36SERVICINGi combi - Installation and Servicing338 CLEaNINg ThE hEaT ExChaNgERnote: Ensure the condensate trap/siphonis fully drained before cleaning. Refer toFrame 53.1. Remove ignition and flame detectionelectrodes. Refer to Frames 44 & 45.2. It is advisable to replace the sump coverprior to the water flush process.3. Thoroughly flush the heat exchangerby pouring water into the top of thecombustion chamber ensuring the full toparea is covered.4. Remove the sump cover and clean loosedeposits from the sump.5. Inspect the ignition and detectionelectrodes. Ensure that they are cleanand in good condition - replace ifnecessary.6. Re-fit the ignition and flame detectionelectrodes. Ensure that earth wire isconnected to the electrode7. Check that the ignition and detection gapsare correct. Refer to Frames 44 & 45.1Ignition ElectrodeEarth WireFlame DetectionReassemble the boiler in the following order:1. Ensure that the condensate trap/siphon is full of water.2. Refit the burner ensuring the sealing gasket is correctlypositioned and free from damage (tighten the 4 fixing screwsin the sequence A,B,C,D, shown below).3. Refit the fan / venturi assembly ensuring the retaining tabsare correctly positioned and the sealing gasket is correctlypositioned and free from damage.4. Reconnect the fan electrical leads.5. Remove the sump cover and refit the lower flue manifold asshown.39 REassEMbLy5A6. Refit the sump cover.7. Refit the boiler upper and lower front panels.IMpORTaNT. Ensure that the boiler upper front panel iscorrectly fitted and that a good seal is made.8. Turn on the gas supply at the gas service cock.9. Reconnect the electrical supply.CBDsERVICINg