11.0 Changing Components
31
11.8
Pressure Gauge
(Fig. 59)
1. Isolate the central heating system and drain
the primary circuit. Hold the square section on the
gauge with a suitable spanner.
2. Undo the nut securing the gauge to the return
pipe. Remove the gauge and examine the sealing
washer, replacing if necessary.
3. Reassemble in reverse order and repressurise
the system.
11.9
Heat Exchanger
(Figs. 60 & 61)
1. Isolate the central heating system and drain
the primary circuit. Undo the screws securing the
combustion box inner panel. Remove the panel
and examine the insulation piece.
2. Using a suitable hexagon key slacken the grub
screw securing the flow pipe boss to the heat
exchanger.
3. Undo the flow pipe nut on the inside of the
combustion box at the top left hand side. Ease
the pipe clockwise so that it will clear the
combustion box flange.
4. Undo the nut securing the sensing probe to the
combustion box right hand side panel. Withdraw
the probe.
5. Whilst supporting the heat exchanger, undo the
return pipe nut on the inside of the combustion
box at the lower right hand side.
6. Allow the heat exchanger to drop slightly and
ease it forwards out of the combustion box taking
care not to damage the side insulation pieces.
7. Pull the flow pipe off the left hand heat
exchanger spigot. Slacken the grub screw in the
return pipe boss and pull it off the right hand
spigot.
8. Engage the flow and return pipes on the
spigots of the new heat exchanger.
9. Identify the rectangular slots at the rear of the
combustion box. Slide the heat exchanger into
the combustion box taking care not to damage
the side insulation pieces.
10. Manoeuvre the heat exchanger so that the
rear manifolds locate in the rectangular slots at
the rear of the combustion box.
11. Support the heat exchanger and connect the
nuts on the flow and return pipes to the fittings in
the combustion box. Ensure that the sealing
washers are fitted, and not damaged in any way.
12. Tighten the grub screws in the flow and return
bosses. Reassemble in reverse order and
repressurise the system.
Side Insulation Piece
Heat
Exchanger
Grub Screw
Return
Pipe
Rear Insulation Piece
Side Insulation
Piece
Flow Pipe
Grub Screw
Pressure
Gauge
Sealing
Washer
Return Pipe
Sealing
Washer
Sensing Probe
Nut
Sensing Pipe
Fig. 61
Fig. 59
Fig. 60
Primary Circuit
Drain Tap