Viessmann VITOTRONIC 300 GW2 Installation And Service Instructions Manual page 7

Heating system types for modulating boilers
Possible applications
Heating systems with manifold
arranged close to the boiler. The boiler
water flow is required to be reduced.
Please note:
This circuit diagram represents a
recommendation only. It is the
responsibility of the customer and/or
the heating contractor to check that
this recommendation is complete and
fully functional. Three-phase equipment
must be connected via additional
power contactors.
Available system accessories
Vitotrol remote control
Flue gas temperature sensor
Coding of Change required
system type
00: 1 If no system circuit A1 is connected, set
coding "00: 3", "00: 4", "00: 7" or "00: 8"
(see page 101)
02: 1 Set coding "02: 2" for operation with
modulating burner
03: 0 Set coding "03: 1" for oil-fired operation
(re-setting is not possible)
4A: 0
4b: 0
When the return temperature falls
below the required minimum value,
the temperature sensor T2 switches
on the shunt pump. If the minimum
return temperature is not reached
despite raising the return temperature,
the flow must be reduced by at least
50% via the temperature sensor T1.
The shunt pump must be sized so that
bypassed water accounts for approx.
30% of the total flow rate of the
boiler.
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Heating system types
(continued)
Temperature sensor T1
Wiring of the temperature sensor
T1 in heating systems with heating
circuit control units which are not
connected via the LON BUS to the
boiler control unit.
Coding required: "4C : 2" – use
plug sÖ for closing the mixing
valves of the heating circuits
connected downstream.
sÖ A1 Close mixing valves
A Contactor relay, field supplied
B Heating circuit controls
connected downstream
Switch contact closed: signal
for "close mixing valve".
Automatic change
The system type is recognized automatically
when the sensors are connected
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Connection of the temperature sensor T1 at
plug aJA;
Coding "4A: 1" is set automatically
Connection of the temperature sensor T2 at
plug aJB;
Coding "4b: 1" is set automatically
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