Cap valve

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

A cap valve is a valve that is secured against unintentional closing with a cap over the operating handle . Often the cap is also fixed with a seal.

The cap valve is installed according to DIN EN 12828 in heating systems, solar or cooling systems between the diaphragm expansion vessel (MAG) and the heat transfer medium and is open during normal operation of the system.
The free flow of liquid to the MAG is essential for the safe operation of the system, because the MAG absorbs the volume changes that occur in the heat transfer medium due to heating and cooling.

The cap ensures that the connection is not accidentally closed by:

• the valve can only be moved after removing the cap, an additional suitable tool being required for this.
• the cap can then only be put on when the valve is open.

function

The cap valve can be closed during regular functional tests of the MAG (checking and setting the pre-pressure) or when it is replaced. It can be emptied (depressurized) at the drain screw, which is usually on the cap valve. It should be closed when flushing and when testing the heating system for leaks in order to protect the membrane in the pressure equalization vessel from the high test pressure.