36
PFP7/REV C/01-08
Figure 9.1.2
: Mixing chamber, impact bead and impeller assembly.
9.1.2
Chimney dismantling
1. Ensure that power, fuel and air supplies to the instrument are disconnected. If the
instrument has been running with the flame alight, allow 30 minutes for the burner
system to cool down. When cool, remove the mixing chamber as detailed in Section
9.1.1.
2. To access the inner chimney for cleaning only, refer to paragraphs (3) and (4) below; for
complete removal of the chimney continue to the end of this sub-section.
3. Pull the ignition cable connector from the ignition electrode housing, unscrew the PTFE
ignition housing and place to one side.
4. Unscrew the three black pozidriv screws that hold the chimney back plate. Loosen the
nut on the rear screw retaining the chimney top plate which passes through the top of
the back plate. The chimney back plate can now be removed taking care not to strain
the thermocouple cable. The stainless steel inner chimney can now be pivoted up and
cleaned with a soft, lint-free cloth, as can the lens mounted on the front of the inner
chimney.
5. The inner chimney can be fully removed by releasing the two screws that form the pivot
and sliding the inner chimney out, taking care to retain the spacers and washers. The
outer chimney can be removed by undoing the two pozidriv screws and two nuts that
retain the fixing brackets at the base of the chimney.
Replacement is the reverse of removal. Clean scale from the ignition electrode, or
replace by loosening the grub screw sealed with plasticine, that clamps the electrode.
Replace with a new electrode setting the protruding length to 10mm before retightening
the grub screw and re-sealing with plasticine. The plasticine also acts as an insulator so
the spark does not jump from the grub screw to the inner chimney.