Monessen Hearth WOODBURNING FIREPLACE 424WBST User manual
For use in U.S./Canada
Underwriter's Laboratories
Report No. MH7603
87D1506 12/09 Rev. 2
Homeowner's Installation
and Operating Manual
342COVER
2
424WBST Designer Woodburning Fireplaces
87D1506
Read all instructions and warnings carefully before starting installation. Failure to
follow these instructions may result in a possible fire hazard and will void the warranty.
The 424WBST fireplaces are multi-side solid fuel, wood-
burning fireplaces. These are radiant models only and
include a preinstalled outside air kit.
Monessen Fireplaces and component parts have been
highly tested and will operate safely when installed in
accordance with instructions provided in this manual.
Carefully read and understand all instructions
beginning installation.
If you notice any damage to fireplace or component parts,
immediately report damage to your Monessen Fireplaces
dealer.
Only use MHSC components or the warranty will be
voided and a fire hazard may be created.
MHSC warranty will be voided by and MHSC disclaims
any responsibility for the following actions:
•
•
•
•
•
Consult local building codes to ensure that you are in
compliance installing the fireplace.
Fireplaces must be vented to the out-of-doors.
Fuels used in gas, wood-
burning or oil fired appliances, and the products of
combustion of such fuels, contain chemicals known to
the State of California to cause cancer, birth defects
and other reproductive harm.
California Health & Safety Code Sec. 25249.6
The fireplace should not be located in areas that create
drafts (ie: frequently opened doors and central heating air
inlets/outlets) that hamper the normal flow of air into the
fire.
If you plan to install a gas log, the gas line should be
installed framing the fireplace. The gas line must
be installed by a certified gas line installer.
Safety Information . . . . . . . . . . . . . . . . . . 2
Specifications and Framing . . . . . . . . . . 3
Parts Identification . . . . . . . . . . . . . . . . . 4
Chimney Requirements . . . . . . . . . . . . . 6
Planning Information . . . . . . . . . . . . . . . . 7
Installation ....................... 8
Replacement Parts . . . . . . . . . . . . . . . . 20
Accessories .....................22
3
424WBST Designer Woodburning Fireplaces
87D1506
424WBST specifications and framing.
12”
(305 mm)
956O”
(241 mm)
49(6”
(1267 mm)
36"
(914 mm)
Gas Line Access
FP702A
STR SPECS
9/24/98
added note 9/21/99
3/09
Outside Air
146”
(372 mm)
20”
(508 mm)
12" (305 mm)
11” (279 mm ) Dia.
C
L
24" Total
Unit Width
Framing Width
Will be 24" Minus
2 x (Drywall Thickness)
1856M”
(464 mm)
STR33 STR36 STR42
A33" 36" 42"
838mm 914mm 1067mm
B37" 40" 46"
940mm 1016mm 1168mm
C1856O" 20" 23"
470mm 508mm 584mm
D49(6" 49(6" 53(6"
1267mm 1267mm 1368mm
E526M" 526M" 566M"
1340mm 1340mm 1442mm
F11" 11" 1356O"
279mm 279mm 343mm
G8" 8" 11"
203mm 203mm 279mm
J266M" 29 6QE"356QE"
680mm 741mm 894mm
8” (203 mm ) Dia.
12”
(305 mm)
526M”
(1340 mm)
36” (914 mm)
40” (1016 mm)
296QE” (741 mm)
756O”
(191 mm)
21”
(533 mm)
37”
(940 mm)
756O”
(191 mm)
4
424WBST Designer Woodburning Fireplaces
87D1506
FP701a
424WBST Parts Identification.
AB
FP1545
hearth dimensions
1/05
424WBST 29" 17Z\,"
(737 mm) (435 mm)
FP1545
Hearth dimensions.
FP701a
STR Parts ID
Gas Line
Access
Outer
Dome
Outside Air
Access
Ledge Brackets
Header Standoffs
Flue Damper Control
(Inside)
Flue Collar
Outer Collar
Gas Line Knock-out
(Both Sides)
Brick liner on
Sides and Hearth
Air Inlet
Hearth
Wood Grate
Firebox
Metal Safety Strips,
shown not in place
(1, 2, or 3 Pieces)
Outside Air
Control
5
424WBST Designer Woodburning Fireplaces
87D1506
Insulation methods shown are optional
for cold climate, not a requirement for
unit operation.
FP704
Fireplace and chase parts identification.
FP704
STR (from FP528)
7/28/98
Termination Cap
Storm Collar
Pan Flashing
Draftstop
Finish Wall
Batt Insulation
(cut out around
firestop)
Firestop
Ceiling Level
Outer Dome
Refer to Figures 21
and 26 for clearance
information.
Ledge Brackets
Nailing Flange
Gas Access
(both sides)
Outside Air Cover Plate
Surround
Screen
Grate
Firebox
Outside Air
Control
6
424WBST Designer Woodburning Fireplaces
87D1506
0 0 0 0 0 3" 11"
1 0 0 0 0 8Z\₄" 20"
0 1 0 0 0 11Z\₄" 25Z\₄"
2 0 0 0 0 13Z\₂" 29Z\₄"
1 1 0 0 0 16Z\₂" 34Z\₄"
0 0 1 0 0 20Z\₄" 40³\₄"
2 1 0 0 0 21³\₄" 43Z\₂"
0 0 0 1 0 26Z\₄" 51Z\₄"
0 1 1 0 0 28Z\₂" 55Z\₄"
1 0 0 1 0 31Z\₂" 60Z\₄”
0 1 0 1 0 34Z\₂" 65Z\₂"
0 0 2 0 0 37Z\₂" 70³\₄"
1 1 0 1 1 41Z\₂" 77³\₄"
0 0 1 1 1 45" 83³\₄"
0 1 2 0 1 47Z\₄" 87Z\₂"
0 0 0 2 1 51" 94"
0 1 1 1 1 53Z\₄" 98"
0 0 3 0 1 56Z\₄" 103Z\₄"
0 1 0 2 1 59Z\₄" 108Z\₂"
0 0 2 1 1 62Z\₄" 113Z\₂"
0 1 3 0 1 64Z\₂" 117Z\₂"
0 0 1 2 1 68Z\₄" 124"
0 1 2 1 1 70Z\₂" 128"
0 0 0 3 1 74Z\₄" 134Z\₂"
0 1 1 2 2 78" 140³\₄"
0 0 3 1 2 81" 146"
0 1 0 3 2 84" 151Z\₄"
0 0 2 2 2 87" 156Z\₂"
0 1 3 1 2 89Z\₄" 160Z\₄"
0 0 1 3 2 93" 166³\₄"
0 1 2 2 2 95Z\₄" 170³\₄"
0 0 0 4 2 99Z\₄" 177³\₄"
0 1 1 3 2 101Z\₄" 181³\₄"
0 0 3 2 2 104Z\₄" 186Z\₄"
0 1 0 4 2 107Z\₄" 191Z\₂"
0 0 2 3 2 110Z\₄" 196³\₄"
0 1 3 2 3 114" 203Z\₄"
0 0 1 4 3 117³\₄" 209³\₄"
0 1 2 3 3 120" 213Z\₂"
0 0 0 5 3 123³\₄" 220"
¹⁄₂
G + H cannot exceed 20 feet.
Air Space Clearances:
SK8 (2-wall) = 1Z\₂"
The following safety rules apply to
offset installations (letters correspond
with illustration above):
Height of the chimney is measured
from the hearth to the chimney exit.
424WBST
Maximum: 90'0"
Minimum:
Without Elbows 15'6"
With 2 Elbows* 17'6"
With 4 Elbows* 21' 0"
Do not use more than 4 elbows per
chimney.
Attach the straps of the return (top)
elbow to a structural framing member.
The offset (first) elbow of any pair does
not have straps.
FP720
The chimney cannot be more than 30°
(45° in Canada) from the vertical plane in
any installation*.
The maximum length of the angled run
of the chimney system is 20 feet. (G
plus H cannot exceed 20 feet.)
A chimney support (Models TCS8A)
is required every 6 feet of angled run of
chimney. Chimney supports are required
for every 30 feet and 60 feet of vertical
chimney height above the hearth.
Determine the offset distance of your
chimney arrangement from the centerline
of the fireplace to the centerline of the
chimney where it is to pass through the
first ceiling.
This offset distance may not be
your full offset distance. See Examples 2
and 3.
IWF282
MBUF
5/26/96
OFFSET
RISE
FP282
* In Canada, two (2) SK845 are allowed.
Chimney system requirements.
D
RISE
BG
H
B
OFFSET
C
E
6 FT.
G
H
A
HEARTH
FLOOR
CHIMNEY
SECTION
CHIMNEY FLUE EXIT
ELBOW
FP720
STR/CVR
6/4/98
30˚
OFFSET
ELBOW
30˚
OFFSET
ELBOW
30˚
RETURN
ELBOW
30˚
RETURN
ELBOW
SKCS8
SUPPORT
Example 1 Example 2 Example 3
7
424WBST Designer Woodburning Fireplaces
87D1506
Preplanning an installation is very important to ensure
safety and to save time and money. An installer must
predetermine where a fireplace will be set and how the
chimney system will be run.
The 424WBST model uses MHSC SK8 (2-wall)
chimney systems.
A fireplace may only be mounted on the following sur-
faces:
1. A flat combustible surface.
2. A raised wooden platform.
3. A concrete block or other solid object placed beneath
each of the four (4) corners of the fireplace.
The fireplace be spaced 1/2" (13 mm) from a
combustible back wall and 1/2" (13 mm) from a com-
bustible side wall or support. (Page 14, Fig. 20)
Determine how the chimney will be run, length of run
and chimney components required to complete the
job. (Fig. 6) install a chimney below minimum
heights.
Major U.S. building codes specify a minimum chimney
height above the roof top. The “Ten Foot Rule” is a fire
safety rule and not a draft rule. To ensure proper draft,
it is recommended that you always meet or exceed the
“Ten Foot Rule,” especially when installing a termination
on a high pitch roof. (Fig. 7)
The key points of the "Ten Foot Rule" are:
1. If the horizontal distance from the chimney to the
peak of the roof is 10' (3 m) or less, the top of the
chimney must be at least 2' (610 mm) above the
peak of the roof, but never less than 3' (914 mm)
in height above the highest point where it passes
through the roof.
2. If a horizontal distance from the chimney to the peak
of the roof is more than 10' (3 m), a chimney height
reference point is established on the surface of the
roof a distance of 10' (3 m) from the chimney in a
horizontal plane. The top of the chimney must be
at least 2' (610 mm) above the reference point, but
never less than 3' (914 mm) in height above the high-
est point where it passes through the roof.
In planning a chimney system, it is important to know:
1. The height of a chimney is measured from the
hearth to the exit point on the termination.
2. A chimney cannot be offset more than 30° from a
vertical plane.
3. A chimney may run straight up or it may be neces-
sary to offset it to avoid obstructions.
4. The maximum length of an angled run (total chimney
system) is 20' (6m).
5. No more than 2 offsets (4 total 30° elbows in U.S./or
2 total 45° elbows in Canada) per fireplace may be
used.
6. A guy wire stabilizer is required for chimneys extend-
ing more than 6' (1.8m) above a roof line.
Installed lengths of chimney sections.
FP705
L1
L1
LTMODEL SK &
2 WALL CHIMNEY
TOTAL
LENGTH
(LT)
INSTALLED
LENGTH
(L1)
SK81
SK818
SK83
SK84
56O"
56O"
56O"
56O"
56O"
56O"
56O"
56O"
FP705
STR/CVR-CHIM SECT. INSTALLED LENGTH
5/28/98
AC246
Ten Foot Rule illustration.
2' Min.
2' Min.
3'
Min.
0 To 10'
3'
Min.
0 To 10'
AC246
4/1/96
Reference
Point
8
424WBST Designer Woodburning Fireplaces
87D1506
If you live in a cold climate, it is not required but
that you insulate fireplace
enclosure to eliminate cold air penetration as much
as possible.
Insulate base of fireplace with a non-combustible
insulation rated for a minimum of 300°F. Insulating
is for outside wall installations over
a concrete slab. If fireplace is installed on a platform,
insulation should be placed on top of the platform
fireplace is set. (Fig. 9)
When a fireplace is installed in a chase or on a
outside wall, enclosure should be treated like any
outside wall in a home. Insulation should be installed
on the inside wall as well as the outside wall(s). In
a chase, it is also a good idea to install a firestop at
the first ceiling level above the fireplace and enclose
the chase with sheeting material. Insulation may
then be installed above sheeting material to assure
the space around the fireplace is totally protected.
(Fig. 4)
When installing the chimney, caulk be-
tween outer pipe and firestop. It is vital that some air
be allowed to flow through this very thin gap.
WHEN INSTALLING A FIREPLACE
IN AN INSULATED ENCLOSURE, BE SURE ALL
REQUIRED AIR SPACES ARE MAINTAINED. (Page
14, Fig. 20)
The chimney system is supported by the fireplace for
vertical chimney heights less than 20' (6 m) above the
hearth. Chimney supports are required if the vertical
height exceeds 20' (6 m). Locate chimney supports
at ceiling holes or other structural framing at 20' (6 m)
heights. Spacing between chimney supports
exceed 20' (6 m). Use Chimney Support Model SKCS8
for SK8 chimney.
Support
provided by elbow straps fulfills the support require-
ment only if they are spaced as previously described. (A
chimney support is 2Z\₂" (64 mm) long when installed.)
Angled chimney runs require a support every 6' (1.8 m)
in addition to the elbow straps. Chimney supports are
used for this function. (Fig. 9)
A chase is a vertical box-like structure which encloses
the fireplace and/or chimney. Chases are typically built
on the outside of the house with fireplace opening cut
into the outer wall of a room. (Page 5, Fig. 4)
If you need help in determining fireplace location or
how the chimney system should be run, contact your
Monessen dealer for assistance.
FP284
Chimney support installation
IWF284
MBUF
5/25/96
Chimney Sup-
port Strap
SKCS8
9
424WBST Designer Woodburning Fireplaces
87D1506
Framing can be constructed before or after the fireplace
is set in place, however, most installers build the frame
before setting the fireplace.
Frame fireplace with 2 x 4 lumber or heavier materi-
als. Refer to framing dimensions in Figures 1, 2, 3 or 4
for basic fireplace specifications. Headers and support
studs must be turned on end as illustrated on Page 5,
Figure 4.
Framing should be positioned to accommodate
wall covering and fireplace facing material.
FP706
Insulating between platform and fireplace.
FP706
STR/CVR
6/1/98
Hard, Flat
Surface
Insulation
Plateform
Since you have already preplanned the chimney run,
you should know exactly how the installation is to
be accomplished — how much pipe is required, the
number of elbows, if any, and type of termination to be
used.
REPORT TO YOUR DEALERS ANY
PARTS DAMAGED IN SHIPMENT, SPECIFICALLY
CHECK THE END CONNECTION OF CHIMNEY SEC-
TIONS AND ELBOWS.
The 424WBST model uses MHSC SK8 (2-wall)
chimney systems.
To locate the centerline of the flue put the fireplace in
final position and place a plumb bob from the ceiling to
the center of the fireplace flue collar. Mark this spot on
the ceiling. Draw a line through that mark to either side
of the firebox and indicate dimension X to locate the
side wall framing. (Fig. 10) Be sure to observe clear-
ance requirements for side and parallel combustible
walls as noted in Page 16, Figure 23.
In order to clear an obstruction, it may be necessary to
offset chimney from vertical. This is accomplished by
using MHSC elbows. Use the 30° Offset Elbow table on
Page 6 to determine proper offset and parts required.
Each offset requires two (2) elbows. The second elbow
is equipped with support straps. It is very important to
install the second elbow in each offset as close to the
ceiling or support as possible so that the elbow straps
can be secured to framing members to help support the
weight of the chimney.
Determine offset distance of your chimney arrangement
from centerline of fireplace to centerline of chimney
where it is to pass through ceiling.
Locate center point of the chimney on ceiling as though
a straight up chimney arrangement is to be used.
Measure your offset dimension from the chimney center
point on the ceiling.
10
424WBST Designer Woodburning Fireplaces
87D1506
The size of the hole in ceiling will vary with the angle at
which the chimney passes through ceiling.
Drive a nail up through ceiling at marked chimney cen-
ter point. Go to floor above and see where hole will be
cut. Check to see where existing ceiling joists and other
possible obstructions are located...i.e. wiring, plumbing
etc... If necessary, re-position chimney and/or fireplace
to avoid obstructions.
Cover fireplace collar opening and cut proper sized
chimney hole in chimney. The SK8 pipe allows you to
run pipe through a typical 16” on center joist without
cutting joists.
Frame the ceiling chimney hole as shown in Figure
12. It is good practice to use framing lumber that is the
same size as the ceiling joists; this is a requirement at
attic level.
The following table gives firestop spacer model num-
bers:
FP707
STR/CVR
LOCATE CENTER LINE
6/1/98
STR 33: 19" (483mm)
STR36 / CVR36: 205/O" 521mm)
STR42 / CVR42: 235/O" (597mm)
MODEL X =
2056O”
(521 mm)
Locate centerline of chimney with plumb line.
FP707
Actual Centerpoint
Chimney
Centerline
Side of STR
Plumb Line
Plumb Bob
Imaginary
Centerpoint
Typical frame for ceiling chimney hole.
FP551A
FP551A
BR/BC
9/23/98
1456O"1456O"
Existing
Ceiling
Joists
Chimney
Hole
New Framing
Members
Ceiling chimney hole sizes necessary for installing
firestop spacer.
8" Flue SKFS2A SKFS6A
"SK" Series 14Z\₂" x 14Z\₂" 14Z\₂" x 25Z\₂"
(368 x 368 mm) (368 x 648 mm)
The of the frame the same
as the hole size selected from Figure 12 in order to
provide the required air space (1Z/₂" (38 mm) with SK8
between the outside diameter of the chimney and the
edges of the framed ceiling hole.
11
424WBST Designer Woodburning Fireplaces
87D1506
Slide fireplace into position.
Lift the fireplace front slightly and slide the metal safety
strips under front bottom edge about 1Z\₂" (38 mm), al-
lowing the remainder to extend in front of firebox. Over-
lap strips at least 1/2" (13 mm) to provide a positive
joint. (Flat safety strips are packed with fireplace.) (Fig. 13)
Safety strips are used to ensure that any combustible
materials in front of the fireplace are protected even
though a noncombustible hearth extension is required.
If fireplace is to be elevated above the floor, a “Z”
shaped metal safety strip must be fabricated and used
to protect combustible surfaces in front of the fireplace.
This “Z” shaped safety strip is not provided but must be
fabricated of metal with each horizontal leg at least 1Z\₂"
(38 mm) wide and equal in length to the metals strips
provided with the fireplace.
Safety strips are not required over non-com-
bustible floors where all supports at the base of the
fireplace are noncombustible.
Eight (8) nailing flanges are supplied with the fireplace
(found on the fireplace hearth). To level the box and
secure it firmly in place, remove the nailing flanges from
the hearth and install at the sides of the fireplace as
shown in Figure 14.
An outside air kit damper is installed in 424WBST Fire-
places. If desired, or if local codes mandate the use of
an air kit, then an AK-MST is required to complete the
installation (from air kit to the outdoors). If the outside
air kit is to be used, the AK-MST Air Termination Kit
be installed the fireplace is enclosed.
Refer to the AK-MST instructions for field installation.
The outside air kit control is located in the lower left
hand side of the fireplace behind the screen panel. (Fig.
15) To operate, simply lift up to close or push down to
open .
WF708
STR/CVR
5/29/98
Metal Safety
Strips
(1, 2 or 3 pieces)
56O" (13mm)
Min. Overlap
56O"
(38mm)
"Z"
Safety
Strip
Fire-
Place
Plat-
Form Hearth Ext.
(not supplied)
FP708
Safety strip installation.
FP709
Fasten fireplace in position.
FP709
7/28/98
STR/CVR
Model STR
Standoffs
Side-Nailing
Flanges
Outside air operation.
CLOSED
OPEN
WF 710
OUTSIDE AIR LEVER
WOOD FIREPLACES
5/28/98
FP710
12
424WBST Designer Woodburning Fireplaces
87D1506
Start by attaching the first chimney section to the collar
on top of the fireplace.
Install the pipe as pictured in Figure 16. When you
get a good lock, you will hear the pipe clearly snap
together. Once sections are snap-locked in place, it is
extremely difficult to get them apart.
When installing elbows, only outer pipe will snap-
lock. Middle pipes simply slide into position. Be sure
to always attach straps on upper elbow to a structural
framing member. (Fig. 17)
Continue installing the pipe as required until pipe is
installed up through the ceiling. At this point, you must
install a firestop spacer. Refer to Figure 18 for appropri-
ate spacer orientation.
A firestop spacer is used to keep pipe spaced properly
and required for safety.
Nail the firestop spacer (at each corner) to the framing
members of the ceiling hole. A firestop spacer
is not required at the roof.
Hole sizes listed in Figure 12 for angled firestop spac-
ers provide minimum required air space to chimney
pipe for ceiling thickness up to 8" (203 mm). When
combined thickness of ceiling material, ceiling joists and
flooring material exceeds 8" (203 mm), adjustments
must be made in framing to assure that minimum air
spaces to chimney are maintained.
Figure 18 shows different installation procedures for
both an area that is an attic and an area that is not an
attic.
If the area above the ceil-
ingan attic, posi-
tion the firestop spacer
with the flange on the ceil-
ing side and the angled
portion extending up into
the hole.
If the area above the
ceiling an attic, position
the firestop spacer with
the flange on the top of
the framed hole and the
angled portion extending
down into the hole.
FP711
Install pipe, listening for the snap-lock to fasten.
UP
Lance
Hem
Pipe Rim
Pipe
Rim
WF711
STR/CVR
5/28/98
Pipe Section
Attach straps to a structural framing member.
FP270/271
FP270/271
CR Series
2/19/99 djt
Support Structure
Elbow Strap
(must be tight)
Ceiling
Hole Fram-
ing
Angle Firestop
Chimney Support
Strap
(must be tight)
FP593
SR/C
11/20/97
Installing firestop spacer.
FP593
Nails (4)
Firestop
Spacer
Joist
Joist
Firestop
Spacer
Nails (4)
If the attic insulation shield is used, the
firestop is not required in the attic installation.
13
424WBST Designer Woodburning Fireplaces
87D1506
Consider this dimension when determining how many
straight chimney sections are needed.
Chimney supports are generally used in long
runs in a chase installation.
If you encounter additional ceilings, repeat same steps
required for first ceiling installation. Refer to firestop
illustration on Page 12, Figure 18.
Run pipe to roofline. Since chimney system must be
vented to the out-of-doors, you use an approved
termination.
If a chase is used, refer to the installation manual pro-
vided with the termination cap.
Use same procedure detailed in locating centerpoint of
the flue system.
Drive a nail up through roof at the centerpoint. This will
determine center point on outside of the roof.
Size of roof hole varies with the type of chimney termi-
nation installed. Refer to installation instructions pro-
vided with the chimney termination to find correct size
of roof hole.
There must be an air space (1Z\₂" (38 mm) with SK8
between outermost portion of chimney sections and any
adjacent combustible surfaces. (Fig. 20) (Combustible
surfaces include burnable materials such as: ceiling
members, joists, flooring, combustible insulation and
roof structures.)
Mark an outline of the roof hole around the center of the
point nail. Hole dimensions given in the chim-
ney top installation instructions are dimen-
sions; therefore, the hole size must be marked on the
roof accordingly.
Cover the opening of the installed chimney so debris
cannot get into the system.
Cut and frame the hole. It is good practice to use fram-
ing lumber that is the same size as the rafters. Install
the frame securely because the chimney top and flash-
ing anchored to the frame must be able to withstand
heavy winds.
Firestop spacers are not available for nor are they re-
quired on vertical walls.
put any sealant around the area where the
outer pipe slides through the firestop spacer. If you
seal this area,
In Canada, an attic insulation shield is required to
prevent attic insulation from contacting the chimney
section. If the attic insulation shield is used, the
firestop is not required in the attic installation. Fram-
ing dimensions for the chimney hole should measure
14Z\₂" x 14Z\₂" (368 x 368 mm). (An attic shield MUST
be installed on top of attic joists (above the floor level).
(Fig. 19)
In the U.S., it is a good idea, although not al-
ways required, to install an attic insulation shield where
blown-in insulation is planned to be used in the attic.
Install the attic insulation shield with the flanges on its
base extending down into the framing hole. Nail each
corner of attic insulation shield to the framing members
of the ceiling hole using 8d nails. Attic shields are not
required at the roof.
FP263
Attic shield installlation (Canadian requirement).
IGF263
MBUF
5/9/96
Attic Insula-
tion Shield
Nails
(4 required)
Attic Joist
Ceiling
Base
Flanges
Continue attaching pipe sections to complete system
to next level always being careful that the pipe is firmly
snapped locked in place before proceeding to next pipe
section.
If chimney supports are required, they are installed the
same as elbows. Nail chimney support straps to ad-
jacent structural framing, as shown on Figure 8, Page
8. Bend straps as necessary and make sure they are
secure so they will support the weight of the chimney.
A chimney support is 2Z\₂" (64 mm) long when installed.
14
424WBST Designer Woodburning Fireplaces
87D1506
Since you have already preplanned the height of your
termination according to the Ten Foot Rule, continue to
install pipe to the predetermined height.
Check the chimney top installation instructions for
details on how high above the roof top the chimney sec-
tions (all pipes) should extend.
Follow the installation instructions provided with the
chimney termination you have selected.
Refer to Page 5, Figure 4 for an illustration of a typical
chase installation.
Treatment of firestop spacers and construc-
tion of chase may vary with type of building. These
instructions are not a substitute for local building codes.
You check your local building codes to determine
specific requirements for your city or state.
Other building materials may be required in addition to
Firestop Spacers.
All joints between the finished wall and the
fireplace surround (top/sides) must be sealed with non-
combustible material to prevent cold air leakage into the
room. Only noncombustible material may be applied
to the facing of the fireplace surround. (Black painted
area) (Fig. 20)
Finish the wall with material of your choice.
If a combustible
material is used below a flat mantel shelf, consult your
local building codes for minimum clearance from top of
fireplace opening to bottom of mantel shelf.
No side wall protection is required for fireplaces
installed at 45° to two (2) side walls (corner installation).
Adjacent combustible side walls that are within 16" (406
mm) of fireplace opening must be protected with an
MHSC Wall Shield Model SP40 or a specifically built
wall shield described in Figure 20 & 24.
Often a decorative surround or vertical portion of the
mantel is desired. If this is constructed of any combus-
tible material, it must be within the safe zone indicated
in Figure 24.
FP717
Minimum clearances to combustibles.
Front View Side View
Standoff
Combustible framing material MUST NOT
penetrate AIR SPACE (shaded areas).
Air Space Clearances
Only noncombustible
material may be applied
as facing to the black
fireplace surround.
Wall
Shield
Hearth
Extension
0" Clearance
to Floor
Firestop
OUTER
DOME
1/2" (13 mm)
Air Space
to Sides
1/2" (13mm)
air space to sides
FP717
STR/CVR
AIR SPACES
9/23/98
156O"
(38 mm)
Maintain
1/2" (13 mm)
air space
to sides
15
424WBST Designer Woodburning Fireplaces
87D1506
MA81
rev. 8/5/97
156O"
Ref.
Combustible materials are
permitted within a shaded area
shown in Figure 23, titled
Minimum Wall Clearances.
*
* *
MA81
Combustible mantel clearances.
Face Plate
FP721
STR/CVR
6/4/98
56O"
1/2"
*
12"
(305mm)
Min.
12"
(305mm)
Max.
1/2"
12"
(305mm)
Min.
12"
(305mm)
Max.
6“
(159mm)
Min.
FP721
Fireplace surround flush with finished wall.
Finished Wall
Standoff
2 x 4 Stud
Noncombustible Mate-
rial
Header
Ledge Bracket
Fireplace
Front
Fireplace Opening
* Minimum width from top of sur-
round to bottom of screen rail
Combustible
Mantel and Trim
Combustible
Mantel and Trim Standoff
Finished Wall
2 x 4 Stud
Noncombustible Mate-
rial
Header
Ledge Bracket
Fireplace
Front
Fireplace Opening
Noncombustible Facing Material
Finished Wall
2 x 4 Stud
Must be sealed with
noncombustible material
Fireplace
Front
16
424WBST Designer Woodburning Fireplaces
87D1506
All joints (top, bottom and sides) where wall or deco-
rative facing material meets fireplace surround must
be completely sealed with a noncombustible material.
(Figs. 20 and 24)
The special wall shield design described in Figure 20 is
an alternate method of adding protection to side walls
and can be used in place of the SP40 with the same
wall clearances specified for the SP40. Rt must =1.85
minimum.
1. Manville - CERAFORM 126, K=.27,
1/2 inches thick
2. MHSC - EH2416, K = .458,
1 inch thick required.
FP723
Minimum firebox dimensions from combustible materials.
FP723
STR/CVR Side Wall clearances
6/21/98
AA
B
B
C
CC D
Perpendicular Side Wall
Parallel Side Wall
(for on-site construction)
Parallel Side Wall A 44"
to Movable Doors (1118 mm)
Perpendicular B 16"
Side Wall to Firebox Opening (406 mm)
Air Space to Sides C 1/2"
or Back of Unit (13 mm)
17
424WBST Designer Woodburning Fireplaces
87D1506
Alternate noncombustible materials may be used
providing the (total) thermal resistance (Rt value) of the
alternate material employed is greater than or equal to
R = 1.09. Thermal resistance (R) or thermal conductivity
(K), may be obtained from manufacturer of the material.
Factors are related by the formula K = 1/R.
T = given thickness
R = thermal resistance for a given thickness (T)
K = thermal conductivity
Noncombustible material with a lower R value may
be used, provided thickness of material is sufficiently
greater to maintain an equivalent (total) thermal resis-
tance (Rt).
A hearth extension is required to protect a combustible
floor in front of the fireplace. Refer to Figure 24 for mini-
mum dimensions and mounting detail.
The hearth extension described in Figure 24 must be a
durable noncombustible material with a minimum (total)
Rt value of 1.09; refer to Figure 25 for examples. The
overall height (above a combustible floor), depth and
width must be as indicated, with the extension centered
to the fireplace opening.
The top of the insulation material must be covered with
a noncombustible decorative covering a piece of
.018” minimum sheet metal, to protect hearth extension
material. (Fig. 24)
Secure the hearth extension to the floor to prevent
shifting, using trim molding or other similar means at
three (3) outer edges. Seal crack between the fireplace
hearth and hearth extension with a noncombustible
material. (Figs. 24 and 26)
Minimum Wall Clearances
WITH
Noncombustible
Surround Facing
WITHOUT
Noncombustible
Surround Facing
Minimum Hearth Extension Dimensions
(for On-Site Construction)
G
HG
J
Seal cracks
between the
fireplace
and hearth
extension with
noncombustible
material
Safety strips
must overlap
56O" minimum
May install
noncombustible
decorative
covering
OR .018" min.
sheet metal Fireplace
Hearth
Combustible
Floor
Minimum
Insulation
Value "R"
4" MIN.
FP714
STR/CVR
6/4/98
Firebox
Opening
A - Min. clearance
to combustible
perpendicular wall
B - Min. clearance
to combustible
perpendicular wall when
using noncombustible wall shield*
Side
Wall Side
Wall
F**
C**
E
ED
4" BRICK
(Example material)
Combustible material permitted within shaded area.
* Noncombustible wall shield requires 1" MHSC
EH2416 insulation (minimum R Value = 1.09) between
decorative noncombustible rigid covering and combustible wall.
Minimum height and width is 40" x 40".
** Dimension/degree of angle will vary depending on thickness
of noncombustible surround facing.
4"
Shaded area starts
1/2" away from
edge of unit
A B C D E F G H J K
424WBST 16" 12" 48° 41° 18" 14" 8" 16" 48" 24"
(406 mm) (305 mm) (457 mm) (356 mm) (203 mm) (406 mm) (1219 mm) (610 mm)
FP714
Combustible side wall protection and hearth extension dimensions.
18
424WBST Designer Woodburning Fireplaces
87D1506
To determine the thickness required for any mate-
rial:
COMMON MATERIALS AND FACTORS
MATERIAL K* RMINIMUM
THICKNESS
EH2416
Common Brick
0.458
5.0
1.09 0.50 in.**
0.10 5.46 in.**
(MHSC)
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR/˚F/IN
** Thickness of Listed Material
FP533ADD
Addendum
6/1/99 djt
8/4/99 changed .2 to .1
one inch to 1/2 inch djt
FP533AD
Hearth extension material factors.
FP719
STR/CVR finish wall treatments
5/28/98
Wall Covering
Noncombustible
Decorative
Facing
Noncombustible
Decorative
Covering
Seal all cracks
between fireplace
surround and wall
materials with
noncombustible
material.
Seal crack
between fireplace
and hearth extension
with noncombustible
material.
2x4" Header -
Do not notch at
standoffs.
2x4"
Stud
Safety Strips -
Must be overlapped
56O" minimum.
Hearth Extension
Insulation
Side View
NOTE: 5/O"
air space
between
Outer Dome
and
combustible
materials
5/O"
5/O"
Outer Dome
FP719
Finish wall treatments and gap sealing.
NEW K of new material (per inch) thickness
required = X of listed
thickness K of listed material (per inch) material
T (new) = 5.0 / 0.458 x 0.50 in. = (new required
thickness).
&0
4YPE"FLOOR
DJT
Safety Strips
Must be Over-
lapped 1/2" Min.
Minimum Insulation
Value R-0.94
1/4" Min. Thickness
Combustible
Floor
Noncombustible
Material 7Z\₂"
Max. Thickness
Seal Cracks Between Fireplace and Hearth
Extension with Noncombustible Material
Noncombustible
Material
Lower Surround
Fireplace
Hearth
FP1170
Hearth extension dimensions.
2”
(51 mm)
2”
(51 mm)
Maximum
14”
(356 mm)
Maximum
10”
(254 mm)
A
A
&0
ALCOVEINSTALLATION
Minimum
33”
(838 mm)
Minimum
36” (914 mm)
6”
(152 mm)
Minimum
Minimum .030 Thick Stain-
less Steel Plate
Insulation with Minimum R
Value of 2.75
Minimum .030
Thick Stainless
Steel Plate
If noncombustible material is not used between the
stainless steel plate and fireplace opening, the steel must
be attached to the front of the unit a minimum of four (4)
places on each piece with sheet metal screws no longer
than 1/2".
Recessed installation.
FP1608
Hearth
Extension
Hearth Extension
Noncombustible
Material
(if desired)
Insulation
with Minimum
R Value
of 2.75
19
424WBST Designer Woodburning Fireplaces
87D1506
Monessen Fireplaces are designed to accept a 1/2"
(13 mm) gas line for installation of an approved gas
appliance. (MHSC manufactures a wide variety of gas
logs for use in Monessen fireplaces.)
Be sure to have the appliance installed in accordance
with building codes.
Gas connection may enter from either left or right side
of the fireplace.
Locate appropriate gas line in the outer casing of fire-
place and remove insulation from gas line tube. (Fig. 29)
From inside the fireplace, locate the knockout on the
firebrick -- be sure you are on the appropriate or "gas
line" side of the fireplace. Using a flat bladed screw-
driver or small chisel and hammer, carefully tap around
the knockout until it loosens and falls out.
Install 1/2" (13 mm) certified gas pipe through opening.
After gas pipe installation is complete, use insulation
that was removed from gas line tube to repack space
around the pipe. Material should be inserted from
outside of the fireplace and packed tightly to totally seal
between the pipe and tube.
Local codes may require removal of flue damper
when installing any type of gas appliance in a fireplace.
When installing an ANSI Z21.11.2 ventless ap-
pliance, the finishing material used for the mantel must
be rated at 250°F or greater.
BTU input of a gas appliance installed in fireplace
should be rated less than 100,000 BTU/Hr.
Gas pipe installation is intended for connection to a
decorative gas appliance only when (1.) incorporating
an automatic shutoff device and (2.) complying with the
Standard for Decorative Gas Appliances for Installation
in Vented Fireplaces (ANSI Z21.60) CSA draft re-
quirements for Gas-Fired Log Lighters for Woodburning
Fireplaces (Draft No. 4, August 1993).
Decorative gas appliance should be installed in accor-
dance with the National Fuel Gas Code, ANSI Z223.1/
NFPA 54 (latest edition).
1"
FP716
CVR/STR Gas Access
5/29/98
FP716
Gas line access.
Hole in
Outer
Casing
Gas Line
Tube
Supply Line
Repack Insu-
lation
Ceramic
Knockout
(Both Sides
on STR)
Hole in
Outer Cas-
ing
Only unvented gas log sets which have been found to comply
with the Standard for Unvented Room Heaters, ANSI Z21.11.2,
are to be installed in this fireplace.
If installing an unvented gas log set, refer to statement below:
20
424WBST Designer Woodburning Fireplaces
87D1506
961
MHSC reserves the right to make changes in design, materials, specifications, prices and discontinue colors and products at any time, without
notice.
5
1, 2, 3
4
6
7
a
b
c
d
8
9
10
11
961
STR parts
5/16/00 djt
12
1. Flue Damper RP102
2. Damper Handle 7548170
3. Damper Handle Push Nut 7512903
4. Screen Rod Assembly (two per fireplace) 3030126
5. Screen Assembly (four per fireplace) 7554338
6. Screen Pulls (four per fireplace) 5584139
7a. Firebrick - Hearth 3102103
7b. Firebrick - Side Ashlip (two per fireplace) 3102102
7c. Firebrick - Side (two per fireplace) 9079147
7d. Side Filler (four per fireplace) 3079148
8. Top Brick Retainers (four per fireplace) 3079130
9. Cable Clips (eight per fireplace) 7512135
10. Nailing Flange (eight per fireplace) 5069164
11. Basket Grate 2056100
12. O.S.A. Assy. 20003212
Table of contents
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