Heatilator MHST36D Manual

08/04 31068 Rev E 1
WARNING!
Improper installation, adjustment, alteration, service or maintenance can cause injury or property damage. Refer to this
manual. For assistance or additional information, consult a qualified installer, service agency or the gas supplier.
INSTALLATION & OPERATING
INSTRUCTIONS
MHST36D
WOODBURNING FIREPLACE
FOR MANUFACTURED HOUSING
Note: An arrow () found in the text signifies change in content.

2 31068 Rev E 08/04
MHST36D INSTALLATION INSTRUCTIONS
CAUTION:
Do not expose the fireplace to the elements (i.e. rain, etc.) and keep the fireplace dry at all times. Wet insula-
tion will produce an odor when the fireplace is used.
Table of Contents
Safety Precautions ...................................................................................................................................... 2
Design and Installation Considerations ....................................................................................................... 3
A. Listings and Code Approvals ...................................................................................................................... 4
B. Description of the Fireplace System ........................................................................................................... 4
C. System Components .................................................................................................................................. 5
D. Pre-Installation Preparation ........................................................................................................................ 8
E. Chimney Requirements ............................................................................................................................ 11
F. Installation of Fireplace ............................................................................................................................. 14
G. Operating Instructions ............................................................................................................................... 22
H. Maintenance Instructions .......................................................................................................................... 26
Index ......................................................................................................................................................... 27
Warranty ................................................................................................................................................... 28
Safety Precautions
1. Please read these installation instructions completely before beginning installation procedures. Failure to follow them
could cause a fireplace malfunction resulting in serious injury and/or property damage.
2. Always check your local building codes prior to installation. The installation must comply with all local, regional, state
and national codes and regulations.
3. An adequate supply of replacement combustion air from outside the house must be available to the fire for the
fireplace to operate properly. To achieve this, the use of the optional outside air kit is highly recommended.
In the event the home is unusually tightly sealed, the optional combustion air kit may not provide all the air required
to support combustion. Hearth & Home Technologies is not responsible for any smoking or related problems that may
result from the lack of adequate combustion air. It is the responsibility of the builder/contractor to ensure that adequate
combustion air has been provided for the fireplace.
4. The fireplace must be installed with the Hearth & Home Technologies SL Series Chimney System.
The chimney system must always terminate outside the building. Be sure to follow all chimney specifications given in
these installation instructions.
5. NEVER leave children unattended when there is a fire burning in the fireplace.
6. This fireplace is built for solid fuel only. NEVER use gasoline, gasoline type lantern fuel, kerosene, charcoal light fluid,
or similar liquids in this fireplace. Keep any flammable liquids a safe distance from the fireplace.
7. DO NOT use chimney cleaners or flame colorants in your fireplace.
8. The flue damper must be open at all times when the fireplace is in use.
9. While servicing this fireplace, always shut off any electricity or gas to the fireplace. This will prevent possible electric
shock or burns. Also, make sure the fireplace is completely cooled before servicing.
10. To ensure a safe fireplace system and to prevent the build up of soot and creosote, inspect and clean the fireplace
and chimney prior to use and periodically during the burning season. See “Maintenance Instructions” in this manual
for cleaning instructions.
WARNING!
This fireplace is tested and listed for use only with the optional accessories listed in these instructions. Use of
optional accessories not specifically tested for this fireplace could void the warranty and/or result in a safety
hazard.

08/04 31068 Rev E 3
MHST36D INSTALLATION INSTRUCTIONS
DESIGN AND INSTALLATION CONSIDERATIONS
When selecting a location for your woodburning fireplace, it is important to evaluate a number of considerations. Modern
construction techniques can create conditions that may not allow your chimney to draft properly. This may result in smoke
spillage from your fireplace, as well as cause other combustion appliances to operate incorrectly.
Tightly sealed construction is important for energy efficiency. Unfortunately, a great deal of effort has been directed to
tightening up sidewall construction, while considerably less attention has been paid to tightening upper portions of the
warm air envelope (insulated ceilings). This has increased the “Stack Effect”, a condition that increases the negative
pressure generated by the structure. This negative pressure will directly affect the drafting performance of a fireplace
chimney. To minimize the negative pressure generated by stack effect, make certain that all duct work installed in the
attic spaces is sealed airtight. Minimize the number of recessed light fixtures installed in the insulated ceiling, and use
sealed recessed light fixtures. Finally, make certain the whole house fans and attic access panels are tightly sealed.
These are important design considerations that must be observed during the design and construction stage of the
home.
If you desire to put a fireplace in your basement, we recommend that you consider a direct vent gas fireplace. Basements
always have a significant negative air pressure that causes the fireplace system to be more susceptible to smoke spillage
and cold flue back drafting. Since direct vent gas fireplaces are sealed, they are not affected by the negative pressure that
exists in basements.
Finally, woodburning fireplaces perform best when their chimney (roof termination) is located on the upper half of the roof,
especially when cathedral ceilings are present. Chimneys that are located on the lower half of the roof realize what is
known as “lazy flue” and will not draft as well as a chimney that is located in the upper portion of the roof. The reason for
this is that the stack effect generated by the overall height of the living spaces inside the house will exceed the draft
generated by the chimney system. If you desire to place a woodburning fireplace in a location where the termination cap
would be located on the lower half of a roof, such as on an outside wall at the base of a cathedral ceiling, we recommend
that you consider using a direct vent gas fireplace. This will assure the homeowner a fireplace that operates correctly.
These properties do not affect just your woodburning factory-built fireplace. They can cause any woodburning fireplace as
well as any conventionally vented (B-vent) gas appliance to operate improperly. Careful planning at this stage of your
project will ensure satisfaction with the operation of your fireplace once it is completed.

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MHST36D INSTALLATION INSTRUCTIONS
WARNING!
This fireplace and its components are designed to be installed and operated as a system. Any alteration to or
substitution for items in this system, unless allowed by these installation instructions, will void the Underwrit-
ers Laboratories listing and may void the product warranty. It may also create a hazardous installation. Read
through these instructions thoroughly before starting your installation and follow them carefully throughout
your project.
1. The Heatilator fireplace system consists of the
following:
a. Fireplace/Integral Grate/Outside Combustion Air
System
b. Refractory
c. Chimney Termination Cap
d. Chimney System
e. Hearth Extension
f. Glass Doors
The CP311 Convenience Pack has been designed for
the convenience of customers wishing to install a
chimney system at the 11 ft minimum straight height.
The CP313 Convenience Pack has been designed for
those wishing to install a chimney system at the 13 ft
minimum straight height.
The following combination of listed parts are included
in both the CP311 and CP313 Convenience Packs:
Note: Illustrations used throughout these instructions
reflect “typical installations” and are for design purposes
only. Actual installation may vary slightly due to indi-
vidual design preferences. However, minimum and maxi-
mum clearances must be maintained at all times.
The illustrations and diagrams used throughout these
installation instructions are not drawn to scale.
Figure 1 - A Typical Fireplace System
B. DESCRIPTION OF THE FIREPLACE SYSTEM
A. LISTINGS AND CODE APPROVALS
This fireplace system has been tested and listed in
accordance with UL 127 standards, and has been listed by
Underwriters Laboratories Inc. for installation and operation
in the United States as described in this manual.
This fireplace has been tested and listed for use with the
optional components listed on page 5. These optional
components may be purchased separately and installed at
a later date. However, installation of an outside air kit will
require significant reconstruction and should be installed
at the time of the initial fireplace installation.
Check with your local building code agency prior to installing
this fireplace to ensure compliance with local codes,
including the need for permits and follow-up inspections. If
you need assistance during installation, please contact your
local dealer or the Heatilator Technical Services
Department, Hearth & Home Technologies, 1915 W.
Saunders St., Mt. Pleasant, Iowa 52641 (1-800-927-6841).
Heatilator® is a registered trademark of Hearth & Home
Technologies.
2. Optional Components Include:
a. Chimney Air Kit
b. Glass Doors
Manufactured Housing Convenience Packs
Cat. #
CP311
Qty.
CP313
Qty. Description:
SL324 1 2 Chimney Section - 24 in. long
SL336 2 2 Chimney Section - 36 in. long
MH842 1 1 Roof Thimble and Flashing
TR344 1 1 Round Termination Cap
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08/04 31068 Rev E 5
MHST36D INSTALLATION INSTRUCTIONS
C. SYSTEM COMPONENTS
1. Fireplace Components
HX3 - Hearth Extension
GR12
Integral Grate
Bi-Fold Glass Doors Perception Glass Doors Outside Air Kit
Fireplace Dimensions
Catalog # Description:
MHST36D Radiant Fireplace, with Integral Grate, Outside Air Kit and Hearth Protection Strips
DM1036 Bi-fold Glass Doors - Black Finish
DM1036B Bi-fold Glass Doors - Polished Brass Finish (included with fireplace)
DM1036S Bi-fold Glass Doors - Stainless Steel Finish
DP1036 Peception Glass Doors - Black Finish
DP1036B Perception Glass Doors - Polished Brass Finish
DP1036S Perception Glass Doors - Stainless Steel Finish
HX3 Hearth Extension
GR12 Integral Grate (included with fireplace)
Outside Air Kit (included with fireplace)

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MHST36D INSTALLATION INSTRUCTIONS
MH841 MH842 - Roof Thimble & Flashing
2. Chimney Components
The following pictures show only those chimney components which may be safely used with this fireplace.
Catalog # Description:
CAK4A Chimney Air Kit
SL306 Chimney Section - 6 in. long
SL312 Chimney Section - 12 in. long
SL318 Chimney Section - 18 in. long
SL324 Chimney Section - 24 in. long
SL336 Chimney Section - 36 in. long
SL348 Chimney Section - 48 in. long
SL315 Chimney Offset/Return - 15 deg
SL330 Chimney Offset/Return - 30 deg
JB877 Chimney Joint Band
CB876 Chimney Bracket
TR344 Round Termination Cap
CP311 Manufactured Housing Convenience Pack - 11 ft
CP313 Manufactured Housing Convenience Pack - 13 ft
MH841 Manufactured Housing 20" Thimble Extension
MH842 Manufactured Housing Thimble and Flashing
RF370 Roof Flashing - 6/12 to 12/12 Pitch
RF371 Roof Flashing - Flat to 12/12 Pitch
AS8 Attic Insulation Shield

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MHST36D INSTALLATION INSTRUCTIONS
JB877
Joint Band
CB876
Chimney Bracket
SL315/SL330
Offset/Return
Chimney Sections
TR344
Round Termination Cap
with Storm Collar
AS8
Insulation
Shield
RF370 Roof Flashing 6/12 to 12/12 Pitch RF371 Roof Flashing Flat to 6/12 Pitch
CAK4A
Chimney Air Kit
Firestop Spacer
Catalog # A B
FS338 0-deg. 14-1/2 in.
FS339 15-deg. 18-3/8 in.
FS340 30-deg. 23 in.
Catalog # A B
SL306 6 in. 4-3/4 in.
SL312 12 in. 10-3/4 in.
SL318 18 in. 16-3/4 in.
SL324 24 in. 22-3/4 in.
SL336 36 in. 34-3/4 in.
SL348 48 in. 46-3/4 in.
A = Actual length
B = Effective length
(length of chimney
part after it has been
snapped to another
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MHST36D INSTALLATION INSTRUCTIONS
CLEARANCES!
A minimum 1/2 in. air
clearance must be
maintained at the sides
of the fireplace as-
sembly.
Chimney sections at
any level require a 2 in.
minimum air space
clearance between
the framing and chim-
ney section.
WARNING!
1. Do not install in sleeping rooms.
2. Combustion air needs of a heavily fired fireplace may deplete the available oxygen supply.
Figure 2 - Fireplace Locations
D. PRE-INSTALLATION PREPARATION
1. Fireplace Locations and Space Requirements
Several options are available to you when choosing a location for your fireplace. This fireplace may be used as a
room divider or installed along a wall. See Figure 2.
Locating the fireplace in a basement, near frequently opened doors, central heat outlets or returns, or other locations
of considerable air movement can affect the performance and cause intermittent smoke spillage from the front of the
fireplace. Consideration should be given to these factors before deciding on a location.

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MHST36D INSTALLATION INSTRUCTIONS
WARNING!
Do not draw outside air from garage spaces. Exhaust products of gasoline engines are haz-
ardous.
Do not install outside air ducts such that the air may be drawn from attic spaces, basements or
above the roofing where other heating appliances or fans and chimneys exhaust or utilize air.
These precautions will reduce the possibility of fireplace smoking or air flow reversal.
WARNING!
To prevent contact with sagging or loose insulation, the fireplace must not be installed against
vapor barriers or exposed insulation. Localized overheating could occur and a fire could re-
sult.
WARNING!
For all manufactured housing installations the out-
side air kit, glass doors and MH842 manufactured
housing roof thimble and flashing kit, must be used.
CAUTION:
The structural integrity of the manufactured
housing floor, wall, ceiling and roof must be
maintained.

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MHST36D INSTALLATION INSTRUCTIONS
Figure 3 - Framing the Fireplace
WARNING!
Do not apply combustible finishing materials over any part of the black face of this fireplace or a structure fire
may result. The black metal fireplace front may only be covered with noncombustible materials such as ce-
ramic tile, brick, or stone. Do not cover or block any cooling air slots. Do not cover any portion of the fireplace
openings that would prevent the installation of an authorized glass door.
2. Frame the Fireplace
The MHST36D fireplace will fit a framed opening of 41 in. wide x 42 in. tall. The finished cavity depth must be no less
than 23 in.
Figure 3 shows a typical framing (using 2 x 4 lumber) of the fireplace, assuming combustible materials are used.
All required clearances to combustibles around the fireplace must be adhered to. Any framing across the top of the
fireplace must be above the level of the top standoffs. Chimney sections at any level require a 2 in. minimum air
space clearance between the framing and chimney section.
CLEARANCES!
A minimum 1/2 in. air clearance must
be maintained at the sides of the fire-
place assembly.
Chimney sections at any level require
a 2 in. minimum air space clearance
between the framing and chimney
section.

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MHST36D INSTALLATION INSTRUCTIONS
Figure 4 - Sidewalls and Surrounds
3. Sidewalls/Surrounds
Adjacent combustible side walls must be located a minimum of 12 in. from the fireplace openings. See Figure 4. If
you are using a decorative surround constructed of combustible material, it must be located within the shaded area
defined in Figure 4. Short stub walls are also acceptable if they are contained within the shaded area.
E. CHIMNEY REQUIREMENTS
When planning your fireplace location, the chimney construction and necessary clearances must be considered. The
fireplace system and chimney components have been tested to provide flexibility in construction. The following figures are
the minimum distances from the base of the fireplace.
1. Minimum overall straight height 14.5 ft
2. Minimum height with offset/return 16 ft
3. Maximum height 20 ft
4. Maximum chimney length between an offset and return 20 ft
5. Maximum unsupported chimney length between the offset and return 6 ft
6. Maximum straight unsupported chimney height above the fireplace 35 ft

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MHST36D INSTALLATION INSTRUCTIONS
WARNING!
Do not combine offsets to create an offset greater than 30 deg from verti-
cal. This may create a fire hazard since the natural draft may be restricted.
1. Using Offsets and Returns
a. To bypass any overhead obstructions, the chimney may be offset using a 15-deg (SL315) or 30- deg (SL330)
offset/return. Perform the following steps to determine the correct chimney component combination for your
particular installation.
b. An offset and return may be attached together or a chimney section(s) may be used between an offset and
return.
1) Measure how far the chimney needs to be shifted to enable it to avoid the overhead obstacle. See Figure 5,
dimension “A” to determine chimney sections required to achieve the needed shift.
2) After determining the offset dimension, refer to Table 1 and find the “A” dimension closest to but not less
than the distance of shift needed for your installation.
3) The “B” dimension that coincides with the “A” dimension represents the required vertical clearance that is
needed to complete the offset and return.
4) Read across the chart and find the number of chimney sections required and the model number of those
particular chimney parts.
5) Whenever the chimney penetrates a floor/ceiling, a firestop spacer must be installed.
6) The effective height of the fireplace assembly is measured from the base of fireplace to top of starter col-
lar (47-1/4 in.).
Example: Your “A”
dimension from Figure 5 is
14-1/2 in. Using Table 1 the
dimension closest to, but
not less than 14-1/2 in. is
14-5/8 in. using a 30-deg
offset/return. It is then
determined from the table
that you would need 33 in.
(Dimension “B”) between
the offset and return. The
chimney components that
best fit your application are
two SL312s.
Figure 5 - Chimney Offset/
Return
* Proper assembly of air cooled chimney parts result in an overlap at chimney joints
of 1-1/4 in. Effective length is built into this chart.
Table 1 Offset Chart*
ABAB
1-5/8in.13-3/8in.3-7/8in.14-1/2in.------
2-7/8in.17-3/4in.6-1/4in.18-5/8in.1-----
4-1/8in.22-3/8in.8-5/8in.22-3/4in.2-----
4-1/2 in. 23-5/8 in. 9-1/4 in. 23-3/4 in. - 1 - - - -
5-3/4 in. 28-1/4 in. 11-5/8 in. 27-7/8 in. 1 1 - - - -
6 in. 29-3/8 in. 12-1/4 in. 29 in. - - 1 - - -
7-1/4 in. 34 in. 14-5/8 in. 33 in. - 2 - - - -
7-3/4 in. 36-1/8 in. 15-1/4 in. 34-1/8 in. - - - 1 - -
8-3/4 in. 39-3/4 in. 17-5/8 in. 38-1/4 in. 1 - - 1 - -
10-3/8 in. 45-5/8 in. 20-5/8 in. 43-1/2 in. - - 2 - - -
10-5/8in.46-3/4in.21-1/4in.44-5/8in.----1-
11-7/8 in. 51-3/8 in. 23-5/8 in. 48-3/8 in. 1 - - - 1 -
13-1/2 in. 57-1/4 in. 26-5/8 in. 53-7/8 in. - - - 2 - -
13-3/4in.58-3/8in.27-1/4in.55-3/4in.-----1
15in.63in.29-5/8in.59in.1----1
16-1/2 in. 68-3/4 in. 32-5/8 in. 64-1/4 in. - 1 - - - 1
18 in. 74-5/8 in. 35-5/8 in. 69-1/2 in. - - 1 - - 1
19-5/8 in. 80-3/8 in. 38-5/8 in. 74-5/8 in. - - - 1 - 1
20-5/8 in. 84-1/8 in. 41 in. 78-3/4 in. 1 - - 1 - 1
22-3/4in.91-7/8in.44-5/8in.85in.----11
24 in. 96-1/2 in. 47 in. 89-1/8 in. 1 - - - 1 1
25-7/8 in.103-1/2 in.50-5/8 in. 95-1/2 in. -----
SL318 SL324 SL336 SL348
15-degree 30-degree
SL306 SL312
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MHST36D INSTALLATION INSTRUCTIONS
Figure 6 - Chimney Height
3. Number of Sections Required
To determine the chimney components needed to
complete your particular installation, follow the steps
below:
a. Determine the total vertical height of the fireplace
installation. This dimension is measured from the
base of the fireplace assembly to the point where
the smoke exits the termination cap.
b. Subtract the effective height of the fireplace
assembly (47-1/4 in.) from the overall height of
the fireplace installation (measured from the
base of the fireplace to the bottom of the
termination cap).
c. Refer to Table 2 to determine what components
must be selected to complete the fireplace
installation.
d. Determine the number of firestop spacers, stabi-
lizers, roof flashing, etc. required to complete the
fireplace installation.
2. Chimney Height Requirements (above roof
line)
a. Major building codes specify a minimum chimney
height above the roof top. These specifications
are summarized in what is known as the Ten Foot
Rule. This rule states:
“If the horizontal distance from the side of the
chimney to the peak of the roof is 10 ft or less, the
top of the chimney must be at least 2 ft above the
peak of the roof, but never less than 3 ft in overall
height above the highest point where it passes
through the roof.
“If the horizontal distance from the side of the
chimney to the peak of the roof is more than 10 ft,
a chimney height reference point is established
on the surface of the roof a distance of 10 ft from
the side of the chimney in a horizontal plane. The
top of the chimney must be at least 2 ft above this
reference point, but never less than 3 ft in height
above the highest point where it passes through
the roof.” See Figure 6.
b. These chimney heights are necessary in the
interest of safety but do not ensure smoke-free
operation. Trees, buildings, adjoining roof lines,
adverse wind conditions, etc. may create a need
for a taller chimney should smoking occur.
Table 2
HEIGHT OF CHIMNEY COMPONENTS
Chimney Stabilizer
SL3 4-3/4 in.
Firestop Spacers
FS338 0 in.
FS339 0 in.
FS340 0 in.
Offsets/Returns
SL315 13-3/8 in.
SL330 14-1/2 in.
Roof Flashing
RF370 0 in.
RF371 0 in.
Chimney Sections*
SL306 4-3/4 in.
SL312 10-3/4 in.
SL318 16-3/4 in.
SL324 22-3/4 in.
SL336 34-3/4 in.
SL348 46-3/4 in.
* Dimensions reflect effective height

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MHST36D INSTALLATION INSTRUCTIONS
F. INSTALLATION OF FIREPLACE
WARNING!
Before starting, do the following:
1. Wear gloves and safety glasses for protection.
2. Keep hand tools in good condition. Sharpen cutting edges and make sure tool handles are secure.
3. Always maintain the minimum air space required to the enclosure to prevent fire.
Important: To ensure proper fit of the glass doors,
check the fireplace openings for square. Measure
diagonal distances of each opening to make sure
the distances are equal. If they are not equal, con-
tinue to shim the fireplace until those diagonals are
equal.
Figure 7 - Positioning the Metal Strips
1. Position the Fireplace
This fireplace may be placed on either a combustible
or noncombustible continuous flat surface. Follow the
instructions for framing on pages 8-11. Slide the
fireplace into position. Be sure to provide the
minimum air clearance at the sides and back of
the fireplace assembly.
2. Place the Protective Metal Hearth Strips
Included with your fireplace you will find four metal
hearth strips measuring approximately 28 in. x
4 in. These strips are used to provide added protection
where the fireplace and the hearth extension meet.
Slide the metal strips 2 in. under the front edge of the
fireplace. The individual pieces must overlap each
other by 1 in. minimum in the middle of the fireplace
to provide continuous coverage of the floor. See
Figure 7. These metal strips should extend from the
front and sides of the fireplace openings by 2 in.
3. Level the Fireplace
Level the fireplace side-to-side and front-to-back. Shim
with noncombustible material, such as sheet metal,
as necessary. Secure the fireplace (using the nailing
flanges located on either side of the fireplace) to the
vertical framing.

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MHST36D INSTALLATION INSTRUCTIONS
Figure 9
Installing the Firestop Spacer
CAUTION:
Firestop spacers must be used whenever the
chimney penetrates a ceiling/floor area.
Figure 8
Assembling Chimney
Sections
WARNING!
Carefully follow the instructions for assembly
of the pipe and other parts needed to install this
fireplace system. Failure to do so may result in
a fire, especially if combustibles are too close
to the fireplace or chimney and air spaces are
blocked, preventing the free movement of cool-
ing air.
4. Assemble the Chimney Sections
Attach either a straight chimney section or an offset to
the top of the fireplace (depending on your installation
requirement). Chimney sections are locked together
by pushing downward until the top section meets the
stop bead on the lower section.
The inner flue is placed to the inside of the flue section
below it. The outer casing is placed outside the outer
casing of the chimney section below it. See Figure 8.
5. Install the Firestop Spacers
Mark and cut out an opening in the ceiling for the
firestop spacer being utilized (14-1/2 in. x (14-1/2 in. for
an FS338, (14-1/2 in. x (18-3/8 in. for an FS339 and
(14-1/2 in. x 23 in. for an FS340). Frame the opening
with the same dimension lumber used in the ceiling
joists.
Install the firestop spacer.
These firestop spacers are designed to provide the
minimum 2 in. air space required around the chimney.
In all situations, the firestop spacers are to be nailed
to the ceiling joists from the bottom or fireplace side,
EXCEPT when the space above is an insulated ceiling
or attic space. In this situation, the firestop spacer must
be nailed from the top side to prevent loose insulation
from falling into the required 2 in. air space around
the chimney. See Figure 9.

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MHST36D INSTALLATION INSTRUCTIONS
WARNING!
Maintain a minimum of 2 in. air clearance to all
parts of the chimney system at all times! Fail-
ure to maintain this 2 in. air clearance will cause
a structure fire.
CAUTION:
Inner flue and outer liner sections cannot be
disassembled once locked together. Plan
ahead to ensure the proper installation height
is achieved with the selected chimney compo-
nents.
Figure 10 - Installing an Attic Insulation Shield
Note: You must provide support for the pipe during
construction and check to be sure inadvertent load-
ing has not dislodged the chimney section from the
fireplace or at any chimney joint.
WARNING!
When chimney sections exceeding 6 ft in length
are installed between an offset and return,
structural support must be provided to reduce
off-center loading and prevent chimney sections
from separating at the chimney joints.
Figure 11 - Offset/Return with Stabilizer
6. Install the Attic Insulation Shield
An insulation shield should be installed when there is
a possibility of insulation coming into contact with the
factory built chimney system.
a. Bend the tabs at the top of the attic insulation
shield inward. This will help keep the chimney
section centered in the shield.
b. Position the shield over the vertical chimney
section where it penetrates a firestop spacer.
c. Slide the shield down until it rests on the firestop
spacer. The firestop spacer will support the
insulation shield. See Figure 10.
7. Double-check the Chimney Assembly
Continue assembling the chimney sections up through
the firestop spacers as needed. While doing so, be
aware of the height and unsupported chimney length
limitations that are given on page 11 under “Chimney
Requirements”.
Check each section by pulling up slightly from the top
to ensure proper engagement before installing the
succeeding sections. If they have been connected
correctly, they will not disengage when tested.
8. Secure the Chimney System
When offsets and returns are joined to straight pipe
sections, they must be locked into position with the
screws provided (outer only), using the predrilled holes.
To prevent gravity from pulling the chimney sections
apart, the returns and the chimney stabilizers have
straps for securing these parts to joists or rafters. See
Figure 11.
WARNING! RISK OF FIRE.
Do not fill the space between the chimney sec-
tion and the insulation shield with insulation.
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MHST36D INSTALLATION INSTRUCTIONS
Figure 12 - Ceiling/Attic Construction
9. Install the MH842 Ceiling/Roof Thimble
See Figures 12 & 13.
a. Locate the point where the chimney will exit the
roof by plumbing down to the center of the
chimney. Lay out, cut and frame a 14-1/2 in. square
opening (measured on the horizontal) through the
ceiling and roof structure. See Chapter 25 of the
Uniform Building Code for roof framing details.
b. The thimble must extend completely through the
roof structure shielding combustible materials.
Five location holes have been provided to allow
for a variety of ceiling/roof thicknesses. An MH841
Thimble Extension is required when the ceiling/
roof thickness exceeds 12-1/2 in. The extension
should overlap the thimble one inch.
c. To attach the extension to the thimble, drill 1/8 in.
holes through the outer shield of the thimble using
the predrilled holes in the extension as guides.
Attach the extension to the thimble using the
screws provided with the extension.
d. Install the thimble assembly and nail it securely
to the framing members.
e. Center the flashing over the chimney and nail it to
the roof using the Stormguard nails provided. Keep
gaps between the flashing plate and the roof to a
minimum.
f. Caulk the flashing plate and roof junction as well
as the vertical seam on the flashing. All nail heads
must be caulked with a roofing sealant.
g. Finish assembling the chimney, storm collar and
termination cap following the installation
instructions provided.
Note: The closed end of
the thimble is positioned
towards the bottom.
Figure 13 - Installing an MH842 Roof Thimble and Flashing Kit

18 31068 Rev E 08/04
MHST36D INSTALLATION INSTRUCTIONS
Figure 15 - Installing a TR344 Round Termination Cap
WARNING!
Detailed instructions for installation of the termination cap and storm collar are packaged with these parts. To avoid
danger of fire, all instructions must be strictly followed, including the provision of air space clearance between
chimney system and enclosure. To protect against the effects of corrosion on those parts exposed to the weather,
we recommend that the termination cap be painted with a rust-resistant paint.
11. Install the Termination Cap
a. Install the chimney sections up through the ceiling/
roof. When using the TR344 round termination
cap, the uppermost section of pipe must extend
6” above the roof to allow installation of the storm
collar and termination cap. See Figure 15.
b. Install the termination cap, following the
instructions provided with it.
Figure 14
Air Kit Handle Location (right side shown)
10. Install the Outside Air Kit
The outside air kit is supplied as a standard feature
with this fireplace and its use is required to minimize
the effects of negative pressure within the structure. It
is recommended to utilize the shortest duct run to
optimize the performance of the outside air kit. The
outside air kit inlet thimble should be positioned at
least 4 ft above the ground level, in a manner that will
not allow snow, leaves, etc. to block the inlet.
The outside air kit is installed on either side of the
fireplace. Remove the cover plate from the side of the
fireplace assembly where the air kit is to be installed.
See Figure 14 for handle location/operation.
WARNING!
Do not pack insulation in spaces between the two
shields or above the shield inside the flashing. This
may affect temperatures to adjacent combustibles. See
page 13 for minimum chimney height above roof.
WARNING!
This fireplace has not been tested for use with
a chase above the roof. To reduce the risk of
fire, do not install a chase above the room.
CAUTION:
The air kit handle may get hot while burning
the fireplace. Use care when operating the
handle.

08/04 31068 Rev E 19
MHST36D INSTALLATION INSTRUCTIONS
Note: Use only a noncombustible material to finish
the face of the fireplace below the level of the front
standoffs. A noncombustible material such as USG
MICORE CV230 Mineral Fiber Board, or USG
DUROCK Cement Board is recommended for this
purpose.
Figure 16 - Air Clearance Around Gas Line
12. Complete the Enclosure
Complete the fireplace enclosure, allowing space for
outside air ducts and gas piping if desired. Electrical
wiring should not come in contact with the fireplace. A
minimum clearance of 1/2 in. must be maintained
between the fireplace sides and the enclosure. See
pages 8, 10 and 11 for framing details.
CAUTION:
When using a gas log set, the fireplace damper
must be set in the fully open position. This en-
sures proper venting of combustion products.
WARNING!
This fireplace was not tested by the fireplace
manufacturer for use with an unvented gas log
heater. To reduce risk of injury, do not install
an unvented gas log heater in this fireplace un-
less it has been specifically tested and listed
by Underwriter’s Laboratories Inc. for use in
this specific model fireplace. Unless the
unvented gas log heater is tested and listed for
use in this factory built fireplace, a fire hazard
may be created that can result in a structure
fire.
13. Gas Log/Lighter Provisions
Knockouts are provided on both sides of the fireplace
to allow for connection of a certified gas log lighter or
a decorative gas appliance with a maximum input of
100,000 BTU/hr, incorporating an automatic gas shut-
off device and complying with the Standard for
Decorative Gas Appliances for Installation in
Vented Fireplaces, ANSI Z21.60. The decorative gas
appliance should be installed in accordance with the
National Fuel Gas Code, ANSI Z223.1-1980. The side
refractories are designed to allow 1/2 in. iron pipe to
pass through. Use a noncombustible sealant to seal
any opening between the gas pipe and refractory on
the inside. Repack the insulation removed to seal
around the gas pipe where it exits the side of the
fireplace. A minimum 1-1/2 in. air clearance must be
provided around the 1/2 in. iron pipe for a minimum of
4 in. beyond the fireplace. See Figure 16.
CLEARANCES!
A minimum 1/2 in. air clearance must be maintained
at the sides of the fireplace assembly.
Chimney sections at any level require a 2 in. mini-
mum air space clearance between the framing and
chimney section.

20 31068 Rev E 08/04
MHST36D INSTALLATION INSTRUCTIONS
Figure 17 - Factory Built Hearth Extension
Figure 18 - Field Constructed Hearth Extension
WARNING!
Hearth extensions are to be installed only as illustrated to prevent high temperatures
from occurring on concealed combustible materials. Hearth sealing strips prevent burn-
ing or hot particles from inadvertently falling directly on combustible surfaces in the event
the building should settle and disturb the original construction.
14. Hearth Extension
A hearth extension must be installed with all fireplaces to protect the combustible floor in front of the fireplace from
both radiant heat and sparks.
The construction of, and materials used for a hearth extension are shown in Figures 17 and 18. A hearth extension of
this construction may be covered with any noncombustible decorative material and may have a maximum thickness
as per the illustration. Seal gaps between the hearth extension and the fireplace with a bead of noncombustible
sealant.
Field constructed hearth extensions should be constructed in accordance with the instructions in Figure 18. The field
constructed hearth extension must be constructed from 1/2 in. MICORE CV230 or a material with an equivalent
insulation value.