The NIBE Low Pressure Switch (Part No. 418937) is a safety component used primarily in classic NIBE Fighter series ground-source heat pumps. 

Key Technical Specifications

• Cut-Out Pressure: 1.5 Bar

• Function: Continuously monitors low-side refrigerant pressure. If pressure drops below 1.5 bar (due to a refrigerant leak, brine loop freezing, or heat exchanger flow issues), the switch opens to trip a Low Pressure (LP) Alarm and stop the compressor. This protects the compressor motor from severe mechanical damage.

Primary Model Compatibility

This part is used across several classic NIBE ground-source and commercial heat pump series:

• Fighter Series: Fighter 1115, 1125, 1130, 1135, 1225, 1230, and 1235

• F1330 Series: Multi-compressor commercial units (e.g., F1330-22, F1330-30, F1330-40)

You typically need to replace or test this component if: 

1. The heat pump’s display shows a persistent Low Pressure Alarm / Defrost Fault even when refrigerant charge and brine/air flow are completely normal.

2. The internal microswitch has failed open, preventing the controller from starting the compressor.