Viessmann VITODENS 242-F Technical Manual page 83

Control units
(cont.)
■ Time, day and standard switching times for central heating, DHW
heating and the DHW circulation pump are factory-set
■ Switching times are individually programmable, i.e. up to four switch-
ing periods per day
Shortest switching interval: 10 minutes
Power reserve: 14 days
Setting the operating programs
The heating system frost protection (see frost protection function)
applies to all heating programs.
The following heating programs can be selected:
■ Heating and DHW
■ Only DHW
■ Standby mode
External heating program changeover in conjunction with EA1 exten-
sion.
Frost protection function
■ The frost protection function will be started when the outside tem-
perature drops below approx. +1 °C.
With frost protection, the heating circuit pump is switched ON and
the boiler water is maintained at a lower temperature of approx.
20 °C.
The DHW cylinder will be heated to approx. 20°C.
■ The frost protection function will be stopped when the outside tem-
perature rises above approx. +3 °C.
Summer mode
Operating program "w"
The burner starts only when the DHW cylinder needs to be heated
up.
Adjusting the heating curves (slope and level)
The Vitotronic 200 controls the boiler water temperature (= flow tem-
perature of the heating circuit without mixer) and the flow temperature
of the heating circuits with mixer (in conjunction with the extension kit
for one heating circuit with mixer) in weather-compensated mode. The
boiler water temperature is automatically boosted by between 0 and
40 K higher than the currently required set flow temperature (delivered
condition 8 K).
The flow temperature required to reach a specific room temperature
depends on the heating system and the thermal insulation of the build-
ing to be heated.
Adjusting the heating curves matches the boiler water temperature and
the flow temperature to these operating conditions.
Heating curves:
The upper boiler water temperature is limited by the temperature limiter
and the temperature set at the electronic maximum thermostat.
The flow temperature cannot exceed the boiler water temperature.
Heating curve slope
90
80
70
60
50
40
30
20
20 15 10 5 0 -5
Outside temperature in °C
VITODENS
1.4
1.2
1.0
0.8
0.6
0.4
0.2
-10 -15 -20 -25 -30
Heating systems with low loss header
When using hydraulic separation (low loss header), connect a tem-
perature sensor for use in the low loss header.
Boiler water temperature sensor
The boiler water temperature sensor is connected to the control unit
and built into the boiler.
Specification
Sensor type
Permissible ambient temperature
– during operation
– during storage and transport
Cylinder temperature sensor
For Vitodens with loading cylinder or solar cylinder also an additional
outlet temperature sensor.
These sensors are connected to the control unit and built into the boiler
or cylinder.
Specification
IP rating
Sensor type
Permissible ambient temperature
– During operation
– During storage and transport
Outside temperature sensor
Installation site:
■ North or north-west facing wall of the building
■ 2 to 2.5 m above the ground, for multi storey buildings in the upper
half of the second floor
Connection:
■ 2-core lead, length max. 35 m with a cross-section of 1.5 mm
per.
■ Never route this lead immediately next to 230/400 V cables
6 6
4 1
Specification
IP rating
Sensor type
Permissible ambient temperature dur-
ing operation, storage and transport
Viessmann NTC, 10 kΩ at
25 °C
0 to +130 °C
–20 to +70 °C
IP 32
Viessmann NTC 10 kΩ at
25 °C
0 to +90 °C
–20 to +70 °C
2 cop-
IP 43 to EN 60529; ensure
through design/installation
Viessmann NTC 10 kΩ, at
25 °C
−40 to +70 °C
VIESMANN
83
7