isolate the mains water supply, drain heating system, remove large white front cover,remone floor panel beneath boiler (if fitted) remove 2 screws holding up control panel and allow to hinge down.
once the panel is laying horizontal cover the panel with plasic sheet or bin liner to prevent any water from entering the control box once the exchanger comes away. remove large flat screw rh side of exchanger an pull out u shaped clip.at the rear of exchanger undo large brass unoin holdin exch to diverter valve, now pull towards you, other 2 connections are push fit o rings, assemble in reverse order ensuring that fibre washer and o rings are renewed.reinstate mains water and repressurise.
danfee, October 2010