Danfoss 120Z0380 Surface Sump Crankcase Heater – 48 W / 230 V, with Bottom Insulation | For SM-SZ 084-161

Danfoss 120Z0380 is a surface sump heater bonded externally to the compressor sump base. When the compressor stops, refrigerant migrates to the sump, the coldest point of the circuit, and condenses in the oil; the heater prevents this migration by keeping the sump base at a temperature above that of the oil. The product comes with a bottom insulation pad — it prevents heat from escaping downward and increases efficiency.

Crankcase Heater for Small and Medium Body Scroll Compressors

This model is the 48 W version suitable for the Danfoss SM / SZ 084-161 body group (approximately 66,000 – 132,000 BTU range). In a system without a crankcase heater, or with a faulty one, the oil is diluted by refrigerant; at the first start the oil film breaks, bearing and piston wear begins, and in severe cases liquid slugging destroys the compressor completely. A crankcase heater is considered mandatory in all units installed outdoors and with long standstill periods; it is also a condition required by compressor warranties.

Technical Specifications (Official Danfoss Catalog)

• Brand / Code: Danfoss 120Z0380 (genuine spare part)
• Type: Surface sump heater + bottom insulation included
• Power: 48 W | Voltage: 230 V
• Certificates: CE + UL
• Compatible Compressors: Danfoss SM / SZ 084 – 161 bodies — except SM 112, SM 124 and SM 147
• Other voltages for the same body: 400 V → 120Z0381 · 460 V → 120Z0382 · 24 V → 120Z0361
• Upper body group equivalent: 80 W for SY/SZ 240-380 → 120Z0372 (230 V)

• 🔧 Clean the sump base before bonding: Oil, rust and paint residue impair heat transfer; the heater can overheat itself and burn out.
• Do not skip the insulation pad — the bottom insulation prevents heat from escaping to the surroundings and noticeably increases heater effectiveness.
• Commissioning: After a long standstill, it is recommended that the heater be energized for at least 8-12 hours before starting the compressor. It is wired so that it is energized when the compressor is stopped and de-energized when it is running (via the contactor auxiliary contact).
• Check: A sound 48 W / 230 V heater has a resistance of approximately 1,100 Ω; if the measurement shows an open circuit, the heater has burned out.
• 🚨 Model selection: This heater is NOT USED on SM 112, SM 124 and SM 147 bodies — Danfoss has separate codes for those models.