Main Combi 30 Eco & 30 Eco Elite Boiler Expansion Vessel 5114692 with PRV 248056

Product Overview

The Main Expansion Vessel 5114692 with Pressure Relief Valve (PRV) 248056 is a replacement component kit designed for use within selected Main heating systems.

The expansion vessel is an important part of a sealed heating system. It absorbs the increase in water volume that occurs as the system heats up, helping to maintain stable operating pressure. The pressure relief valve (PRV) works alongside the expansion vessel by releasing excess pressure if the system exceeds safe operating limits.

Together, these components help protect the boiler and heating system from pressure-related issues and support reliable operation.

Technical Insight & Common Failure Symptoms

The expansion vessel contains an internal diaphragm and air chamber that provides a cushion for pressure changes within the heating system. Over time, the vessel may lose its charge or the internal diaphragm may deteriorate, affecting pressure control.

The PRV is a safety component designed to discharge excess system pressure. If it operates repeatedly due to pressure problems, it may require replacement to ensure correct sealing and operation.

Typical symptoms linked to a faulty expansion vessel or PRV include:

• Boiler pressure rising excessively when heating is operating
• Pressure relief valve leaking or discharging water
• Frequent need to repressurise the heating system
• Boiler pressure dropping after operation
• Water escaping from the PRV discharge pipe
• Pressure-related boiler faults or lockouts

Replacing the expansion vessel and PRV together may help restore stable system pressure and reliable boiler operation.

Compatibility

Manufacturer Part Number (MPN): 5114692
Pressure Relief Valve (PRV): 248056

This part is designed for selected models within the Main range.

Please strictly verify the manufacturer part numbers 5114692 and 248056 against your boiler's technical manual, exploded parts diagram, or existing components before ordering to guarantee correct fitment.

Safety Advice

Boiler parts involve gas, water, pressure, and heating system components. Installation and servicing must be carried out by a Gas Safe registered engineer in accordance with current regulations and manufacturer instructions.