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Vermont Castings Defiant
Alignment Notches
Left Wedge
Brick Guide
Brick Clip
Bricks
ST556
Fig. 37 Remove the bricks and the brick retainer.
Right Wedge
Lower Fireback
ST557
Fig. 38 Remove the lower fireback.
3. Carefully remove the catalytic combustor’s refractory
access cover, then remove the combustor. The
refractory material is brittle; handle it carefully. (Fig.
39)
4. Check the combustor's honeycomb-like element for
a buildup of fly ash. If any is evident, take the
combustor outside and clean it by blowing air gently
through it. Do not push anything through the honey-
comb; do not use compressed air to clear the
passages. Such abrasion can scrape the thin
coating of platinum (the catalyst) off the ceramic
base, shortening the catalyst's life and reducing its
effectiveness.
Catalytic
Element
Catalytic Access
Panel
ST558
Fig. 39 Remove and inspect the catalytic element.
5. Inspect the element for damage or degradation.
Although small hairline cracks will not affect perfor-
mance, the element should be essentially intact. If
the element is broken in pieces or has sections
missing, it should be replaced. Call your local
Vermont CastingsMajestic Products Company
Authorized Dealer for a replacement element.
While the catalytic element is removed, check the
condition of the secondary air probe. Use an inspection
mirror to locate the probe within the combustion
chamber. (Fig. 40) The probe should extend 1” to 1¹⁄₂”
into the chamber and show no signs of excessive
deterioration, such as warping, corrosion, or short
length. A damaged secondary air probe can affect
catalytic performance. If the probe needs replacement,
contact your local dealer.
1"
ST559
Fig. 40 Use an inspection mirror to check the reflected view
of the secondary probe.