NIBE Expansion Vessel

Description

Original expansion vessels from NIBE are adapted to maintain an even and stable system pressure in the heat pump or indoor module. When the heating medium water expands during temperature changes, the expansion vessel absorbs the pressure variations, which counteracts unnecessary wear on valves and pipe systems and reduces the risk of operational disruptions.

The vessel is a direct replacement part developed for exact fit and long-term reliability. Properly functioning pressure maintenance ensures that the entire heating system maintains good energy efficiency, low energy consumption and minimal maintenance requirements.

The importance of the correct pre-pressure and system pressure

A well-functioning closed expansion vessel is crucial for the efficiency and service life of the heat pump. If the vessel's internal rubber membrane loses pre-pressure or is damaged, the pressure in the system can start to fluctuate greatly between operation and standstill.

This can in turn lead to the safety valve being triggered unnecessarily, oxygen entering the heating system or the circulation pump being damaged by cavitation. By replacing a worn expansion vessel with a factory-fitted original part, an even pressure profile is recreated, which prevents recurring alarms and unwanted temperature drops in the home.

Common signs that the expansion vessel needs to be replaced

• The pressure gauge shows large and rapid fluctuations between hot and cold operation
• The safety valve drips or opens regularly despite normal settings
• The heating system loses pressure continuously and requires frequent refilling
• Water seeps out through the air valve (Schrader valve) when checking the pre-pressure
• Recurrent air pockets occur in radiators and underfloor heating coils

Installation and service instructions

When replacing the internal expansion vessel in an indoor module or exhaust air heat pump, the unit must be depressurized and de-energized in accordance with applicable safety regulations. The vessel is mounted directly on the existing pipe connection using the supplied seals and fasteners.

Before refilling the system with water, it is recommended that the pre-pressure of the vessel is checked and adjusted to the static height of the installation to ensure perfect interaction with the rest of the heating circuit.

Components included

• Expansion vessel: 1 piece
• Locking clip 15: 1 piece
• O-ring: 2 pieces

Compatibility and model adaptation

This expansion vessel is developed as an original part and fits the following NIBE units:

• NIBE indoor modules: VVM 225, VVM 320, VVM 325
• NIBE exhaust air heat pumps: F370, F470, F730, F750
• NIBE intelligent exhaust air heat pumps: S735

Technical specifications

• Spare part type: Closed membrane expansion vessel for heating medium circuit
• Primary function: Volume compensation and pressure stabilization during thermal expansion
• Construction: Molded and corrosion-resistant steel housing with durable rubber membrane
• Installation kit: Includes factory-fitted locking clip 15 and double O-rings
• Manufacturer: NIBE original part manufactured according to strict quality standards