5
Mode of operation
Through use of the instantaneous heating concept, drinking water is heated both hygienically and
with low energy consumption in the
FRISTAR
freshwater station.
If water is drawn from the mains, the
primary circuit
pump transports tank water from a buffer tank
through the plate heat exchanger.
On the
secondary side
of the heat exchanger the drinking water flowing through is heated to the set
temperature. The cooled tank water is returned to bottom layer of the buffer tank.
The
speed control
of the primary circuit pump takes place in the FRISTAR3 controller based on the
readings from the volume flow sensor in the hot water line (flow rate VWW and temperature TWW)
and the temperature sensors in the cold water line (TKW) and the primary flow (TPri). The pump is
controlled with PWM signals. Optimal matching of the control behaviour with the pump, valve and
heat exchanger ensures perfect stabilisation of the outlet temperature.
The controller has an integral heat meter, which enables the values to be read via DL bus.
The controller automatically initiates anti-corrosion measures for the pump and valve. If the pump is
not actuated for 7 days or the valve for one day (regardless of whether through automatic mode,
manual mode or otherwise), that component is operated briefly. This takes place while ensuring that
there is no DHW demand.
Hydraulic circuit diagram
Pre-mixer (recommended)
Temperature
Primary flow
Flow rate sensor and DHW
temperature
Co
ld
w
ate
r te
m
pe
ra
tu
re
Safety valve max. 6 bar
Primary pump
