INSTALLATION INSTRUCTIONS
MPB B-Vent
Gas Fireplaces
P/N 506015-05 Rev. NC 07/2012
This manual is one of a set of two supporting this product.
Refer to P/N 506017-04 for Care and Operation Instructions.
Ce manuel est disponible en francais, simplement
en faire la demande. Numéro de la pièce 506223-45.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
INSTALLATEUR : Laissez cette notice avec l’appareil.
CONSOMMATEUR : Conservez cette notice pour
consultation ultérieure.
WARNING
/
AVERTISSEMENT
MODELS
MPB33CNM
MPB33CPM
MPB35CNM
OTL Report No. 116-F-36d-5
Please read and understand these instructions
MILLIVOLT: ELECTRONIC:
MPB35CPM
MPB40CNM
MPB45CNM
Portland
US
before starting installation.
MPB33CNE
MPB35CNE
/
AVISO
MPB40CNE
MPB45CNE
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WARNING: If the information in these instructions
is not followed exactly, a fire or explosion may
result, causing property damage, personal injury,
or death.
$ONOTSTOREORUSEGASOLINEOROTHERFLAMMABLE
vapors and liquids in the vicinity of this or any other
appliance.
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s$ONOTTry to light any appliance.
s$ONOTTOUCHANYELECTRICALSWITCHDONOTUSEANY
phone in your building.
s)MMEDIATELYCALLYOURGASSUPPLIERFROMA
neighbor’SPHONE&OLLOWTHEGASSUPPLIER’s
instructions.
s)FYOUCANNOTREACHYOURGASSUPPLIERCALLTHEFIRE
department.
- Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
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AVERTISSEMENT : Assurez-vous de bien suivre les
instructions données dans cette notice pour réduire au
minimum le risque d’incindie ou d’explosion ou pour
éviter tout dommage matériel, toute blessure ou la mort.
- Ne pas entreposer ni utilizer d’essence ni d’autres vapeurs
ou liquides inflammables dans le voisinage de cet appareil
ou de tout autre appareil.
15%&!)2%3)6/533%.4%:5.%/$%52$%'!:
s.EPASTENTERDALLUMERDAPPAREIL
s.ETOUCHEZÜAUCANINTERRUPTEUr. Ne pas vous servir des
téléphones se trouvant dans le bâtiment où vous trouvez.
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un voisin. Suivez les instructions du fournisseur.
s3IVOUSNEPOUVEZREJOINDRELEFOURNISSEURDEGAZ
appelez le service des incindies.
- ,’installation et l’entretien doivent être assurés par un
installateur ou un service d’entretien qualifié ou par le
fournisseur de gaz.
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LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
TABLE OF CONTENTS
Packaging .................................................... 2
Introduction ................................................. 2
General Information ..................................... 2
Requirements for the
Commonwealth of Massachusetts ............ 4
Cold Climate Insulation ................................ 4
Manufactured Housing ................................. 4
Location ........................................................5
Vent Termination Clearances ....................... 5
Appliance and Vent Clearances .................... 6
Pre-Installation Steps ................................... 7
Typical Installation Sequence ...................... 7
Detailed Installation Steps ............................ 7
Step 1. Framing ............................................ 7
Framing Specifi cations ................................ 8
Fireplace Specifi cations .............................. 9
Step 2. Routing Gas Line ............................. 9
Step 3. Installing Vent System ................... 10
Step 4. Field Wiring ................................... 11
Step 5. Wiring Optional
Forced Air Blower Kit .................... 12
Step 6. Connecting Gas Line ..................... 12
Step 7. Installing Optional Outside Air Kit ..13
Step 8. Verifying Appliance Operation ........... 14
Step 9. Installing Volcanic Stone, Glowing
Embers, and Logs ........................ 14
Step 10. Removing and
Installing the Glass Door ............. 19
Step 11. Burner Adjustments ..................... 19
Step 12. Testing Vent Operation ..................21
Step 13. Hood Installation .......................... 21
Step 14. Finishing Requirements ............... 21
Step 15. Attaching Safety-in-Operation
Warnings ............................ 22
Gas Conversion Kits ......................... 23
PACKAGING
The assembled vented gas fi replace is
packaged with:
• (1 set) Logs (packaged in a carton inside
the fi rebox).
• (1 bag) Volcanic Stone (included in the
fi rebox or bottom compartment).
• (1 bag) Glowing Embers (in bottom
compartment).
• Literature Kit (envelope in bottom compartment containing Care and Operation
Instructions, Installation Instructions,
Safety-In-Operation Warning Labels,
Warranty).
• (1) Hood (behind the top louver assembly).
INTRODUCTION
The Millivolt appliances have a millivolt gas
control valve with piezo ignition system. If
any optional accessories that will require
electrical power are to be installed, the
electrical power must be provided at the time
of appliance installation.
The Electronic appliances are designed
to operate on natural or propane gas. An
electronic intermittent pilot ignition system
provides safe, effi cient operation. External
electrical power is required to operate these
units. In the event of a power outage, four (4)
"AA" batteries (in battery holder) provide
backup power for appliance operation
(excluding [optional] blower).
APPROVED VENT COMPONENTS
These vented gas fi replaces are designed for
residential applications. They must be installed
with approved Type-B, double wall vent pipe
systems and a listed vent termination routed to
the outside atmosphere. Use only the proper
size listed below.
REQUIRED PIPE DIAMETER:
MPB33 series: Requires 4 in. (102 mm)
MPB35 series: Requires 5 in. (127 mm)
MPB40 series: Requires 5 in. (127 mm)
MPB45 series: Requires 6 in. (152 mm)
GENERAL INFORMATION
WARNING
Young children should be carefully supervised when they are
in the same room as the appliance. Toddlers, young children
and others may be susceptible
to accidental contact burns. A
physical barrier is recommended
if there are at risk individuals in
the house. To restrict access to
a fi replace or stove, install an
adjustable safety gate to keep
toddlers, young children and
other at risk individuals out of
the room and away from hot
surfaces.
AVERTISSEMENT
Les jeunes enfants devraient être
surveillés étroitement lorsqu’ils
se trouvent dans la même pièce
que l’appareil. Les tout petits,
les jeunes enfants ou les adultes
peuvent subir des brûlures s’ils
viennent en contact avec la surface chaude. Il est recommandé
d’installer une barrière physique
si des personnes à risques habitent la maison. Pour empêcher
l’accès à un foyer ou à un poêle,
installez une barrière de sécurité; cette mesure empêchera les
tout petits, les jeunes enfants et
toute autre personne à risque
d’avoir accès à la pièce et aux
surfaces chaudes.
WARNING
B-Vent appliances are not
designed to operate in negatively
pressured environments (pressure within the home is less than
pressures outside). Signifi cant
negatively pressured environments caused by weather, home
design, or other devices may
Children and adults should be alerted to
the hazards of high surface temperature
and should stay away to avoid burns or
clothing ignition.
Les enfants et les adultes devraient
être informés des dangers que posent
les températures de surface élevées
et se tenir à distance afi n d’éviter des
brûlures ou que leurs vêtements ne
s’enfl amment.
impact the operation of these
appliances. Negative pressures may result in poor fl ame
appearance, sooting, damage to
property and/or severe personal
injury. Do not operate these
appliances in negatively pres-
2
sured environments.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
DO NOT ATTEMPT TO ALTER OR MODIFY
THE CONSTRUCTION OF THE APPLIANCE
OR ITS COMPONENTS. ANY MODIFICATION
OR ALTERATION MAY VOID THE WARRANTY, CERTIFICATION AND LISTINGS OF
THIS UNIT.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
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.
WARNING
Failure to comply with these installation instructions will result
in an improperly installed and
operating appliance, voiding its
warranty. Any change to this appliance and/or its operating controls
is dangerous.
WARNING
Clothing or other flammable
material should not be placed
on or near the appliance.
AVERTISSEMENT
On ne devrait pas placer de
vêtements ni d’autres matières
infl ammables sur l’appareil ni à
proximité.
WARNING
Any safety screen or guard removed for servicing the appliance must be replaced prior to
operating the appliance.
AVERTISSEMENT
Tout écran ou protecteur retiré
pour permettre l’entretien de
l’appareil doit être remis en
place avant de mettre l’appareil
en marche.
WARNING
Improper installation or use of
this appliance can cause serious
injury or death from fi re, burns,
explosion or carbon monoxide
poisoning.
WARNING
Failure to position the parts in
accordance with these diagrams
or failure to use only parts
specifi cally approved with this
appliance may result in property
damage or personal injury.
AVERTISSEMENT
Risque de dommages ou de
blessures si les pièces ne sont
pas installées conformément à
ces schémas et ou si des pièces
autres que celles spécifi quement
approuvées avec cet appareil sont
utilisées.
Note: Installation and repair should be
done by a qualifi ed service person. The
appliance should be inspected before use
and at least annually by a professional
service person. More frequent cleaning
may be required due to excessive lint from
carpeting, bedding material, etcetera. It
is imperative that control compartments,
burners and circulating air passageways of
the appliance be kept clean.
Remarque: L’installation et la
réparation devrait être confi ées à un
technicien qualifi é. L’appareil devrait
faire l’objet d’une inspection par un
technicien professionnel avant d’être
utilisé et au moins une fois l’an par la
suite. Des nettoyages plus fréquents
peuvent être nécessaires si les tapis,
la literie, et cetera produisent une
quantité importante de pous-sière. Il
est essentiel que les compartiments
abritant les commandes, les brûleurs
et les conduits de circulation d’air de
l’appareil soient tenus propres.
Do not use these appliances if any part
has been under water. Immediately
call a qualifi ed, professional service
technician to inspect the appliance
and to replace any parts of the control
system and any gas control which have
been under water.
Ne pas utiliser cet appareil s’il a été
plongé, même partiellement, dans
l’eau. Appeler un technicien qualifi é
pour inspecter l’appareil et remplacer
toute partie du système de commande
et toute commande qui a été plongée
dans l’eau.
Only trim kit(s) supplied by the
manufacturer shall be used in the
installation of this appliance.
Seules les trousses de garniture
fournies par le fabricant doivent être
utilisées pour l’installation de cet
appareil.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
These appliances comply with National
Safety Standards and are tested and listed
by OMNI-Test Laboratories, Inc. (Report
No. 116-F-36d-5) to ANSI Z21.50b-2009 (in
Canada, CSA 2.22b-2009), and CAN/CGA-
2.17-M91 (R2009) in both USA and Canada,
as vented gas fi replaces.
Both millivolt and electronic versions of
these appliances may be used in bedrooms
only when the room is an "uncon ned
space" as de ned by the National Fuel Gas
Code. Use in bedrooms may not be allowed
by your local building codes. You should
obtain prior approval from the Authority
having jurisdiction prior to installation.
MISC. CODES / STANDARDS
The Installation must conform to local codes or,
in the absence of local codes, with the National
Fuel Gas Code, ANSI Z223.1 / NFPA 54—latest
edition (In Canada, the current CAN/CGA-B149.1
installation code).The appliance, when installed,
must be electrically grounded and wired in
accordance with local codes or, in the absence
of local codes, with the National Electrical Code,
ANSI/NFPA 70—latest edition, or the Canadian
Electrical Code, CSA C22.1—latest edition.
Provide adequate clearances around air
openings and adequate accessibility clearance
for service and proper operation. Never obstruct
the front or back openings of the appliance.
These appliances are designed to operate
on natural or propane gas only. The use
of other fuels or combination of fuels will
degrade the performance of this system and
may be dangerous.
These replaces are designed as decorative
appliances and are not intended for use as
area heaters. They must not be equipped
with wall thermostats or remote controls
with thermostat functions.
OUTSIDE COMBUSTION AIR HOOK UP
These appliances are equipped with an
integral combustion air door and actuator arm.
Combustion air kits are optional. Install as
shown in Step 7 on Page 13.
These appliances must not be connected to a
chimney or fl ue serving a separate solid fuel
burning appliance.
Both millivolt and electronic systems can be
operated during a power outage, and feature
manually operated hi-low fl ame control. The
BTU Input for these appliances is shown in
Table 1.
Natural Gas Propane Gas
Model Input Rate
MPB33 13,500 to
MPB35 16,000 to
MPB40 24,000 to
MPB45 24,750 to
Table 1: BTU Input Ratings
(BTU/HR)
17,500
20,000
30,000
31,000
Input Rate
BTU/HR)
13,500 to
17,500
16,500 to
20,000
22,300 to
28,000
23,000 to
29,000
3
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
it
GAS PRESSURE—ALL MODELS
Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:
Fuel # Minimum Maximum
Natural Gas
Propane
4.5 in. WC
(1.12 kPa)
11.0 in. WC
(2.74 kPa)
10.5 in. WC
(2.61 kPa)
13.0 in. WC
(3.23 kPa)
Table 2: Inlet Gas Supply Pressure
Fuel # Low High
Natural Gas
Propane
1.6 in. WC
(0.40 kPa)
6.3 in. WC
(1.57 kPa)
3.5 in. WC
(0.87 kPa)
10.0 in. WC
(2.49 kPa)
Table 3: Manifold Gas Supply Pressure
Test gauge connections are provided on
the front of the millivolt and electronic gas
control valve (identifi ed IN for the inlet and
OUT for the manifold side). The control
valves have a 3/8 in. (10 mm) NPT thread
inlet and outlet side of the valve (refer to
Figures 1 and 2).
Propane tanks are at pressures that will
cause damage to valve components. Verify
that the tanks have step down regulators to
reduce the pressure to safe levels.
The appliance and its appliance main gas
valve must be disconnected from the gas
supply piping system during any pressure
testing of that system at test pressures in
excess of 1/2 psi (3.5 kPa).
The appliance must be isolated from
the gas supply piping system by closing
its equipment shutoff valve during any
pressure testing of the gas supply piping
system at test pressures equal to or less
than 1/2 psi (3.5 kPa).
ORIFICE SIZES—SEA LEVEL TO HIGH
ALTITUDE (ALL MODELS)
These appliances are tested and approved
for installation at elevations of 0–4500 ft
(0–1372 m) above sea level using the
standard burner orifi ce sizes (marked with an
"*" in Table 4). For elevations above 4500 ft,
contact your gas supplier or qualifi ed service
technician.
Deration—At higher elevations, the amount
of BTU fuel value delivered must be reduced
by either:
• Using gas that has been derated by the
gas company.
• Changing the burner orifi ce to a smaller
size as regulated by the local authorities
having jurisdiction and by the (USA)
National Fuel Gas Code NFPA 54—latest
edition / ANSI Z223.1 or, in Canada, the
CAN/CGA-B149.1 codes—latest edition.
4
Install the appliance according to the
regulations of the local authorities having
jurisdiction and, in the USA, the National Fuel
Gas Code NFPA 54—latest edition / ANSI
Z223.1 or, in Canada, the CAN/CGA-B149.1—
latest edition.
Flame breadth, height and width will diminish
4% for every 1,000 feet of altitude. Gas Valve
Diagrams
. See Figure 1 for millivolt models
and Figure 2 For electronic models.
In Canada - CAN/CGA-2.17-M91 (R2009)
(high altitude): THE CONVERSION SHALL
BE CARRIED OUT BY A MANUFACTURER’S
AUTHORIZED REPRESENTATIVE, IN
ACCORDANCE WITH THE REQUIREMENTS
OF THE MANUFACTURER, PROVINCIAL
OR TERRITORIAL AUTHORITIES HAVING
JURISDICTION AND IN ACCORDANCE
WITH THE REQUIREMENTS OF THE
CAN/CGA-B149.1 OR CAN/CGA-B149.2
INSTALLATION CODES.
REQUIREMENTS FOR THE
COMMONWEALTH OF MASSACHUSETTS
These fi replaces are approved for installation
in the US state of Massachusetts if the
following additional requirements are met:
• Install this appliance in accordance with
Massachusetts Rules and Regulations
248 C.M.R.
Main Gas Control Knob
OFF/PILOT/ON
N
O
T
O
L
I
P
O
F
F
OUT
IN
Manifold Pressure Tap
Inlet Pressure Tap
Figure 1: SIT Millivolt Gas Valve
(from DFC Wire Harness)
Inlet (IN) Test Port
Manifold (OUT) Test Port
Orange Wire
(from DFC Wire
Harness)
Main Gas Inlet
3/8 in. NPT
Figure 2: SIT Electronic Gas Valve
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Pilot Adjustment
I
P
W
O
L
H
I
HI/LO Variable
Flame Height
Adjustment
Green Wire
Screw
T
O
L
H
TPT
HT
P
T
Model
Series
MPB33
MPB35
MPB40
MPB45
* Standard size installed at factory
• Part /Cat. Number
Nat.Gas
drill size (inches)
#47 (.0785") *
99K74 •
#44 (.086") *
60J80 •
#38 (.102") *
99K76 •
#36 (.104") *
24M10 •
Propane
drill size (inches)
(.048")*
99K78 •
#55 (.052") *
19L52 •
(.0625") *
21L01 •
#52 (.0635") *
37G00 •
Table 4: Burner Orifi ce Sizes
Elevation 0-4500 feet
(0-1372 meters)
• Installation and repair must be done by
a plumber or gas fi tter licensed in the
Commonwealth of Massachusetts.
• The fl exible gas line connector used shall
not exceed 36 in. (92 cm) in length.
• The individual manual shut-off must be a
T-handle type valve.
COLD CLIMATE INSULATION
For cold climate installations, seal all cracks
around your appliance with noncombustible
material and wherever cold air could enter the
room. It is especially important to insulate
outside chase cavity between studs and
under fl oor on which appliance rests, if fl oor
is above ground level. Gas line holes and
other openings should be caulked or stuffed
with unfaced fi berglass insulation.
If the fi replace is being installed on a
cement slab in cold climates, a sheet of
plywood or other raised platform can be
placed underneath to prevent conduction
of cold transferring to the fi replace and into
the room. It also helps to sheetrock inside
surfaces and tape for maximum air tightness
and caulk fi restops.
MANUFACTURED HOUSING
B-Vent Fireplaces are not approved for use in
OEM or aftermarket manufactured housing
built to HUD standards.
Hi/Lo Flame
Control Knob
Yellow Ground Wire
(from DFC Wire Harness)
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
LOCATION
In selecting the location, the aesthetic and
functional use of the appliance are primary
concerns. However, vent system routing to
the exterior and access to the fuel supply are
also important.
Due to high temperatures, the appliance
should be located out of traffi c and away
from furniture and draperies (Figure 3).
En raison des températures élevées,
l’appareil devrait être installé dans un
endroit où il y a peu de circulation et loin
du mobilier et des tentures (Figure 3).
The location should also be free of electrical,
plumbing or other heating/air conditioning
ducting.
Be aware that this is a heat producing
appliance. Objects placed above the unit
are exposed to elevated temperatures.
Do not insulate the space between the
appliance and the area above it (see
Figure 9 on Page 8).
The appliance must be mounted on a
fully supported base extending the full
width and depth of the unit. The appliance
may be located on or near conventional
construction materials. However, if installed
on combustible materials, such as carpeting,
vinyl tile or other combustible material other
than wood fl ooring, the appliance shall be
installed on a metal or wood panel extending
the full width and depth of the appliance.
Vertical
Venting
Shown with Outside Air Kit
installed (model FOAK-4 or
FOAK-4LD)
When the unit is installed with one side flush with a
wall, the wall on the other side of the unit must not
extend beyond the front edge of the unit.
Figure 3: Typical Installations
Offset
Venting
VENT TERMINATION CLEARANCES
Gas Vent Rule - Gas vent caps are not
permitted within 8 feet (2.4 mm) of a vertical
wall or similar obstruction. Gas vent caps
that are located 8' or more from a portion of
a building which extends at an angle greater
than 45° upward from the horizontal may
terminate in accordance with Figure 4,
provided that in no case shall any discharge
opening on the cap be less than 2' (610 mm)
horizontally from the roof surface (National
Fuel Gas Code ANSI Z223.1 (NFPA 54) Gas
Vent Termination) (CAN/CGA B149.1).
MULTIPLE TERMINATIONS
These appliances may vent adjacent to and at
the same level with any other gas appliances
(including direct-vent appliances) provided
that there is at least 2 ft. (0.6m) between
the proximal edges of the vent caps. These
appliances may be vented adjacent to a
chimney vent servicing a solid fuel fi replace
provided the B-vent cap is at least 2 ft.
(0.6m) away from the nearest point of the
chimney opening.
X
12
Roof Pitch is X/12
Minimum Height from Roof to
Lowest Discharge Opening
1“ (25 mm)
Minimum
Termination Heights For Vents
Above Flat Or Sloped Roofs
Ref. NFPA 54 / ANSI Z223.1
Roof Pitch Feet Meters
Flat to 6/12 1.0 0.3
6/12 to 7/12 1.25 0.38
7/12 to 8/12 1.5 0.46
8/12 to 9/12 2.0 0.61
9/12 to 10/12 2.5 0.76
10/12 to 11/12 3.25 0.99
11/12 to 12/12 4.0 1.22
12/12 to 14/12 5.0 1.52
14/12 to 16/12 6.0 1.83
16/12 to 18/12 7.0 2.13
18/12 to 20/12 7.5 2.29
20/12 to 21/12 8.0 2.44
Figure 4: Vertical Vent Termination Clearances
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
5
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
12 (305) MANTEL
10 (254) MANTEL
8 (203) MANTEL
6 (152) MANTEL
4 (102) MANTEL
4
(102)
12
(305)
10
(254)
2 (51) MANTEL
TOP OF
APPLIANCE
6
(152)
NOTE - Hood shown as positioned in louvered
front model. The hood position in the flush
faced front model is lower than shown.
8
(203)
MANTEL CLEARANCES
Inches (mm)
APPLIANCE AND VENT CLEARANCES
MINIMUM CLEARANCES TO COMBUSTIBLES
The appliance is approved with zero
clearance to combustible materials on all
sides (as detailed in Table 5), with the
following exception: When the unit is
installed with one side fl ush with a wall,
the wall on the other side of the unit must
not extend beyond the front edge of the
unit. In addition, when the unit is recessed,
the side walls surrounding the unit must not
extend beyond the front edge of the unit (see
Figure 3).
Back
Sides
Top Spacers
Floor
Bottom of
Appliance
To Ceiling
Vent
SERVICE CLEARANCES Feet (meters)
Front
1/2 (13)
1/2 (13)
0 (0)
0 (0)
64 (1626)
1 (25.4)
3 ft. (0.9 m)
Table5:Minimum Clearances
[inches (millimeters)]
HEARTH EXTENSION
A hearth extension is not required with this
appliance. If a hearth extension is used, do
not block the control compartment panel.
Any hearth extension used is for appearance
only and does not have to conform to any
requirements for thermal protection.
WALL FINISHES / SURROUNDS / MANTELS
Note: Combustible wall fi nish materials and/
or surround materials must not be allowed
to encroach the area defi ned by the appliance
front face (black sheet metal). Never allow
combustible materials to be positioned in
front of or overlapping the appliance face (see
Figure 35 on Page 21).
Non-combustible materials, such as
surrounds and other appliance trim, may be
installed on the appliance face with these
exceptions: they must not cover any portion
of the removable glass panel, louvers, or
control compartment.
Figure 5: Minimum Mantel Clearances
Vertical installation clearances to combustible
mantels vary according to the depth of the
mantel (See Figure 5). Mantels constructed
of non-combustible materials may be
installed at any height above the appliance
opening; however, do not allow anything to
hang below the fi replace hood.
WARNING
Failure to position the parts in
accordance with these diagrams
or failure to use only parts specifi cally approved with this appliance
may result in property damage or
personal injury.
0” Clearance
to Combustible
Side Wall
Ceiling
64 in.
(1626 mm)
Bottom of Fireplace
Minimum clearance requirements include any
projections such as shelves, window sills,
mantels, etc. above the appliance.
NOTE: We recommend the use of high temperature paint (rated 175 °F, or higher) on the
underside of the mantel.
AVERTISSEMENT
Risque de dommages ou de
blessures si les pièces ne sont
pas installées conformément à
ces schémas et ou si des pièces
autres que celles spécifi quement
approuvées avec cet appareil sont
utilisées.
6
Figure 6: Clearance References
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
Anchor
Ta b
PRE-INSTALLATION STEPS
The appliance is shipped with all gas controls
and components installed and pre-wired.
Before installing the appliance, follow these
steps:
1. Remove the shipping carton.
2. Remove the shipping pad, exposing
the front glass door.
3. Open the spring latch securing
the glass door (under the fi rebox
fl oor). Remove the door by tilting
it outward at the bottom and lifting
it up. Set the door aside, taking
care to protect it from inadvertent
damage. See Removing the Glass
Enclosure Panel on Page 19.
4. Remove the log set from the fi rebox.
Handle logs carefully to prevent
breakage.
5. Remove the embers and
volcanic stone from the control
compartment.
TYPICAL INSTALLATION SEQUENCE
The typical sequence of installation is
outlined below; however, each installation
is unique and may result in variations to the
steps described. See the pages referenced in
the following steps for detailed procedures.
Step 1. FRAMING (Page 7): Construct the
appliance framing. Position the appliance
within the framing and secure with nailing
nailing fl anges and fl oor anchor tabs.
Bend out the appropriate nailing fl anges for
the drywall/fi nish material to be used. Nailing
fl anges are provided for fl ush framing, 1/2 in.
and 5/8 in. framing depths (see Figure 10).
Step 2. ROUTING GAS LINE (Page 9): Route
gas supply line to appliance location.
Step 3. INSTALLING VENT SYSTEM
(Page 10): Install the vent system and
exterior termination.
Step 4. FIELD WIRING (Page 11).
a. Millivolt Appliances—Install the operating
control switch (not factory provided). If
installing the optional forced air circulating
blower, bring in electrical service line.
b. Electronic Appliances—Field wire and
install operating control switch.
Step 5. WIRING—OPTIONAL FORCED AIR
BLOWER KIT (Page 12).
Step 6. CONNECTING GAS LINE (Page 12):
Make connection to gas supply.
Step 7. INSTALLING OPTIONAL OUTSIDE
AIR KIT (Page 13)
Step 8. VERIFYING APPLIANCE OPERATION
(Page 14).
Step 9. INSTALLING VOLCANIC STONE,
GLOWING EMBERS, AND LOGS (Page 14).
Step 10. REMOVING AND INSTALLING THE
GLASS DOOR (Page 19).
Step 11. BURNER ADJUSTMENTS (Page 19):
Adjust burner primary air shutter to achieve
proper fl ame appearance.
Step 12. TESTING VENT OPERATION
(Page 21)
Vent operation test and (safety limit) switch
operation.
Step 13. HOOD INSTALLATION (Page 21).
Step 14. FINISHING REQUIREMENTS (Page 21)
Step 15. ATTACHING SAFETY-IN-
OPERATION WARNINGS (Page 21).
DETAILED INSTALLATION STEPS
STEP 1. FRAMING
Frame the appliance as illustrated in Figure 9
on Page 8. All framing details must allow for
a minimum clearance to combustible framing
members as shown in the table on Page 8.
If the appliance is to be elevated above fl oor
level, a solid continuous platform must be
constructed below the appliance.
Note: The framed depth, 16 in. (406 mm) from
a framed wall, must always be measured from
a fi nished surface. If a wall covering such as
drywall is to be attached to the rear wall, then
the 16 in. (406 mm) must be measured from
the drywall surface. It is important that this
dimension be exact.
Headers may be in direct contact with the
appliance top standoff spacers, but must
not be supported by them or notched to
fi t around them. All construction above the
appliance must be self-supporting. DO NOT
use the appliance for structural support.
Secure the fi replace to the side framing
members using the unit’s nailing fl anges
— one top and bottom on each side of the
fi replace front (See Figure 7). Use 8d nails or
their equivalent.
FLOOR NAILING TABS
Fireplace may be anchored to fl oor. Bend
down two anchor tabs (one on each side)
located at the base of the fi replace and
secure to the fl oor by nailing with 8d nails or
equivalent (see Figure 8).
Side
Framing
Left Side Front Corner of Fireplace Shown
(Right Side Requirements the Same)
Note: The nailing flanges, combustible members
and screw heads located in areas directly adjacent
to the nailing flanges, are EXEMPT from the 1/2”
clearance to combustible requirements for the
firebox outer wrapper.
in
direct contact with the nailing flanges and may
be located closer than 1/2” from screw heads and
the firebox wrapper in areas adjacent to the nailing
flanges. Frame the opening to the exact dimensions
specified in the framing details of this manual.
Combustible framing may be
Unit Nailing Flange
(No clearance to
combustible
framing is required)
Figure 7: Unit Secured to Framing by
Nailing Flange
Figure 8: Floor Anchor Tabs
Note: Some units only have one anchor tab
on each side.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
7
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
. o N l e d o M
A
t i n U
e z i S
A
g n i m a r F
e z i S
BCD E FGHJ K
. n i5 38 / 1 -5 34 / 1 -5 34 / 1 -9 18 / 5 - 9 17 52 / 1 -4 / 3 - 8 26 14 6 1 / 9 - 68 / 5 - 0 4
m m2 9 85 9 85 9 83 8 48 9 40 6 4 10 3 76 0 42 0 17 6 12 3 0 1
. n i8/
1 - 0 44 / 1 - 0 44 / 1 - 0 44 28 / 5 - 4 26 1 / 3 1 - 1 66 1 / 1 - 0 36 14 6 1 / 9 - 62 3 / 1 1 - 3 4
m m9 1 0 12 2 0 12 2 0 10 1 65 2 60 7 5 19 7 76 0 42 0 17 6 11 0 1 1
. n i8 / 1 - 0 44 / 1 - 5 44 / 1 - 0 44 28 / 5 - 9 28 / 3
- 6 66 1 / 3 - 3 36 14 6 1 / 9 - 66 1 / 5 1 - 6 4
m m6 4 1 19 4 1 12 2 0 10 1 62 5 76 8 6 13 4 86 0 42 0 17 6 12 9 1 1
MPB33
MPB35
MPB40
MPB45
in.
mm
845
842
33-1/4
845
33-1/4
546
21-1/2
286
11-1/4
1232
48-1/2
616
24-1/4
330
13
102
4
103
4-1/16
872
34-5/16
33-1/8
12-3/4
14-11/16
17-3/16
437
373
324
1146
45-1/8
24-7/8
29-7/8
34-7/8
886
759
632
30-11/16
7-1/16
7-1/16
7-1/16
179
179
179
Back Wall of Chase/Enclosure
*Optional FOAK
Outside
Air Kit
Including Finishing Materials
C
if any
B
Fireplace Framing
K
Corner Installation
Header
A
Back Wall of Chase/Enclosure
Including Finishing Materials
D
C
A
E
if any
G
Rough
Framing Face
(Unfinished Shown)
J
A
Rough Framing Face
(Unfinished Shown)
Outside Chase
Back Wall of Chase/Enclosure
Including Finishing Materials
C
F
HH
A
Inside Chase
if any
G
G
Rough
Framing Face
(Unfinished Shown)
8
All framing dimensions calculated for 1/2" dry wall at the appliance face. If sheathing the chase or finishing with other thickness materials,
calculations will need to be made.
* Outside air kit - FOAK (without adaptor). See Figure 22 on Page 16.
Figure 9: Framing Specifi cations
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
ELECTRICAL INLET
(See Also
Right Side View )
5-1/2
OUTSIDE AIR
SHUTTER
GAS INLET
(See Also
Right Side View
ELECTRICAL
INLET
(Optional)
)
(140)
9-3/8
(238)
8-15/16
(227)
Left Side View
. o N l e d o MA BC DE F G
MPB33
MPB35
MPB40
MPB45
in.
mm
. n i538 / 1 -8 / 1 - 2 39 12 / 1 - 9 25 38 / 1 -8 / - 6 1 / 7 - 25 8-3/4
m m29 86 1 83 8 49 4 72 9 82 3 66 1 37 2 1 222
. n i8/ 1 - 0 48 / 1 - 7 34 22 / 1 - 4 38 / 1 - 0 48 / 7 - 9 21 6 1 / 5
m m9 1 0 13 4 90 1 66 7 89 1 0 19 5 79 7 37 2 1
. n i8 / 1 - 0 48 / 1 - 7 34 22 / 1 - 9 38 / 1 - 5 48 / 7 - 4 36 1 / 7 - 7 16 8-3/4
m m6 4 1 13 4 90 1 63 0 0 16 4 1 16 8 83 4 42 5 1 222
Figure 10: Fireplace Specifi cations
FRAMING
STANDOFFS
(Top, Sides,
and Rear)
G
A
3
1-3/8
(76)
7-3/8
(187)
(35)
33-1/8
841 432
765 841
17 30-1/8
27-1/2
F
H
T op View
E
D
Front View
699
C
33-1/8
21-1/2
546
24-7/8
621
J
NOTE - Hood shown
3 (76)
GAS INLET
(Either Side
and bottom )
OPTIONAL ELECTRICAL
INLET KNOCKOU T
REQUIRING A FIELD
PROVIDED JUNCTION
B
BOX (Either Side)
10-3/4
12-7/16
1 - 45 8-3/4
Flue Outlet For B-V ent Connection
ELECTRICAL INLET
as positioned
in louvered
front model.
1 ³⁄ ₈
(35)
3 (76)
2-3/4 x 2 (70 x 51) COVER
PLA TE with KNOCKOUT)
K
1/2 (13)
5-1/2
(140)
9-3/8
(238)
2
(53)
Right Side View
K
J
H
4
6-1/2
102 273
165
13
330
16
406
16
2
22
406
16
406
STEP 2. ROUTING GAS LINE
Route a 1/2" (13 mm) gas line as shown
in Figure 11. Gas lines must be routed,
constructed and made of materials that are
in strict accordance with local codes and
regulations. The appliance, as set up at the
factory, is best suited for use with a gas line
routed from the left side. The gas line may
however be alternately routed from the right
side. All appliances are factory-equipped
with a fl exible gas line connector and 1/2 inch
shutoff valve. (See Step 6 on Page 12).
Pipe Coupling
(Recommended)
6-1/2"
(152 mm)
3"
(76 mm)
Figure 11: Route Gas Line
Also see Figure 12.
PROPER SIZING OF GAS LINE
Properly size and route the gas supply
line from the supply regulator to the area
where the appliance is to be installed per
requirements outlined in the National Fuel
Gas Code, ANSI Z223.1 (NFPA 54)—latest
edition (USA) or CAN/CGA-B149.1—latest
edition (Canada).
Never use galvanized or plastic pipe. Refer to
Table 6 for proper sizing of the gas supply
line, if black iron pipe is being used. Gas lines
must be routed, constructed and made of
materials that are in strict accordance with
local codes and regulations. We recommend
that a qualifi ed individual such as a plumber
or gas fi tter be hired to correctly size and
route the gas supply line to the appliance.
Installing a gas supply line from the fuel
supply to the appliance involves numerous
considerations of materials, protection,
sizing, locations, controls, pressure,
sediment, and more. Certainly no one
unfamiliar and unqualifi ed should attempt
sizing or installing gas piping.
Notes:
• All appliances are factory-equipped with
a fl exible gas line connector and 1/2 inch
shutoff valve (see Figure 46 on Page 25).
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
0–10 1/2 in. 3/8 in.
10–40 1/2 in. 1/2 in.
40–100 1/2 in. 1/2 in.
100–150 3/4 in. 1/2 in.
150–200 3/4 in. 1/2 in.
Table 6: Schedule 40 Black Iron Pipe—
Inside Diameter
• See Massachusetts Requirements on
Page 4 for additional requirements for
installations in the state of Massachusetts
in the USA.
• The gas supply line SHOULD NOT be
connected to the appliance until Step 6 on
Page 12).
• A pipe joint compound rated for gas
should be used on the threaded joints.
Ensure propane resistant compounds are
used in propane applications. Be very
careful that the pipe compound does not
get inside the pipe.
• It is recommended to install a sediment
trap in the supply line as close as possible
to the appliance.
• Check with local building offi cial for local
code requirements.
9
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
IMPORTANT: If propane is used, be aware
that if tank size is too small (i.e. under
100 lbs, if this is the only gas appliance
in the dwelling. Ref. NPFA 58), there
may be loss of pressure, resulting in
insuffi cient fuel delivery (which can result
in sooting, severe delayed ignition or other
malfunctions). Any damage resulting from
an improper installation, such as this, is
not covered under the limited warranty.
STEP 3. INSTALLING VENT SYSTEM
These instructions should be used as a
guideline and do not supersede local codes
in any way. Install venting according to
local codes, these instructions, the current
National Fuel Gas Code (ANSI-Z223.1) in
the USA or the current standards of CAN/
CGA-B149.1 in Canada.
Ensure clearances are in accordance
with local installation codes and the
requirements of the gas supplier.
Dégagement conforme aux codes
d'installa tion locaux et aux exigences du
foumisseunde gaz.
Type B-Vent - 4 in. (102 mm) for MPB33 Models,
5 in. (127 mm) for MPB35 / 40 Models or 6 in.
(152 mm) for MPB45 Models
Securing
Screws
Flue Outlet
Collar
Figure 12: Initial B-Vent Installation
USE ONLY APPROVED B-VENT DIAMETER
MPB33, MPB35, MPB40 and MPB45 series
fi replaces must be vertically vented using
listed type-B, double-walled vent pipe with
the proper diameter as listed below and a
listed vent termination.
Required Pipe Diameter:
MPB33 series: Requires 4 in. (102 mm)
MPB35 series: Requires 5 in. (127 mm)
MPB40 series: Requires 5 in. (127 mm)
MPB45 series: Requires 6 in. (152 mm)
CAUTION
This appliance cannot be vented
horizontally.
Refer to the vent manufacturers installation
instructions for variations of venting techniques.
If common venting of several units is contemplated, it should be discussed with an architect
and the local Building Department.
Do not place insulation materials within 1 in.
of the gas vent system.
Use only approved venting
components. (see Approved Vent
Components on Page 2.)
These fi replaces must be vented vertically
to the outside.
Slip the fi rst section of B-Vent over the
fi replace fl ue outlet and secure with sheet
metal screws (# 8 or larger), then install
the remainder of the B-Vent vertically to the
outside. Minimum overall height of the vent
system and appliance must be 10' (2.54 m)
vertical with no offset, or 12' (3.7 m) when
an offset up to 45 degrees from the vertical is
used; or 15' (4.6 m) when an offset is greater
than 45 degrees and up to 60 degrees (see
Figure 13).
The offset may start at the fi replace fl ue
collar. The maximum overall height of the
vent system and appliance should not exceed
40 feet.
Install the B-vent system in accordance with
the vent manufacturer's instructions.
Vertical
Installations
10 ft.
Minimum
Back View
Of Appliance
The maximum overall height of the vent system
and appliance should not exceed 40 feet.
Figure 13: Vent System Installation
Installations
*12 ft. Min.
**15 ft. Min.
Back View
Of Appliance
*with an offset up to 45 degrees
** with an offset greater than 45
degrees and up to 60 degrees
Offset
10
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
T
STEP 4. FIELD WIRING
CAUTION
The ground supply lead must be
connected to the wire attached to
the green ground screw located
on the outlet box (see wiring
diagrams). Failure to do so
will result in a potential safety
hazard. The appliance must be
electrically grounded in accordance with local codes or, in
the absence of local codes, the
National Electrical Code, ANSI/
NFPA 70
—latest edition (in
Canada, the current CSA C22.1
Canadian Electrical Code).
CAUTION: Label all wires prior to disconnection when servicing controls. Wiring
errors can cause improper and dangerous
operation.
ATTENTION: Au moment de l’entretien
des commandes, étiquetez tous les fils
avant de les débrancher. Des erreurs de
cáblage peuvent entraîner un fonctionnement inadéquat et dangereux.
Verify proper operation after servicing.
S’assurer que l’appareil fonctionne adéquatement une fois l'entretien terminé.
Refer to Section A for millivolt appliances
and Section B for electronic appliances. The
gas valve is set in place and pre-wired at the
factory on both models.
JUNCTION BOX
120V AC
B
W
G
OPTIONAL
REMOTE RECEIVER
ON/OFF SWITCH
WALL SWITCH
WIRING COLOR CODE
B = BLACK
BR = BROWN
GY = GRAY
PU = PURPLE
R = RED
P/N 580491-01
HOT
NEUTRAL
GROUND
SAFETY LIMIT SWITCH
B-VENT MODELS ONLY
BL = BLUE
G = GREEN
O = ORANGE
W = WHITE
Y = YELLOW
SCHEMATIC REPRESENTATION ONLY
Figure 16: Wiring Diagram—Electronic Gas Valves
R
BATTERY HOLDER
AC/DC
POWER
ADAPTOR
Y
G
O
B
B
CAUTION: ENSURE THAT WIRES ARE POSITIONED AWAY FROM HOT SURFACES AND
SHARP EDGES.
If any of the original wire as supplied must be replaced,
it must be replaced with Type AWM105 ° C – 18 GA. wire.
BK
H C T I W
S
T
I M I
L
BK
Thermopile
BK
AB
*OPTIONAL ON/OFF SWITCH,
WALL SWITCH, OR REMOTE
CONTROL RECEIVER
*TWIST WIRES “ A ” AND “ B ” TOGETHER TO OPERATE UNIT
SOLELY BY MANIPULATING THE GAS VALVE CONTROL KNOB;
OR CONNECT WIRES TO OPTIONAL ON/OFF SWITCH OR WALL
SWITCH OR REMOTE CONTROL RECEIVER TO OPERATE UNI
Schematic Representation Only
WT
T
P
T
T
H
P
T
H
Figure 14: SIT Milivolt Wiring Diagram
See Figure 10 on Page 10
for Optional Electrical Inlet
Knockout Location.
* Field-Provided
Junction Box and
Duplex Receptacle
* Narrow (2-1/8 Inch Wide)
J-Box Required
Figure 15: Optional J-Box/Outlet Box
(Left Side Shown)
ELECTRONIC PILOT ASSEMBLY
IGNITER ROD
FLAME SENSOR
B
B
Y
G
O
W
BL
G
CPI SWITCH
OFF (O) = INTERMITTENT PILOT MODE
ON (-) = STANDING PILOT MODE
PILOT
SENSOR
CABLE
PROFLAME DFC BOARD
DFC WIRE HARNESS
PROFLAME VALVE
W
R
PILOT TUBE
SPARK WIRE CABLE
PILOT GROUND WIRE
R
BL
HOOD
Y
B
R
B
A. Millivolt Wiring (see Figure 14)
Millivolt units are not provided with any
factory-installed controls; therefore, one
of the optional control switches is required
to operate the unit (ON/OFF Wall Switch,
Unit-Mountable ON/OFF Switch*, Remote
Control). See the fi replace Care and Operation
Instructions for details.
[*If using a Unit-Mountable ON/OFF Rocker
Switch with an optional Style View Door,
mount the Rocker Switch on the door instead
of the unit.]
1. If installing an ON/OFF wall switch or
receiver, mount it in a convenient location
on a wall near the f replace.
2. Wire the control switch within the millivolt
control circuit using the 15 feet of 2
conductor wire supplied with the unit.
Note: The supplied 15 feet of 2 conductor wire
has one end of each conductor connected to
the gas valve circuit and the other end of each
conductor placed loose inside the bottom
compartment.
CAUTION
In millivolt systems, do not connect
optional control switch to 120 v power
supply.
B. Electronic Wiring (see Figure 16)
One of the following optional controls also
may be used: ON/OFF Wall Switch, Remote
Control (see fi replace Care and Operation
Instructions for details.).
Note: Electronic models must be connected
to the main power supply.
1. Route a 3-wire 120Vac 60Hz 1ph power
supply to the appliance junction box.
2. Remove the electrical inlet cover plate
from the side of the unit by removing the
plate’s securing screws (see Figure 10 on
Page 9).
3. Remove the cover plate knockout; then
feed the power supply wire through
the knockout opening and into the unit
junction box.
4. See Figure 17. Connect the black power
supply wire to the lower outlet’s red
pigtail lead.
Connect the white power supply wire to
the outlet’s common terminal.
5. Connect the ground supply wire to the
pigtail lead attached to the outlet’s green
ground screw.
Note: Remote receiver should be located in the
wall, or if installed in the control compartment,
pulled all the way forward and completely to the
left or right against the corner posts.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
11
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
6. If wall-mounted ON/OFF control is to be
used, mount it in a convenient location
on a wall near the fi replace.
7. If an optional control is to be used, wire
it in the low voltage circuit as shown in
Figure 16.
Note: The supplied 15 feet of 2 conductor
wire has one end of each conductor
connected to the gas valve circuit and the
other end of each conductor placed loose
inside the bottom compartment.
8. After the wiring is complete, replace the
cover plate.
WARNING
Electronic models of these appliances are equipped with a threeprong (grounding) plug utilized
in connecting the electronic
components to the junction box
in the lower compartment. This
grounding plug provides protection against shock hazard and
should be plugged directly into
the properly grounded threeprong receptacle. DO NOT cut
or remove the grounding prong
from the plug.
STEP 5. WIRING OPTIONAL FORCED
AIR BLOWER KIT
FBK-100, FBK-200, and FBK-250 Kits
(See Figure 17)
An electrical outlet box is provided for the
installation of the FBK-100, FBK-200 and
FBK-250 forced air blower kits. Electrical
power must be provided to this box to
operate these blowers. Install the blower
kits according to the installation instructions
provided with the kits.
Note: The tab connecting the two receptacles
of the outlet box must be broken in the
FBK-100 and FBK-200 blower kit applications
(see Figure 17).
120V, 60HZ, 1PH
n
e
ti
e
e
h
r
W
G
-
-
lar
dn
t
u
u
o
e
r
N
G
Black
White
Green
Plug blower
into this
receptacle
Blower
Ground
Figure 17: Junction Box Wiring
* Wall-mounted
ON/ OFF Blower
Switch or Variable
Speed Control Switch.
120 VAC - Black
Junction Box
Tab Intact
Field Wired
Factory Wired
Tab
Broken
Red
Hot
Side of
Receptacle
Neutral
Side of
Receptacle
Green
Ground
Screw
STEP 6. CONNECTING GAS LINE
Make gas line connections. All codes require
a shut-off valve mounted in the supply line.
The orientation of the shut-off valve should
face the front (see Figure 19). Figure 18
illustrates two methods for connecting
the gas supply. The fl ex-line method is
acceptable in the U.S.; however, Canadian
requirements vary depending on locality.
Installation must be in compliance with local
codes.
A sediment trap is recommended in the gas
piping within the home to prevent moisture
and debris in the line from damaging the
valve.
These appliances are equipped with a gas fl ex
line for use (where permitted) in connecting
the unit to the gas line. A gas fl ex line is
provided to aid in attaching the direct vent
appliance to the gas supply. The gas fl ex line
can only be used where local codes permit.
Refer to Figure 18 for fl ex line description.
The fl ex line is rated for both natural and
propane gas. A manual shut off valve is also
provided with the fl ex line.
The gas control valve is located in the lower
control compartment.
To access the valve, open the control
compartment access panel. Actuate the
spring loaded magnetic catches securing the
panel. First, gently depress the upper right
top corner of the panel until the magnet catch
"pops" the door free. Then, gently pulling the
panel forward, disengage the left magnet
catch and allow the panel to swing down to
open.
The control valves have a 3/8" (10 mm)
NPT thread inlet and outlet side of the valve
(refer to Figures X [Electronic] and Figure x
[Millivolt] on Page X).
Secure all joints tightly using appropriate
tools and sealing compounds (ensure
propane resistant compounds are used in
propane applications). Optional: Seal around
the gas line to prevent cold air leakage. Gas
line holes and other openings can be caulked
or stuffed with unfaced fi berglass insulation.
TEST ALL CONNECTIONS FOR GAS LEAKS
(FACTORY AND FIELD)
WARNING
Never use an open fl ame to
check for leaks.
Turn on gas supply and test for gas leaks,
using a gas leak test solution (also referred to
as bubble leak solution).
Note: Using a soapy water solution is an
effective leak test solution but it is not
recommended, because the soap residue
that is left on the pipes/fi ttings can result in
corrosion over time.
A. Light the appliance (refer to the
lighting instructions label in the control
compartment or in the Care and Operation
Instructions manual).
B. Brush all joints and connections with the
gas leak test solution to check for leaks. If
bubbles are formed, or gas odor is detected,
turn the gas control knob (off/pilot/on) to the
“OFF” position (millivolt units), or turn the
receiver, remote control or control switch to
the “OFF” position (electronic units). Either
tighten or refasten the leaking connection,
then retest as described above.
C. When the gas lines are tested and
leak free, be sure to rinse off the leak
testing solution.
12
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
Gas
Stub
1/2" x 3/8" Flare
Shut-Off Valve
3/8" Flex Tubing
3/8" NPT x 3/8"
Flare Fitting
3/8" Nipple
3/8" Union
3/8" Close Nipple
3/8" Shut-Off Valve
1/2" x 3/8"
Reducer
Gas
Valve
Optional Gas Flex Line Connector
Piezo
(Optional) Burner
ON/OFF Switch
Main Gas
Shut-Off Valve
Gas Valve
B-Vent Units Have
A Single Door Latch
Figure 18: Gas Connection
To open the outside air shutter, open the
bottom control access panel, reach into the
control compartment, and pull the outside
air control lever all the way out. The outside
air shutter should be fully open when the
fi replace is in use and completely closed
when the fi replace is not being used. Closing
it when not in use will prevent outside cold
air from entering the dwelling.
WARNING
DO NOT operate the outside
air control lever with a fi re in
the fi rebox unless a complete
outside combustion air vent
system has been installed with
the appliance.
Outside Air Control Lever
Figure 19: Millivolt Gas Valve—Lower Control Compartment
STEP 7. INSTALLING OUTSIDE AIR KIT
Optional outside make-up air kits, Model
FOAK-4 or FAOK-4LD (see Figure 21 on Page
14), may be used with these appliances.
Refer to the installation instructions packaged
with the air kits for specifi c installation
information. If used, the outside air kit must
be installed before the fi replace is framed and
enclosed in the fi nished wall.
Outside air drawn into the fi replace supplies
air to the fi re for combustion. Only one
outside air duct is necessary, if installed. See
Figure 3 on Page 5 for the location of the
unit's outside air inlet.
If additional length of duct is necessary,
purchase locally available U.L. Class 0
or Class 1 metallic ducting. The duct may
extend up to 50' (15.24 m) in any direction.
Note: When installing the air duct vertically, DO
NOT terminate the duct closer than 3' below
the chimney top.
Outside supplemental combustion air ducting
may be run upwards or vertically through
framing and ceiling joists, with the hood
installed through an outside wall and 3' (1 m)
below the termination. Ducting may also
be run downward through fl oor joists and
under the home to a ventilated crawlspace
not considered part of the living area of the
home.
Note: Do not terminate an outside air kit in the
attic space under any circumstances.
After completing the installation of the
optional outside air vent system the outside
air control lever must be put in service and
tested to ensure proper operation before
completing any enclosure around the fi rebox.
Failure to do so may result in extensive and
costly rework. Before the operation of the
vent system can be tested, the lever securing
screw must be removed (see Figure 20).
The hand operated outside air control lever
is located on the left side of the fi replace
opening (see Figure 20).
CAUTION
Never locate inlet where it can be
blocked by shrubs, snow drifts,
etc. Never locate inlet in garage
or any area where there is another
fuel burning appliance or products
emitting combustible gases such
as paint, gasoline, etc. In cold
climates, it is recommended the
outside air duct be insulated.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Outside Air Control Lever
Securing screw
Air Shutter in Closed Position
Outside Air Control Lever
Outside Air Control Lever
Securing Screw Removed
Air Shutter in Open Position
Figure 20: Outside Air Control Lever
Operate the actuator through several
cycles including the closed position.
Ensuring proper operation and freedom of
movement. Return the actuator arm to the
closed position.
13
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
Outside Combustion Air Kits
Cat. No. Model No. Description
81L87 FOAK-4 Combustion Air Kit (w/duct)
81L88 FOAK-4LD Combustion Air Kit (w/o duct)
Figure 21: Outside Combustion Air Kits
STEP 8. VERIFYING APPLIANCE
OPERATION
With gas line installed, run initial system checkout
before closing up the front of the unit. Follow the
pilot lighting instructions provided in the Care and
Operation Instructions. For piezo igniter location
on millivolt appliances, (see Figure 19).
Note: Lighting Instructions are also found on the
literature tag tied to the gas piping next to the gas
valve. To access the tag, open the lower control
compartment door (see Figure 19). To open the
control compartment access panel, actuate the spring
loaded magnetic catches securing the panel. First,
gently depress the upper right top corner of the panel
until the magnet catch "pops" the door free. Then,
gently pulling the panel forward, disengage the left
magnet catch and allow the panel to swing down
to open. When fi rst lighting the appliance, it will
take a few minutes for the line to purge itself of
air. Once purging is complete, the pilot and burner
will light and operate as indicated in the instruction
manual. Subsequent lighting of the appliance will
not require such purging. Inspect the pilot fl ame
(remove logs, if necessary, handling carefully).
MILLIVOLT APPLIANCE CHECKOUT
The pilot fl ame should be steady, not lifting
or fl oating. Flame should be blue in color
with traces of orange at the outer edge.
The top 3/8 in. (10 mm) at the pilot generator
(thermopile) and the top 1/8 in. minimum
(tip) of the quick drop out thermocouple
should be engulfed in the pilot fl ame.
The fl ame should project 1 in. (25 mm)
beyond the hood at all three ports (see
Figure 22). Replace logs if removed for pilot
inspection.
To light the burner; turn “ON” the remote wall
switch and rotate the gas valve control knob
counterclockwise to the “ON” position (“ON”
will be at the top side of the valve).
Hood Igniter Rod
Thermocouple
3/8 in.
(9 mm)
Pilot
Nozzels
Thermopile
Figure 22: Millivolt Pilot
ELECTRONIC APPLIANCE CHECKOUT
To light the burner, turn ‘ON’ the wall or
remote control switch. Ensure the igniter
lights the pilot. The pilot fl ame should engulf
the fl ame rod as shown in Figure 23.
Igniter
Sensor
Flame Rod
(sensor)
Figure 23: Electronic Pilot
Min
Pilot
Hood
STEP 9. INSTALLING VOLCANIC
STONE, GLOWING EMBERS, AND LOGS
Locate the packaged carton of logs (which
were located in the fi rebox). The decorative
volcanic stone and glowing embers were
packaged separately in plastic bags located
in the control area of the fi replace.
DO NOT attempt to install the logs until the
appliance installation has been completed,
the gas line connected and tested for leaks,
and the initial burner operation has been
checked out.
Proper log placement is critical to encourage
outstanding fl ame appearance and prevent
sooting. When positioned properly as shown,
logs will be positioned between fl ame peaks
and will not impinge any fl ames.
Refer to Figure 26 for MPB33 Series
appliances, Figure 27 for MPB35 Series
appliances and Figure 28 for MPB40 and
MPB45 Series appliances.
NOTE: Turn off all electricity to the appliance
before you install volcanic stone, embers
and logs.
WARNING
• DO NOT attempt to install the
logs until the appliance installation has been completed, the gas
line connected and tested for leaks
and the initial burner operation
has been checked out.
•
The size and position of the log set
was engineered to give the appliance a safe, reliable and attractive
fl ame pattern. Any attempt to use
a different log set in the fi replace
will void the warranty and will
result in incomplete combustion,
sooting, and poor fl ame quality.
•
Logs get very hot and will remain
hot up to one hour after gas supply
is turned off. Handle only when logs
are cool. Turn off all electricity to the
appliance before you install grate,
volcanic stone, embers and logs.
•
This appliance is not designed to
burn wood. Any attempt to do so
could cause irreparable damage to
the appliance and prove hazardous
to your safety.
•
If logs are not installed according to the log installation instructions, fl ame impingement and
improper combustion could
occur and result in soot and/or
excessive production of carbon
monoxide (CO), a colorless,
odorless, toxic gas.
14
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 1. Remove the appliance front door
(see Removing the Glass Enclosure Panel
on Page 19).
Step 2. Install decorative volcanic
stone—Sprinkle the decorative volcanic
stone in a pleasing pattern. The volcanic
stone should be placed directly on top of
the firebox bottom, along the front and
to the back at the right and left sides of
the burner. Position any optional ceramic
fiber liners before placing the stone.
Logs should be positioned after the
volcanic stone.
Note: This appliance is provided with
enough glowing embers for several applications, do not feel compelled to use
all that is in a new bag. For best glowing
effect, replace the ember material annually.
Replacement glowing embers are available
(Catalog Number 88L53).
Glowing Embers
Separate into Quarter
Size (separate) Pieces
Bag of Glowing
Embers (rockwool)
Glowing Embers
Figure 25: Glowing Embers Placement
Step 4. Placement of Logs—All top
logs that rest on lower logs, do so over
notches, indents or nubs. Proper log
placement is critical to prevent sooting.
Logs should be placed in the gaps between
the flame peaks and should be positioned
so they do not impinge the flames.
Step 5. Position the individual logs as
shown in Figures 26, 27, and 28. Logs
should be placed in the order shown. All
logs that have notches to fi t over the grate
tines should be positioned with these
notches directly against the grate. Handle
logs carefully to prevent breakage.
Figure 24:
Step 3. Separate the glowing embers
(rockwool) into pieces about the size
of a quarter (see Figure 24). Keep the
pieces fluffed up, not matted. Distribute
these pieces over the front surface of
the burner, as shown in Figure 25. Do
not use more than is necessary. When
properly positioned, the Glowing Embers
will cover approximately 65% of the
front burner and with no appreciable
gaps or openings. Ensure that the main
burner ports remain uncovered by the
ember material.
REFERENCE
Cat. No. Model No. Description
88L53 FGE Bag of Glowing Embers
80L42 FDVS Bag of Decorative
Volcanic Stone
Table 7: Firebox Accessories/Parts
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
15
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
MPB33 LOG PLACEMENT
* Item
1
1
2
3
4
3
2
5
6
Description (stamped #)
Log, Rear (39-12)
Log, Left (39-1)
Log, Right (39-2)
Log, Top Center (39-
13)
Log, Top/Left (39-3)
Log, Top/Right (39-4)
Catalog Number for the entire log set: 24M15
Position the individual logs as shown below. Logs should be
4
6
5
1
placed in the order shown. Position the rear log on the brackets
at the rear of the firebox with the log's notches directly over the
brackets. Position the right log (log no. 3) by inserting the pin
from the rear log into the hole on its upper end. Place the left log
and then the smaller left and right top logs. All logs that have
notches to fit over the grate tines should be positioned with these
notches directly against the grate. All top logs that rest on lower
logs, do so over flattened mounting faces in the bottom logs.
Proper log and twig placement is critical to encourage
outstanding flame appearance and prevent sooting.
4
3
2
5
6
16
Figure 26: Log Set 24M15 Placement
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
MPB35 LOG PLACEMENT
Log
1
3
2
Number Description (Stamped #)
1 Log, Rear (39-5)
2 Log, Left (39-1)
3 Log, Right (39-2)
4 Log, Top Center (39-6)
5 Log, Top/Left (39-3)
6 Log, Top/Right (39-4)
Catalog Number for the entire log set: H6197
4
5
6
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the rear log on the brackets at the rear
of the fi rebox with the log's notches directly over the brackets.
Position the right log (log no. 3) by inserting the pin from the rear
log into the hole on its upper end. Place the left log and then the
smaller left and right top logs. All logs that have notches to fi t over
the grate tines should be positioned with these notches directly
against the grate. All top logs that rest on lower logs, do so over
fl attened mounting faces in the bottom logs.
Proper log and twig placement is critical to encourage outstanding
fl ame appearance and prevent sooting.
1
4 3
2
Figure 27: Log Set H6197 Placement
5
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
6
17
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
MPB40 AND MPB45 LOG PLACEMENT
Log
1
2
3
Number Description (Stamped #)
1 Log, Center (39-8)
2 Log, Rear (138)
3 Log, Right (39-10)
4 Log, Left (39-9)
5 Log, Top/Left (39-11)
6 Log, Top/Right (39-11)
Catalog Number for the entire log set: 24M25
4
5
6
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the center log on the burner fi rst, then
place the glowing embers as shown in Figure 52. Place the rear
log, both the right and left, and then the smaller left and right top
logs. All logs that have notches to fi t over the grate tines should
be positioned with these notches directly against the grate. All top
logs that rest on lower logs, do so over fl attened mounting faces
in the bottom logs.
Proper log and twig placement is critical to encourage outstanding
fl ame appearance and prevent sooting.
1
4
3
2
18
Figure 28: Log Set 24M25 Placement
5
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
6
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
STEP 10. REMOVING AND INSTALLING
THE GLASS DOOR
WARNING
• Do not attempt to substitute
the materials used on the
door, or replace cracked or
broken glass.
• Handle this glass with
extreme care! Glass is
susceptible to damage – Do
not scratch or handle roughly
while reinstalling the glass
door frame.
• The glass door of this
appliance must only be
replaced as a complete
unit as provided by the
manufacturer. Do not attempt
to replace broken, cracked or
chipped glass separately.
•
Do not attempt to touch
the front enclosure glass
with your hands while the
fi replace is in use.
WARNING
Do not operate appliance with
the glass front removed, cracked
or broken.
AVERTISSEMENT
Ne pas utiliser l'appareil si le
panneau frontal en verre n'est
pas en place, est craqué ou
brisé.
Only doors certifi ed with the appliance
shall be used.
Seules des portes certifi ées pour cet
appareil doivent être utilisées.
WARNING: DO NOT abuse glass door by
striking or slamming shut.
Removing the Glass Enclosure Panel
(see Figure 29)
Remove the top louver assembly. Open
the lower control compartment door (see
Figure 29 ) by pressing in simultaneously at
the left and right top corners of the door (the
door is hinged at the bottom).
Remove the bottom compartment door by
sliding the hinge pin, located at the door’s left
side, to the right until it disengages from the
left corner post hole. Pull the door diagonally
to the left, away from the fi replace.
Locate the latch at the top of the control
compartment and disengage it from the door
frame bottom vee-fl ange, pulling down on the
handle to open it.
Installing the Glass Enclosure Panel
(see Figure 29)
Retrieve the glass door. Visually inspect the
gasket on the backside of the frame. Gasket
surface must be clean, free of irregularities
and seated fi rmly.
Position the door in front of the fi rebox
opening with the bottom of the door held
away from the fi replace (see Figure 29).
Hook the top fl ange of the door frame over
the top of the fi rebox frame.
Let the bottom of the door frame swing
gently in towards the fi replace ensuring
that the gasket seats evenly as the door
frame draws shut. Fasten the latch located
underneath the fi rebox fl oor to the door's
vee-fl ange. Close the latch securely.
Top Flange on
Glass Door
Glass Door
Latch
Bottom Vee-fl ange
Glass Door
NOTE: When installing the glass door, ensure
the spacing on both sides are equal.
Figure 29: Installing or Removing
Glass Door
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Firebox Floor
STEP 11. BURNER ADJUSTMENTS
Flame Appearance and Sooting
Proper fl ame appearance is a fl ame that is
blue at the base and becomes yellowishorange in the body of the fl ame.
When the appliance is fi rst lit, the entire
fl ame may be blue and will gradually turn
yellowish-orange during the fi rst 15 minutes
of operation. If the fl ame remains blue, or if
the fl ame is orange with evidence of sooting
(black tip), the air shutter opening may need
to be adjusted.
If the air shutter opening is closed too far,
sooting may develop. Sooting is indicated
by black puffs developing at the tips of very
long orange fl ames. Sooting results in black
deposits forming on the logs, appliance
inside surfaces and on exterior surfaces
adjacent to the vent termination.
Sooting is caused by incomplete combustion
in the fl ames and lack of combustion air
entering the air shutter opening. To achieve
a warm yellowish-orange fl ame with an
orange body that does not soot, the shutter
opening must be adjusted between these two
extremes.
Air Shutter Adjustment Guidelines
• If there is smoke or soot present, fi rst
check the log set positioning to ensure
that the fl ames are not impinging on
any of the logs. If the log set is properly
positioned and a sooting condition still
exists, then the air shutter opening should
be increased.
• The more offsets in the vent system, the
larger the air shutter opening will need
to be.
• An appliance operated with the air shutter
opened too far, may have fl ames that
appear blue and transparent. These weak,
blue and transparent fl ames are termed
anemic.
• Propane models may exhibit fl ames
which candle or appear stringy. If this is
present and persists, adjust the air shutter
to a more closed position, then operate
the appliance for a few more minutes to
ensure that the fl ame normalizes and the
fl ames do not appear sooty.
Note: The following chart is provided to aid you
in achieving the correct air shutter adjustment
for your installation.
Air Shutter Adjustment Guidelines
Amount of
Primary Air
If air shutter is
closed too far
If air shutter is
open too far
Flame
Color
Flame will
be orange
Flame will
be blue
Air Shutter
Adjustment
Air shutter
gap should be
increased
Air shutter
gap should be
decreased
19
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNING
• Air shutter adjustment should
only be performed by a
qualifi ed professional service
technician.
Ensure the front glass panel
•
is in place and sealed during
adjustment.
CAUTION
• Soot will be produced if the
air shutter is closed too much.
Any damage due to sooting,
resulting from improperly
setting the air shutter, is not
covered under the warranty.
• The air shutter door and
nearby appliance surfaces
are hot. Exercise caution to
avoid injury while adjusting
fl ame appearance.
1. Refer to Figures 30, 31, and 32 for
proper fl ame appearance. To adjust the
fl ame, move the rod up and down (the
adjustment rod is located in the lower
control area). Position the air shutter to
the factory setting as shown in Table 8.
2. Light appliance (follow lighting procedure
on lighting label in control compartment
or in the Care and Operation
Instructions).
3. Allow the burner to operate for at least
15 minutes while observing the fl ame
continuously to ensure that the proper
fl ame appearance has been achieved.
If the following conditions are present,
adjust accordingly.
• If fl ame appears weak or sooty, adjust
the air shutter, incrementally, to a
more open position until the proper
fl ame appearance is achieved.
• If fl ame remains blue, adjust the air
shutter, incrementally, to a more
closed position until the proper fl ame
appearance is achieved.
4. When satisfi ed that the burner fl ame appear-
ance is normal, reinstall the lower control
compartment door, then proceed to fi nish
the installation.
20
Figure 30: MPB33 MODEL
Figure 31: MPB35 MODEL
Figure 32: MPB40 AND MPB45 MODEL
Adjusting Set Screw
Adjustment Rod Up
(minimum air
Burner Tube
Air Shutter
Adjustment Rod Down
(fully open position)
Figure 33: Air Shutter
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
opening position)
Main Burner Factory Air Shutter
Opening Setting - Inches (millimeter)
Model Natural Gas Propane Gas
MPB33 Fully Closed 3/16" (4.76 mm)
MPB35 Fully Closed 3/16" (4.76 mm)
MPB40 Fully Closed 3/16" (4.76 mm)
MPB45 Fully Closed 3/16" (4.76 mm)
Table 8: Air Shutter Opening Setting
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
STEP 12. TESTING VENT OPERATION
After appliance installation, perform this vent
operation test to verify that proper venting
conditions exist:
1. Place unit in its normally-operated
condition, that is, with the glass
enclosure panel in place.
2. Close all doors and windows in the room.
Turn on all exhaust fans in the house.
3. Light the appliance.
4. Wait 15 minutes.
5. To check for venting action, start by
holding a smoke producing device
below the glass enclosure panel.
The smoke should be drawn into the
control compartment. Continue the
test by moving the smoke producing
device along the entire length of
below the glass door.
6. If the smoke is not drawn into the
control compartment, turn off the
appliance and call a qualified service
technician.
RESETTING THE SAFETY LIMIT SWITCH
This appliance is equipped with a manually
resetable safety limit switch. Refer to
Figure 34 for its location. If, during appliance
operation, the flame goes out (independently
of the burner on/off wall switch), it may
be due to a blocked vent. If this condition
occurs, the safety limit switch will activate,
causing the fireplace burner to shut off. To
reset this switch, first allow the appliance
to cool, then remove the top louver panel.
Reset the safety limit switch by pushing the
red reset button, located between the wire
terminals on the back of the switch (See
Figure 34, Detail A).
The appliance should then relight and remain lit.
Reinstall the top louver panel. If the appliance
does not relight, turn off the appliance and call
for a qualified service technician.
To replace the blocked flue safety limit switch
(see Figure 34, Details B & C).
This procedure should only be performed by a
qualified service technician.
IMPORTANT - TURN ELECTRICAL POWER
OFF BEFORE BEGINNING THIS PROCEDURE.
1. Lower the bottom control
compartment access panel.
Remove the glass enclosure panel:
open the latch (located in the center
of the unit front opening, under the
fi rebox fl oor) securing the glass
enclosure panel. Remove the panel
by tilting it outward at the bottom
and lifting it up. Set the door aside
protecting it from inadvertent
damage (see Figure 29 on Page 19).
2. Remove the lintel securing screws
(3) and then remove the lintel. One
of the lintel cabinet top holes is
shown in Figure 34, Detail B.
3. Remove the scoop securing screws
(3) and then remove the scoop (see
Figure 34, Detail B).
4. Remove the safety switch bracket
securing screws (2), and pull the
switch/bracket assembly, with low
voltage wires attached, through the
side panel slot into the fi rebox (see
Figure 34, Detail C).
5. Replace the switch.
6. Reinstall the switch/bracket
assembly.
7. Reinstall the scoop and lintel.
8. Reinstall the glass enclosure panel.
9. Raise the bottom control
compartment access panel.
10. The appliance should then relight
and remain lit. If this does not
occur, check unit for a blocked fl ue
condition.
Wire
Terminals
Reset Button
Cabinet
Corner
Back Of
Limit
Switch
Door
Frame
Detail A
Lintel Securing Screw
Firebox Top
Detail B
Firebox Top
Detail C
Blocked Flue Safety Limit Switch Location, Inside
View of Firebox, Top/Right Side Intersection
Figure 34: Safety Limit Switch
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Hole in Cabinet Top
Scoop
Scoop Securing Screws
Lintel Securing-Screw
Hole in Cabinet Top
Limit Switch/Bracket
Securing Screws
Limit Switch
View Without Scoop
STEP 13. HOOD INSTALLATION
Refer to Figure 35. All models must have
hoods installed prior to operating.
On louvered face units, slide the hood into the
slots on the lower edge of the cabinet top above
the louvered vent (see Figure 35).
STEP 14. FINISHING REQUIREMENTS
Wall Details
Complete fi nished interior wall. To install the
appliance facing fl ush with the fi nished wall,
position framework to accommodate the
thickness of the fi nished wall (see Figure 9
on Page 8).
See Page 4 for
Cold Climate Insulation and
Page 8 for Clearances.
Combustible
Finished Wall
Materials
Combustible
material may
touch top of
appliance.
Combustible
materials
NOT allowed
below this point
on face
of appliance.
Hood must be installed as shown.
Figure 35: Louver Face Models
This area must remain
clear of combustible
materials.
Min. 1 in.
(25 mm)
Header
Spacing
Top Standoff
Top of Appliance
Louvers
Top of Door Frame
21
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
STEP 15. ATTACHING SAFETY-IN-OPERATION WARNINGS
It is the installer’s responsibility to ensure these warnings are properly affi xed during installation. These warning labels are a
critical step in informing consumers of safe operation of this appliance.
ATTACHING SAFETY IN OPERATION WARNINGS
It is required that the safety instruction labels furnished with the fireplace be affixed to the operation
and control point of the fireplace. A safety instruction
label must be affixed to the wall switch plate where
the fireplace is turned on and off (See Figure A) and
if used on the remote control handheld transmitter
(Figure B). To properly complete the installation of
this fireplace, locate the multi-lingual adhesive labels
provided with the Care and Operation Instructions
and proceed as follows:
1. Locate the wall switch that controls the fireplace
(verify the switch operates the fireplace by turning it on and off). Clean the wall switch plate
thoroughly to remove any dust and oils. Affix the
label to the surface of the plate of the wall switch
that controls the fireplace (Figure A). Choose
the language primarily spoken in the home. If
unknown, affix the English language label.
2. If a remote control is used to control the fireplace,
locate the transmitter and clean it thoroughly
to remove any dust and oils. Affix the label to
the surface of handheld transmitter (Figure B) .
Choose the language primarily spoken in the
home. If unknown, affix the English language
label.
3. If you are unable to locate the labels, please call
Lennox Hearth Products or your nearest Lennox
Hearth Products dealer to receive additional
safety instruction labels free of charge.
Cat. No. H8024 Replacement Label Kit
LENNOX HEARTH PRODUCTS
1-800-655-2008
Note: English is red text on clear label. French and
Spanish are white text on black label.
APPOSITION DES MISES EN GARDE RELATIVES
À LA SÉCURITÉ D’UTILISATION
Il est impératif que les étiquettes de sécurité fournies avec
le foyer soient collées à côté des dispositifs de contrôle
du foyer. Une étiquette de sécurité doit être collée sur la
plaque de l’interrupteur contrôlant l’allumage du foyer
(voir Figure A) et, le cas échéant, sur le boîtier de la
télécommande (Figure B). Pour achever l’installation
correcte de ce foyer, procédez comme suit avec les
étiquettes adhésives en langues étrangères fournies
avec les instructions d’utilisation et d’entretien :
1. Repérez l’interrupteur qui contrôle le foyer (vérifiez
que l’interrupteur contrôle le fonctionnement du
foyer en le faisant basculer de Marche à Arrêt, et
vice-versa). Nettoyez soigneusement la plaque
murale de l’interrupteur pour éliminer la poussière
et les traces de graisse ou d’huile. Collez l’étiquette
sur la surface de la plaque de l’interrupteur mural
qui contrôle le foyer (Figure A). Choisissez la
langue qui est principalement parlée dans la
résidence du propriétaire. En cas de doute, collez
l’étiquette en anglais.
2. Si une télécommande est utilisée pour contrôler
le foyer, nettoyez la soigneusement pour éliminer
Collez l’étiquette sur le boîtier de la télécommande
(Figure B). Choisissez la langue qui est principalement parlée dans la résidence du propriétaire. En
cas de doute, collez l’étiquette en anglais.
3. Si vous ne trouvez pas les étiquettes, veuillez
appeler Lennox Hearth Products ou votre distributeur Lennox Hearth Products local pour recevoir
gratuitement des étiquettes supplémentaires.
Étiquettes de remplacement, n° cat. H8024
LENNOX HEARTH PRODUCTS
1-800-655-2008
Remarque : Le texte anglais est rouge sur un support
transparent. Le texte français et espagnol est blanc
sur un support noir.
COLOCACIÓN DE ADVERTENCIAS DE SEGURIDAD
EN OPERACIÓN
Se requiere que las etiquetas de instrucciones de
seguridad incluidas con la chimenea se coloquen en
el punto de operación y control de la misma. Se debe
colocar una etiqueta de instrucciones de seguridad
en la placa del interruptor de pared desde el cual se
enciende y se apaga la chimenea (ver la Figura A) y
en el transmisor de control remoto (Figura B) si se
usa. Para completar correctamente la instalación de
esta chimenea, encuentre las etiquetas adhesivas
multilingües incluidas con las instrucciones de cuidado
y operación y haga lo siguiente:
1. Identifique el interruptor de pared que controla
la chimenea (verifique que el interruptor opera la
chimenea encendiéndola y apagándola). Limpie bien
la placa del interruptor de pared para quitar el polvo
y aceite. Pegue la etiqueta en la superficie de la placa
del interruptor que controla la chimenea (Figura A).
Seleccione el idioma que más se habla en la casa.
Si no sabe cuál es, use la etiqueta en inglés.
2. Si se usa un control remoto para controlar la
chimenea, encuentre el transmisor y límpielo bien
para quitar el polvo y aceite. Pegue la etiqueta en
la superficie del transmisor (Figura B). Seleccione
.eliuh’d uo essiarg ed secart sel te erèissuop al
el idioma que más se habla en la casa. Si no sabe
cuál es, use la etiqueta en inglés.
3. Si no puede encontrar las etiquetas, sírvase llamar a
Lennox Hearth Products o al distribuidor de Lennox
Hearth Products más cercano para recibir etiquetas
de instrucciones de seguridad adicionales gratuitas.
Juego de etiquetas de repuesto - Nº de cat. H8024
LENNOX HEARTH PRODUCTS
1-800-655-2008
Nota: La etiqueta en inglés es transparente con texto
rojo. Las etiquetas en francés y español son negras
con texto blanco.
Illustrations are for example only. Your
accessories may be different.
Les illustrations sont par exemple
uniquement. Vos accessoires peuvent
être différents.
Las ilustraciones son sólo ejemplos.
Tu accesorios pueden ser diferentes.
22
SAFETY LABEL
DIAGRAMS
Figure A
DIAGRAMMES DES ÉTIQUETTES
DE SÉCURITÉ
Figure B
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
DIAGRAMAS DE ETIQUETAS
DE SEGURIDAD
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
GAS CONVERSION KITS
WARNING
This conversion kit shall be installed by a qualifi ed service agency in
accordance with the manufacturer’s instructions and all applicable codes
and requirements of the authority having jurisdiction. If the information in
these instruction is not followed exactly, a fi re, explosion or production of
carbon monoxide may result causing property damage, personal injury
or loss of life. The qualifi ed service agency is responsible for the proper
installation of this kit. The installation is not proper and complete until the
operation of the converted appliance is checked as specifi ed in the manufacturer’s instructions supplied with the kit.The qualifi ed service agency
performing this installation assumes responsibility for this conversion.
AVERTISSEMENT
Cette trousse de conversion doit être installée par un technicien agréé,
selon les instructions du fabricant et selon toutes les exigences et tous les
codes pertinents de l’autorité compétente. Assurez-vous de bien suivre
les instructions dans cette notice pour réduire au minimum le risque
d’incendie, d’explosion ou la production de monoxyde de carbone pouvant
causer des dommages matériels, des blessures ou la mort. Le tecnicien
agréé est responsable de l’installation de cette trousse. L’installation n’est
pas adéquate ni complète tant que le bon fonctionnement de l’appareil
converti n’a pas été vérifi é selon les instructions du fabricant fournies avec
la trousse. Le fournisseur de service qualifi é ayant réalisé l'installation
assume les responsabilités liées à la conversion.
In Canada:
THE CONVERSION SHALL BE CARRIED
OUT IN ACCORDANCE WITH THE
REQUIREMENTS OF THE PROVINCIAL
AUTHORITIES HAVING JURISDICTION
AND IN ACCORDANCE WITH THE
REQUIREMENTS OF THE CAN/
CGA-B149.1 INSTALLATION CODE.
LA CONVERSION DEVRA ÊTRE
EFFECTUÉE CONFORMÉMENT AUX
RECOMMANDATIONS DES AUTORITÉS
PROVINCIALES AYANT JURIDICTION
ET CONFORMÉMENT AUX EXIGENCES
DU CODE D'INSTALLATION CAN/
CGA-B149.1.
Gas conversion kits are available to adapt
your appliance from the use of one type of
gas to the use of another. These kits contain
all the necessary components needed to
complete the task including labeling that
must be affi xed to ensure safe operation.
Kit part numbers are listed here and the
following steps detail the conversion
procedure. Refer to the instructions provided
with the conversion kit when performing any
gas conversion.
Table 9: Millivolt Conversion Kits
Millivolt SIT Systems
Natural Gas To Propane Gas
Conversion Kits
Models Catalog No.
MPB33 H2009
MPB35 H2011
MPB40 H2013
MPB45 H2015
Millivolt SIT Systems
Propane Gas to Natural Gas
Conversion Kits
Models Catalog No.
MPB33 H2010
MPB35 H2012
MPB40 H2014
MPB45 H2016
Electronic SIT Systems
Natural Gas To Propane Gas
Conversion Kits
Models Catalog No.
MPB33 H8632
MPB35 H8634
MPB40 H8636
MPB45 H8638
Electronic SIT Systems
Propane Gas To Natural Gas
Conversion Kits
Models Catalog No.
MPB33 H8631
MPB35 H8633
MPB40 H8635
MPB45 H8637
Table 10: Electronic Conversion Kits
INSTALLATION INSTRUCTIONS
Step 1. TURN OFF THE GAS SUPPLY TO THE
APPLIANCE and disconnect power supply at
the circuit breaker. Ensure appliance is cold.
CAUTION: THE GAS SUPPLY SHALL BE
SHUT OFF PRIOR TO DISCONNECTING
THE ELECTRICAL POWER, BEFORE
PROCEEDING WITH THE CONVERSION.
ATTENTION: AVANT D’EFFECTUER
LA CONVERSION, COUPEZ D’ABORD
L’ALIMENTATION EN GAZ, ENSUITE,
COUPEZ L’ALIMENTATION ÉLECTRIQUE.
Step 2. Open the lower control compartment
door (see Figure 19 on Page 13) by pushing
on the right top corner of the door (the door
is hinged at the bottom).
[Optional] Remove the control compartment
door by sliding the hinge pin, located at the
door’s left side, to the right until it disengages
from the left corner post hole. Pull the
control compartment door diagonally to the
left, away from the fi replace.
Step 3. Remove the front glass door/frame
from the appliance (see Page 19).
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
23
LENNOX HEARTH PRODUCTS • MERIT PLUS® B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 4. Carefully remove the logs. Exercise
care so as not to break the logs.
Step 5. Refer to Figures 26, 27, or 28.
A. Remove the grate and sub fl oor.
B. Remove the two (2) screws securing the
burner assembly.
C. Remove the burner assembly with
attached venturi tube.
MILLIVOLT AND ELECTRONIC IGNITION
SYSTEM APPLIANCES
Step 6. SIT Systems—Refer to Figure 37
and the instructions provided with the SIT
Regulator Conversion Kit. Using a Torx T20
driver to remove and discard the pressure
regulator mounting screws (two screws for
electronic models, three screws for millivolt
models), pressure regulator tower, the
diaphragm assembly (if applicable) and the
spring. Discard all removed components.
Step 7. Install the new pressure regulator
assembly using the supplied screws. Tighten
the screws with a torque of 25 lb-in.
Pressure
Regulator
Remove
These
Components
Millivolt Valve
Electronic Valve
Figure 37: Regulator Conversion
Step 8. Install the enclosed identifi cation
label to the valve body where it can be easily
seen.
Step 9. Refer to Figure 38. Remove the
pilot hood assembly to access the hexed
pilot orifi ce. Remove and replace the orifi ce
with the one provided with the kit. Exercise
extreme care to prevent damage to or
breakage of the igniter assembly.
Pilot
Orifice
Figure 38: Millivolt Pilot
Step 10. Remove the burner orifi ce from the
manifold and replace it with the one provided
in the kit. See Table 11 for orifi ce sizes for
natural and propane models. Figure 39
illustrates the orifi ce.
Figure 39: Orifi ce
Use pipe joint compound or Tefl on tape on
all pipe fi ttings before installing (ensure
propane resistant compounds are used in
propane applications, do not use pipe joint
compounds on fl are fi ttings).
Step 11. Retrieve the burner and hold the
venturi tube above the orifi ce. Set the burner
assem bly into position and secure with the
two screws previously removed.
Step 12. Reassemble the remaining
components by reversing the procedures
outlined in the Steps 1–5.
Step 13. Attach the conversion label provided
in the conversion kit next to the rating plate
on the appliance.
Step 14. Turn on gas supply and test for gas
leaks (refer to Page 27).
Step 15. Reapply electrical power at the
circuit breaker.
Step 16. Relight the main burner. The
lighting instructions can be found on the
lighting label in the control compartment
or in the Care and Operation Manual
provided with the appliance. Verify proper
burner ignition and operation. See Burner
Adjustments and Burner Flame Appearance
on Page 19.
Step 17. Inspect the pilot system for proper
fl ame. The pilot fl ame should engulf the
fl ame sensor as shown in Figure 23 on
Page 14.
Step 18. Using a manometer, test the inlet
and manifold gas pressures (see Tables 3
and 4 on Page 4).
ALWAYS TEST PRESSURES WITH THE
REGULATOR CONTROL VALVE AT THE
HIGHEST SETTING.
Model
Series
MPB33
MPB35
MPB40
MPB45
Nat.Gas
drill size (inches)
#47 (.0785") *
99K74 •
#44 (.086") *
60J80 •
#38 (.102") *
99K76 •
#36 (.104") *
24M10 •
* Standard size installed at factory
• Part /Cat. Number
Propane
drill size (inches)
(.048")*
99K78 •
#55 (.052") *
19L52 •
(.0625") *
21L01 •
#52 (.0635") *
37G00 •
Table 11: Burner Orifi ce Sizes
Elevation 0–4500 ft
( 0–1372 m)
24
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Lennox Hearth Products reserves the right to make changes at any time, without notice, in design,
materials, specifi cations, prices and also to discontinue colors, styles and products.
Consult your local distributor for fi replace code information.
LENNOX®, the LENNOX design, DAVE LENNOX, the image of DAVE LENNOX and other related
LENNOX marks are registered or common law trademarks of Lennox Industries Inc. and are used
with permission.
Printed in U.S.A. © 2012 Lennox Hearth Products LLC
P/N 506015-05 Rev. NC 07/2012
26
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
1508 Elm Hill Pike, Suite 108 • Nashville, TN 37210
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