Viessmann VITOTRONIC300 Installation And Service Instructions Manual page 82

Function Description
Heating Circuit Control
Heating circuit pump logic (economy mode)
The heating circuit pump is switched off [set supply
temperature set to 32°F (0°C)] if the outside temperature
exceeds the value selected via coding address "A5" in the
"Heating circuit..." group.
Extended economy mode
The heating circuit pump is switched off (set supply
temperature set to 32°F (0°C) if one of the following
criteria is met:
H The adjusted outside temperature exceeds the value
selected via coding address "A6" in the "Heating
circuit..." group.
H The heating circuit pump can be switched off for a time
calculated by the control unit when changing over from
heating mode to reduced mode.
Requirement:
- There is no risk of frost.
- Coding address "b0" in the "Heating circuit..." group
must be set to 0.
The idle period can be individually adjusted via coding
address "A9" in the "Heating circuit..." group.
Note: If, during the pump idle period, the system
is switched over to heating mode or the set room
temperature is increased, the heating circuit
pump is switched on, even if the period has not
yet expired.
H The actual room temperature exceeds the value
selected via coding address "b5" in the "Heating
circuit..." group.
H The mixing valve has been closed for 12 min. (mixing
valve economy function, coding address "A7" in the
"Heating circuit..." group).
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(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.
Therm-Control
The output is reduced if the actual temperature at the
Therm-Control sensor falls below the set temperature.
This closes the heating circuit mixing valves.
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.
Vitotronic 300, GW2B Installation and Service