Lennox MLBV-35NM, MLBV-40NM, MLBV-35PM, MLBV-40NE, MLBV-40PM Installation Instructions Manual

INSTALLATION INSTRUCTIONS

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.

WARNING /AVERTISSEMENT/AVISO

• 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.

B-Vent Gas Fireplaces
MLBV 35/40 Models

P/N 506015-04 Rev. C 01/2012

This manual is one of a set of two supporting this product.
Refer to P/N 506017-03 for Care and Operation Instructions.

Ce manuel est disponible en francais, simplement
en faire la demande. Numéro de la pièce 506223-21.

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.

MODELS

MLBV-35NM
MLBV-35PM

ITS Report No. 100017854

Please read and understand these instructions

MILLIVOLT:

MLBV-40NM
MLBV-40PM

before starting installation.

ELECTRONIC:

MLBV-35NE
MLBV-40NE

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

TABLE OF CONTENTS

Packaging .........................................Page 2

Introduction ......................................Page 2

General Information ..........................Page 2

Gas Pressure Requirements ..............Page 4

Orifice Sizes ......................................Page 4

Gas Valve Diagrams ..........................Page 4

Requirements for the Commonwealth

of Massachusetts .......................Page 4

New York City Approval .....................Page 4

Cold Climate Insulation .....................Page 5

Location ............................................Page 5

Vent Termination Clearances:

Multiple Terminations.....................Page 6

Gas Vent Rule ................................Page 6

Minimum Clearances to Combustibles:

Appliance and Vent Clearances ......Page 7

Hearth Extension ............................Page 7

Wall Finishes / Surrounds /

Mantels .......................................Page 7

Pre-Installation Steps (Remove

Glass Enclosure Panel) ...............Page 8

Typical Installation Sequence ............Page 8

Detailed Installation Steps:
Step 1. Construct Appliance

Framing ............................Page 8

Fireplace and Framing

Specifications ...................Page 9

Step 2. Route the Gas Line ..............Page 11

Step 3. Install Venting System and

Exterior Termination .........Page 11

Step 4. Install Field Wiring ..............Page 12

Wiring Diagrams .................Page 13

Step 5. [Optional] Install Outside

Combustion Air Kit ............Page 14

Installation Accessories ......Page 14

Step 6. Connect the Gas Line ..........Page 15

Step 7. Verify Appliance

Operation .........................Page 16

Step 8. Install Volcanic Stone, Glowing

Embers, and Logs ...........Page 17

MLBV-35 Log Placement ....Page 18

MLBV-40 Log Placement ....Page 19

Step 9. Install the Glass Enslosure

Panel ...............................Page 20

Step 10. Burner Air Shutter

Adjustments .....................Page 20

Step 11. Perform Spillage Test ..........Page 22

Manually-Reset Safety Limit

Switch ..............................Page 22

Step 12. Install Hood .........................Page 23

Step 13. Finishing Requirements ......Page 23

Step 14.

Warnings ......................................Page 24

Gas Conversion Kits .........................Page 25

2

Attach Safety-in-Operation

PACKAGING

The assembled vented gas fireplace is packaged
with the following items:

1 - One log set located in firebox area.

2 - One envelope containing the literature

package which consists of the care and
operations manual, installation instruc­tions, safety-in-operation warning labels
and warranty; envelope is located in the
control compartment.

3 - One hood located behind the glass enclo-

sure panel assembly.

4 - One bag of decorative volcanic stone located

in the lower control compartment.

5 - One bag of glowing embers located in the

lower control compartment.

INTRODUCTION

The Millivolt appliances have a millivolt gas
control valve with piezo ignition system.

The Electronic appliances have a battery
backed-up electronic intermittent pilot ignition
system. No external electrical power is required
to operate these appliances; however, 120V
AC is recommended (see Step 4, “Install Field
Wiring,” on Page 12).

Use Only These Approved Vent Components:

These vented gas fireplaces 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.

• 4" B-Vent for 35" models and 5" B-Vent for
40" models.

GENERAL INFORMATION

WARNING

B-Vent appliances are
not designed to operate
in negatively pressured
environments (pressure within
the home is less than pressures
outside). Significant negatively
pressured environments caused
by weather, home design, or
other devices may impact the
operation of these appliances.
Negative pressures may result
in poor flame appearance,
sooting, damage to property
and/or severe personal
injury. Do not operate these
appliances in negatively
pressured environments.

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 infor-més 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.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

GENERAL INFORMATION

(continued)

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 qualied 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 ammable
material should not be placed
on or near the appliance.

AVERTISSEMENT

On ne devrait pas placer de
vêtements ni d’autres matières
in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
re, burns, explosion or
carbon monoxide poisoning.

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 ITS
(Report No. 100017854) to ANSI Z21.50 (in
Canada, CSA-2.22) and to CAN/CGA-2.17-M91
in both USA and Canada (latest editions at time
of manual publication) as vented gas fireplaces.

Both millivolt and electronic versions of
these appliances are listed by ITS for instal­lation in bedrooms in the United States (not
approved in Canada).

These appliances must not be connected to a
chimney or flue serving a separate solid fuel
burning appliance.

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), or the Natural Gas and Propane Instal­lation Code, CAN/CSA B149.1 (latest edition).

The appliance, when installed, must be electri­cally grounded and wired in accordance with
local codes or, in the absence of local codes, with
the USA National Electrical Code, ANSI/NFPA

70 (latest edition) or, in Canada, 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 opening 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.

MILLIVOLT MODELS: The millivolt appliances
are manually controlled and feature a spark
igniter (piezo) that allows the appliance's pilot
gas to be lit without the use of matches or bat­teries. This system provides continued service
in the event of a power outage.

ELECTRONIC MODELS: The electronic appli­ances are manually controlled and feature an
electronic intermittent pilot ignition system.
External electrical power is required to operate
these units.

ALL MODELS: Both millivolt and electronic
models come standard with a manually­modulated gas valve; flame appearance and
heat output can be controlled at the gas valve.
BTU input rates for all models are listed in
Table 1, below.

Input (BTU/hr) Manually-Modulated

Gas Valves (all models)

Models

MLBV-35

MLBV-40

Table 1

Input Rate (BTU / HR)

Natural Gas Propane Gas

17,000 high

13,000 low

22,000 high

17,000 low

17,000 high

14,000 low

20,000 high

15,500 low

3

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

GAS PRESSURE REQUIREMENTS

(All Models)

Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:

Inlet Gas Supply Pressure

(All models)

Fuel # Minimum Maximum

Natural Gas

Propane

4.5" WC

(1.12 kPa)

11.0" WC

(2.74 kPa)

Table 2

Manifold Gas Supply Pressure

(All models)

Fuel # Low High

Natural

Gas

Propane

(Lo) 2.2" WC

(0.55 kPa)

(Lo) 6.3" WC

(1.57 kPa)

Table 3

Test gauge connections are provided on the
front of the gas control valve, identified IN for
the inlet and OUT for the manifold side (see
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.

These appliances must be isolated
from the gas supply piping system (by
closing their individual manual shut-off
valve) during any pressure testing of
the gas supply piping system at test
pressures equal to or less than 1/2 psig
(3.5 kPa).

These appliances and their individual
shut-off valves must be disconnected
from the gas supply piping system
during any pressure testing of that
system at pressures greater than 1/2
psig (3.5 kPa).

4

10.5" WC

(2.61 kPa)

13.0" WC

(3.23 kPa)

(Hi) 3.5" WC

(0.87 kPa)

(Hi) 10.0" WC

(2.49 kPa)

ORIFICE SIZES

Sea Level to High Altitude

(All Models)

These appliances are tested and approved for
installation at elevations of 0–4500 feet (0–1372
meters) above sea level using the standard
burner orifice sizes (marked with an asterisk
(*) in Table 4, below).

For elevations above 4500 feet, contact your
gas supplier or a 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 orifice to a smaller size

as regulated by the local authorities having
jurisdiction and by the (USA) National Fuel Gas
Code NFPA 54/ANSI Z223.1 - latest edition or,
in Canada, the CAN/CSA-B149.1 codes - latest
edition.

Install the appliance according to the regulations
of the local authorities having jurisdiction and,
in the USA, the National Fuel Gas Code NFPA
54 / ANSI Z223.1 - latest edition or, in Canada,
the CAN/CSA-B149.1 - latest edition.

NOTE: Flame appearance will diminish
4% per thousand feet of altitude.

Burner Orifice Sizes

Elevation 0-4500 feet ( 0-1372 meters)

Model

Series

MLBV-35

MLBV-40

Table 4

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Nat.Gas

drill size (inches)

#48 (0.076")*

drill size (inches)

#56 (0.046")*

H1236•

#43 (0.089")*

#55 (0.052")*

99K75•

Standard size installed at factory.

*

• Part /Catalog Number.

Propane

62L37•

19L52•

GAS VALVE DIAGRAMS

See Figure 1 for millivolt models and Figure 2
for electronic models.

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

Pilot Adjustment

I

P

W

O

L

H

I

HI/LO Variable
Flame Height
Adjustment

Screw

T

O

L

HTPTHTPT

Figure 1 - SIT Millivolt Gas Valve

Supply
Gas
Inlet

Pressure-Tap
(Manifold)

IN

PILOT

Pilot Gas
Outlet

Regulator
Mounting Screw

Pressure-Tap
(Inlet)

Burner Stage

Terminal

VENT

OUT

IN

HI

Ground
(TP)

LO

TH

TH

TP

Pilot Stage
Terminal

TP

Figure 2 - Dexen Electronic Gas Valve

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.

• Installation and repair must be done by a
plumber or gas fitter licensed in the Com­monwealth of Massachusetts.

• The flexible gas line connector used shall
not exceed 36 inches (92 centimeters) in
length.

• The individual manual shut-off must be a
T-handle type valve.

NEW YORK CITY APPROVAL

New York City, NY (MEA)

These fireplaces are approved for installation
in New York City in the US state of New York
if the following additional requirement is met:

• An Outside Combustion Air Kit (FOAK-4,
FOAK-4LD, or DK-4) must be installed. See
Step 5 on Page 14.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • 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. Check local codes for

additional requirements.

If the fireplace is being installed on a cement
slab in cold climates, a sheet of plywood or
other raised, insulated platform can be placed
underneath to prevent cold transfer to the
fireplace and into the room. It also may help
to sheetrock the inside surfaces and/or tape
for maximum air tightness.

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 appliances are equipped with an inte­gral combustion air door and actuator arm.

Combustion air kits are optional and must be
installed before removing the securing screw
allowing the movement of the combustion air
actuator arm (see Step 5 on Page 14).

Be aware that this is a heat-producing ap­pliance. Objects placed above the unit are
exposed to elevated temperatures.

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.

These appliances may be used for bedroom
installations in the United States and are listed
accordingly. These units may not be installed
in bedrooms in Canada.

Figure 3: Typical Locations

Note: When the unit is installed with one side
flush with a wall, see Figure 5 on Page 7.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

5

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

VENT TERMINATION
CLEARANCES

Multiple Terminations

These appliances may vent adjacent to and at
the same level with any other gas appliances
(including direct vent appliances), provided
there is at least 2 ft (0.6 m) between the proxi­mal edges of the vent caps. These appliances
may be vented adjacent to a chimney vent
servicing a solid fuel fireplace, provided the
B-vent cap is at least 2 ft (0.6 m) away from the
nearest point of the chimney opening.

Gas Vent Rule

Gas vent caps are not permitted within 8 ft (2.4
m) of a vertical wall or similar obstruction. Gas
vent caps that are located 8 ft or more from a
portion of a building that extends at an angle
greater than 45° upward from the horizontal
may terminate in accordance with Figure 4,

provided that any discharge opening on
the cap is NEVER LESS THAN 2 ft (0.6 m)
horizontally from the roof surface (National

Fuel Gas Code ANSI Z223.1 (NFPA 54) “Gas
Vent Termination” section) (CAN/CGA B149.1).

Gas Vent Rule

Figure 4

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

Table 5

6

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

5 (127)

8-1/4

(209)

14

(356)

12 (305)

19

(483)

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • 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 6), 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 (see Figure 5).

MINIMUM CLEARANCES

Back 0 in. (0 mm) to Standoffs or Dimples

Sides 0 in. (0 mm) to Standoffs or Dimples**

Top 3 in. (76 mm)

Floor 0 in. (0 mm)

From Bottom of Unit

to Ceiling

Vent 1 in. (25.4 mm)

SERVICE CLEARANCES

Front 3 ft. (0.9 m)

Table 6

**Note: See Step 1 on Page 8 for clearance requirements to the
nailing flange at each side of the unit and any screw heads adjacent to it.

64 in. (1626 mm)

At 14" minimum side
wall clearance, a
combustible wall can
project to any length.

At 8-1/4" side
wall clearance, a
combustible wall
can project 12".

o

45

Protected wall
shown in white

Top View of

Fireplace

Combustible Materials
Allowed In Shaded Area
“Safe Zone”

Combustible walls
shown in dark gray.

Combustible materials
may project beyond
one side of the
fireplace opening
as long as they are
kept within the shaded
areas illustrated here.

Inches (millimeters)

Figure 5 - Minimum Distance to Unprotected Side Wall

Mantel Depth

18 (457)

16 (406)

inches (millimeters)

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.

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 Figure 5; also see
Figure 30 on Page 23).

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.

Vertical installation clearances to combustible mantels vary according
to the depth of the mantel. See Figure 6. Mantels constructed of non­combustible materials may be installed at any height above the appliance
opening; however, do not allow anything to hang below the fireplace hood.

Note: We recommend the use of high-temperature paint (rated 175°F or
higher) on the underside of the mantel.

14 (356)

12 (305)

10 (254)

8 (203)

12

(305)

10

(254)

(203)

6

8

(152)

(102)

2

4

(51)

Figure 6 - Minimum Mantel Clearances

Header

Top of
Appliance

Note - Hood shown
as positioned.

7

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Top
Standoff
Spacers*

Flush
Nailing

1/2"
Nailing
Flange

5/8"
Nailing
Flange

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

PRE-INSTALLATION STEPS

(Remove Glass Enclosure Panel)

The appliance is shipped with all gas controls
and components installed and pre-wired.

Note: Remove the glass enclosure panel
before installing the fireplace.

To remove the glass enclosure panel:

1. Remove the shipping carton, and then re­move the shipping pad, exposing the front
glass panel.

2. Open the two latches securing the glass
panel (under the firebox floor).

3. Remove the glass panel by tilting it outward
at the bottom and lifting it up.

4. Set aside the glass enclosure panel in a
safe location to protect it from inadvertent
damage.

TYPICAL INSTALLATION
SEQUENCE

The typical sequence of installation is outlined
below, with page number references to the
related detailed instructions.

NOTE: Each installation is unique and may
result in variations to these steps.

Step 1. (Pages 8–10) Construct the appliance

framing.

Position the appliance within the

framing and secure with nailing
brackets.

IMPORTANT! Bend up the appropri-

ate top standoff spacers for the
drywall/finish material thickness to
be used (see Figure 7). Bend up the

outer pair for 1/2" ma terials and the
inner pair for 5/8" materials.

Bend up the outer pair for 1/2" ma-

terials and the inner pair for 5/8"
materials.

Bend out the appropriate nailing

flanges for the drywall/finish material
to be used.

Nailing flanges are provided for flush

framing, 1/2 inch and 5/8 inch fram­ing depths (see Figure 7).

Step 2. (Page 11) Route the gas supply line

to the appliance location.

Step 3. (Page 11) Install the vent system and

exterior termination.

Step 4. (Page 12) Install field wiring.
a. Millivolt Appliances: Install the

operating control switch (not factory
provided).

b. Electronic Appliances: Field wire

8

and install operating control switch.

Step 5. (Page 14) [OPTIONAL]: Install

outside supplemental combustion
air kit.

Step 6. (Page 15) Make connection to gas

supply.

Step 7. (Page 16) Verify appliance operation.

Step 8. (Page 17) Install the logs, decorative

volcanic stone, and glowing embers.

Step 9. (Page 20) Install the glass enclosure

panel.

Step 10. (Page 20) Adjust burner air shutter

to ensure proper flame appearance.

Step 11. (Page 22) Perform spillage test.

Step 12. (Page 23) Install hood.

Step 13. (Page 23) Complete finished interior

wall.

Step 14. (Page 24) Attach "Safety-in-

Operation" warnings.

DETAILED INSTALLATION STEPS

Step 1. Construct Appliance
Framing

Frame the appliance as illustrated in Figures
8-1 and 8-2. All framing details must allow for

a minimum clearance to combustible framing
members as shown in Table 6, Page 7.

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" 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 7. Use 8d nails or equivalent.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Header
Spacing
Top
Standoffs

*IMPORTANT!
Bend up the
Top Standoff
Spacers before
installation.

Use outer pair
for 1/2" materials
and inner pair
for 5/8" materials.

Side

Framing

(Left side front corner of fireplace shown.

NOTE: The nailing flanges, combustible
members, and screw heads in areas directly
adjacent to the nailing flanges are EXEMPT
from the 1/2” 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” 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 7

~

Nailing flanges are
provided at all four
corners at 5/8", 1/2",
and flush settings.

Fireplace secured to framing

by nailing flanges

Right side requirements are the same.)

5/8”
Nailing
Flange

1/2”
Nailing
Flange

Fireplace
Nailing
Flanges

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.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

FIREPLACE AND FRAMING SPECIFICATIONS

NOTE: Diagrams, illustrations and
photographs are not to scale. Product
designs, materials, dimensions,
specifications, colors, and prices are
subject to change or discontinuance
without notice.

Input (BTU/hr) Manually-Modulated

Gas Valves (all models)

Model

MLBV-35

MLBV-40

Input Rate (BTU / HR)
Natural Gas Propane Gas
17,000 high

13,000 low

22,000 high

17,000 low

17,000 high

14,000 low

20,000 high

15,500 low

FIREPLACE FRAMING DIMENSIONS

Construct framing with 2x4 or larger lumber.

B

C

1/2

A

A

Framing Dimensions

Model No. A B C

MLBV-35

MLBV-40

in. 35-1/4 35-1/4 16

mm 895 895 406

in. 40-1/4 40-1/4 16

mm 1022 1022 406

“C” is the required framing depth dimension
when the finish material (drywall) thickness
is 1/2 in. (13mm).

Figure 8-1

CORNER FRAMING DIMENSIONS

F

D

E

Back wall of chase/enclosure
(including any finishing materials)

Corner Framing Dimensions

Model No. D E F G

MLBV-35

MLBV-40

in. 35-1/4 57-1/2 40-5/8 28-3/4

mm 895 1461 1032 730

in. 40-1/4 61-13/16 48-11/32 30-11/16

mm 1022 1554 1101 779

G

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

9

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

J

(13 mm)

M

Front View

H

L

K

J

Q

N

P

Top View

Flue Outlet for
B-Vent Connection:
35 Models = 4 in. (102 mm)
40 Models = 5 in. (127 mm)

9-1/4 in. (235 mm)

1/2 in.

(13 mm)

APPLIANCE SPECIFICATIONS

M

N

P

1/2 in.

Top View

Flue Outlet for
B-Vent Connection:
35 Models = 4 in. (102 mm)
40 Models = 5 in. (127 mm)

9-1/4 in. (235 mm)

H

K

L

Q

Front View

Figure 8-2

in.

mm

in.

mm

32-1/4

819

37-1/4

946

H J L M N P QK

28-1/8

23-1/4

714

28-1/4

33-1/8

841

59032813

71837940

35-1/4

89525635

40-1/4

1022307621538138965

12-1/2

31733838

Model No.

MLBV-35

MLBV-40

Vertical Venting Through Ceiling

Frame Ceiling Opening: To locate the center of the vertical run, use a plumb line from the ceiling above the appliance.

ELECTRICAL INLET

2-3/4 in. x 2 in.

(70 mm x 51 mm)

COVER PLATE with

KNOCKOUT (Right Side)

GAS INLET KNOCKOUT*

*NOTE: It is recommended that gas
be stubbed in from LEFT side only.

Optional Electrical Inlet

Knockout requiring a

field-provided Junction

3 in. (76 mm)

Box (Either Side)

3 in. (76 mm)

Hood

16 in.

(406 mm)

5-7/8 in.
(149 mm)

Right Side View

9-1/2 in. (241 mm)

1-5/8 in. (42 mm)

9-1/2 in. (241 mm)

7-1/8 in. (181 mm)

7-3/8 in. (187 mm)

Hood

16 in.

(406 mm)

5-7/8 in.

(149 mm)

Left Side View

10

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 2. Route the Gas Line

Route a 1/2" (13 mm) gas line to either side
of the appliance (left side routing is shown
in Figure 9 ). Gas lines must be routed, con­structed, and made of materials that are in strict
accordance with local codes and regulations.
All appliances are factory-equipped with a flex­ible gas line connector and 1/2-inch shutoff
valve. (See Step 6 on Page 15.)

NOTE: Gas line can be routed to either
side. Reverse this illustration if routing
to right side.

Also see Figures 8-1 and 8-2.

Figure 9: 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).

Never use galvanized or plastic pipe. Gas lines
must be routed, constructed and made of ma­terials that are in strict accordance with local
codes and regulations.

IMPORTANT: It is critical that a licensed
installer perform this step strictly per
NFPA.

We recommend that a qualified, licensed
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.

Notes:

• All appliances are factory-equipped with
a flexible gas line connector and 1/2 inch
shutoff valve (see Figure 17 on Page 15).

• 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

15).

• A pipe joint compound rated for gas should
be used on the threaded joints. Ensure that

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. Appliances using propane should
have a sediment trap at the base of the tank.

• Check with local building official for local
code requirements (e.g., whether below­grade penetrations of the gas line are al­lowed, etc.).

IMPORTANT: If propane is used, be aware that
if the 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 pressure loss
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.

Step 3. Install Venting System
and Exterior Termination

These instructions should be used as a
guideline and do not supercede local codes
in any way.

Install venting according to local codes, these
instructions, the current National Fuel Gas
Code in the USA (ANSI-Z223.1) or the current
standards in Canada (CAN/CSA-B149.1).

MLBV-35 and MLBV-40 series fireplaces
must be vertically vented using listed type­B, double-walled vent pipe with the proper
diameter as listed below and a listed vent
termination.

Required Pipe Diameter

MLBV-35 series: Requires 4 in. (102 mm)
MLBV-40 series: Requires 5 in. (127 mm)

WARNING

Sharp Edges.
Watch Your Fingers!

WARNING: EDGES OF SHEET METAL ARE
SHARP! WEAR PROTECTIVE GLOVES AND USE
EXTREME CARE WHEN HANDLING.

Required tools:

• Sheet Metal-resistant Gloves

• Tin Snips

1. Using tin snips, cut the three connecting

points securing the slug to the three tabs
in the flue collar (as shown in Figure 10a),
and remove the slug.

Carefully dispose of slug in an appropriate

container.

Cutting

points

Slug

Figure 10a

2. Connect the proper size Type B-vent system

to the fireplace flue collar by bending up the
three tabs and securing with three sheet
metal screws (No. 8 or larger) bend up tabs.
See Figure 10b. Then install the remainder
of the Type B-vent to the outside.

Type B-Vent

MLBV-35 models: 4 in. (102 mm)
MLBV-40 models: 5 in. (127 mm)

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Figure 10b

11

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Back View

Of Appliance

*12 ft. Min.

**15 ft. Min.

Installations

10 ft.

Minimum

Back View

Of Appliance

Figure 11

3. Refer to Figure 11. The following venting

configurations may be installed:

Vertical Installations

• Minimum overall height of the vent

system and appliance without an offset
must be 10 ft (2.54 m).

Offset Installations

• Offset up to 45 degrees from vertical:

Minimum overall height of the vent
system and appliance must be 12 ft
(3.66 m). The lower part of the offset
may start at the fireplace flue collar.

• Offset greater than 45 degrees and up

to 60 degrees from vertical: Minimum
overall height of the vent system and
appliance must be 15 ft (4.57 m). The
lower part of the offset may start at the
fireplace flue collar.

Maximum overall height of the vent system

and appliance should not exceed 40 ft
(12.19 m).

Install the B-vent system in accordance with
the vent manufacturer's instructions.

CAUTION: THIS APPLIANCE CANNOT BE
VENTED HORIZONTALLY.

Note: 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.

12

Vertical

Offset

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

Step 4. Install Field Wiring

CAUTION

Ground supply lead must be con­nected to the wire attached to the
green ground screw located on the
outlet box. See

Figure 13. 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 installing.

A. All Models

• An optional unit-mounted ON/OFF switch
may be installed in the lower control com­partment.

• An optional wall-mounted ON/OFF switch or
optional ON/OFF remote control kit also may
be used.

• If a wall-mounted ON/OFF control switch is
used, mount it in a convenient location on a
wall near the fireplace.

• If an optional Style View Door is used in
conjunction with an optional unit-mounted

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

ON/OFF switch, the switch may be mounted
onto the Style View Door per instructions
provided in kit.

• The gas valve is set in place and pre-wired at
the factory on all models.

Refer to Section B (below) for millivolt appli­ances and Section C (below) for electronic
appliances.

B. Millivolt Wiring (see Figure 12)

1. Read Section A, “All Models,” at left.

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: Do NOT connect the optional wall
switch to a 120V power supply.

C. Electronic Wiring (see Figure 13)

Note: The electronic appliance must be con­nected to the main power supply.

1. Read Section A, “All Models,” at left.

2. Route a 3-wire 120Vac 60Hz 1ph power

supply to the appliance junction box.

3. Remove the electrical inlet cover plate from

the side of the unit by removing the plate's
securing screws (see Figures 8-1 and 8-2

on Pages 9 and 10).

4. Remove the cover plate's knockout; then feed

the power supply wire through the knockout
opening and into the unit junction box.

5. Connect the black power supply wire to the

lower outlet's red pigtail lead and the white

power supply wire to the common terminal
of the outlet as shown in Figures 13 and 14.

6. Connect ground supply wire to pigtail lead

attached to 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. The glass
enclosure panel must be removed first to place
the receiver in the lower control compartment.

7. If using an optional control, wire it in the low

voltage circuit as shown in Figure 13.

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 wiring is complete, replace cover plate.

Note: Do NOT install batteries in the battery
holder until needed (i.e., in the event of a

power outage or if operating the appliance
solely by batteries). The battery holder requires
two [2] "D" batteries.

H

I

L

O

W

P

I

L

O

T

O

N

ti

O

F

F

IN

OUT

TRANSFORMER 3V

BROWN

BROWN

BLACK

BATTERY BACK-UP

BLACK (SENSOR)

BLACK (IGNITER)

IGNITER MODULE

3V

RED

PILOT

IN

OUT

VENT

LO

HI

TH

TP

TH

TP

IN

ORANGE (THTP)

BLACK (TP)

GREEN (TH)

HIGH LIMIT SWITCH

Pilot Burner

Pilot Tube

Assembly

Schematic Representation Only

Electronic Gas Control Valve - DEXEN

B-Vent appliances only - High limit
switch must be factory installed as
shown. If wires to this switch are
replaced, wires must be Type AWM
200°C - 18 gage wire ONLY.

CONTROL
SWITCH *

UNIT MOUNTED

ON/OFF SWITCH,

IF SUPPLIED

Junction Box

J-Box Wiring

BK
W

G

CAV 021

* Control Switches: Wall On/Off
Switch, Unit Mounted On/Off Switch
or Remote Control Switch.

NOTES:

1. If any of the original wire as supplied
must be replaced, use Type AWM
105°C - 18 gage wire ONLY.

2. 120 VAC, 60 Hz - Less than 3 Amps.
CAUTION: label all wires prior to
disconnection when servicing controls.
Wiring errors can cause improper and
dangerous operation. Verify proper
operation after servicing.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

MILLIVOLT WIRING DIAGRAM

CAUTION: WHEN SERVICING CONTROLS, LABEL ALL WIRES PRIOR TO DISCONNECTION.
WIRING ERRORS CAN CAUSE IMPROPER AND DANGEROUS OPERATION.

VERIFY PROPER OPERATION AFTER SERVICING.

Figure 12

B-VENT APPLIANCES ONLY: The High Limit
Switch must be factory installed in series,
as shown. If wires to this switch must be
replaced, use Type AWM 200°C - 18 gage
wire ONLY.

High Limit Switch

Control Switch*

If any of the original wire must be replaced,
use Type AWM 105º C - 18 gage wire ONLY.

_________
*Control switch options: ON/OFF wall switch, unit-mountable

ON/OFF switch, or ON/OFF remote control system (see "Accessory
Components" in the Care and Operation Instructions).

Thermopile

Gas Control

Valve Terminals

J-BOX/RECEPTACLE WIRING

J-BOX / RECEPTACLE

120V, 60HZ, 1PH

120V, 60HZ, 1PH

Neutral - White

Ground - Green

120 VAC - Black

WIRING

Junction Box

T

TP HTP

Black

Tab Intact

Hot Side of

TH

White

Green

Receptacle

Neutral Side
of Receptacle

Tab Intact

Field Wired

Green Ground
Screw

Factory Wired

Figure 14

Figure 13

ELECTRONIC IGNITION WIRING DIAGRAM

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

See Figure 14 for detailed drawing of junction box / receptacle wiring.

_________
*Control switch options: ON/OFF wall switch, unit-mountable

ON/OFF switch, or ON/OFF remote control system (see "Accessory
Components" in the Care and Operation Instructions).

13

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 5. [OPTIONAL] Install Outside
Combustion Air Kit

An optional outside combustion air kit (model
FOAK-4, FOAK-4LD, or DK-4) may be used
with these appliances (see "Installation Acces­sories," at right).

Refer to the instructions included with the
air kits for specific installation information.
If used, the outside air kit must be installed
before the fireplace is framed and enclosed in
the finished wall.

Outside air drawn into the fireplace supplies
supplemental combustion air to the fire. Only
one outside air duct is necessary, if installed.

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 one continuous piece.

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 upward 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 floor joists and under the home
to a ventilated crawlspace not considered part
of the living area of the home.

Note: NEVER terminate an outside supple­mental combustion air kit in attic space
under any circumstances.

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 15.

The hand-operated outside air control lever
is located on the left side of the lower control
compartment opening. See Figure 15.

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 fireplace is in use and
completely closed when the fireplace is not being
used. Closing it when not in use will help limit the
amount of outside cold air entering the dwelling.

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.

Securing
Screw
Installed

Outside Air Control
Lever pushed UP
(Air Shutter CLOSED)

IMPORTANT: Do NOT move Air Control
Lever if securing screw is installed
(or if not sure it was removed).

INSTALLATION ACCESSORIES

The following accessory items are available for
use in the installation of this appliance.

Outside Combustion Air Kits
Models FOAK-4 and FOAK-4LD

Outside combustion air kits are available with
duct (FOAK-4) and without duct (FOAK-4LD)
for use if supplemental outside combustion
air is required or desired. If model FOAK-4LD
is used, it must be used in conjunction with
locally purchased, non-combustible Class 1 or
Class 0 flexible duct.

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)

H5377 DK-4 Single 4" Duct Kit

After completing 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 firebox.

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.

14

Securing
Screw
Removed

Outside Air Control
Lever pulled DOWN
(Air Shutter OPEN)

Left Side of

Lower Control Compartment

Figure 15

WARNING

Do not operate the shutoff lever
unless a complete outside com­bustion air system has been
installed with your appliance.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Gas
Valve

3/8" NPT x

Flare Fitting

3/8" Flex Tubing

3/8" Nipple

3/8" Union

3/8" Close
Nipple

3/8" Shut-off Valve

1/2" x 3/8"

Reducer

Gas

Stub

1/2" x 3/8" Flare

Shut-off Valve

Gas Solid Line Connector

Gas Flex Line Connector

*Sediment
Trap

3"

Mi

n

Note: Millivolt system shown. Electronic system controls are similarly located.

Step 6. Connect the Gas Line

All codes require a shut-off valve mounted in
the supply line. The orientation of the shut­off valve should face the front. Figure 16
illustrates two methods for connecting the gas
supply. A sediment trap is recommended in the
gas piping within the home to prevent moisture
and debris in the line from damaging the valve.

The flex-line method is acceptable in the U.S.A.
where local codes permit, however, Canadian
requirements vary depending on locality. Instal­lation must be in compliance with local codes.
These appliances are equipped with a gas flex­line for use in connecting the unit to the gas line.
See Figure 16 for flex-line description. The
flex-line is rated for both natural and propane
gas. A manual shut off valve is also provided
with the flex-line.

The gas control valve is located in the lower
control compartment.

Access the valve compartment by removing the
lower control compartment panel (see Figure

17) by lifting and pulling the panel forward.
The panel is mounted on supporting tabs at
the extreme right and left hand sides. Engage
the tabs into the reliefs in the panel.

The millivolt and electronic control valve has a
3/8" (10 mm) NPT thread inlet port.

Secure all joints tightly using appropriate
tools and sealing compounds (ensure propane
resistant compounds are used in propane ap­plications). It is recommended to seal around
the gas line to prevent cold air leakage.

Gas line connection may be performed largely
outside of the confines of the control compart­ment and without having to enter the firebox
behind the glass. Proceed as follows:

Acquire the shut-off valve and gas flex-line and
pull the assembly forward out of the compart­ment. Separate the shut-off valve from the gas
flex-line. Determine the length of pipe needed
to route the gas line from the last fitting (shown
in Figure 9) to a point within the control com­partment that will allow the shut-off valve to
be easily attached by hand to the gas flex-line.

Using pipe-dressing materials appropriate for
the gas type, securely affix the shut-off valve
to this determined pipe length at a convenient
location outside of the appliance lower control
compartment.

Refer to Figure 18. Insert the last length of gas
pipe with its attached shut-off valve into the
lower control compartment, and pass it through
the gas line access hole on the left side of the
appliance outer wrapper.

Using appropriate materials for the gas type,
thread the last length of pipe into the end of
the gas vent run and tighten in place using a

pipe wrench external to the appliance between
the appliance outer wrapper and the framing.

Important: Turn the last piece of gas pipe in
the last fitting until the shut-off valve is posi­tioned in a way that allows the shut-off valve
handle to be accessed in the lower control
compartment, easily operated throughout its
full range of motion.

Bring the flex-line to the shutoff valve by hand
and align the flare fittings. Tighten the fittings
by hand, and then use wrench to tighten com­pletely, 1/4-turn at a time.

Figure 16: Gas Connection

Gas Flex Line

(Gas Shut-Off Valve is behind

door latch; see DETAIL, below)

DETAIL:

Gas Shut-Off Valve

in ON position (gas line OPEN)

To shut OFF gas: Turn valve handle
perpendicular (cross-wise) to gas line.

Figure 17

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Gas Control

{

Valve

Optional

Unit-Mounted

ON/OFF Switch

Note: The gas supply
line must be installed in
accordance with building
codes by a qualied installer
approved and/or licensed
as required by the locality.
In the Commonwealth of
Massachusetts, installation
must be performed by a
licensed plumber or gas tter.

~

Piezo

(Millivolt

units only)

DETAIL: Lower Control Compartment

Length of pipe with attached

Gas Shut-Off Valve in OFF position

Figure 18

Spring

Door Latch

(one of two)

Lower Control

Compartment

Door Tab

(gas line CLOSED)

(shaded area)

15

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

MILLIVOLT

Thermocouple

Hood Igniter Rod

3/8" Min
(9 mm)

Thermopile

Pilot
Nozzels

Test All Connections for Gas Leaks
(Factory and Field)

WARNING

Never use an open flame 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/fittings 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. 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.

Step 7. Verify Appliance
Operation

Turn on burner then observe the individual
tongues of flame on the burner. Make sure
all ports are open and producing flame evenly
across the burner. If any ports are blocked, or
partially blocked, clean out the ports.

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 manual. For
piezo igniter location, see Figure 17 (millivolt
appliances only).

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 by pulling
the panel forward (see Figures 17 and 25).

When first 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 flame
(remove logs, if necessary, handling carefully).

Millivolt Appliance Checkout

The pilot flame should be steady, not lifting
or floating. Flame should be blue in color with
traces of orange at the outer edge.

The top 3/8" (10 mm) at the pilot generator
(thermopile) and the top 1/8" minimum (tip)
of the quick drop out thermocouple should be
engulfed in the pilot flame.

The flame should project 1" (25 mm) beyond
the hood at all three ports (see Figure 19).
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).

Figure 19

Electronic Appliance Checkout

To light the burner, turn ‘ON’ the unit mounted
On/Off switch or the optional remote wall switch.
Ensure the igniter lights the pilot. The pilot
flame should engulf the flame rod as shown
in Figure 20.

ELECTRONIC

Sensor

Igniter

Figure 20

Pilot
Hood

16

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 8. Install Volcanic Stone,
Glowing Embers (Rockwool),
and Logs

NOTE: Turn OFF all electricity to the fire­place before installing volcanic stone,
glowing embers, or logs.

1. Remove the front glass enclosure panel

(see “Removal and Installation of Glass
Enclosure Panel,” on previous page).

2. Install ceramic brickaded panel liners.

3. Install decorative volcanic stone. Refer to

Figure 21. Sprinkle the decorative volcanic
stone in a pleasing pattern directly on the
firebox bottom, along the slope and to the
back, at the right and left sides of the burner.

Volcanic Stone

Place Volcanic
Stone As Shown

Figure 21

4. Place the glowing ember material
(rockwool).

Note: The bag of Glowing Embers
contains enough rockwool for several
applications; therefore, do not use the
entire bag at one time. For best glow­ing effect, replace the ember material
annually.

Refer to Figure 22. Separate the glowing

ember material into pieces about the size
of a quarter. Keep the pieces fluffed up, not
matted. Distribute the pieces over the sur­face of the burner, as shown in Figures 23
and 24. Do not use more than is necessary.
Position the embers on the small holes of
the ember bed area.

Note: Make sure the glowing ember
material does NOT cover the main
burner slots.

Bag of Glowing
Embers (Rockwool)

Separate into individual
“Quarter-sized” pieces.

Figure 22

5. Install the Logs.

The logs have locating notches or slots to
help ensure that they are properly positioned.
The 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. Follow the
log placement instructions exactly.

MLBV-35: Install logs as shown in Figure 23.
MLBV-40: Install logs as shown in Figure 24.

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 flame pattern. Any
attempt to use a different log
set in the fireplace will void
the warranty and will result
in incomplete combustion,
sooting, and poor flame
quality.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

• 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, flame
impingement and improper
combustion could occur and
result in soot and/or excessive
production of carbon monoxide
(CO), a colorless, odorless,
toxic gas.

17

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

MLBV-35 LOG PLACEMENT INSTRUCTIONS

Rear Log

4

Left Cross Log Right Cross Log

2

Left Rear Log Bracket

1

Left Front Log

5

Right Front Log

3

Right Rear Log Bracket

Note:

• Ceramic fiber logs are FRAGILE! Handle carefully to prevent breakage.

• Install volcanic stone and glowing embers BEFORE installing logs.

• To prevent sooting, make sure logs do not cover any burner openings.

MLBV Firebox Accessories/Parts

Cat. No. Model No. Description

H7666 — MLBV-35 Log Set Assembly

88L53 FGE Bag of Glowing Embers (Rockwool)

80L42 FDVS Bag of Decorative Volcanic Stone

Fit onto left rear log bracket

1

and rear bar of grate.

Right Rear

Log Bracket

Glowing Embers

GrateVolcanic Stone

(Do not place glowing embers over burner openings.)

NOTE: Install volcanic stone and glowing embers FIRST.

Position against left front corner of grate.

2

1

Position against right front

3

corner of grate.

Step 2. Fit bottom slots of Left Front Log (2) onto left front

corner of grate.

Step 3. Fit bottom slots of Right Front Log (3) onto right front

corner of grate.

Step 1. Fit bottom slots of Rear Log (1) onto left rear log bracket

and rear bar of grate.

Position over Rear Log (1)

4

and against front bar of grate.

1

2

Position over Right Front Log (3);

5

then fit onto right rear log bracket.

3

Step 4. Place Left Cross Log (4) over Rear Log (1); then fit

the bottom slot over the center front bar of grate.

Step 5. Place Right Cross Log (5) over and behind Right Front Log

(3); then fit the bottom slot onto the Right Rear Log Bracket.

18

Figure 23

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

MLBV-40 LOG PLACEMENT INSTRUCTIONS

Rear Log

4

Left Cross Log Right Cross Log

2

Fit onto left rear log bracket

1

and rear bar of grate.

1

Left Front Log

5

Right Front Log

3

Right Rear Log Bracket

Note:

• Ceramic fiber logs are FRAGILE! Handle carefully to prevent breakage.

• Install volcanic stone and glowing embers BEFORE installing logs.

• To prevent sooting, make sure logs do not cover any burner openings.

MLBV Firebox Accessories/Parts

Cat. No. Model No. Description

H7667 — MLBV-40 Log Set Assembly

88L53 FGE Bag of Glowing Embers (Rockwool)

80L42 FDVS Bag of Decorative Volcanic Stone

Position against left front corner of grate.

2

1

Glowing Embers

GrateVolcanic Stone

(Do not place glowing embers over burner openings.)

NOTE: Install volcanic stone and glowing embers FIRST.
Step 1. Fit bottom slots of Rear Log (1) onto left rear log bracket

and rear bar of grate.

Position over Rear Log (1)

4

and against front bar of grate.

1

2 3

Step 4. Place Left Cross Log (4) over Rear Log (1); then fit

the bottom slot over the center front bar of grate.

Figure 24

Position against right front

3

corner of grate.

Step 2. Fit bottom slots of Left Front Log (2) onto left front

corner of grate.

Step 3. Fit bottom slots of Right Front Log (3) onto right front

corner of grate.

Position over Right Front Log (3);

5

then fit onto right rear log bracket.

4

2 3

1

Step 5. Place Right Cross Log (5) over and behind Right Front

Log (3); then fit the bottom slot onto the right rear
log bracket.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

19

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Top
Standoff
Spacers*

Flush
Nailing

1/2"
Nailing
Flange

5/8"
Nailing
Flange

Step 9. Install the Glass Enclosure
Panel

WARNING

• Do not attempt to substitute the
materials used on these doors, 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(s) 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 fireplace 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 certified with the appliance
shall be used.

Seules des portes certifiées pour cet
appareil doivent être utilisées.

CAUTION: DO NOT abuse glass enclosure
panel by striking or slamming shut.

Installing the Glass Enclosure Panel

1. Refer to Figure 25. Position the glass enclo-

sure panel in front of the firebox opening,
with the bottom of the enclosure panel held
away from the fireplace. Hook the top flange
of the enclosure panel frame over the top of
the firebox frame.

2. Gently move the bottom of the enclosure

panel frame toward the fireplace, ensuring
that the gasket seats evenly. Fasten the
two latches under the firebox floor to the
vee-flange on the enclosure panel. Close

20

both latches securely.

3. Install the hood. Note the location of the

three clips inside the top air channel above
the glass enclosure panel. The clips are
equally spaced on the top surface of the air
channel opening. If needed, use a screw­driver to open the clips slightly. Engage
the back edge of the hood into the clips to
secure.

Removing the Glass Enclosure Panel

1. Refer to Figure 25. To access the spring

latches securing the front glass enclosure
panel, open the lower control compartment
door by lifting and pulling the bottom panel
forward.

2. Pull the spring latches forward and down to

release them from the lower door channel.

3. Pull the bottom of the glass enclosure panel

out a few inches, and grasp it on the right
and left sides. Gently lift to release the panel
from its upper channel, and then pull the
enclosure panel forward to remove it.

4. Visually inspect the gasket on the backside

of the enclosure panel frame. The gasket
surface must be clean, free of irregularities,
and firmly seated.

This appliance is designed to operate only
when the glass enclosure panel is installed.

Do NOT remove the glass enclosure panel un­less necessary (e.g., to gain access to compo­nents within the firebox or to clean the glass).

Top
Standoff
Spacers*

*IMPORTANT!

*IMPORTANT!

Bend up the

Bend up the

Top Standoff

Top Standoff
Spacers before

Spacers before

installation.

installation.

Use outer pair

Use outer pair

for 1/2" materials

for 1/2" materials

and inner pair

and inner pair

for 5/8" materials.

for 5/8" materials.

Glass
Enclosure
Panel

Enclosure Panel
Spring Latch

Lower
Control
Compartment
Panel

Note: When installing the glass enclosure
panel, make sure spacing on both sides is
even and equal.

Figure 25

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Hood

5/8"
Nailing
Flange

1/2"
Nailing
Flange

Flush
Nailing
Flange

Step 10. Burner Air Shutter
Adjustments

(QUALIFIED TECHNICIANS ONLY)

Flame Appearance and Sooting

Proper flame appearance is a flame which is
blue at the base and becomes yellowish-orange
in the body of the flame. When the appliance
is first lit, the entire flame may be blue and will
gradually turn yellowish-orange during the first
15 minutes of operation. After 15 minutes of
operation, if the flame is blue, or if the flame 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 flames.
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 flames and lack of combustion air enter­ing the air shutter opening. To achieve a warm
yellowish-orange flame 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, first check
the log set positioning to ensure that the
flames 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 flames that appear
blue and transparent. These weak, blue and
transparent flames are termed anemic.

• Propane models may exhibit flames which
candle or appear stringy. If this is present and
persists, adjust the air shutter to a more open
position, then operate the appliance for a few
more minutes to ensure that the flame normal­izes and the flames do not appear sooty.

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

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Burner Air Shutter Adjustment Procedure

WARNING

• Air shutter adjustment should only be performed
by a qualified professional service technician.

• Ensure front glass panel are 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 flame appearance.

1. Locate adjustment rod and adjust air shutter to the standard set-

ting as shown in Figure 26 (adjustment rod is located in the lower
control compartment).

Note: Move the adjustment rod DOWN to decrease air
and UP to increase air.

Adjustment Set-Screw

Adjustment
Rod Up

Burner
Tube

Air Shutter

Adjustment Rod Down

min. air opening position)

Main Burner Factory Air Shutter

Opening Setting - inches (millimeters)

Model Nat.Gas Propane Gas

MLBV-35 Closed 3/32 (2.362)
MLBV-40 Closed 3/32 (2.362)

Figure 26: Burner Air Shutter Adjustment

(Fully Open
Position)

2. Light appliance (follow lighting procedure on lighting label in con-

trol compartment or see the Care and Operation manual).

3. Allow the burner to operate for at least 15 minutes while observing
the flame continuously to ensure that the proper flame appearance has
been achieved (see Figure 27 and 28). If the following conditions
are present, adjust accordingly:

• If flame appears weak or sooty, adjust the air shutter, incremen­tally, to a more open position until the proper flame appearance is
achieved.

• If flame stays lowered blue, adjust the air shutter, incrementally,
to a more closed position until the proper flame appearance is
achieved.

4. Leave the control knob (off/pilot/on) in the ON position and the
burner OFF/ON switch OFF (and remote switches, if applicable).

5. When satisfied that the burner flame appearance is normal, re­install the lower control compartment door then proceed to finish the
installation.

Figure 27: Burner Flame Appearance – Model MLBV-35

Figure 28: Burner Flame Appearance – Model MLBV-40

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

21

Frame

Upper Right Side of Firebox

Lintel Screw Hole

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 11. Perform Spillage Test

After appliance installation, perform this spillage
test to verify proper venting conditions:

1 - Place unit in its normally-operated condi-

tion, 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 hold-

ing a smoke producing device below the
glass enclosure panel. The smoke should
be drawn into the control compartment.
Continue the test by moving the smoke­producing device along the entire length
of the lower edge of the glass enclosure
panel.

6 - If the smoke is NOT drawn into the con-

trol compartment, turn off the appliance
and call a qualified service technican.

Manually-Reset Safety Limit Switch

This appliance is equipped with a manually­reset safety limit switch in the upper RIGHT
side of the firebox, behind the right side scoop.
Refer to Figure 29 for its location.

If, during appliance operation, the flame
goes out (independently of the burner ON/
OFF switch), the safety limit switch may have
tripped.

Some causes for a tripped safety limit switch
include the following:

• Incorrect flue configuration

• Blocked flue

• Negative pressure inside house

Before resetting the safety limit switch, have
a qualified service technician inspect the
fireplace and venting for these conditions and
repair as needed.

To RESET the safety limit switch, push the

reset button located between the wire terminals
on the back of the switch. Follow the steps be-

low to access the switch (also see Figure 29-C).

To REPLACE the safety limit switch, follow
the steps below.

IMPORTANT: This procedure should only be

performed by a qualified service technician.

Figure 29-A

Figure 29-B

Figure 29-C

Figure 29

Lintel Screw Hole

in Cabinet Top

Right Side

Scoop

Right Side

of Firebox

(right side Scoop removed)

~

~

Bracket (right side Scoop removed)

To access the Safety Limit Switch, reach in and up
behind the Bracket, and push the red reset button
located between the two Wire Terminals.

Safety Limit Switch / Reset Button Location

Inside View of Firebox (upper right side)

~

~

3 Scoop Screws

in Cabinet Top

Limit Switch
Wire Terminals

(Red reset button
is between the
two terminals.)

Cabinet
Corner

Door

1 - Turn OFF electrical power to appliance.
2 - Allow the appliance to cool.
3 - Remove the lower control compartment

access panel.

4 - Refer to Figure 25 on Page 20. Open both

latches under the firebox floor securing
the glass enclosure panel. Remove the
panel by tilting it outward at the bottom

22

and lifting it up. Set aside the panel, taking
care to protect it from damage.

5 - Remove the (3) screws securing the lintel,

and then remove the lintel. One of the lintel
cabinet top holes is shown in Figure 29.

6 - Remove the (3) screws securing the

scoop, and then remove the scoop. Refer
to Figure 29 for correct location for model
size.

7 - Reset the limit switch per Figure 29-B. If

unit does not reset, remove the (2) screws
securing the safety switch bracket, and

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

pull the switch/bracket assembly (with
low voltage wires attached) through the
side panel slot into the firebox.

8 - Replace the switch, if necessary..
9 - Reinstall the scoop and lintel.
10 - Reinstall the glass enclosure panel and

control compartment access panel.

The appliance should then relight and remain
lit. If this does not occur, contact your dealer.

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 12. Install Hood

NOTE: All models must have a hood installed
prior to operating.

Refer to Figure 30. Install hood by sliding it into
the slots on the lower edge of the cabinet top.

Combustible Finished

Wall Materials

1 in (25 mm) min.

Header

Step 13. Finishing Requirements

Wall Details

Complete finished interior wall.
To install the appliance facing flush with the

finished wall, position framework to accom­modate the thickness of the finished wall

(Figure 30).

For Cold Climate Insulation, see Page 5.
For Clearances, see Page 7.

IMPORTANT!

Bend up standoffs

to vertical position.

Combustible material
may touch appliance top.

Hood

Figure 30: Combustible Wall Framing

Top of Appliance

3" Clearance min.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

23

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Step 14. Attach Safety-In-Operation Warnings

It is the installer's responsibility to ensure these warning labels are properly affixed during installation.
These warning labels are a critical step in informing consumers of the 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
1-800-9-LENNOX

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
la poussière et les traces de graisse ou d’huile.
Collez l’étiquette sur le boîtier de la télécommande
(Figure B). Choisissez la langue qui est principale-
ment 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
1-800-9-LENNOX

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
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
1-800-9-LENNOX

Nota: La etiqueta en inglés es transparente con texto
rojo. Las etiquetas en francés y español son negras
con texto blanco.

24

SAFETY LABEL

DIAGRAMS

Figure A Figure B

DIAGRAMMES DES ÉTIQUETTES

DE SÉCURITÉ

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

DIAGRAMAS DE ETIQUETAS

DE SEGURIDAD

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

GAS CONVERSION KITS

WARNING

This conversion kit shall be installed by a qualified 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 fire, explosion or production of
carbon monoxide may result causing property damage, personal injury
or loss of life. The qualified 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 specified in the manu­facturer’s instructions supplied with the kit.The qualified 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 vérifié selon les instructions du fabricant fournies avec
la trousse. Le fournisseur de service qualifié 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/
CSA-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/CSA-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 affixed 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.

Millivolt SIT Systems

Natural Gas To Propane Gas

Conversion Kits

Models Catalog No.
MLBV-35 H8270
MLBV-40 H7673

Millivolt SIT Systems

Propane Gas to Natural Gas

Conversion Kits

Models Catalog No.
MLBV-35 H8271
MLBV-40 H7675

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Electronic DEXEN Systems

Natural Gas To Propane Gas

Conversion Kits

Models Catalog No.
MLBV-35 H8268
MLBV-40 H7669

Electronic DEXEN Systems

Propane Gas To Natural Gas

Conversion Kits

Models Catalog No.
MLBV-35 H8269
MLBV-40 H7671

Gas Conversion Kit 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. Remove the front glass enclosure

panel. See Figure 25 on Page 20.

Step 3. Carefully remove the logs.

Note: Logs are fragile. Handle gently

to prevent breakage.

Step 4. Refer to Figure 31. Remove the burner

assembly with attached venturi tube.

For Millivolt Systems, continue to Step 5.
For Electronic Systems, skip to Step 8.
Step 5. SIT Millivolt Valve: Refer to Figure 32

and the instructions provided with the
kit.

a. Using a Torx T20 (with 1/4" shank

and center hole), remove and dis­card the three pressure regulator
mounting screws.

b. Remove the pressure regulator,

spring, poppet, diaphragm and
bushing.

c. Discard all removed components.
d. Make sure the rubber gasket in-

stalled on the back of the replace­ment pressure regulator is properly
positioned. Tighten screws to 25
in.-lb. torque.

25

PILOT

OUT

VENT

LO

TH

TP

TH

TP

HI

IN

IN

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

ELECTRONIC

Burner Assembly

Gas Valve
Assembly

Orifice

Figure 31: SIT Millivolt System

Pressure

Regulator

Electronic Appliances

Step 8. Dexen Electronic Valves: Refer to

Figure 34 and the instructions pro­vided with the kit.

a. Remove and discard the two pres-

sure regulator mounting screws.

b. Remove the pressure regulator and

diaphragm.

c. Discard all removed components.
d. Make sure the provided diaphragm

is installed properly onto the re­placement pressure regulator.

e. Install the new pressure regulator

using the new screws supplied with
the kit; tighten the screws.

Supply Gas
Inlet

Pressure-Tap
(Manifold)

Regulator
Mounting
Screw

Burner Stage
Terminal

Gas

Outlet

To Burner

All Models

Note the following:
Use pipe joint compound or Teflon tape on

all pipe fittings before installing.
Ensure propane-resistant compounds are

used in propane applications.
Do NOT use pipe joint compounds on flare

fittings.

Step 10. Refer to Figure 31.

a. VERIFY PROPER ORIFICE SIZE

BEFORE INSTALLING IT.

b. Remove the orifice from the mani-

fold and replace it with the one
provided in the kit. See Table 7 for
orifice sizes for natural and propane
models. Figure 36 illustrates the
orifice. Always check and verify
orifice size.

c. Retrieve the burner. Slide the venturi

tube over the orifice.

d. Adjust the burner air shutter as

shown in Figure 26 on Page 21.

Remove
These
Components

Figure 32: SIT Millivolt System

Step 6. (Millivolt systems only): Attach ma-

nometer to the manifold side pressure
test fitting and verify manifold pressure
reads 3.5 inches water column (0.87
kPa) for natural gas, and 10.0 inches
water column (2.49 kPa) for propane
gas.

Step 7. (Millivolt systems only): Refer to Figure

33. Remove the pilot hood assembly to

access the hexed pilot orifice. Remove
and replace the orifice with the one
provided in the kit.

Skip to Step 10.

Pressure-Tap
(Inlet)

Pilot Gas Outlet

Ground (TP)

Pilot Stage
Terminal

Figure 34: Dexen Electronic Gas Valve

Step 9. Refer to Figure 35. Follow these steps

to replace the pilot orifice:
a. Remove pilot hood assembly to

access the phillipped pilot orifice.

b. Remove and replace the orifice

with the one provided with the kit.

Exercise extreme care to prevent
damage to or breakage of the
igniter assembly.

Sensor

Igniter

Pilot
Hood

Burner Orifice Sizes

Elevation 0-4500 feet ( 0-1372 meters)

Model

Series

MLBV-35

MLBV-40

Table 7

Nat.Gas

drill size (inches)

#48 (0.076")*

H1236•

#43 (0.089")*

99K75•

Standard size installed at factory.

*

• Part /Cat. Number.

Propane

drill size (inches)

#56 (0.046")*

62L37•

#55 (0.052")*

19L52•

Figure 36

Step 11. Reassemble the remaining compo-

nents by reversing the procedures
outlined in the preceding steps.

Step 12. Attach the conversion label (provided

in the conversion kit) next to the rat­ing plate on the appliance.

Step 13. Turn on gas supply and test for gas

leaks (refer to Page 16).

Pilot
Orifice

Figure 35: Dexen Electronic System

ALWAYS TEST PRESSURES WITH THE VALVE
REGULATOR CONTROL AT THE HIGHEST
SETTING.

Figure 33: SIT Millivolt System

26

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Notes

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

27

LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS

Lennox Hearth Products reserves the right to make changes at any time, without notice, in design,
materials, specifications, prices and also to discontinue colors, styles and products.
Consult your local distributor for fireplace code information.

Printed in U.S.A. © 2010/2012 Lennox Hearth Products

P/N 506015-04 Rev. C 01/2012

28

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

1508 Elm Hill Pike, Suite 108 • Nashville, TN 37210