DuraVent DuraPlus HTC - Manual (Page 17)

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Figure 20
sealant. Attach the bottom end of the
Adjustable Legs to the Roof Brackets using
the nuts & bolts provided.
ROOF SUPPORTED INSTALLATIONS
There are two types of Roof Supported
Installations: (1) Using a Square Ceiling
Support Box, a Reduced Clearance Support
Box, or the CAS Ceiling Support, and
(2) Using a Roof Support.
(1) Square Ceiling Support Box
installations: The Ceiling Support Box can
support a maximum of 40-feet (12.2 m) of
DuraPlus HTC chimney. Be sure that the
bottom of the Support Box extends at least
3” (75 mm) below the low side of the finished
ceiling (Fig 18 & 19). The Support Box must
remain level, and the top edge of the box
must cover the edge of the roof’s decking
material. Mobile home chimney installations
are roof supported. Do not seal openings in
flashing.
1. Place Appliance: Place the appliance
in its proper location, referring to the
manufacturer’s instructions as to allowable
distances from combustibles, etc.
2. Cut Openings: Cut a roof opening in
your desired location, just as in a Ceiling-
Supported Installation (Steps 1 through 5). If
a separate ceiling and roof exists, as shown
in Figure 18 (Low Attic), first cut and frame
a ceiling opening as described in Ceiling-
Supported Installations (Step 2). Refer to
Table 2 for framing dimensions. If it is desired
to install through a cathedral ceiling (Fig 19),
then the hole is cut in the roof.
3. Install Support Box: Slip the Support Box
into the framed opening so the square bottom
projects at least 3 inches (75 mm) below the
finished ceiling and rafters, and extends above
the ceiling to framing or decking materials
that it can be nailed to. Level the Support Box,
and slit the corners to the roofline where they
extend beyond it. Bend the flaps (created
by the slitting) flush with the roof, and nail
the Support Box to the roof or framing with
at least three (2) 8-penny nails, or (2) 1-1/2”,
#8 screws, per side (Fig 20). Be sure to keep
the bottom of the Support Box level. To help
keep the Support Box level during installation,
optional Support Box Guide Rails are available.
Place the Guide Rails on the Support Box
at the proper height so the bottom of the
Support Box will be at the correct distance
from the ceiling (Fig 7A). Secure the Guide
Rails in place using 4 sheet metal screws.
IMPORTANT: the Guide Rails are only used
to help install the Support Box level and are
not used to help support the weight of the
chimney installation. Screw the trim sections
into the ceiling (Fig 6).
4. Complete Installation: Refer to Steps 7,
9 & 10 in the Ceiling Supported Installation
section to complete the Roof
Supported installation.
(2) For Roof Support installations: A Roof
Support is also used in installations where
there is a cathedral ceiling, and a Square
Ceiling Support is not desired. The Roof
Support allows the DuraPlus HTC chimney
to come down into the room below the level
of the ceiling (Fig 21). The Roof Support
can support a maximum of 30 feet (9.1 m) of
DuraPlus HTC Chimney total, and maximum
of 20 feet (6.1 m) below the support.