7. TO REPLACE THE GAS CONTROL (TAP/FSD)
" Withdraw the burner assembly as detailed in 2.1 to 2.7.
" Disconnect the three gas pipes and the thermocouple from the control.
" Pull off the knob and lay to one side.
" Undo the retaining nut at the front of the tap niting assembly to withdraw control from the mounting
bracket.
" Replace in reverse order of removal. Check for gas soundness.
8. TO REPLACE THE PIEZO IGNITER
" Withdraw the burner assembly as detailed in 2.1 to 2.7.
" Unplug the igniter lead from the rear of the piezo igniter and unscrew the igniter-fixing nut. Replace the
piezo igniter.
" Reassemble all components in reverse order of removal. Check spark.
9. TO REPLACE THE CONTROL BOX
" Withdraw the burner tray as detailed in 2.1 to 2.7. See Figs. 4 & 7.
" Remove the control box heat shield by unscrewing the self-tap screw securing the cover in position and
remove.
" Remove the securing plate by removal of the self-tap screw and sliding the control box to the left.
" Pull out the multi-pin connector at the rear of the control box.
" Reassemble all the components in reverse order of removal. Check operation. Note the multi-pin plug can
only be located one way due to a polarising pin located in the connector plug.
10. TO REPLACE THE FLOW SENSE SWITCH (APS)
" Disconnect from the electrical supply.
" Remove the 4 screws securing the terminal guard (if fitted) and remove the guard. 3. Remove the 6 taptite
screws securing the fan box cover, remove cover and unscrew the 3 screws locating the deflector plate in
position.
" Disconnect the three leads from the flow sense switch noting their positions. (See Fig. 23).
" Remove the silicon tubing from the pressure switch, noting their positions e.g., positive (red) and negative
pressure (blue) remove the two screws and shake-proof washers securing the flow sense switch and
remove from the mounting bracket.
" To replace the flow sense switch, reassemble in the reverse order and ensure that the brass damper is clean
and that the small hole in the centre is clear of any obstruction. The installer or service engineer must not
adjust the setting of the air pressure switch.
11. TO CHECK THAT THE FLOW SENSE SWITCH (APS) FUNCTIONS CORRECTLY
The flow sense switch is calibrated to operate on the differential pressure between the positive and negative
pressures from the pilot tubes, it is therefore important that these are not adjusted or repositioned. To check
that the switch changes from the normally closed position when a simulated back pressure e.g., (severe
prevailing wind conditions), carry out the following procedure: -
" Start the appliance and allow to heat up for approximately 10 minutes.
" Place a non-combustible flat plate over the flue outlet for approximately 10 seconds during which time the
switch should move to the normally open position and cut off the power to the fan and simultaneously
close the gas solenoid valve, cutting off the supply to the fire.
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