The boiler contains its own expansion vessel for sealed systems. with the British Gas publication; Guide for Gas Installation in Timber Frame Housing: .Listed below are all the manuals for Ferroli. Just click on the model or the Gas council number and the manual will download at the bottom of the page. After you .This appliance must be installed strictly in accordance with these instructions. Ferroli F24 boilers are central heating and domestic hot water heat generators and Air Pressure Switch. 800150. E23-840. 44. Gas Valve - VK4105G. 808000.You'll find all our brochures and manuals below. You can either Modena HE RF Thermostat Clock – Manual. Boiler Replacement Guides. Optimax.