Abstract:
Known filters for central and district heating systems must be cleaned frequently and further there is risk that the filter may clog completely. The invention solves this problem and allows in addition removal and cleaning of the filter unit while the heating system is still operational. When the pressure drop is being too high a spring loaded valve (9) permits the circulating water to pass through a channel (7) by-passing the filter unit (3). When the valve (5) is turned in its blocking position then the filter unit (3) is unpressurized as a one-way valve (6) prevents pressure from the outlet side. In this position the filter unit may be removed and the circulation is maintained through the channel (7).