scope:

This guideline applies to fluid circuits of heating systems where there is interruption of heating or recirculation (such as in summer or for night setback) represents a regular operating condition. The guideline is intended to assist in the design of pressure maintenance systems and in checking these systems during operation and preventive maintenance.

Worksheet AGFW FW 442 applies to water circuits of heat supply systems where heating and recirculation are uninterrupted except in the event of fault or repair and maintenance activities (such as districtheat networks).

The guideline does not deal with faults and pipe bursts and gives limited consideration to effects of pressure maintenance on water quality (in this context, see VDI 2035 or worksheet AGFW FW 510).

Pressure safety systems and safety devices are not included in the scope of this guideline.

The principles of this guideline are also applicable to pressure maintenance systems in fluid circuits of cooling systems and chillers as well as solar heating systems.