Onyx Expansion Vessel 300L Red 1 1/2 1.5 Bar ONYX300LHEAT

The Onyx 300L Red Heating Vessel is a diaphragm expansion vessel for sealed heating systems, part of the Onyx expansion vessel range. It absorbs the expansion of heated water within a closed circuit to limit pressure rise and protect system components. The vessel has a 300 litre capacity, a 1 1/2 in connection and a 1.5 bar rating.

• Discharge from the system pressure relief valve as the circuit heats
• System pressure rising sharply when the boiler runs and falling again when it cools
• Boiler or heat pump losing pressure repeatedly, with no visible leak on pipework or radiators
• The vessel feels heavy or full of water when tapped on the shell
• Water escaping from the air charge valve on the vessel

• Confirm the required vessel volume suits the system water content and pressure regime
• Check the connection size matches the pipework or bracket arrangement, 1 1/2 in on this vessel
• Verify the 1.5 bar rating is suitable for the system's cold fill and relief valve setting
• Check the available space and support for a vessel of this capacity, including access for servicing