Danfoss 7773108 Belt-Type Crankcase Heater – 75 W / 230 V | For SM/SZ 175-185, SH 180-485, DSH 240-600

The Danfoss 7773108 is a belt-type crankcase heater wrapped around the outside of the compressor shell like a belt. When the compressor stops, refrigerant migrates to the crankcase, the coldest point in the circuit, and condenses in the oil. The heater prevents this migration by keeping the crankcase above the temperature of the oil.

Crankcase Heater That Protects the Compressor from Refrigerant Migration

In a system without a crankcase heater or with a faulty one, the oil is diluted by refrigerant; at the first start the oil foams, the oil film breaks down and bearing-piston wear begins. In severe cases liquid slugging destroys the compressor completely. For this reason, a crankcase heater is considered mandatory on all units installed outdoors and with long off-cycles — it is also a requirement in compressor warranties.

Technical Specifications (Official Danfoss Catalog)

• Brand / Code: Danfoss 7773108 (original spare part)
• Type: Belt-type crankcase heater
• Power: 75 W | Voltage: 230 V
• Certifications: CE + UL + UKCA
• Compatible Compressors: Danfoss SM / SZ 175-185 · SH 180 – 485 · DSH 240 – 600 · NTZ 215-271 · MT(Z) 100-160 · LT(Z) 088-100 · MFZ 250 · LFZ 250 · VSH 170 / VZH 170 · VTZ 171-215-242
• Net Weight: 0.29 kg | EAN: 5702428981163
• Other voltages of the same body: 110 V → 7773110 · 400 V → 7773118 · 460 V → 120Z0464 · 575 V → 120Z0465

• 🔧 Mounting height is the key point: The heater is wrapped around the lower part of the compressor, where the oil collects — below the sight glass. If fitted higher, it does not heat the oil and is as good as not fitted.
• Make sure the belt is in full contact with the shell along its entire length; wherever a gap remains, the heater overheats on itself and burns out. The clamp screw is tightened to a maximum of 2 Nm.
• ⚠️ Belt heaters are not self-regulating. External control is essential: wire it so that it is energized when the compressor stops and de-energized while running (via the contactor auxiliary contact).
• Target temperature: The crankcase oil should be kept 10 K above the saturated low pressure (LP) temperature of the refrigerant.
• Commissioning: After a long shutdown, it is recommended that the heater be energized for at least 8-12 hours before starting the compressor.
• On cold and windy sites (below −5 °C, wind above 5 m/s), additional thermal insulation of the compressor is recommended; otherwise the heater cannot keep up.
• Check: The resistance of a sound 75 W / 230 V heater is approximately 705 Ω; if you see an open circuit on measurement, the heater has burned out.