Danfoss AVPQT (003H6811) — self-acting multi-functional controller combining differential-pressure control, flow limitation and return-temperature limitation, PN 25, DN 40, return-pipe mounting, for district heating and domestic-hot-water substations. The AVPQT combines three self-acting functions in one valve: differential-pressure control, flow (volume) limitation and, via a thermostatic element, temperature limitation of the return. It maintains a constant differential pressure across the integrated flow-limiting valve while the thermostatic actuator throttles on rising return temperature — no auxiliary energy required. kVS 20 m³/h; flow-rate range 0.8 – 12 m³/h at Δpb 0.2 bar; differential-pressure setting 0.2 – 1 bar; maximum differential pressure 12 bar; medium temperature 2–150 °C; leakage 0.05% of kVS (IEC 534). Valve body ductile iron EN-GJS-400-18-LT (GGG 40.3), valve seat stainless steel 1.4571, valve cone dezincing free brass CuZn36Pb2As, control diaphragm EPDM. Connection flange PN 25. OEM P/N 003H6811, EAN 5702421543320. Technical data quoted verbatim from store.danfoss.com (code 003H6811). differential pressure 12 bar); Temperature range: 2 – 150 °C (medium); HS code: 8481.80. Used in commercial refrigeration, provision-room cooling and reefer plant rooms across HFC, HFO and CO2 (R744) refrigerants.