Danfoss APT — self-acting differential-pressure controller, OEM order code 003Z5701. Fourth-generation self-acting (automatic) differential-pressure controller for automatic hydronic balancing. Installed in the return of a riser and connected by an impulse tube to an ASV-BD/ASV-M partner valve on the supply, it holds a constant differential pressure across the riser regardless of load changes elsewhere in the system. Constant differential pressure keeps two-way control-valve authority high and prevents flow noise at part load. Integral shut-off; adjustable setting range. APT is the self-acting differential-pressure controller supplied without insulation. Nominal size DN 15, Kvs 1.6 m³/h, PN 16, Internal thread connection, Brass body, media temperature 0 °C to 120 °C. Differential-pressure setting range 5-25 kPa (factory setting 10 KPa), max. differential pressure over the valve 250 KPa, impulse tube 1.5 m. Net weight 0.681 Kilogram. Genuine Danfoss part; technical data quoted verbatim from store.danfoss.com (code 003Z5701). OEM P/N 003Z5701, EAN 5710104094618. Used in commercial refrigeration, provision-room cooling and reefer plant rooms across HFC, HFO and CO2 (R744) refrigerants.