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Viessmann AirflowPLUS AH2A Installation, Operating and Service
Override Settings
S1
S2
Off
Off
On
Off
Off
On
On
On
The adjustments are made on dip switch interface S1 (refer to the wiring diagram on page 58).
System Select Dip Switch Settings
S5
S6
OFF
ON
ON
OFF
ON
OFF
ON
OFF
The adjustments are made on dip switch interface S1 (refer to the wiring diagram on page 58).
Maximum heating override
90°F (32°C)
85°F (29.5°C)
80°F (26.5°C)
75°F (24°C)
S7
S8
ON
ON
OFF
OFF
OFF
ON
ON
OFF
Dip switch settings
The dip switch will allow the selection of custom setup
options. Refer to Variable Table for system options.
Maximum heating override
The return air temperature will be monitored for
unreasonably high values. When the upper limit is reached
the unit will override the thermostat and maintain the
temperature at the set value.
Minimum cooling override
The return air temperature will be monitored for
unreasonably low values. When the lower limit is reached
the unit will override the thermostat and maintain the
temperature at the set value.
IMPORTANT
Start-up: Do not power the unit until the water supply
has been connected and the system purged of air. The
circulating pump may come on at anytime. Dry operation
of the pump will damage the pump and void warranty.
S3
S4
Off
Off
On
Off
Off
On
On
On
Four system settings are available. Two for use when the
evaporator is in the supply air stream, two for use when
the evaporator is in the discharge air stream. In each
configuration, the hot water threshold of 85°F or 110°F
(29°C or 43°C) may be selected, this ensures that only
warm air is available during heating operations.
System
Evaporator in Supply Air / 110°F (43°C)
Evaporator in Return Air / 110°F (43°C)
Evaporator in Supply Air / 85°F (29°C)
Evaporator in Return Air / 85°F (29°C)
Installation
Minimum cooling override
65°F (15.5°C)
68°F (20°C)
70°F (21°C)
72°F (22°C)
27
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