4
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 temperature set in the controller. 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
FRISTAR
controller based
on the measurements of the volume flow sensor in the hot water pipe (temperature
T
ww
and
volume flow
V
ww
) and the temperature sensor in the primary flow
T
Pri
). The pump is con-
trolled using wave packet control. The optimum matching of the control behaviour to the
pump and the heat exchanger guarantees perfect constant maintenance of the outlet tem-
perature.
Hydraulic circuit diagram
Temperature
Primary flow
Volume flow sensor
Hot water temperature
T
ww
Volume flow
V
ww
Pre-mixer
(recommended)
Safety valve max. 8 bar
Pump
