Danfoss GDA fixed gas detection unit, code 148H6020, a factory-calibrated wall-mount detector for ammonia (R717) in refrigeration machinery rooms, cold stores and process plant. Electrochemical sensing element with a 0–1000 ppm measuring range and two-level alarm relays (pre-alarm 500 ppm, main alarm 900 ppm). On-board LCD display, flexible/remote-capable sensor for local annunciation. Supplied as a complete unit with mounting kit, cable gland and a factory calibration certificate. Supply 19–29 V DC. Integrates with Danfoss AK-SM system managers and standard alarm panels. HS 9027.10. OEM P/N 148H6020.