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Viessmann AirflowPLUS AH2A Installation, Operating and Service
External Heat Demand via Switching Contact -
Heating System Operation
Outside temperature
Legend
A Selector dial "tr" setting: 1
B Selector dial "tr" setting: 2
C Selector dial "tr" setting: 3
D Selector dial "tr" setting: 4
E Factory default
F Selector dial "tr" setting: 5
G Selector dial "tr" setting: 6
Contact closed:
Set address 3A to 3A:2, for external demand upon
closure of DE1.
• The burner is switched ON subject to load. The boiler
heats to the set boiler water temperature selected in
coding "9b" in the "General" group.
Limiting the boiler water temperature by means of the
set boiler water temperature and the electronic
maximum limit of the boiler water temperature
(coding "06" in the "Combustion Controller" group)
- Vitodens 100 WB1B
Note: When using the RT connection, refer to the wiring
diagram on page 22.
Factory
default
Room dependent control:
Outdoor temperature sensor not connected
With no outdoor sensor installed, the "tr" dial will
provide a constant temperature set-point for the boiler
based on the dial position selected.
Setting the dial between 1 and 6 will provide a set-point
value of 81°F to 178°F (27°C to 81°C) respectively. The
dot between 4 and 5 represents the factory default set-
point value of 140°F (60°C).
Weather dependent control
Outdoor temperature sensor connected
With the outdoor sensor connected, the boiler will
automatically recognize the sensor and switch the set-
point dial operation from constant temperature calculated
to outdoor reset calculated.
Adjusting the "tr" dial will select the heating curve
corresponding with the heating curve chart. The set-
point will be calculated from the design boiler water
temperature associated with the heating curve selected,
and reset from the actual outdoor air temperature. Setting
the dial between 1 and 6 will select the corresponding
curve from the chart. The dot between 4 and 5 is the
factory default curve.
The display "tr" indicates when a heat request has
been made.
Note: When using the weather compensated operation,
ensure that the minimum temperature of the
selected heating curve exceeds minimum entering
water temperature set on page 27 'System Select
Dip switch Settings'.
Boilers equipped with HO1B User Interface
Operation
39
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