Technical data

22
Diagram 23
To replace heating water thermistor
• Locate thermistor (b) clipped onto flow pipe to left hand side of sealed chamber below overheat thermostat,
see diagram 22.
• Unclip thermistor from pipe.
• Pull off electrical connections from thermistor.
• Fit replacement thermistor in reverse order to removal.
Note: No heat sink compound is required. The polarity of the connections is not important.
To replace hot water thermistor
• Pull off electrical connections from thermistor and unscrew thermistor (b) from left part of hydraulic block,
see diagram 21.
• Remove gas valve module as described previously.
• Fit replacement thermistor in reverse order to removal.
Note: The polarity of the connections is not important.
To replace printed circuit board (PCB)
Important: Isolate boiler from electrical supply before this operation.
• Gently squeeze metal clip securing the control panel box, lift it up and hinge down.
• From behind control panel box, unscrew and remove 4 screws securing PCB cover to panel.
• Pull off electrical plugs from PCB.
• Remove 4 screws securing PCB to panel and lift out PCB.
• Fit replacement PCB in reverse order to removal.
To replace display and control panel board
Important: Isolate boiler from electrical supply before
this operation.
• Remove PCB cover as described in ‘To replace PCB’.
• Pull off electrical plug of display (A) from PCB, see
diagram 23.
• Remove 4 screws securing PCB to panel and lift out
PCB.
• Remove 4 screws securing display and control panel
bord to panel and gently lift it out.
• Fit replacement display and control panel board in re-
verse order to removal.
To replace timeclock
• Remove PCB cover as described in ‘To replace PCB’.
• Disconnect clock electrical connections from PCB. Unclench plastic clips securing
timeclock to lower front panel and remove timeclock from panel.
• Fit replacement timeclock in reverse order to removal.
To replace pressure gauge
• Drain boiler as described in ‘To replace pump’.
• Unclip pressure gauge clip and pull it out.
• Disconnect pressure gauge cable.
• Fit replacement pressure gauge in reverse order to removal.
To replace heat exchanger
• Drain down heating circuit of boiler only as described previ-
ously.
• Remove sealed and combustion chamber covers and side
cases as described previously.
• Remove overheating termostats from heat exchanger pipes.
• Pull off spring clips securing heat exchanger pipes to heat
exchanger.
• Manoeuvre heat exchanger pipes down to disengage from heat
exchanger.
• Remove heat exchanger by sliding forward and out of boiler.
• Fit replacement heat exchanger in reverse order to removal.
• Open isolating valves on flow and return connections, refill,
vent and pressurise boiler. Check for leaks.
Diagram 24