The Worcester Bosch part is based around the diverter valve section. The diverter valve is a directional water device that only appears in combi boilers. It allows the hot water to be directed to the central heating (radiators, etc.) or to the domestic hot water system (taps, etc.). This feature is what makes a combi boiler so popular since the boiler can provide hot water and heating without the need for a cylinder.

Brand Name	Worcester Bosch