Technical data

Functional description
87
Heating circuit control
Brief description
The control unit has control loops for a
system circuit and two mixing valve
circuits.
The supply temperature set-point value
is determined by the outdoor
temperature, the desired room
temperature, the operating mode and
the heating curve.
The supply temperature of the mixing
valve circuits is controlled by opening
and closing the mixing valves in steps.
The mixing valve motor control varies
the actuation and interval times as a
function of the control difference
(control deviation).
The supply temperature of the system
circuit corresponds to the boiler water
temperature.
Coding addresses which influence the
heating circuit control
9F
A2 to A7, A9,
C4 to C7, C8
F1, F2.
See page 114 onwards for description.
Functions
The heating circuit is dependent on the
boiler water temperature and its control
range limits.
The only control element is the heating
circuit pump.
The supply temperature of the mixing
valve circuits is measured by the
supply temperature sensor (contact
sensor).
Time program
The timer of the control unit changes
the operating mode at the programmed
times in the ”Central heating and
DHW” heating program, switching
between ”Central heating with normal
room temperature” and ”Central
heating with reduced room
temperature”.
Each operating mode has its own
set-point value.
Outdoor temperature
A heating curve must be adjusted to
match the control unit to the building
and the heating system.
The heating curve determines the
set-point boiler water temperature
value as a function of the outdoor
temperature. Control takes place on
the basis of the mean outdoor
temperature. This is derived from the
actual and the damped outdoor
temperature.
The heating curve can be changed via
the set-point or operating mode
selector switches.
Domestic hot water temperature
With priority control:
While the DHW tank is being heated,
the set-point supply temperature
value is set to 0°C / 32°F .
The heating circuit pump is
switched off.
Without priority control:
The heating circuit control continues
to operate as normal with the
set-point value unchanged.
With modulating priority control
(only in conjunction with mixing
valve circuit):
The heating circuit pump remains
switched on. The set-point supply
temperature of the heating circuit
is lowered as long as the set-point
boiler water temperature is not
reached while the DHW tank is
being heated. The set-point supply
temperature is dependent on the
difference between the set-point and
the current boiler water temperature,
the outdoor temperature, the heating
curve slope and the setting of the
coding address ”A2”.
Room temperature
In conjunction with room
temperature dependent control:
Compared with the outdoor
temperature, the room temperature
has a greater influence on the
set-point boiler water temperature.
The magnitude of this influence can
be changed via coding address ”b2”.
In conjunction with mixing valve
circuit:
With control differences
(i.e. deviations from the current
value) of over 2°C / 4°F room
temperature, this influence can be
intensified (via coding address ”b6”,
rapid heating/setback).
5285 941 v.1.5