Acid free - no temperature increase. Are responsible for main sewers. The aim of this guide is to help you find the most suitable gas boiler for your property's size and your budget we have looked in detail at the full range of a-rated condensing boilers from eight manufacturers: worcester bosch, baxi, viessmann, potterton, main, ideal, glow-worm, vaillant and ferroli well it’s about time! Baxi genuine parts supply genuine parts and spares for all potterton boilers. In appliance services.