The NIBE High-Pressure Switch 24.5 Bar (Part Number: 418874), also referred to a high-pressure pressostat, is a critical safety component popular range of exhaust air and ground source heat pumps.

Technical Function

This switch acts as a mechanical guardian for your heat pump's refrigeration circuit.

• The Job: It constantly monitors the pressure of the refrigerant.

• The Limit: If the internal pressure spikes to 24.5 bar (often due to restricted water flow, a failing circulation pump, or a blocked air filter), the switch instantly trips.

• The Result: It cuts power to the compressor to prevent catastrophic physical damage to the system. When this trips, your heat pump will register a High Pressure (HP) fault code and lock out.

Compatibility

This specific 24.5 bar switch (418874) is used extensively across NIBE's classic Fighter exhaust air series, as well as some older ground source units.

A Note on Diagnostics

If your heat pump is continuously locking out on a High-Pressure error, don't assume the switch itself is broken.

Before replacing the switch, a heating engineer should check the actual root causes of high pressure:

1. Air in the heating system: Bleed your radiators and underfloor manifolds.

2. Dirty filters: A choked air filter or a blocked "Y-strainer" on the central heating pipework will choke the heat transfer, causing pressure to skyrocket.

3. Circulation Pump failure: If the pump isn't moving water fast enough, the heat pump can't shed its heat, tripping the 24.5 bar limit.

Crucial Safety Rule: Because this switch is integrated directly into the pressurized refrigerant circuit, replacing it requires reclaiming the refrigerant. This work must be carried out by an F-Gas certified heating engineer.