Danfoss 7750009 Discharge Gas Thermostat Kit (DGT) – Scroll Compressor Overheat Protection, 135 °C

Danfoss 7750009 is an external thermostat kit that protects scroll compressors against excessive discharge gas temperature (DGT – Discharge Gas Temperature protection). The kit contains all the parts required for installation: thermostat, connection cable, bracket and thermal insulation material.

Discharge Gas Temperature Protection: Catches the Fault That Pressure Switches Cannot See

High and low pressure switches protect the circuit according to pressure limits — but the compressor can overheat even while the pressures appear normal. Low refrigerant charge, insufficient suction gas cooling, a high compression ratio or excessive superheat are such situations: the discharge gas temperature climbs, the oil thins, and the winding insulation and scroll sets are damaged.

The DGT thermostat closes exactly this gap. The sensor in contact with the discharge tube measures the temperature directly and stops the compressor when the limit is exceeded. Danfoss makes DGT mandatory in applications where the pressure switch settings do not protect the compressor against operating outside its operating envelope.

Technical Specifications (Official Danfoss Data)

• Model: Danfoss 7750009 | Type: Discharge gas thermostat kit (DGT)
• Opening Temperature: 135 °C (275 °F) and below — not to be set above this value
• Kit Contents: Thermostat + connection cable + bracket + thermal insulation
• Mounting Location: Discharge line, max. 150 mm (5.91") from the compressor discharge port
• Mounting Requirement: Must be firmly fixed to the tube and thermally insulated (the insulation in the kit is for this)
• Sister code: 7973008 — same kit, industrial pack of 50

Compatible Danfoss Scroll Compressors

Listed in the Danfoss spare parts catalog as "all models except DSF":

• Commercial / air conditioning scroll: SH · SM · SY · SZ · WSH · PSH · DCH series
• Variable speed: VSH088-117-170 & VZH088-117-170
• Refrigeration scroll: MLZ · MLM series
• Exception: DSF series (this kit is not used on DSF models)

• 🔧 Follow the 150 mm rule. If the thermostat is placed far from the discharge port, the gas cools along the way, the thermostat cannot see the real temperature and the protection kicks in late.
• 🧣 Do not skip the insulation. An uninsulated sensor is affected by the ambient air; the thermostat may not open even if the compressor reaches a critical temperature.
• ⚠️ If the DGT has tripped, find the cause. Do not just reset it and carry on — look for low charge, a blocked filter/capillary tube, a dirty condenser or an excessive compression ratio. Recurring overheating permanently wears out the compressor.
• The safety chain must stop the compressor; do not wire the DGT contact only as an alarm/warning.
• The 2nd image shows Danfoss's official installation diagram (thermostat · discharge line · bracket · insulation).