Viessmann VITOTRONIC 200 Installation And Service Instructions Manual page 60

Function Description, Vitotronic 200/300-K
Heating Circuit Control Unit of the Vitotronic 300-K
60
Vitotronic 200, HO1B and 300-K, MW2C Installation/Service
(continued)
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 outdoor temperature exceeds the value
set in coding "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.
Requirements:
– There is no risk of frost.
– Coding "b0" in the "Heating circuit..." group must
be set to 0.
The duration of the idle time can be adjusted individually
in coding "a9" in the "Heating circuit..." group.
Note: If, during the pump idle time, the system is
switched to heating mode or the set room
temperature is increased, the heating circuit
pump is switched ON, even if the time has not
yet elapsed.
H The actual room temperature exceeds the value set in
coding "b5" in the "Heating circuit..." group.
H The mixing valve has been closing for 12 min. (mixing
valve economy function, coding "a7" in the "Heating
circuit..." group).
System dynamics
The mixing valve control characteristics can be influenced
at coding "a4" in the "Heating circuit..." group.
Central control
Central operation can be set for one heating circuits at
coding "7a" in the "General" group.
The operating and holiday program then applies to all
additional heating circuits of the system.
For these heating circuits, when the operating and holiday
program is enabled, "Central control" is displayed.
Any holiday programs that may have been set will be
deleted.
Comfort and economy modes cannot be enabled on all
control units.
Frost protection
The supply temperature is held in accordance with the
heating curve for the reduced set room temperature,
but at least at 32°F (0°C).
A variable frost limit can be set in line with coding "a3"
in the "Heating circuit..." group.