Technical data

21
To replace pump
Drain down heating circuit only of boiler as follows:
• From below boiler, close isolating valves on flow and
return connections to boiler.
• Open boiler drain valve on left hand side of hy-
draulic block.
Note: It is not necessary to drain down entire heat-
ing circuit to carry out this work.
Simplification: for simpler work remove gas valve
module and right side cover.
• Disconnect pump cable.
• Remove 2 clips fixing pump, see diagram 20.
• Unscrew 2 screws securing the pump to boiler
bottom.
• Lift up the pipe and remove pump by lifting forward and out of boiler.
• Fit replacement pump in reverse order to removal.
• Open isolating valves on flow and return connections.
• Refill, vent and pressurise boiler. Check for leaks.
To replace safety valve
• Drain down heating circuit of boiler as described previously.
Simplification: for simpler work remove gas valve module and pump as described previously.
• Remove expansion vessel hose from hydraulic block.
• Remove draining pipe from safety valve and unscrew safety valve.
• Fit replacement safety valve in reverse order to removal.
Important: Seal the safety valve thread by jointing compound.
To replace domestic heat exchanger
• Drain down heating circuit of boiler as described previ-
ously.
Drain down hot water circuit of boiler as follows:
• From below of boiler, close cold water inlet isolating valve.
• Open a hot tap to drain hot water circuit.
• Remove gas valve.
• Unclip pump and pull forwards.
• Disconnect expansion flexible hose at connection to
vessel fixing.
• Remove fixing screws and plate exchanger over hydrau-
lic block, see diagram 21.
• Fit replacement heat exchanger in reverse order to remov-
al, ensuring seals are correctly positioned in hydraulic
block.
• Open isolating valves on flow and return connections,
refill, vent and pressurise boiler. Check for leaks.
• Open cold water isolating valve. Check for leaks.
To replace overheat thermostats
Important: Isolate boiler from electrical supply before this
operation – connections to overheat thermostats are
mains voltage.
• Locate overheat thermostats (a) and (c) to left hand side
of sealed chamber above thermistor, see diagram 22.
• Unclip thermostat from pipe.
• Pull off electrical connections from thermostat.
• Fit replacement thermostat in reverse order to removal.
Note: No heat sink compound is required. The polarity of
the connections is not important.
Diagram 21
Diagram 20
Diagram 22