Glowworm Seal Heat Exchanger Door 801635, there are two kinds of heat exchangers that can be installed, they are 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 only appears on combination boilers and allows the heat to be transferred between one closed system to another. Glowworm Seal Heat Exchanger Door 801635 is a Genuine Boiler Parts. If you are replacing a faulty heat exchanger, or a leaking Heat Exchanger use a Genuine Boiler Part, and have it fitted by someone competent IE a Gas Safe Registered Installer. Heatingspares247.com is one of the UK?s largest independent Boiler Parts & Heating Spares Stockist, We specialise in the supply of Genuine Boiler Spare Parts from all the leading Manufacturers. Services available are trade counter pick up, Next working day standard delivery, next working day AM delivery and Saturday delivery. We also operate same day express delivery service. Our Opening timers are Monday to Saturday, 8AM to 5.30PM Heatingspares247.com is an Approved Boiler Spare Parts Stockist, and we guarantee to supply Genuine Heating Spares from the Boiler Manufacturers.