
system and is determined only by the travel of the control
valve.
PICVs provide the same actuator interface as standard
control valves. It isn’t necessary to have additional external
energy supply or an electrical sensor. The energy to operate
the differential pressure controller is provided by the
hydronic system itself.
Another core function of PICVs is to limit the maximum
desired flow. Typically this is done either by limiting the
flow control valve’s travel or by limiting the free control
path area (#2).
PICVs Are Relevant in the Whole Hydronic System
PICVs can be used in almost all heating and cooling
applications in a building, including energy generation,
distribution and consumption. The most typical are:
Energy Consumption
o Chilled ceilings
o Radiators
o Heating/chilled water zone control
o Heating/cooling coils in:
- Fan coil units
- Air handling units
- VAV systems (Variable Air Volume)
Energy Distribution
o Heating group
o Chilled water group
Energy Generation
o District heating
Enabling Energy Savings in Three Different Ways
In heating and cooling applications in a building, the auto-
balancing function generates energy savings in three
different ways:
o It eliminates heat exchanger overflow at anytime
and under any operating condition.
o It improves control accuracy by eliminating
hydraulic cross-coupling between neighboring
control loops.
o It enables advanced energy distribution strategies
by eliminating the risk of heat exchanger
starvation.
PICVs in the Hydronic Context
Figure 1: Schematics of a mechanical PICV
1. Flow control valve
2. Pre-setting
3. Differential pressure regulator
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3
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