Heatilator MHST36D User manual

1
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
WOODBURNING FIREPLACE
MANUFACTURED HOME APPROVED
Fire Risk.
WARNING
For use with solid wood fuel only.
Other fuels may overre and generate
poisonous gases (i.e. carbon monoxide).
Model(s):
Installation Manual
Installation and Fireplace Setup
WARNING
HOT SURFACES!
Glass and other surfaces are hot during
operation AND cool down.
Hot glass will cause burns.
• DO NOT touch glass until it is cooled
• NEVER allow children to touch glass
• Keep children away
• CAREFULLY SUPERVISE children in same room as
replace.
• Alert children and adults to hazards of high temperatures.
High temperatures may ignite clothing or other ammable
materials.
• Keep clothing, furniture, draperies and other ammable
materials away.
INSTALLER: Leave this manual with party responsible for use and operation.
OWNER: Retain this manual for future reference.
MHST36D
NOTICE: DO NOT discard this manual!
• DO NOT store or use gasoline or other am-
mable vapors and liquids in the vicinity of this
or any other appliance.
• DO NOT overre. Overring will void your
warranty.
• Comply with all minimum clearances to com-
bustibles as specied. Failure to comply may
cause house re.
WARNING: If the information in these
instructions is not followed exactly, a re
or explosion may result causing property
damage, personal injury, or death.
Installationand service of thisappliance shouldbe performed by

2Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
Safety Alert Key:
• DANGER! Indicates a hazardous situation which, if not avoided will result in death or serious injury.
• WARNING! Indicates a hazardous situation which, if not avoided could result in death or serious injury.
• CAUTION! Indicates a hazardous situation which, if not avoided, could result in minor or moderate injury.
• NOTICE: Indicates practices which may cause damage to the replace or to property.
Table of Contents
1 Product Specic & Important Safety Information
A. Fireplace Certication 4
B. Non-Combustible Materials 4
C. Combustible Materials 4
2 Getting Started
A. Typical Fireplace System 5
B. Design and Installation Considerations 6
1. Selecting Fireplace Locations 6
2. Locating Fireplace & Chimney 7
C. Tools and Supplies Needed 8
D. Inspect Fireplace and Components 8
E. Fireplace System Requirements 8
3 Framing and Clearances
A. Fireplace Dimensions 9
B. Clearances 10
Minimum Clearances to Combustibles 10
C. Frame the Fireplace 11
D. Secure and Level the Fireplace 11
E. Protective Metal Hearth Strips 12
F. Outside Air Kit 12
4 Chimney and Termination Requirements
A. Chimney Requirements 14
B. Offsets/Returns 15
C. Termination Requirements 16
5 Chimney Installation
A. Typical Chimney System 17
B. Assemble Chimney Sections 18
C. Secure Offset/Return 19
D. Install Ceiling Firestops 19
E. Install Attic Insulation Shield 20
F. Roof Penetration 21
G. Install MH842 Ceiling/Roof Thimble 22
H. Termination Cap Requirements 23
6 Finishing
A. Finishing Material 23
B. Hearth Extension, Building and Finishing 24
1. Fireplace Installed Flush on the Floor
and Hearth Extension Raised to Bottom
of Firebox Opening 25
2. Raised Hearth Extension and Raised Fireplace 26
C. Non-Combustible Sealant Material 27
D. Mantel and Wall Projections 28
E. Sidewalls/Surrounds 29
8 Fireplace Setup
A. Gas Log/Lighter Provision 30
9 Reference Materials
A. Chimney Components 31
B. Optional Components 33
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Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
Customer:
Lot/Address
Model (circle one): MHST36D
Fireplace Install YES IF NO, WHY?
Hearth extension installed per manual requirements.
Hearth & Home Technologies recommends the following:
Comments communicated to party responsible
4012-087 • Rev A • 09/09/14
Dealer/Distributor Phone #
Serial #:
Roof flashing installed.
Terminations installed.
• Photographing the installation and copying this checklist for your file.
Combustible materials not installed in non-combustible areas.
Mantels and wall projections comply with installation manual requirements.
All packaging and protective materials removed.
Doors properly installed.
Molded brick panels installed correctly.
Grate is properly installed.
Firescreen installed properly.
Fireplace Setup Section 7 (Pg. 30)
Mobile home thimble installed.
Protective hearth strips installed per manual requirements. (Pg. 12)
Outside air kit installed. (Pg 12)
ATTENTION INSTALLER:
Follow this Standard Work Checklist
This standard work checklist is to be used by the installer in conjuction with, not instead of, the instructions contained in this installation
manual.
Date Installed:
Location of Fireplace:
Installer:
WARNING! Risk of Fire or Explosion! Failure to install fireplace acording to these instructions can lead to a fire or
explosion.
Manual bag and all of its contents are removed from the fireplace and given to the party
responsible for use and operation.
Verified clearances to combustibles. (Pg. 10)
Fireplace is leveled and secured. (Pg. 11)
Hearth extension size/height decided. (Pg. 24)
Chimney configuration complies with diagrams.
Chimney installed, locked and secured in place with proper clearance.
Firestops installed.
• That this checklist remain visible at all times on the fireplace until the installation is complete.
Verified all clearances meet installation manual requirements.
Chimney Section 4 & 5 (Pg. 14)
Finishing Section 6 (Pg. 23)
__________________________ by ______________________on _________
(Builder/Gen. Contractor) (Installer) (Date)
Comments: Further description of the issues, who is responsible (Installer/Builder/Other Trades, etc.) and corrective action needed:

4Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
1 Product Specic & Important Safety Information
This replace may be installed in manufactured homes,
except sleeping rooms. If installed with a gas log set, pro-
visions for the National Fuel Gas Code must be met.
This replace has been tested and listed for use with
the optional components specied in this manual. These
optional components may be purchased separately and
installed at a later date. An outside air kit, gas insert, gas
log set or gas log-lighter should be installed at the time of
replace installation.
This replace complies with the installation requirements
for HUD.
Heatilator is a registered trademark of Hearth & Home
Technologies.
WARNING! Risk of Fire! Hearth & Home Technologies
disclaims any responsibility for, and the warranty and
agency listing will be voided by the following actions.
DO NOT:
• installoroperatedamagedreplace
• modifyreplace
• install other than as instructed by Hearth & Home
Technologies
• operate the fireplace without fully assembling all
components
• overre
• install unvented gas log set
• install any component not approved by Hearth & Home
Technologies
• install parts or components not Listed or approved
Improper installation, adjustment, alteration, service or
maintenance can cause injury or property damage. For
assistance or additional information, consult a qualied
installer, service agency or your dealer.
B. Non-Combustible Materials
• Materials which will not ignite and burn, composed of
any combination of the following:
- Steel - Iron
- Brick - Tile
- Concrete - Slate
- Glass - Plasters
• Materials reported as passing ASTM E 136, Standard
Test Method for Behavior of Materials, in a Vertical
Tube Furnace at 750° C
C. Combustible Materials
• Materials made of or surfaced with any of the following
materials:
- Wood - Compressed paper
- Plant bers - Plastic
- Plywood/OSB - Sheet rock (drywall)
• Any material that can ignite and burn; ame proofed or
not, plastered or un-plastered
A. Fireplace Certication
This replace system has been tested and listed in accor-
dance with UL 127 standards by Underwriters Laborato-
ries Inc. for installation and operation in the United States.

5
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
2 Getting Started
A. Typical Fireplace System
Figure 2.1 Typical Fireplace System
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
Non-combustible
roof flashing maintains
minimum clearance
around chimney
Additional lateral
support for chimney
above roof (or enclosed
in chase) if needed
Ceiling firestop
on floor of attic
Support straps
on rafter support
chimney (not shown)
Termination cap
Chimney penetrates roof
preferably without affecting
roof rafters
Offset & Return (with hanger straps)
Framing headed off
in ceiling joists
Enclosed space above
and around fireplace
Mantel and surround
Decorative facing
and trim
Hearth extension
Factory-built fireplace
Protective metal
hearth strip(s)
Outside
combustion air
Combustible framing/header
on top of V-shaped standoffs
Chimney system
Attic insulation shield (not shown)
must be used here to keep
insulation away from chimney
if attic is insulated
Storm Collar

6Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
1/2 in. (13 mm)
all configurations
52 in.
(1321 mm)
36 in.
(914 mm)
16 in. (406 mm)
(hearth
extension)
48 in.
(1219 mm)
12 in. (305 mm)
min. to
perpendicular
wall.
Figure 2.2 Fireplace Locations
NOTICE:
• Illustrationsandphotosreecttypicalinstallationsand
are FOR DESIGN PURPOSES ONLY.
• Illustrations/diagrams are not drawn to scale.
• Actual installation/appearance may vary due to individual
design preference.
• Hearth & Home Technologies reserves the right to alter
its products.
NOTICE: In addition to these framing dimensions, also
reference the following section:
• Clearances (Section 3).
NOTICE:
A minimum 1/2 in. air clearance at the sides of the
replaceassemblymustbemaintained.
Chimney sections at any level require a 2 in. mini-
mum air space clearance between the framing
and chimney sections.
B. Design and Installation Considerations
NOTICE: Check building codes prior to installation.
• Installation MUST comply with local, regional, state and
national codes and regulations.
• Consult insurance carrier, local building inspector, re
ofcials or authorities having jurisdiction over restrictions,
installation inspection and permits.
• Before installing, determine the following:
- Where the replace is to be installed.
- The vent system conguration to be used.
- Gas supply piping.
- Electrical wiring.
- Framing and nishing details.
- Whether optional accessories - devices such as a
fan, wall switch or remote control - are desired.
1. Selecting Fireplace Locations
This replace may be used as a room divider, installed
along a wall. See Figure 2.2.
Locating the replace in a basement should be avoided.
Locating near frequently opened doors, central heat
outlets or returns, or other locations of considerable air
movement can affect the performance.
Outside air must be used for combustion. This replace
comes equipped with an outside air inlet to feed combus-
tion air from outside the home, along with an outside air
termination cap; the duct is required but not supplied.
Consideration should be given to these factors before
deciding on a location.

7
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
2. Locating Fireplace & Chimney
Location of the replace and chimney will affect perfor-
mance.
• Install within the warm airspace enclosed by the building
envelope. This helps to produce more draft, especially
during lighting and die-down of the re.
• Installing the replace in a basement is not recommended.
• Penetrate the highest part of the roof. This minimizes
the effects of wind loading.
• Locate termination cap away from trees, adjacent
structures, uneven roof lines and other obstructions.
• Minimize the use of chimney offsets.
• Consider the replace location relative to oor and ceiling
and attic joists.
• Take into consideration the termination requirements in
Sections 4 and 5.
Marginal Location:
• Below peak
Location NOT recommended:
• Not the highest point of the roof
• Wind loading possible
Multi-level Roofs
Windward
Leeward
Recommended Location:
• Above peak
Recommended:
• Insulated exterior chase
in cooler climates
Recommended Location:
• Above peak
• Inside heated space
Location NOT recommended:
• Too close to tree
• Below adjacent structure
• Lower roof line
• Avoid outside wall
Marginal Location:
• Wind loading possible
Not recommended in basement due
to high negative pressure concerns
that effect draft
Figure 2.3 Recommended Chimney Locations
• Install the outside air kit with the intake facing prevailing
winds during the heating season.
• Ensure adequate outdoor air for all combustion
appliances and exhaust equipment.
• Ensure furnace and air conditioning return vents are not
located in the immediate vicinity of the replace.
• Avoid installing the replace near doors, walkways or
small isolated spaces.
• Recessed lighting should be a “sealed can” design.
• Attic hatches weather stripped or sealed.
• Attic mounted duct work and air handler joints and seams
taped or sealed.

8Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
C. Tools and Supplies Needed
Before beginning the installation be sure the following
tools and building supplies are available:
Reciprocating saw Framing material
Pliers Non-combustible sealant
Hammer Gloves
Phillips screwdriver Framing square
Flat blade screwdriver Electric drill and bits
Plumb line Safety glasses
Level Tape measure
1/2-3/4 in. length, #6 or #8 self-drilling screws
Misc. screws and nails
D. Inspect Fireplace and Components
WARNING! Risk of Fire and/or Explosion! Damaged
parts could impair safe operation. DO NOT install dam-
aged,incompleteorsubstitutecomponents.Keepre-
place dry.
• Remove replace and components from packaging and
inspect for damage.
• Vent system components and doors are shipped in
separate packages.
• Report to your dealer any parts damaged in shipment.
• Read all the instructions before starting the
installation. Follow these instructions carefully
during the installation to ensure maximum safety
and benet.
E. Fireplace System Requirements
The Heatilator replace system requirements consist of
the following:
• Fireplace
- Refractory (included with replace)
- Firescreen (included with replace)
- Grate (included with replace)
- Hearth Extension (required, sold separately)
• Outside Air System
- Air Inlet Hood (included with replace)
- Flex (required, sold separately)
• Chimney System
- Attic Insulation Shield (included with replace)
- Chimney termination cap (required, sold separately)
• Non-combustible nish material

9
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
3 Framing and Clearances
A. Fireplace Dimensions
47-1/4 in.
(1200 mm)
(effective height)
41-1/2 in.
(1054 mm)
36 in.
(914 mm)
20-7/8 in.
(530 mm)
7-1/2 in.
(191 mm)
10-1/2 in.
(267 mm)
dia.
12 in.
(305 mm)
8-1/4 in.
(210 mm)
35 in.
(889 mm)
7-1/8 in.
(181 mm)
9-5/8 in.
(244 mm)
Gas
Knockout 8-1/4 in.
(210 mm)
40 in.
(1016 mm)
24 in.
(610 mm)
20 in.
(508 mm)
12 in.
(305 mm)
12 in.
(305 mm)
Outside
Air
Gas
Knockout
6 in.
(152 mm)
Figure 3.1 Fireplace Dimensions

10 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
B. Clearances
WARNING! Risk of Fire!
You must comply with all minimum air space clearances
tocombustiblesasspeciedinFigure3.2.DO NOT pack
required air spaces with insulation or other materials.
Framing or nishing material used on the front of, or in
frontof,thereplacecloserthantheminimumslistedmust
be constructed entirely of non-combustible materials (i.e.,
steel studs, concrete board, etc.). Failure to comply may
causere.
Figure 3.2 Clearances to Combustible Materials
Minimum Clearances to Combustibles
WITHIN ENCLOSURE AREA
Fireplace to sidewall 1/2 in. (13 mm)
Top standoffs to header 0 in. (0 mm)
Door opening to sidewall 12 in. (305 mm)
MANTEL
Mantel minimum height 40 3/8 in. (1026 mm)
Maximum mantel depth 12 in. (305 mm)
(insulation)
0 in. to level
of standoffs
Attic
Insulation
Shield
(ceiling)
(roof)
(attic)
(ceiling)
Ceiling Firestop
Offset/Return (secured
with hanger straps)
Storm Collar
Roof Flashing
1/2 in. (13 mm) to
sides of appliance
Must have 2 in. (51 mm)
minimum clearance
to header
0 in.
to floor
2 in. (51 mm) min.
Shaded areas
represent
2 in. (51 mm) min.
air space clearance
required around pipe
Combustible Object
48 in.
1219 mm

11
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
C. Frame the Fireplace
NOTICE: Hearth extension design must be determined
before installation of replace.
If the replace is placed on the oor the maximum height
of a nished raised hearth is 6 in.; if you want a higher
raised hearth the replace must be placed on a platform.
WARNING! Risk of Fire! You must comply with all
minimum air space clearances to combustibles. DO NOT
pack required air spaces with insulation or other materi-
als.
WARNING! Risk of Fire! Comply with all minimum clear-
ancesspecied.
• A minimum 1/2 in. (12 mm) air clearance must be
maintainedatthesidesofthereplaceassembly.
• Chimney sections at any level require a 2 in. (51 mm)
minimum air space clearance between the framing and
chimney section.
Figure 3.5 shows a typical framing (using 2 x 4 lumber)
of the replace, assuming combustible materials are
used. All required clearances to combustibles around the
replace must be adhered to. See Figure 3.2. Any framing
across the top of the replace must be above the level of
the top standoffs. (No recess above standoffs.)
The nished cavity depth must be no less than 23 in.
(584 mm). Framing must extend straight up all the way to
the ceiling.
CAUTION! Risk of Cuts/Abrasions. Wear protective gloves
and safety glasses during installation. Sheet metal edges
are sharp.
WARNING! Risk of Fire! Prevent contact with sagging,
loose insulation.
• DO NOT install against vapor barriers or exposed
insulation.
• Secure insulation and vapor barriers.
• Provide minimum air space clearances at the sides and
backofthereplaceassembly.
D. Secure and Level the Fireplace
This replace may be placed on either a combustible
or noncombustible continuous at surface. Follow the
instructions for framing in Section 3. Slide the replace
into position. Be sure to provide the minimum 1/2 in. air
clearance at the sides of the replace.
The replace should be positioned so the face of the non-
combustible material on the replace will be ush with the
face of the drywall on the walls.
Level the replace and shim as necessary.
23 in.
(584 mm)
Note: Fireplace
Header cannot be
positioned until after
the fireplace assembly
is in place.
41 in.
(1041 mm)
14-1/2 in. (368 mm)
framing.
Figure 3.5 Framing the Fireplace
1/2 in.
(13 mm)
Fireplace must be set out
1/2 in. (13 mm) in front of
the face of the framing
material.
►

12 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
Protective metal strips are placed 2 in. (51 mm) under the
front of the fireplace and must extend beyond the front
and sides of fireplace opening by 2 in. (51 mm).
1 in. (25 mm)
overlap
Raised Platform
Floor
2 in.
(51 mm)
1 in. (25 mm) min.
overlap
2 in.
(51 mm)
Top piece must overlap
bottom piece
Figure 3.7 Protect the Front of an Elevated Platform
E. Protective Metal Hearth Strips
Figure 3.6 Position the Protective Metal Hearth Strips
• Locate the two protective metal hearth strips measuring
approximately 26 in. x 4 in. (660 mm x 102 mm) included
with this replace.
• Slide each metal strip 2 in. (51 mm) under front edge of
replace.
• Overlap strips in the middle of replace opening by 1 in.
(25 mm) minimum.
• Metal strips must extend beyond the front and sides
of the replace opening by at least 2 in. (51 mm),
Figure 3.6).
• Protect the front of a platform elevated above the hearth
extension with metal strips (not included with replace)
per Figure 3.6. See Section 7 for hearth extension
instructions.
WARNING! Risk of Fire! Protective metal hearth
strips MUST be installed on combustible surfaces. DO
NOT cover metal strips with combustible materials.
Sparksorembersmayigniteooring.
WARNING! Risk of re! High temperatures, sparks,
embers or other burning material falling from the
replacemayigniteooringorconcealedcombustible
surfaces.
• Protective metal hearth strips MUST be installed.
• Hearth extensions MUST be installed exactly as
specied.
F. Install the Outside Air Kit
The outside air kit is supplied as a standard feature with
this replace 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 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
replace. Remove the cover plate from the side of the
replace assembly where the air kit is to be installed.
See Figure 3.9 for handle location/operation.
CAUTION! The air kit handle may get hot while burning
the replace. USE CARE when operating the handle.
Locate outside air inlet hood to prevent blockage from
leaves, snow/ice, or other debris. Blockages could cause
combustion air starvation.

13
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
CAUTION! Risk of Cuts/Abrasions. Wear protective
gloves and safety glasses during installation. Sheet metal
edges are sharp.
Outlet placed
higher than 3 ft
below the
termination cap
Attic space
Garage or
combustible
liquids storage
Outlet blocked by
snow, leaves, etc.
Clear area
outside
house or in
ventilated
crawl space
YES
NO
NO
NO
NO
Factory-built
fireplace
• Use UL181 Class 1 or Class 0 rigid or flexible ducting.
• Install with short run or mainly straight duct, except small
dip for cold air trap which will help prevent flow of cold air.
• Secure flex duct with screws or wire ties.
Figure 3.8 Outside Air Installation
• The hinge will be toward the front of the replace.
• Insert the narrow end of the handle into the upper slot.
• Pivot the handle in the slot toward the hinge.
• Remove the cover plate or knockout from the side of the
replace and discard. Remove the semi-perforated piece
of insulation covering the opening (insulated replaces
only).
• Partly open the air kit door and insert the handle into the
appropriate hole in the side column of the replace. The
hinge on the door assembly should be located toward
the front of the replace. If the hinge and the handle are
not positioned in this manner, the door will not function
correctly.
• Attach the door assembly to the replace using the
screws provided.
Outside Air
Plate
Assembly
2 Wire Ties
Flexible Duct
2 Wire Ties
(
((
(
(
(
(
(
)
)
)))
Flexible Duct
• Check operation by pulling the handle out to open and
pushing it in to close.
• Mark and cut out a 6 1/2 in. (165 mm) hole in the building
side for air entry. This hole should allow some framing
(two sides) so the 6 in. (152 mm) diameter inlet tube
assembly may be fastened properly.
• Assemble exible duct (not supplied) between the door
assembly and the inlet tube assembly. Secure it in
position with the supplied wire ties.
• Seal between the wall and the pipe with silicone to
prevent moisture penetration and air leaks.
• Seal between the outside air inlet hood and the house
with silicone to prevent air inltration.
Figure 3.9 Outside Air Installation

14 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
20 ft (6.10 m) max.
pipe between an
offset & return
Ceiling firestop
35 ft (10.67 m) max. straight
unsupported chimney height
16 ft (4.88 m) min. height (single offset-return)
20 ft. (6.10 m) min. height (double offset-return)
90 ft (27.4 m) max. height
6 ft (1.83 m) max.
unsupported chimney
above roof
47-1/4 in.
(1200 mm)
Effective
Height
Figure 4.1 Chimney Requirements
NOTICE: A maximum of two pairs of offsets and returns
may be used.
WARNING! Risk of Fire! You must maintain 2 in. (51 mm)
air space clearance to insulation and other combustible
materials around the chimney system. Failure to do so
maycauseoverheatingandre.
NOTICE: You must provide support for the pipe during
construction and check to be sure inadvertent loading has
notdislodgedthechimneysectionfromthereplaceorat
any chimney joint.
A. Chimney Requirements
Vertical distances are measured from the base of the
replace as shown in Figure 4.1.
4 Chimney and Termination Requirements
Table 4.2 Chimney Component Dimensions
Table 4.1 Chimney Requirements
ft meters
•Minimum overall straight height 14.5 4.42
•Minimum height with offst/return 16 4.88
•Maximum height 90 27.43
•Maximum chimney length bewtween an offset
and return
20 6.10
•Maximum distance between chimney stabilizers 35 10.67
•Double offset/return minimum height 20 6.10
•Maximum unsupported chimney length between
the offset and return
6 1.83
•Maximum unsupported chimney height above the
replace
35 10.67
•Maximum unsupported chimney above roof 6 1.83
HEIGHT OF CHIMNEY COMPONENTS in. mm
Chimney Stabilizer
SL3 4-3/4 121
Offsets/Returns
SL315 13-3/8 340
SL330 15-1/2 394
Chimney Sections*
SL306 4-3/4 121
SL312 10-3/4 273
SL318 16-3/4 425
SL324 22-3/4 578
SL336 34-3/4 883
SL348 46-3/4 1187
* Dimensions reect effective height.

15
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
B. Offsets/Returns
• Use an offset/return to bypass overhead obstructions.
• An offset and return can be used as a single entity or separated by chimney section(s).
WARNING! Risk of Fire! DO NOT use offset/returns greater than 30°. Chimney draft will be restricted and could cause
overheatingandre.Secureoffsetswithscrews(nottoexceed1/2”/13mminlength)Securereturnswithstrapping.
Straight chimney sections may be secured with screws. Keep chimney sections from separating or twisting.
• Measure the shift needed to avoid the overhead obstruction. Refer to dimension A in Figure 4.2.
• Find the appropriate A dimension listed in Table 4.3. The B dimension coinciding with the A dimension measurement in
Table 4.3 represents the required vertical clearance needed to complete the offset/return.
• Read across the chart to nd the number of chimney sections/model numbers needed between the offset and return.
A
B
1-1/4 in. (32 mm)
OVERLAP
Figure 4.2 Chimney Offset/Return
Table 4.3 Offset Dimensions
Example:
Your “A” dimension from Figure 4.2 is 14-1/2 in. (368
mm). Using Table 4.3 the dimension closest to, but not
less than 14-1/2 in. (368 mm) is 14-1/2 in. (368 mm) us-
ing a 30° offset/return.
You determine from the table that you need 34-1/8 in.
(867 mm) (Dimension “B”) between the offset and re-
turn.
The chimney component that best ts your application is
one SL324.
15-degree 30-degree
SL306 SL312 SL318 SL324 SL336 SL348
A B A B
in. mm in. mm in. mm in. mm
1 5/8 41 13 3/8 340 3 5/8 92 15 1/2 394 ------
2 7/8 73 17 3/4 451 5 1/2 140 18 5/8 473 1 - - - - -
4 1/8 102 22 3/8 568 7 1/4 184 21 3/4 552 2 - - - - -
4 1/2 114 23 5/8 600 8 1/2 216 23 3/4 603 - 1 - - - -
5 3/4 146 28 1/4 718 10 1/4 260 27 686 1 1 - - - -
6 152 29 3/8 746 11 1/2 292 29 737 - - 1 - - -
7 1/4 184 34 864 13 1/4 337 32 1/8 816 - 2 - - - -
7 3/4 197 36 1/8 918 14 1/2 368 34 1/8 867 - - - 1 - -
8 3/4 222 39 3/4 1010 16 1/4 413 37 3/8 949 1 - - 1 - -
10 3/8 264 45 5/8 1159 19 1/4 489 42 1/2 1080 - - 2 - - -
10 5/8 270 46 3/4 1187 20 1/2 521 44 5/8 1133 - - - - 1 -
11 7/8 302 51 3/8 1305 22 1/4 565 47 3/4 1213 1 - - - 1 -
13 1/2 243 57 1/4 1454 25 1/4 641 52 7/8 1343 - - - 2 - -
13 3/4 349 58 3/8 1483 26 1/2 673 55 1397 -----1
15 381 63 1600 28 1/4 718 58 1/8 1476 1 - - - - 1
16 1/2 419 68 3/4 1746 31 1/4 794 63 1/4 1607 - 1 - - - 1
18 457 74 5/8 1895 34 1/4 870 68 1/2 1740 - - 1 - - 1
19 5/8 498 80 3/8 2042 37 1/4 946 73 3/4 1873 - - - 1 - 1
20 5/8 524 84 1/8 2137 39 1/8 994 76 7/8 1953 1 - - 1 - 1
22 3/4 578 91 7/8 2334 43 1/4 1099 84 1/8 2137 - - - - 1 1
24 610 96 1/2 2451 45 1/8 1146 87 1/4 2216 1 - - - 1 1
25 7/8 657 103 1/2 2629 49 1/4 1251 94 1/2 2400 -----2
Proper assembly of air-cooled chimney parts result in an overlap at chimney joints of 1-1/4 in. (32 mm). Effective
length is built into this chart.

16 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
Figure 4.3 Multiple Chimney Locations
C. Termination Requirements
• Install a cap approved and listed for this replace system.
• Locate cap where it will not become plugged by snow or other materials.
• Locate cap away from trees or other structures.
• The bottom of the termination cap must be at least 3 ft (.91 m) above the roof AND at least 2 ft (.61 m) above any portion
of roof within 10 ft (3.05 m).
• The distance required between caps is shown below.
Slanted Roofs
Flat Roofs
Chimney must
extend 3 ft (.9 m)
above the roof
Chimney must extend 2 ft (.6 m)
above any portion of the roof or
adjacent structures within
10 ft (3 m) of the chimney
Chimney must
extend 3 ft (.9 m)
above the roof
Chimney must extend 2 ft (.6 m)
above any portion of the roof or
adjacent structures within
10 ft (3 m) of the chimney

17
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
5 Chimney Installation
Chimney must extend
beyond combustible
roof structure
Maintain minimum
height of chimney
above roof
Additional
support for
tall chimneys
Install roof flashing
according to minimum
requirements
Maintain minimum
clearances to
combustibles as
specified
Offsets/returns
may not exceed
30° from vertical
Lock chimney
sections together
firmly to resist
movement
Ceiling firestops
are required where
chimney passes
through ceiling or
floor
Support straps for offsets
(not shown) must be
secured to adequate framing
Termination Cap
Storm Collar
Offsets/returns must be
secured with screws
(outer pipe only)
Attic shield
Figure 5.1 Typical Chimney System - Guidelines for Chimney System Installation
NOTICE: Chimney performance may vary.
• Trees, buildings, roof lines and wind conditions affect performance.
• Chimney height may need adjustment if smoking or overdraft occurs.
A. Typical Chimney System

18 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
NOTICE: Chimney sections cannot be disassembled once
locked together. Plan ahead!
• Lock chimney sections and/or offsets/returns together by
pushing downward until the top section meets the stop
bead on the lower section.
• Pull on the top section to make sure it is fully engaged
and will not separate.
• You may use #6 or #8 sheet metal screws no longer than
1/2 in. (13 mm) to fasten chimney sections together. Do
NOT penetrate inner ue.
WARNING! Risk of Fire! You MUST use screws (pro-
vided) to fasten offset/returns to chimney sections to
keep the chimney parts from twisting. Failure to do so
couldcausere.
• Fasten offset/returns to chimney sections. Insert the
screws (provided) through the predrilled holes. Do NOT
penetrate inner ue.
• Secure chimney returns with hanger straps provided;
fasten to studs or joists.
• Vertical straight runs of chimney must be supported every
35 ft (10.7 m).
B. Assemble Chimney Sections
Use only those components described in this manual.
Substitute or damaged chimney components could impair
safe operation and cause overheating and re.
Attach either a straight chimney section or an offset to
the top of the replace (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 ue is placed to the inside of the ue section
below it. The outer casing is placed outside the outer cas-
ing of the chimney section below it. See Figure 5.2.
WARNING! Risk of Fire! DO NOT install substitute or
damaged chimney components.
Figure 5.2 Assembling Chimney Sections

19
Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
C. Secure Offset/Return
D. Install Ceiling Firestops
CAUTION! Risk of Fire! Ceilingrestopsmustbeused
wheneverthechimneypenetratesaceiling/oor.
• Theceilingrestopslowsspreadofreandreduces
coldairinltration.
• Install a ceiling restop whenever chimney penetrates
ceiling/oor.
• Mark and cut an opening in ceiling as shown in Figure 5.4.
• Frame the opening with the same size lumber used in
the ceiling joists.
• Nail the ceiling restop to the bottom of the ceiling joists
when there is a room above.
• Use an attic insulation shield if the ceiling is insulated.
The ceiling restop may then be attached above or below
the joists.
ROOM ABOVE (non-insulated ceiling)
ATTIC ABOVE (insulated ceiling)
B
A
Ceilng firestop
attached to bottom
of framing
Ceiling firestop
attached to top of
framing
Note: Use same dimensional lumber for framing
ceiling firestop and joists.
2 in. (51mm)
clearance
2 in. (51mm)
clearance
WARNING! Risk of Fire! DO NOT seal area between
restopopeningandchimneypipeexceptwheretheyen-
ter the attic or leave the warm air envelope of the home
(use 600° F sealant).
Figure 5.4 Installing the Ceiling Firestop
When offsets and returns are joined to straight pipe sec-
tions, they must be locked into position with the screws
provided* (outer only), using the predrilled holes. To pre-
vent gravity from pulling the chimney sections apart, the
returns and the chimney stabilizers have hanger straps for
securing these parts to joists or rafters. See Figure 5.3.
* Use # 6 or # 8 sheet metal screw, or larger, no longer
than 1/2 in. (13 mm).
WARNING! Risk of Fire!
• Secure offsets with screws (not to exceed 1/2 in./13 mm
In length).
• Secure returns with strapping.
• Straight chimney sections may be secured with screw
(not to exceed 1/2 in./13 mm In length) at the joints.
• Keep chimney sections from separating or twisting.
Ceiling
Firestop
Straps
Optional
Additional
Support
Joint
Band
(Optional)
Figure 5.3 Secure the Chimney
Catalog #
A B
in. mm in. mm
FS338 14-1/2 368 14-1/2 368
FS339 14-1/2 368 18-3/8 467
FS340 14-1/2 368 23 584

20 Heatilator • MHST36D Installation Manual • 4012-086 • Rev D • 03/17
Installation of a ceiling restop is required:
• Refer to Figures 5.5, 5.6, 5.7.
• If the attic shield is pre-rolled continue. If it is a at part,
try and roll it up to aid in wrapping it around the chimney.
• Pre-bend all the tabs in at the top to 45°.
• Wrap the shield (around the chimney if already installed)
until you have an overlap and the three holes on each
side match up (large holes on top).
• Insert three screws into the matching holes to form a
tube starting at the bottom.
• Bend the tabs on the bottom of the tube inward to 90° to
maintain chimney air space.
• Rest the insulation shield on the ceiling restop below.
• Tape off any opening around the bottom.
If you wish to make a custom shield or barrier, follow
these guidelines:
• Metal is preferred, although any material stiff enough to
hold back the insulation can be used.
WARNING! Risk of Fire! Use of cardboard or other
materialsthatcandeectunderhumidityorotherenvi-
ronmental conditions is not recommended.
• The shield or barrier must be tall enough to extend
above the insulation and prevent blown-in insulation from
spilling into the cavity.
• Maintain specied air spaces around chimney.
• Check instructions and local codes for further details.
Insert three
screws
Pre-bend the tabs to
rest against pipe to
prevent insulation
from falling in.
(5)Tabs bent
in 90°
Figure 5.5 Prepare Attic Insulation Shield
E. Install Attic Insulation Shield
WARNING! Risk of Fire! You MUST install an attic insu-
lation shield when there is any possibility of insulation or
other combustible material coming into contact with the
chimney.
• DO NOT pack insulation between the chimney and the
attic insulation shield.
• Failure to keep insulation and other materials away from
chimneypipecouldcausere.
• DO NOT offset chimney inside insulation shield.
Double-check the Chimney Assembly
Continue assembling the chimney sections up through
the ceiling restops as needed. While doing so, be
aware of the height and unsupported chimney length
limitations given under Section 5.
Check each section by pulling up slightly from the top
to ensure proper engagement before installing the suc-
ceeding sections. If they have been connected correct-
ly, they will not disengage when tested.
Figure 5.6 Install Attic Insulation Shield (restop above ceiling)
5 Tabs bent
in 90°
Tabs bent in to
rest against pipe
Attic Insulation Shield
Ceiling Firestop
10-1/2 in.
(267 mm)
14-1/2 in. (368 mm)
diameter
InsulationInsulation
Pipe
Pipe
2 in. (51 mm)
air space
Seal with tape
5 Tabs bent
in 90°
Tabs bent in to
rest against pipe
Attic Insulation Shield
Ceiling Firestop
10-1/2 in.
(267 mm)
14-1/2 in. (368 mm)
diameter
InsulationInsulation
Pipe
Pipe
2 in. (51 mm)
air space
Seal with tape
Figure 5.7 Install Attic Insulation Shield (restop below ceiling)