Viessmann Vitotronic 300 Installation And Service Instructions Manual page 51

Vitotronic 300, GW5B Installation and Service
Heating Circuit Control Unit
Supply temperature control
Outside temperature
Legend
A Max. boiler water temperature
B Slope = 1.8 for heating circuit without mixing valve
C Slope = 1.2 for heating circuit with mixing valve
D Boiler water temperature (with a differential
temperature = 8 K)
E Lower boiler water temperature, defaulted by the
boiler coding card
(continued)
System dynamics
You can influence the control characteristics of the mixing
valves via coding address "C4" in the "Heating circuit..."
group.
Central control
Central control for a heating circuit can be programmed
via coding address "7A" in the "General" group.
The heating and holiday program then applies to all
additional heating circuits of the system.
For these heating circuits, when the heating and holiday
program is enabled, "Central control" is displayed.
Any holiday programs that may have been set will be
deleted. Party and economy modes cannot be enabled
on all control units.
Frost protection
The supply temperature is maintained in accordance with
the heating curve for the reduced set room temperature,
but at min. 50°F (10°C).
A variable frost limit can be set in accordance with coding
address "A3" in the "Heating circuit..." group.
Differential temperature:
The differential temperature is adjustable via coding
address "9F" in the "General" group,
delivered condition: 8 K.
The differential temperature is the minimum value by
which the boiler water temperature should be higher than
the highest currently required supply temperature of the
heating circuit with mixing valve.
System with only one heating circuit with mixing valve:
The set boiler water temperature will be automatically
regulated to 8 K above the set supply temperature.
System with heating circuit without mixing valve
and heating circuit with mixing valve: The set boiler
water temperature operates in accordance with a
special heating curve. The differential temperature of
8 K towards the set supply temperature is set at the
factory.
Function Description
51