HAMWORTHY HEATING LTD19CHESIL-ELECTRONIC 500001181/KFigure 26 - Display PCB10.5 Replacement Of Controls PCB (Part No 533901784 - Single pump PCB / 533901785 - Twin PumpPCB)The main control PCB of the wall mount and floor standing units are enclosed in a plastic box at the same positionon the hinged door of the unit. To replace the mains PCB :-1) Ensure the unit has been isolated from the 230V / 50Hz mains supply & connecting circuitry.2) Remove the front cover of the unit Remove the lid of the box.3) Disconnect the wires to the terminals of the PCB.4) Loosen the nuts securing the PCB to the stand offs in the box.5) Locate the replacement PCB over the stand-offs and secure the PCB to the stand-offs by reassembling thenuts.6) Reconnect the wires to the correct terminal of the PCB as defined in the wiring schematic of Appendix A1.7) Reassemble the lid of the box and reconnect the power to the unit.10.6 Replacement Of Display PCB (Part No. 533901786) on Wall Mount Unit.1) Isolate the mains electrical supply.2) Remove the sheet metal front cover as previously described.3) Remove the lid of the plastic box.4) Remove the ribbon cable plug of the from the main PCB.5) Remove the earth lead connection.6) Remove the nuts securing the display PCB to the stand-offs in the lid of the box.7) Replace the display PCB to the stand offs in the lid and secure using the nuts.8) Replace the earth lead connection.9) Reconnect the new display PCB ribbon cable plug to the main PCB and reassemble the lid.10) Replace and secure the sheet metal front cover & reconnect the electrical supply.Figure 25 - Main Control PCB (Single Pump Unit)