The Worcester Bosch spare fixing kit is for use in the heat exchanger of i Junior Series, i Series, and SBi Series boilers. The heat exchanger transfers heat from a boiler's burner to water. A primary heat exchanger is found in all boilers, using heat from a burner to raise the temperature of the water in the system, while a secondary heat exchanger is present only in combis and allows the heat to be transferred between closed systems. It carries the widest range of spares.

Brand Name	Worcester Bosch