Danfoss AVPA (003H6597) — self-acting differential pressure relief controller, PN 16, DN 20, for district heating and cooling systems. The AVPA is a self-acting differential pressure relief controller; it is normally closed and opens on rising differential pressure, relieving (limiting) the differential pressure across the controlled circuit. It has a control valve, an actuator with one control diaphragm and a spring for the differential-pressure setting. Differential-pressure setting 0.2–1 bar adjustable; Kvs 6.3 m³/h. Maximum differential-pressure range 12 bar; media temperature 2–150 °C; cavitation factor z ≥ 0.6; seat leakage 0.02 % Kvs (IEC 60534). Valve body Red bronze CuSn5ZnPb (Rg5); valve cone Dezincing free brass CuZn36Pb2As; seat Stainless steel, mat. 1.4571; control diaphragm and DP sealing EPDM. Connection External thread G 1 A (ISO 228/1), via tailpieces. Mounting version Bypass. Permissible media: District heating/cooling circulation water (glycolic water up to 30%). OEM P/N 003H6597. Technical data quoted verbatim from store.danfoss.com (code 003H6597). 1.4571; control diaphragm and DP sealing EPDM; Pressure rating: PN 16 (max. differential-pressure range 12 bar); Temperature range: 2 to 150 °C (district heating/cooling water); HS code: 8481.80. Used in commercial refrigeration, provision-room cooling and reefer plant rooms across HFC, HFO and CO2 (R744) refrigerants. No.