Viessmann VITOGAS Technical Manual Download Page 54

Page: 54 / 64

The requirements of DIN EN 12831 for heat load calculation are met.
To reduce the heat-up load, the reduced room temperature will be
raised in case of low outside temperatures. The flow temperature will
be raised for a limited time to reduce the heat-up time after a setback
period.
According to the Energy Savings Order [Germany], the temperature in
each room must be individually controlled, e.g. through thermostatic
radiator valves.

Control characteristics

■ Boiler control unit:

P-characteristics with two-point output when using a burner with
multiple stages

■ Heating circuit control unit:

PI characteristics with three-point output

■ Thermostat for limiting the max. boiler water temperature:

75 °C, adjustable to 87 °C

■ Adjustment of the high limit safety cut-out:

110 °C, adjustable to 100 °C

■ Heating curve setting range:

– Slope: 0.2 to 3.5
– Level:

−

13 to 40 K

– Max. limit: 20 to 130 °C
– Min. limit: 1 to 127 °C
– Differential temperature for a heating circuit with mixer: 0 to 40 K

■ Set DHW temperature setting range:

10 to 60 °C; can be changed to 10 to 95 °C

Boiler coding card

For matching to the boiler (supplied with the boiler).

Time switch

Digital time switch
■ Individual day and 7-day program, annual calendar
■ Automatic summer/winter time changeover
■ Automatic function for DHW heating and DHW circulation pump
■ 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 backup: 5 years

Setting heating programs

The heating system frost protection (see frost protection function)
applies to all heating programs.
You can select the following operating programs with the program
keys:
■ Heating and DHW
■ Only DHW
■ Standby mode
External heating program changeover via control module V.

Summer mode

("DHW only")
The burner starts only when the DHW cylinder needs reheating (con-
trolled by the cylinder thermostat).
The respective low-end boiler water temperature of each boiler is
maintained if necessary.

Frost protection

■ The frost protection function will be started when the outside tem-

perature drops below approx. +1 °C.
With active frost protection, the heating circuit pumps are switched
ON and the boiler water is maintained at the set value for reduced
mode, i.e. at a low-end temperature of approximately. 20 °C. The
allocated temperature is maintained for boilers with a low-end tem-
perature limit.

■ The frost protection function is stopped when the outside tempera-

ture rises above approx. +3 °C, i.e. the heating circuit pump and
burner will be switched off.

Adjusting the heating curves (slope and level)

The Vitotronic 200 regulates the boiler water temperature (= flow tem-
perature of the heating circuit without mixer)

and

the flow temperature

of the heating circuit with mixer, subject to weather conditions. 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 both heating curves matches the boiler water temperature
and the flow temperature to these operating conditions.
The upper boiler water temperature is limited by the thermostat and
the electronic maximum temperature limiter.

0,2

Outside temperature in °C

Boiler water or flow temperature in °C

Slope

2,4

2,6

2,8

3,0

3,2

3,4

90
80
70
60
50
40
30

0 -5 -10 -15 -20