Table of Contents
Advertisement
Service
Troubleshooting
Power is on at the air handler.
Air handler ambient air sensor
is activated by a temperature,
less than 40°F (4°C).
The red light is illuminated
on the housing.
The internal pump and
circulation fan is running.
The air handler is in home freeze
protect mode. Once return air
exceeds 45 ° F (7 ° C), pump, fan
and red light will turn off.
44
Viessmann AirflowPLUS AH2A Installation, Operating and Service
Yes
Yes
Yes
Yes
Pump does not run
Often, closing the isolation valve on the return leg and
opening the drain port so that water flows through the
pump can free the pump. For the integrated Grundfos
pumps, remove the screw-on cover from the face of
the pump, and rotate the shaft one turn with a slotted
screwdriver.
If either method fails to free the pump, removal for cleaning
or replacement is necessary. The pump exercise function
will help prevent pump seizing.
Pump is noisy at start-up
Air is present in heating loop. If sound has not diminished
within 1 minute, purge air in accordance with the Start-Up
procedures.
Insufficient or no heat
- Plugged air filter or coil. Refer to Maintenance section
for filter care and coil cleaning.
- Air in heating loop; purge system.
- Inlet and outlet connections to air handler backwards;
reverse connections.
- Supply water temperature set too low or not calibrated
properly; check water temperature.
- Restriction in heating loop; remove restrictions, check
valves stick, valves too restrictive, left partially closed
after purging or closed valve.
Fan runs for cooling but not for heating
Room thermostat may be connected improperly.
Heating during standby mode
Probable cause is thermal Siphoning. See check valve
description for details; repair or replace check valve.
Home freeze protection
This sequence is initiated by extreme low air temperatures
[less than 40°F (4°C)] and are detected by the ambient
air temperature sensor.
Advertisement
Table of Contents
