5.Control system - Meibes

3. Equipment and functional description
■ The freshwater station allows for a hygienic and
energy-saving preparation of warm water via a
stainless steel plate heat exchanger. It provides fresh
hot water for one to two apartment units. The source
of supply is a storage tank with a variable temperature
of 60 to 95°C. At very high storage temperatures
(up to 95°C) a temperature reduction of the
heat transfer media is recommended by admixture.
The primary pump P1 is controlled via block
modulation in such a way that the desired hot water
temperature is kept constant as much as possible.
For the control system to calculate the necessary
pump capacity, it uses the heat transfer media
temperature on the primary side, the inlet temperature
of the cold water and the circulation on the
secondary side as well as the current flow.
■ In addition to the preparation of freshwater, the
circulation can also be activated. In the “basic
setting” menu the circulation is switched ON or
OFF.
■ For circulation, up to 3 time slots can be specified in
the “programming” menu.
■ For the stainless steel plate heat exchanger there
are three modes of operation besides the drawing of
hot water:
water temperature-cold, water temperature -hot
and water temperature-timed heating
(See 5.3.3).
4
■ After-run
Should water temperature-cold be selected, it is
possible to set the circulation pump at an after-run,
to allow the stainless steel plate heat exchanger
to cool down and to prevent calcification.
The after-run function is however, only possible and
meaningful outside the circulation time!
■ Activating the hot water controller and reheating
With the additional T5 sensor (not included in
delivery), it is possible to put the control system in
operation only after a specified buffer temperature
has been attained. With the T5 sensor it is furthermore
possible to activate a boiler for reheating via a
potential-free contact. Both functions are deactivated
in the factory setting.
■ Disinfection
With this function it is possible to disinfect the
circulation pipes against the danger of legionella.
This function is only activated when a circulation
pipe is available and the circulation has been
switched on.
■ Data logging
With a „data stick” all measured values and the
status of pump outputs can be recorded for a
specific time period. A special computer programme
is used to analyse the measured values at the
freshwater station manufacturer.
T1 = Domestic hot water
T2 = Heat transfer media flow
T3 = Cold water and
circulation temperature
T4 = Heat transfer media return
T5 = Storage tank sensor for
„reheating“ and release of the
hot water controller and
circulation
P1 = Primary heat transfer pump
P2 = Circulation pump
DFZ = Flow rate metre
1 = Heat transfer unit
2 = Return flow preventer
3 = Control
4 = Shut-off valve
5 = Flow rate restrictor 3l
6 = Filling and draining tap
A = Flow heating
B = Return heating
C = Domestic hot water outlet
D = Hot water circulation
E = Cold water (domestic water)