Viessmann AirflowPLUS AH2A Installation, Operating and Service
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Service and Maintenance
Air filter
The Viessmann AirflowPLUS AH2A series of air handlers
are provided with a disposable filter media. This filter
should be inspected monthly and removed and replaced
as required.
Circulator
The circulator is water lubricated and should require no
regular maintenance. The system control has a pump
exercise function during prolonged periods of no heat
to avoid seizing from long idle periods.
Checking temperature sensor
1. Remove cables from temperature sensor.
2. Check the sensor resistance and compare the actual
values with the curve in the chart.
3. Replace sensor in case of severe deviation.
Temperature sensors
Resistance in k Ohms
Service
Uninstalled sensors
Systems may elect to not use one, or more, of the five
sensors. In this case, the absent sensor temperature is
replaced by one long green blink following the red sensor
number blinks.
Failed Sensors
When a sensor is incorrectly installed or defective,
the LED indication will substitute red 8-8 for a normal
temperature reading. The alarm beeper will also beep
periodically to indicate a problem. The alarm beeper will
sound for 1 minute after power on and then stop.
In normal operation, after installation, the alarm beeper
will sound to indicate a failed temperature sensor. The
alarm may be silenced for 24 hours by cycling the power
on the unit. Note that the beeper will sound for the first
minute after cycling power and then remain silent for 24
hours.
Coils
The heating coil should not require cleaning if the filter
maintenance schedule is adhered to. If a filter is damaged
or collapses from plugging, dust may foul the coils. If this
happens, remove the front covers, replace the filter and
carefully vacuum the bottom of the heating coil. During
this process, avoid dust from falling into the fan below.
