Heating Circuit Control - Viessmann VITOTRONIC300 Installation And Service Instructions Manual

Vitotronic 300, GW2B Installation and Service

Heating Circuit Control

Brief description
H Type GW2B:
The control unit has control circuits for one heating
circuit without mixing valve A1 (heating circuit 1)
and two heating circuits with mixing valve M2 (heating
circuit 2) and M3 (heating circuit 3).
H The set supply temperature of every heating circuit
is determined from the following parameters:
– Outside temperature
– Set room temperature
– Operating mode
– Heating curve slope and shift
H The boiler coding card defaults a minimum boiler water
temperature that must be maintained to protect the
boiler.
H The supply temperature of heating circuits without
mixing valve is equal to the boiler water temperature.
H The supply temperature of the heating circuits with
mixing valve is regulated by the stepped opening
or closing of the mixing valves.
The mixing valve motor control changes the actuating
and pause times subject to the control differential
(control deviation).
Functions
The heating circuit without mixing valve is subject to the
boiler water temperature and its control range limits.
The heating circuit pump is the only actuator.
The supply temperature of the heating circuits with
mixing valve is recorded by the supply temperature sensor
of the relevant heating circuit.
Time program
In accordance with the time program in the "Heating
and DHW" heating program, the control unit regulates
between "Central heating with standard room
temperature" and "Central heating with reduced room
temperature".
Every operating mode has its own set level.
4 time phases per day can be selected.
Outside temperature
A heating curve must be set for matching the control unit
to the building and the heating system.
The heating curve characteristics determine the set boiler
water temperature subject to outside temperature.
The control unit uses an average outside temperature.
This comprises the actual and the adjusted outside
temperature.
Room temperature
In conjunction with the remote control and room
temperature hook-up (coding address "b0" in the "Heating
circuit..." group):
Compared with the outside temperature, the room
temperature has a greater influence on the set boiler
water temperature (changed via coding address "b2"
in the "Heating circuit..." group).
In conjunction with heating circuits with mixing valve:
For control differentials (actual value deviation) above 2 K
room temperature, the influence can be increased again
(coding address "b6" in the "Heating circuit..." group):
H Quick heat-up
The set room temperature must be raised by at least 2 K
by the following measures:
– Activating party mode
– Changeover from central heating with reduced temp.
to central heating with standard temp.
– Start optimization (coding address "b7" in the
"Heating circuit..." group)
Quick heat-up will stop when the set room temperature
has been reached.
H Quick setback
The set room temperature must be reduced by at least
2 K by the following measures:
– Activating economy mode
– Changeover from central heating with standard
temp. to central heating with reduced temp.
– Stop optimization (coding address "C1" in the
"Heating circuit..." group)
Quick setback will end when the set room temperature
has been reached.
DHW temperature - Priority control
H With priority control: (code "A2:2" in the "Heating
circuit..." group):
The set supply temperature is set to 32°F (0°C)
during DHW tank heating. The mixing valve closes
and the heating circuit pump is switched off.
H Without priority control:
The heating circuit control unit continues to operate
with the same set value.
H With modulating priority control in conjunction with
heating circuits with mixing valve:
The heating circuit pump remains switched on. The
set supply temperature of the heating circuits will be
reduced, for as long as the set boiler water temperature
has not been reached during DHW tank heating.
The set supply temperature is determined from the
following parameters:
– Outside temperature
– Differential between the set and the actual boiler
water temperature
– Heating curve slope and shift
– Setting of coding address "A2" in the "Heating
circuit..." group
Function Description
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