There are two kinds of heat exchanger that can be installed, the primary heat exchanger and the secondary heat exchanger. The primary is present in almost all boilers and it allows the heat to be transferred from the burner to the water within the system. The secondary heat exchanger is exclusive to combination boilers and allows the heat to be transferred between one closed system and another.
This part is present in 17 different boilers in the Glowworm range including the Glowworm HXI 12 , HXI 15 , HXI 18 , SXI 18 , CXI 24secondary heat exchanger is only present in combination boilers and allows the heat to be transferred between two closed systems. The Primary Heat exchanger is sometimes known as the heat engine or "main" heat exchanger. The secondary heat exchanger can also be known as the plate heat exchanger or the domestic hot water heat exchanger .