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.
WARNING: If the information in these instructions
is not followed exactly, a fire or explosion may
result, causing property damage, personal injury,
or death.
• HOT GLASS WILL CAUSE
BURNS.
• DO NOT TOUCH GLASS
UNTIL COOLED.
• NEVER ALLOW CHILDREN
TO TOUCH GLASS.
• UNE SURFACE VITRÉE CHAUDE
PEUT CAUSER DES BRÛLURES.
• LAISSER REFROIDIR LA SURFACE
VITRÉE AVANT D'Y TOUCHER.
• NE PERMETTEZ JAMAIS À UN ENFANT
DE TOUCHER LA SURFACE VITRÉE.
• EL VIDRIO CALIENTE
CAUSARÁ QUEMADURAS.
• USTED DEBE NUNCA
TOCAR EL VIDRIO CALIENTE.
• LOS NIÑOS DEBEN NUNCA
TOCAR EL VIDRIO.
- Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.
- WHAT TO DO IF YOU SMELL GAS:
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
• If you cannot reach your gas supplier, call the fire
department.
- Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
- 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.
- QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ :
• Ne pas tenter d’allumer d’appareil.
• Ne touchez à aucan interrupteur. Ne pas vous servir des
téléphones se trouvant dans le bâtiment où vous trouvez.
• Appelez immédiatement votre fournisseur de gaz depuis
un voisin. Suivez les instructions du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de gaz,
appelez le service des incindies.
- L’installation et l’entretien doivent être assurés par un
installateur ou un service d’entretien qualifié ou par le
fournisseur de gaz.
MPD Direct-Vent
Gas Fireplaces
P/N 506015-07 Rev. NC 05/2012
This manual is one of a set of two supporting this product.
Refer to P/N 506017-06 for Care and Operation Instructions.
Ce manuel est disponible en francais, simplement
en faire la demande. Numéro de la pièce 506223-43.
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.
This appliance may be installed in an aftermarket permanently located, manufactured home (USA only) or mobile
home, where not prohibited by local codes. This appliance is only for use with the type of gas indicated on the rating
plate. This appliance is not convertible for use with other gases, unless a certified kit is used.
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, efficient 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).
These vented gas fireplace heaters are sealed
combustion, air-circulating gas fireplaces
designed for residential applications.
Approved Vent Components
These fireplaces are designed, tested and
listed for operation and installation with the
following vent components only:
• Secure Vent® Direct-Vent System
Components manufactured by Security
Chimneys International,
• Secure Flex® Flexible Vent Components
manufactured by Security Chimneys
International and
• Z-FLEX® Model GA Venting Systems listed
to UL1777 and ULCS635 manufactured by
Flexmaster Canada Limited.
Use only the correct size venting (4 1/2 in.
inner and 7 1/2 in. outer).
These approved vent system components are
labeled for identification. DO NOT use any
other manufacturer’s vent components with
these appliances.
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 fireplace 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.
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 afin d’éviter des
brûlures ou que leurs vêtements ne
s’enflamment.
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.
2
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNING
I m p ro pe r i n s ta ll at i o n ,
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
inflammables 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 fire, burns,
explosion or carbon monoxide
poisoning.
WARNING
Failure to position the parts in
accordance with these diagrams
or failure to use only parts
specifically 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 spécifiquement
approuvées avec cet appareil sont
utilisées.
Note: Installation and repair should be
done by a qualified 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 confiées à un
technicien qualifié. 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 qualified, 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 qualifié
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.
These appliances comply with National
Safety Standards and are tested and listed
by OMNI-Test Laboratories, Inc. (Report
No. 116-F-13-4) to ANSI Z21.88-2009 (in
Canada, CSA-2.33-2009), and CAN/CGA-
2.17-M91(R2009) in both USA and Canada,
as vented gas fireplace heaters.
Both millivolt and electronic versions of
these appliances are listed by OMNI-Test
Laboratories for installation in bedrooms
and Manufactured Homes.
Misc. Codes / Standards
The Installation must conform to local codes
or, in the absence of local codes, with the
National Fuel Gas Code, ANSI Z223.1-2009
/ NFPA 54—latest edition (In Canada, the
current CAN/CSA-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 fireplaces are designed as supplemental
heaters. Therefore, it is advisable to have an
alternate primary heat source when installed in
a dwelling.
These appliances must not be connected to a
chimney or flue 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 flame control. The
BTU Input for these appliances is shown in
Table 1.
Models
MPD33
MPD35
MPD40
MPD45
Table 1: Input (BTU/HR) Gas Valves
(Millivolt and Electronic)
Input Rate (BTU/HR)
Nat. GasProp. Gas
17,500 high
11,700 low
20,000 high
12,800 low
27,000 high
18,500 low
29,000 high
20,500 low
17,500 high
14,000 low
20,000 high
15,200 low
27,000 high
21,500 low
29,000 high
22,500 low
3
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Gas Pressure—All Models
Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:
Fuel #MinimumMaximum
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 #LowHigh
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 (identified 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 orifice sizes (marked with an
"*" in Table 4). For elevations above 4500 ft,
contact your gas supplier or qualified 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 orice 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 Z223.1-2009 or, in Canada,
the CAN/CSA-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 Z223.1-2009 or, in Canada, the CAN/
CSA-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 fireplaces 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
it
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
HTPTHTPT
Model
Series
MPDT33
MPDR33
MPD35
MPD40
MPD45
Nat.Gas
drill size (inches)
#37 (0.104 in.)*
24M10•
#45 (0.0820 in.)*
39L66•
#38 (0.1015 in.)*
99K76•
#47 (0.0785 in.)*
99K74•
* Standard size installed at factory
• Part /Cat. Number
Propane
drill size (inches)
0.048 in.
99K78•
#55 (0.0520 in.)*
19L52•
0.063 in.
21L01•
#52 (0.0635 in.)*
37G00•
Table 4: Burner Orifice Sizes
Elevation 0–4500 ft ( 0–1372 m)
• Installation and repair must be done by
a plumber or gas fitter licensed in the
Commonwealth of Massachusetts.
• The 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.
Massachusetts Horizontal Vent Requirements
in the Commonwealth of Massachusetts,
horizontal terminations installed less than
seven (7) feet above the finished grade
must comply with the following additional
requirements:
• A hard wired carbon monoxide detector
with an alarm and battery back-up must
be installed on the floor level where the
gas fireplace is installed. The carbon
monoxide detector must comply with
NFPA 720, be ANSI/UL 2034 listed and be
ISA certified.
• A metal or plastic identication plate must
be permanently mounted to the exterior
of the building at a minimum height of
eight (8) feet above grade and be directly
in line with the horizontal termination.
The sign must read, in print size no less
than one-half (1/2) inch in size, GAS VENT
DIRECTLY BELOW. KEEP CLEAR OF ALL
OBSTRUCTIONS.
Hi/Lo Flame
Control Knob
Yellow Ground Wire
(from DFC Wire Harness)
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
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 floor on which appliance rests, if
floor is above ground level. Gas line holes
and other openings should be caulked or
stuffed with unfaced fiberglass insulation.
If the fireplace 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 fireplace and into
the room. It also helps to sheetrock inside
surfaces and tape for maximum air tightness
and caulk firestops.
MANUFACTURED HOME
REQUIREMENTS
This appliance may be installed in
an aftermarket permanently located,
manufactured home and must be installed
in accordance with the manufacturer's
instructions.
Cet appareil peut être installé cómme
du matériel d'origine dans une maison
préfabriquée (É.U. seulement) ou mobile
et doit être installé selon les instructions
du fabricant.
This appliance is only for use with the type
of gas indicated on the rating plate. This
appliance is not convertible for use with other
gases, unless a certified kit is used.
Cet appareil doit être utilisé uniquement
avec le type de gaz indiqué sur la plaque
signalétique. Cet appareil ne peut être
converti à d'autres gaz, sauf si une
trousse de conversion est utilisée.
CAUTION: Ensure that the cross
members are not cut or weakened
during installation. The structural
integrity of the manufactured home
floor, wall, and ceiling / roof must be
maintained.
CAUTION: This appliance must
be grounded to the chassis of the
manufactured home 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.
REAR VENT
APPLICATION
TOP VENT
APPLICATION
APPLICATION
TOP VENT
INSTALLATION
VERTICAL VENT
(Rear Vent Application)
HORIZONTAL VENT
(Rear Vent Application with a chase)
RECESSED
REAR VENT
APPLICATION
TOP VENT
TOP VENT
APPLICATION
TOP VENT
APPLICATION
HORIZONTAL VENT
(Rear Vent Application without a chase)
APPLICATION
TOP VENT
APPLICATION
HORIZONTAL VENT
(Top Vent Application)
Figure 3: Typical Locations
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 traffic 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.
These direct-vent appliances are uniquely
suited for installations requiring a utility shelf
positioned directly above the fireplace. Utility
shelves like these are commonly used for
locating television sets and decorative plants.
VERTICAL VENT
(Top Vent Application)
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 8).
The minimum height from the base of the
appliance to the underside of combustible
materials used to construct a utility shelf in
this fashion is shown in Figure 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 flooring, the appliance shall be
installed on a metal or wood panel extending
the full width and depth of the appliance.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
5
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
LOWEST DISCHARGE OPENING OF VENT
TERMINATION HEIGHTS FOR VENTS ABOVE
VENT TERMINATION CLEARANCES
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-Z223.1-2009) in the USA or the
current standards of CAN/CSA-B149.1 in
Canada.
Vertical Vent Termination Clearances
Terminate multiple vent terminations
according to the installation codes listed
above and Figures 4 and 5.
12 in.
(305mm)
Minimum
Figure 4: Multiple Terminations
Vertical Vent Termination Clearances
The vent / air intake termination clearances
above the high side of an angled roof are as
Horizontal Overhang
2 FT MIN.
Termination
Storm Collar
Flashing
Concentric
Vent Pipe
FLAT OR SLOPED ROOFS
Vent
*H = MINIMUM HEIGHT FROM ROOF TO
2 FT
MIN.
Lowest
Discharge
Opening
H*
1 inch (25.4 mm) Minimum
Clearance to Combustibles
Vertical
Wall
X
12
Roof Pitch is X/12
Figure 5: Termination Heights for Vents
Above Flat or Sloped Roofs
The horizontal vent termination must have a minimum of 6 in. (152 mm) clearance to any
overhead combustible projection of 2 1/2 in. (64 mm) or less, see Figure 6. For projections
exceeding 2 1/2 in. (64 mm), see Figure 6. For additional vent location restrictions, refer to
Figure 7 on Page 7.
Horizontal Vent Termination Clearances
Combustible Projection
inches or less in length
2-1/2
Combustible Projection greater
than 2-1/2 inches in length
Ventilated
Soffit
Unventilated
Soffit
18"
(457 mm)
12"
(305 mm)
Side Elevation View
Termination Kit
Figure 6: Horizontal Vent
Termination Clearances
6"
(152 mm)
All horizontal terminations
may be located as close as
6” (152mm) to any
(non-combustible and
combustible) exterior
sidewall. This distance
may be decreased to 2”
(51mm) for non-combustible exterior
sidewalls only, if the
SV4.5HT-2 termination
is used.
Termination Kit
Note: See Figure 34 on Page 20 for the exterior wall recess
allowances of the square horizontal termination.
6
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MINIMUM CLEARANCES TO COMBUSTIBLES
Appliance And Vent Clearances
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 flush 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).
Hearth Extension—A hearth extension is not required with this
appliance. If a hearth extension is used, do not block the lower control
compartment door. Any hearth extension used is for appearance only
and does not have to conform to standard hearth extension installation
requirements.
Shelf Height—To provide for the lowest possible shelf surface, use
the alternate rear vent outlet, the venting attached to the top vent
should be routed in a way to minimize obstructions to the space above
the appliance. Do not insulate the space between the appliance and the area above it (seeFigure 8). The minimum height from the base
of the appliance to the underside of combustible materials used to
construct a utility shelf in this fashion is shown in Figure 8.
The appliance should 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, etc., a metal or
wood barrier covering the entire bottom surface must be used.
1/2 in. (13 mm)
Back
0 in. (0 mm) from Spacers Or
Dimples
1/2 in. (13 mm)
Sides
0 in. (0 mm) from Spacers Or
Dimples **
3 in. (76 mm)
Top of Fireplace
0 in. (0 mm) with standoff(s) in
vertical position (see Figure 11)
Floor0 in. (0 mm)
From Bottom of Unit To Ceilingminimum of 64 in. (1626)
Vent
3 in. (76 mm) Top* / 1 in. (25.4 mm)
Sides & Bottom
SERVICE CLEARANCES Feet (meters)
Front3 ft (0.9 m)
Table 5: Minimum Clearances*
*Note: 3 in. (75 mm) above any horizontal/inclined vent component.
**Note: See Page 10, Step 1 for clearance requirements to the nailing
flange located at each side of the unit and any screw heads adjacent to it.
Do not insulate the
space between the
appliance and the area
above it.
Combustible Shelf Height—in. (mm)
Do not insulate the
space between the
appliance and the
area above it.
Shelf Height
(see table)
Figure 8:
Shelf Height Minimum Clearances
8
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
12 (305) MANTEL
10 (254) MANTEL
8 (203) MANTEL
6 (152) MANTEL
4 (102) MANTEL
4
(102)
14
(356)
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)
Wall Finishes / Surrounds / Mantels
Note: Combustible wall finish materials and/or surround materials must not be allowed to encroach the area defined by the appliance front face (black
sheet metal). Never allow combustible materials to be positioned in front of or overlapping the appliance face (see Figures 65 and 66 on Page 34).
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 or control compartment.
Vertical installation clearances to combustible mantels vary according to the depth of the mantel. See Figure 9. 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
fireplace hood.
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.
At 6 in. minimum
side wall clearance,
a combustible wall
can project to any
length.
Top View of
Fireplace
Figure 9: Minimum Mantel Clearances
WARNING
Failure to position the parts in accordance with these
diagrams or failure to use only parts specifically
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 spécifiquement
approuvées avec cet appareil sont utilisées.
Combustible Materials
Allowed In Shaded Area
“Safe Zone”
Combustible Walls
shown in dark gray
Combustible materials may
project beyond either side
of the fireplace opening
as long as they are kept
within the shaded area
illustrated here.
6 in.
(152 mm)
o
45
3 1/2 in.
(89 mm)
Figure 10: Minimum Distance to Side Wall
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
9
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
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 two spring latches securing the
glass door (under the firebox floor). 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 Glass Panels on Page 32.
5. Remove the log set from the firebox. Handle
logs carefully to prevent breakage.
6. 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 10): Construct the
appliance framing. Position the appliance
within the framing and secure with nailing
brackets.
IMPORTANT! Bend up the appropriate
header spacing standoffs for the drywall/
finish material thickness to be used
(see Figure 11).
Bend up the outer pair for 1/2 in. materials
and the inner pair for 5/8 in. materials.
Bend out the appropriate nailing flanges for
the drywall/finish material to be used. Nailing
flanges are provided for flush framing, 1/2 in.
and 5/8 in. framing depths (see Figure 11).
Step 2. ROUTING GAS LINE (Page 12):
Route gas supply line to appliance location.
Step 3. PREPARING APPLIANCE VENT
COLLAR (MPD35/-40/-45 models with
combined top/rear vent) (Page 13).
Step 4. INSTALLING VENT SYSTEM
(Page 13): Install the vent system and
exterior termination.
Step 5. FIELD WIRING (Page 25).
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 6. WIRING—OPTIONAL FORCED AIR
BLOWER KIT (Page 26).
Step 7. CONNECTING GAS LINE (Page 26):
Make connection to gas supply.
Step 8. VERIFYING APPLIANCE OPERATION
Frame the appliance as illustrated in Figures
13 and 14 on Pages 10 and 11 (Figure 13
applies to corner framing installations only).
All framing details must allow for a minimum
clearance to combustible framing members
as shown in Table 5 on Page 8.
If the appliance is to be elevated above floor
level, a solid continuous platform must be
constructed below the appliance.
Headers may be in direct contact with the
appliance top standoff spacers when they are bent up vertically, maintaining the 3 in.
clearance to the fireplace top, but must not
be supported by them or notched to fit
around them. All construction above the appliance must be self-supporting. DO NOT
use the appliance for structural support.
Secure the fireplace to the side framing
members using the unit’s nailing flanges
— one top and bottom on each side of the
fireplace front. See Figure 11. Use 8d nails
or their equivalent.
Bend up the appropriate header spacing top
standoffs before installing the fireplace.
Header Spacing Top Standoffs
(two pairs on front edge of firebox top)
Lift up outer pair for
1/2 in. finish materials
Side
Framing
NOTE: The nailing flanges, combustible
members, and screw heads in areas directly
adjacent to the nailing flanges are EXEMPT
from the 1/2 in. clearance to combustible
requirements for the firebox outer wrapper.
Combustible framing may be in direct contact
with the nailing flanges and may be located
closer than 1/2 in. 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 in this manual.
Figure 11: Unit Secured to Framing by
Nailing Flange
IMPORTANT!
Lift up inner pair for
5/8 in. finish materials
Unit Nailing Flange
(No clearance to
combustible framing
is required)
10
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Top View
Right Side View
Front View
Framing
.oNledoMABCDE
MPDT33
MPDR33
MPD35
MPD40
MPD45
Diagrams, illustrations and photographs are not to scale. Consult installation
instructions. Product designs, materials, dimensions, specifications, colors,
and prices are subject to change or discontinuance without notice.
.ni4/133
mm
.ni
mm
.ni4/1534/15361/11124/39361
mm5985981550101604
.ni4/1044/10461/11624/34461
mm220122018767311604
.ni4/1544/10461/11624/34461
mm941122018767311604
Notes
Thermal Efficiency (%)
Fireplace
Model
MPDT33
MPDR33
MPD35
MPD40
MPD45
Natural GasPropane
AFUE EnerGuide
AFUE EnerGuide
(P4)
62456449
61536455
62536055
67596760
67596759
—37 3/4 12 7/833 1/4
—959327845845
19 5/8—12 7/833 1/4 33 1/4
498—327845845
(P4)
Based on CSA P.4.1-09
VENT FRAMING:
TOP VENT WITH ONE
90° ELBOW
VENT FRAMING:
REAR VENT WITH
NO ELBOWS
B
1/2
10-1/2
(
)
267
7
(178)
5-1/8
(130)
7
(178)
5-1/8
D
(130)
C
E
A
A
Dimension “E” is the required framing depth when the
finish material (drywall) thickness is 1/2 in. (13mm).
Framing should be
constructed of 2x4
or larger lumber.
12-1/8
(308)
12-1/8
(308)
Inches (mm)
Vertical Venting through the Ceiling
Frame ceiling opening: Use a plumb line from the ceiling above the appliance to locate center of the vertical run. Cut and/or frame an opening,
10 1/2 in. x 10 1/2 in. (267 mm x 267 mm) inside dimensions, about this center mark (see Figure 17).
3 (76)
N
Gas Inlet (either
side and bottom)
Optional Electrical Inlet
Knockout requiring a
C
B
Field-Provided Junction
Box (either side)
6 (152)
L
1-3/8 (35)
K
1/2 (13)
See Note [2].
1-5/8 (42)
M
F (rear vent
models only)
Electrical Inlet
2-3/4" x 2"
(70 x 51 mm)
Cover Plate
with Knockout
Rear/Side
Framing
Spacers
Header
Spacing
Top
Standoffs
Notes:
[1] MPD models have a top and rear vent. MPDR models
have a rear vent only. MPDT models have a top vent only.
[2] Collars protrude one inch on MPDT33 and MPDR33 models.
G
H
Concentric Flue:
Flue
4-1/2 in. (114 mm);
Combustion Air
7-1/2 in. (190 mm).
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
FIREPLACE FRAMING SPECIFICATIONS
.oNledoMABCDEF
MPDT33
MPDR33
MPD35
MPD40
MPD45
Note:
•Rear Vent Applications in Corner Installations: The horizontal vent length
(from a to b) must not exceed 28 inches (711 mm).
•MPDT33 and MPDR33 Models: Dimensions A through F occur when one
45-degree elbow is connected directly to the appliance collar.
•MPD35, MPD40, and MPD45 Models: Dimensions D through F occur when
one 45-degree elbow is connected directly to the appliance collar.
.ni8/1332/18461/54361/371
mm1482321278734616721
.ni8/1532/1758/50461/3914/3828/16
mm29816412301784037651
.ni8/10461/31623/113461/39161/11038/77
mm910145511011784977002
.ni8/1548/36661/516461/39161/3334/39
mm641168612911784348842
Figure 13: Corner Framing with Horizontal Termination
Step 2. ROUTING GAS LINE
Route a 1/2 in. (13 mm) gas line to the
left side of the appliance as shown in
Figure 14. Gas lines must be routed,
constructed and made of materials that
are in strict accordance with local codes
and regulations. All appliances are factoryequipped with a flexible gas line connector
and 1/2 in. shutoff valve. (See Step 6 on Page 25).
Left Side Front
Corner of Fireplace
Framing
Pipe Coupling
(Recommended)
6-1/2"
(152 mm)
3"
(76 mm)
Also see Figure 12.
Figure 14: Route Gas Line
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, NFPA 54—latest edition (USA) or
CAN/CSA-B149.1—latest edition (Canada).
12
24 1/45
MPD and MPDT units
MPD and MPDR units
C
Back wall of chase/enclosure (including any finishing materials)
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 qualified individual such as a plumber
or gas fitter 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 unqualified should attempt
sizing or installing gas piping.
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
0–101/2 in.3/8 in.
10–401/2 in.1/2 in.
40–1001/2 in.1/2 in.
100–1503/4 in.1/2 in.
150–2003/4 in.1/2 in.
Table 6: Schedule 40 Black Iron Pipe—
Inside Diameter
Notes:
• All appliances are factory-equipped with
a flexible gas line connector and 1/2 inch
shutoff valve (see Figure 46 on Page 25).
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
b
F
7"
(178 mm)
E
D
a
A
B
• 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
(Page 25).
• 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 ofcial for local
code requirements.
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
insufficient 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.
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