Viessmann AWO-M-AC 101.A06, Assembly And Servicing Instructions

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5.6.7 Service sleeves
2 service sleeves with cap (1/4”G) are installed in the unit’s water circuit,
downstream and upstream of the circulator (ref. SM unit functional diagram
paragraph 5.6.2); when disassembling/fitting on the cap use 2 spanners as
pictured to prevent damaging the pipes.
5.6.8 Air venting valve
The unit is fitted with an air venting valve to automatically remove air that has built up in the
circuit, preventing undesirable effects such as premature corrosion and wear, lower performance
and low exchange output.
The device also features a safety function because, in the event of exchanger breakdown, it allows
the refrigerant gas to escape outside, preventing it fro being conveyed to the internal terminals.
The valve can be kept in a closed position by closing the plug on the drain; by loosening the plug,
the valve remains in
open position and air is vented automatically.
In the event of observing a water leak, it is mandatory to replace the component, by loosening it
with a wrench, as pictured below.
When it is required to top up the circuit
or to adapt the glycol level, please use
the service valve. Unscrew and remove
the cap from the service valve and
connect a 14 or 12 mm pipe (inside
diameter - check the valve model
installed on your unit), connected to the
water mains, to the hose connector and
then drain the circuit by unscrewing the
specific ring nut. After the end of the
operation, retighten the ring nut and
screw the cap back on. In any case it is
recommended to use an external valve
to fill the system which can be set up by
the installer.
Cap with gasket
Ring nut