Important: To replace air pressure switch •Locate air pressure switch in upper left hand cor- ner of sealed chamber. •Pull off plastic tube from left hand connection. •Grasp pressure switch and disengage it from bracket clips by pulling from the top. •Remove electrical connections from switch. •Fit electrical connections to terminals 1 and 3 of replacement switch. •Fit replacement switch in reverse order to re- moval.

ROUTINE CLEANING AND INSPECTION

Make sure that fan outlet is correctly fit-ted into either the flue elbow for top outlet flue, or the rear connector for rear outlet flue. Before commissioning boiler, remove the two plas- tic transit clips from replacement fan. To replace fan •Disconnect power supply and earth leads to fan. •Unscrew and remove two fan retaining screws located at front edge of fan mounting plate. •Remove fan with mounting plate attached by pulling forwards and out of boiler. •Unscrew and remove three screws securing fan to fan mounting plate. •Fit replacement fan to mounting plate and se- cure with screws. •Fit replacement fan to boiler in reverse order to removal making sure that mounting plate retain- ing lugs are properly engaged into flue hood. •Reconnect power supply and earth leads.

REPLACEMENT OF PARTS

To replace microswitch assembly exept SB models) •Disconnect microswitch by pulling off plug. •Unclip external controls connector from mount- ing bracket. •Undo two screws securing microswitch assembly to reversing valve assembly, see diagram 29.
microswitch on THEMA F 23 E •Remove microswitch assembly from reversing valve. •Fit replacement microswitch assembly in reverse order to removal. •Reconnect plug and refit external controls con- nection to bracket.
Diagram 29 Sch 228 see diagram 30. To replace main printed circuit board (PCB) •Open cover and unclip plastic clip securing pump cable to lower front panel. •Pull off pump connector and earth lead. •Undo and remove four screws securing PCB cover to lower front panel. •Lift off PCB cover. •Pull off connectors CN6, CN7, CN8 and CN9 on PCB. •Undo and remove screw holding PCB to lower front panel. •Lifting PCB up slightly on LHS, pull PCB out of elec- trical connector on ignition PCB. Leave ignition PCB in place. •With lower front panel down as described previ- ously, undo and remove screw holding pump con- nection cover to PCB cover,
Diagram 30 Hab 286 •Undo and remove screw securing spark genera-tor to bracket and remove spark generator. •Fit replacement spark generator in reverse order to removal. •Reconnect two grey power supply leads and two clear ignition leads to spark generator, the polarity is not important. •Refit lower terminal cover. 19