Function Description Boiler Water Temperature Control; Brief Description; Functions - Viessmann VITOTRONIC 200 Installation And Service Instructions Manual

Function description
Boiler water temperature control

Brief description

The boiler water temperature is regulated by starting
■
or stopping the burner or through modulation. In the
delivered condition, the switching differential is
relative to the current set value.
■ The set boiler water temperature is determined from
the following parameters:
Set flow temperature of the heating circuits con-
–
nected to the control unit and the heating circuits
connected via the LON BUS
– External demand
– Set DHW temperature

Functions

The boiler water temperature is captured by the follow-
ing equipment:
High limit safety cut-out STB (liquid expansion)
■
■ Temperature controller TR (liquid expansion)
■ Boiler water temperature sensor NTC 10 k
Upper control range limits:
High limit safety cut-out STB 110/100/95 °C
■
Temperature controller TR 75/87/95 °C
■
Electronic maximum temperature limit:
■
– Setting range: 20 to 127 °C
– Changed via coding address "06" in the "Boiler"
group.
The limit is only effective within the control range
(not for DHW cylinder heating).
Lower control range limits:
In standard mode and when frost protection is ena-
bled, the boiler water temperature will be regulated
subject to the respective boiler.
Auxiliary circuits
■ Extension for controlling a two-stage/modulating
burner (see page 21).
■ External hook-ups (messages) via EA1 extension
(see page 91).
Plug "X12" for external burner start (see page 18).
■
Plug for external demand (see page 19) or exter-
■ lH
nal blocking (see page 20).
Switching hysteresis, burner
Permanent switching hysteresis
Code "04:0"
76
The boiler coding card specifies a minimum boiler
■
water temperature that must be maintained to protect
2 K, the boiler.
±
■ When the DHW cylinder is heated, the default set
boiler water temperature is 20 K above the set DHW
temperature (adjustable via coding address "60" in
the "DHW" group).
ON
OFF
+2
Ω
set
-2
low
heat demand
Fig.40
Heat demand-dependent switching hysteresis
The heat demand-dependent switching hysteresis
takes the boiler utilisation level into account.
The switching hysteresis, i.e. the burner runtime, var-
ies subject to the current heat demand.
ERB50 function
Code "04:1"
Depending on the heat demand, values between 6 and
12 K result.
ON
OFF
+9
+3
set
-3
low
heat demand
Fig.41
ERB80 function
Code "04:2"
Depending on the heat demand, values between 6 and
20 K result.
average
high
heat demand heat demand
average
high
heat demand heat demand
Time
Time