Soft Start Module – Thermia / Danfoss

Part Number: 086L3505
Component: Soft Start Device
Application: Reduces electrical inrush current when starting compressors or other high-load components in heat pumps.

🔧 Functionality

• Protects electrical systems by gradually ramping up compressor power

• Prevents tripped breakers, voltage dips, and component wear

• Increases system longevity and improves performance in areas with sensitive or limited electrical infrastructure

✅ Compatibility

Danfoss Units:

• DHP-H

• DHP-H Opti Pro

• DHP-L

• DHP-L Opti Pro

Thermia Units:

ATEC series
Diplomat series:

• Diplomat 4–16 kW

• Diplomat G2 (6–16 kW)

• Diplomat G3 (6–17 kW)

• Diplomat TWS (6–16 kW)

These are ground source and air source heat pumps, often installed in residential or small commercial buildings. The soft start is critical for single-phase and smaller 3-phase units.

Common Use Cases

• Retrofitting older units that experience high start-up current draw

• Replacement of a faulty soft start module causing start-up issues

• Used to protect compressors in installations with:

  • Limited grid capacity

  • Generator backup

  • High sensitivity to voltage drop