Lennox Mpdt33rnm User manual

MODELS

OTL No. 116-F-13g-5

Portland

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.

INSTALLATION INSTRUCTIONS

MPD Direct-Vent

Gas Fireplaces

MILLIVOLT: ELECTRONIC:

MPDT33RNM

MPDT33RPM

MPDR33RNM

MPDR33RPM

MPD35CNM

MPD35RNM

MPD35RPM

MPD40CNM

MPD40RNM

MPD40RPM

MPD45RNM

MPD45RPM

MPDT33RNE

MPDR33RNE

MPD35CNE

MPD35RNE

MPD35RNE-R

MPD40CNE

MPD40RNE

MPD45RNE

MPD40RNE-R

P/N 506015-07 Rev. B 06/2013

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.

Please read and understand these instructions

before starting installation.

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.

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.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

PACKAGING

The assembled vented gas ﬁreplace heater is

packaged with:

• (1 set) Logs (packaged in a carton inside the

ﬁrebox).

• (1 bag) Glowing Embers (in bottom compart-

ment).

• Literature Kit (envelope in bottom com-

partment containing Care and Operation

Instructions,InstallationInstructions,Safety-

In-Operation Warning Labels, Warranty).

• (1) U-Shaped Vent Restrictor (attached to

Literature Kit envelope).

• (1) Hood (inside rebox).

INTRODUCTION

The Millivolt appliances have a millivolt gas

control valve with piezo ignition system. If any

optional accessories that will require electrical

power are to be installed, the electrical power

must be provided at the time of appliance

installation.

The Electronic appliances are designed to

operateonnaturalorpropanegas.Anelectronic

intermittentpilot ignitionsystem providessafe,

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 Compo-

nents manufactured by Security Chimneys

International,

•Secure Flex®Flexible Vent Components

manufactured by Security Chimneys Inter-

national 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" inner

and 7-1/2" outer).

These approved vent system components are

labeled for identiﬁcation. DO NOT use any

other manufacturer’s vent components with

these appliances.

TABLE OF CONTENTS

Packaging .................................................... 2

Introduction ................................................. 2

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

Requirements for the

Commonwealth of Massachusetts ............ 4

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

Manufactured Home Requirements ............. 5

Location........................................................5

Vent Termination Clearances ....................... 6

Appliance and Vent Clearances .................... 8

Pre-Installation Steps................................... 9

Typical Installation Sequence ...................... 9

Detailed Installation Steps............................ 9

Step 1. Framing............................................ 9

Fireplace and Framing Speciﬁcations ....... 10

Step 2. Routing Gas Line ........................... 11

Step 3. Preparing Appliance Vent Collar..... 12

Step 4. Installing Vent System................... 12

Vertical Termination Systems.................. 13

Vent Section Length Chart ...................... 13

Vertical Vent Tables and Figures.............. 16

Horizontal Termination System ............... 18

Horizontal Vent Tables and Figures ......... 20

Venting Using Flexible Vent Pipe............. 23

Step 5. Field Wiring................................... 24

Step 6. Optional Blower Kit Wiring............ 25

Step 7. Connecting Gas Line ..................... 25

Step 8. Verifying Appliance Operation........... 26

Step 9. Installing Logs ............................. 27

Step 10. Remove/Install Glass Door .......... 31

Step 11. Burner Adjustments ..................... 31

Step 12. Hood Installation.......................... 33

Finishing Requirements ............................. 33

Step 13. Attaching Safety-in-Operation

Warnings.................................... 34

Installation Accessories ............................. 35

Gas Conversion Kits................................... 37

Please read and understand these

instructions before beginning your

installation.

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.

WARNING

Young children should be care-

fully supervised when they are

in the same room as the appli-

ance. Toddlers, young children

and others may be susceptible

to accidental contact burns. A

physicalbarrierisrecommended

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

Lesjeunesenfantsdevraientêtre

surveillésétroitementlorsqu’ils

se trouvent dans la même pièce

que l’appareil. Les tout petits,

lesjeunesenfantsoulesadultes

peuvent subir des brûlures s’ils

viennent en contact avec la sur-

face chaude. Il est recommandé

d’installerunebarrièrephysique

si des personnes à risques habi-

tent la maison. Pour empêcher

l’accès à un foyer ou à un poêle,

installez une barrière de sécu-

rité;cettemesureempêcherales

tout petits, les jeunes enfants et

toute autre personne à risque

d’avoir accès à la pièce et aux

surfaces chaudes.

GENERAL INFORMATION

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

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.

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.Itisimperativethatcontrol

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

ceteraproduisentunequantitéimportante

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 this appliance if any part has

been under water. Immediately call a

qualiﬁed service technician to inspect the

appliance and to replace any parts of the

control system and any gas control which

has 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.

Onlytrim kit(s)suppliedby themanufacturer

shall be used in the installation of this

appliance.

Seules les trousses de garniture fournies

parlefabricant doiventêtreutiliséespour

l’installation de cet appareil.

Models Input Rate (BTU/HR)

Nat. Gas Prop. Gas

MPD33 17,500 high

11,700 low 17,500 high

14,000 low

MPD35 20,000 high

12,800 low 20,000 high

15,200 low

MPD40 27,000 high

18,500 low 27,000 high

21,500 low

MPD45 29,000 high

20,500 low 29,000 high

22,500 low

Table 1 - Input (BTU/HR) Gas Valves

(Millivolt and Electronic)

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

approuvéesaveccetappareilsont

utilisées.

These appliances comply with National Safety

Standards and are tested and listed by OMNI-

TestLaboratories,Inc.(ReportNo.116-F-13g-5)

to ANSI Z21.88-2009 (in Canada, CSA-2.33-

2009),andCAN/CGA-2.17-M91(R2009)inboth

USAandCanada,asventedgasﬁreplaceheaters.

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 / NFPA

54 - latest edition (In Canada, the current CAN/

CGA-B149.1 installation code).The appliance,

when installed, must be electrically grounded

and wired in accordance with local codes or, in

the absence of local codes, with the National

Electrical Code, ANSI/NFPA 70 - latest edition,

or the Canadian Electrical Code, CSA C22.1 -

latest edition.

Provide adequate clearances around air

openings and adequate accessibility clearance

forserviceandproperoperation.Neverobstruct

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

manuallyoperatedhi-lowﬂamecontrol.TheBTU

Input for these appliances is shown in Table 1.

WARNING

Improper installation, adjust-

ment, 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.

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

Any safety screen or guard

removed for servicing the appli-

ance must be replaced prior to

operating the appliance.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

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" (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.

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 orice to a smaller size

as regulated by the local authorities having

jurisdiction and by the (USA) National Fuel

Gas Code NFPA 54 - latest edition / ANSI

Z223.1 or, in Canada, the CAN/CGA-B149.1

codes - latest edition.

Installtheapplianceaccordingtotheregulations

of the local authorities having jurisdiction and,

Fuel # Low High

Natural

Gas

1.6" WC

(0.40 kPa)

3.5" WC

(0.87 kPa)

Propane 6.3" WC

(1.57 kPa)

10.0" WC

(2.49 kPa)

Table 3: Manifold Gas Supply Pressure

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

equipmentshutoffvalveduringanypressure

testing of the gas supply piping system at

test pressures equal to or less than 1/2 psi

(3.5 kPa).

Fuel # Minimum Maximum

Natural

Gas

4.5" WC

(1.12 kPa)

10.5" WC

(2.61 kPa)

Propane 11.0" WC

(2.74 kPa)

13.0" WC

(3.23 kPa)

Table 2: Inlet Gas Supply Pressure

Gas Pressure - All Models

Tables 2 and 3 show the appliances' inlet and

manifold gas pressure requirements:

Burner Oriﬁce Sizes

Elevation 0-4500 feet ( 0-1372 meters)

Model

Series

Nat.Gas

drill size (inches)

Propane

drill size (inches)

MPD33 #47 (0.0785")*

99K74 •

0.048"

99K78 •

MPD35 #44 (0.086")*

60J80 •

#55 (0.052")*

19L52 •

MPD40 #38 (0.102") *

99K76 •

0.062"

21L01 •

MPD45 #37 (0.104")*

24M10 •

#52 (0.0635")*

37G00 •

Table 4 * Standard size installed at factory

• Part /Cat. Number

REQUIREMENTS FOR THE

COMMONWEALTH OFMASSACHUSETTS

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 exible gas line connector used shall

not exceed 36 (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 identication plate must be

permanently mounted to the exterior of the

buildingataminimumheightofeight(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.

in the USA, the National Fuel Gas Code NFPA

54 - latest edition / ANSI Z223.1 or, in Canada,

the CAN/CGA-B149.1 - latest edition.

Flame breadth, height and width will diminish

4% for every 1,000 feet of altitude. Gas Valve

Diagrams. See Figure 1 for Millivolt models

and Figure 2 For Electronic Models.

In Canada - CAN/CGA-2.17-M91 (R2009)

(high altitude): THE CONVERSION SHALL

BE CARRIED OUT BY A MANUFACTURER’S

AUTHORIZED REPRESENTATIVE,IN

ACCORDANCE WITH THE REQUIREMENTS

OF THE MANUFACTURER, PROVINCIAL

OR TERRITORIAL AUTHORITIES HAVING

JURISDICTION AND IN ACCORDANCE WITH

THEREQUIREMENTSOFTHECAN/CGA-B149.1

OR CAN/CGA-B149.2 INSTALLATION CODES.

HTPTHTPT

IN OUT

HI/LO Variable

Flame Height

Adjustment

Figure 1 - SIT Millivolt

Gas Valve

Manifold Pressure Tap

Inlet Pressure Tap

Pilot Adjustment

Screw

Main Gas Control Knob

OFF/PILOT/ON

Orange Wire

(from DFC Wire

Harness)

Main Gas Inlet

3/8" NPT

Green Wire

(from DFC Wire Harness)

Inlet (IN) Test Port

Manifold (OUT) Test Port

Figure 2 - SIT Electronic Gas Valve

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

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

HORIZONTAL VENT

(Rear Vent Application with a chase) HORIZONTAL VENT

(Top Vent Application)

VERTICAL VENT

(Top Vent Application)

(Rear Vent Application)

VERTICAL VENT (Rear Vent Application without a chase)

HORIZONTAL VENT

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).

Enraisondestempératuresélevées,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. Util-

ity shelves like these are commonly used for

locating television sets and decorative plants.

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 ap-

pliance and the area above it (see Figure 8).

Theminimum height fromthe baseof theappli-

ance 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.

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

groundlevel. Gasline holesandother 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

otherraised platformcan beplacedunderneath

to prevent conduction of cold transferring to

the ﬁreplace and into the room. It also helps to

sheetrockinsidesurfacesandtapeformaximum

air tightness and caulk ﬁrestops.

MANUFACTURED HOME

REQUIREMENTS

Thisappliancemaybeinstalledinanaftermarket

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

gasindicated onthe ratingplate.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 mem-

bers 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 ground-

ed 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.

Figure 3 - Typical Locations

APPLICATION

REAR VENT

APPLICATION

TOP VENT

APPLICATION

TOP VENT

REAR VENT

APPLICATION

TOP VENT

APPLICATION

RECESSED

INSTALLATION

TOP VENT

APPLICATION

TOP VENT

APPLICATION

TOP VENT

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Roof Pitch is X/12

2 FT

MIN.

2 FT MIN.

Lowest

Discharge

Opening

*H = MINIMUM HEIGHT FROM ROOF TO

LOWEST DISCHARGE OPENING OF VENT

TERMINATION HEIGHTS FOR VENTS ABOVE

FLAT OR SLOPED ROOFS

Horizontal Overhang

Vertical

Wall

Vent

Termination

Storm Collar

Concentric

Vent Pipe

Flashing

1 inch (25.4 mm) Minimum

Clearance to Combustibles

Figure 5 -Termination Heights forVents

Above Flat or Sloped Roofs

Vertical Vent Termination Clearances

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,theseinstructions,thecurrentNational

Fuel Gas Code (ANSI-Z223.1) in the USA or

the current standards of CAN/CGA-B149.1

in Canada.

Vertical Vent Termination Clearances

Terminatemultipleventterminationsaccording

to the installation codes listed above and

Figures 4 and 5.

NOTE: See Figure 34 on Page 20 for the exterior wall recess

allowances of the square horizontal termination.

Termination Heights For Vents

Above Flat Or Sloped Roofs

Ref. NFPA 54 / ANSI Z223.1

Roof Pitch *H (ft) *H (m)

Flat-6/12 1.0 0.3

6/12-7/12 1.25 0.38

7/12-8/12 1.5 0.46

8/12-9/12 2.0 0.61

9/12-10/12 2.5 0.76

10/12-11/12 3.25 0.99

11/12-12/12 4.0 1.22

12/12-14/12 5.0 1.52

14/12-16/12 6.0 1.83

16/12-18/12 7.0 2.13

18/12-20/12 7.5 2.29

20/12-21/12 8.0 2.44

The vent / air intake termination clearances

above the high side of an angled roof are as

shown in the following chart:

Figure 6 - Horizontal Vent

Termination Clearances

(152 mm)

12"

(305 mm)

Combustible Projection greater

Horizontal Vent Termination Clearances

Combustible Projection

2-1/2”

or less in length

18"

(457 mm)

Ventilated

Soffit Unventilated

Soffit

than 2-1/2” in length

Termination Kit

Side Elevation View

Termination Kit

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.

Horizontal Vent Termination Clearances

The horizontal vent termination must have a minimum of 6" (152 mm) clearance to any overhead

combustible projection of 2-1/2" (64 mm) or less, see Figure 6. For projections exceeding 2-1/2"

(64 mm), see Figure 6. For additional vent location restrictions, refer to Figure 7 on Page 7.

Figure 4 - Multiple Terminations

12"

(305mm)

Minimum

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

Figure 7 - Exterior Horizontal Vent Termination Clearance Requirements

EXTERIOR HORIZONTAL VENT TERMINATION CLEARANCE REQUIREMENTS

Fixed

Closed

Window

Operable

Window

= Area where Termination is not Permitted

= Air Supply Inlet

X= Vent Termination

3 ft.

= 9” in U.S.

= 12” in Canada

Inside

Corner Detail

*18”

Ventilated Soffit

Horizontal

Termination

Detail D

Exterior Wall

6”

Inside Corner

* See Item D in the Text Below.

NOTE: Local Codes Or Regulations

May Require Different Clearances.

NOTE: Location Of The Vent Termination

Must Not Interfere With Access To The

Electrical Service.





Minimum Clearances Canadian Installation * US Installation **

A = Clearance above grade, veranda, porch, deck

or balcony.

12" (30 cm) * 12" (30 cm) **

B = Clearance to window or door that may be opened 6" (15.2 cm) for appliances < 10,000 BTU/hr (3kW),

12" (30 cm) for appliances > 10,000 BTU/hr (3kW)

6" (15.2 cm) for appliances < 10,000 BTU/hr (3kW),

9" (23 cm) for appliances > 10,000 BTU/hr (3kW) and

< 50,000 BTU/hr (15kW), 12" (30 cm) for appliances >

50,000 BTU/hr (15kW)**

C = Clearance to permanently closed window 12" (305 mm) recommended to prevent window conden-

sation

9" (229 mm) recommended to prevent window con-

densation

D = Vertical clearance to ventilated sofﬁt located

above the terminal within a horizontal distance of

18" (458 mm)

18" (458 mm) 18" (458 mm)

E = Clearance to unventilated sofﬁt 12" (30 cm) 12" (30 cm)

F = Clearance to outside corner 5" (12.7 cm) 5" (12.7 cm)

G = Clearance to inside corner 2" (5.08cm) minimum - SV4.5HT-2 •

6" (15.2cm) minimum - SV4.5HTSS •

2" (5.08cm) minimum - SV4.5HT-2 •

6" (15.2cm) minimum - SV4.5HTSS •

H = Clearance to each inside of center line extended

above meter / regulator assembly

3 feet (91 cm) within a height of 15 feet above the meter /

regulator assembly *

3 feet (91 cm) within a height of 15 feet above the meter

/ regulator assembly **

I = Clearance to service regulator vent outlet 3 feet (91 cm) * 3 feet (91 cm) **

J = Clearance to non-mechanical air supply inlet

to building or the combustion air inlet to any other

appliance

6" (15.2 cm) for appliances < 10,000 BTU/hr (3kW), 12"

(30 cm) for appliances > 10,000 BTU/hr (3kW)

6" (15.2 cm) for appliances < 10,000 BTU/hr (3kW), 9"

(23 cm) for appliances > 10,000 BTU/hr (3kW) and <

50,000 BTU/hr (15kW), 12" (30 cm) for appliances >

50,000 BTU/hr (15kW)**

K = Clearance to mechanical air supply inlet 6 feet (1.83 meters) * 3feet(91cm)above,ifwithin10feet(3m)horizontally**

L = Clearance above paved sidewalk or paved

driveway located on public property

7 feet (2.13 m) ‡ 7 feet (2.13 m) ‡

M = Clearance under veranda, porch, deck or

balcony

12" (30 cm) * ‡ 12" (30 cm) ‡

N = Depth of Alcove (Maximum) 6 feet (1.83m)* 6 feet (1.83m)**

O = Clearance to Termination (Alcove) 6" (15.2mm)* 6" (15.2mm)**

P = Width of Alcove (Minimum) 3 feet (91cm)* 3 feet (91cm)**

Q = Clearance to Combustible Above (Alcove) 18" (457mm)* 18" (457mm)**

* In accordance with the current CAN/CGA-B149.1 National Gas and Propane Installation Code.

** In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Codes.

‡ A vent shall not terminate directly above a sidewalk or paved driveway which is located between two single family dwellings and serves both dwellings.

*‡ Only permitted if veranda, porch, deck or balcony is fully open on a minimum 2 sides beneath the ﬂoor.

• 2" Clearance to Non-Combustibles for SV4.5HT-2 Only.

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

(102)

(356) 12

(305) 10

(254) 2 (51) MANTEL

TOP OF

APPLIANCE

(152)

NOTE - Hood shown as positioned in louvered

front model. The hood position in the flush

faced front model is lower than shown.

(203)

MANTEL CLEARANCES

Inches (mm)

Figure 9 - Minimum Mantel Clearances

Figure 10 - Minimum Distance to Side Wall

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).

MINIMUM CLEARANCES*Inches (millimeters)

Back 1/2 (13)

0 (0) from Spacers or Dimples

Sides 1/2 (13)

0 (0) from Spacers or Dimples **

Top of Fireplace

3 (76)

0" (0 mm) with standoff(s) in vertical

position (see Figure 11)

Floor 0 (0)

From Bottom of Unit To Ceiling 64 (1626)

Vent 3 (76) Top* / 1 (25.4) Sides & Bottom

SERVICE CLEARANCES Feet (meters)

Front 3 feet (0.9 meters)

Table 5

Figure 8 -

Shelf Height Minimum Clearances

Shelf Above Fireplace With Rear Venting Shelf Above Fireplace With Top Venting

Shelf Height

(see table)

Shelf Height

(see table)

Do not insulate the

space between the ap-

pliance and the area

above it.

Do not insulate the

space between the

appliance and the area

above it.

*NOTE: 3" (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.

HearthExtension-Ahearthextensionisnotrequiredwiththisappliance.

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

routedin awayto minimizeobstructionsto thespaceabove theappliance.

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.

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 61 and 62 on Page 34).

Non-combustible materials, such as surrounds and other appliance trim,

maybe installedon theapplianceface withthese exceptions:they mustnot

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,donot allowanythingtohangbelow the ﬁreplacehood.

Minimumclearancerequirements includeanyprojectionssuchasshelves,

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.

3-1/2

(89)

(152)

Top View of

Fireplace

45o

Inches (millimeters)

Combustiblematerialsmay

project beyond either side

of the fireplace opening

as long as they are kept

within the shaded area

illustrated here.

Combustible Materials

Allowed In Shaded Area

“Safe Zone”

Combustible Walls

shown in dark gray

At 6" minimum

sidewall clearance,

a combustible wall

can project to any

length.

Inches (millimeters)

Models Combustible Shelf Height - inches (millimeters)

Top Vent - with One 90 Degree Elbow Rear Vent - Straight Out The Back

Secure Vent

Secure Flex

Secure Vent Secure Flex

MPDT33

MPDR33 43-3/4 (1111) 45-1/2 (1156) 33-1/4 (845) 33-1/4 (845)

MPD35 45-3/4 (1162) 47-1/2 (1207) 35-1/4 (895) 35-1/4 (895)

MPD40

MPD45 50-3/4 (1289) 52-1/2 (1334) 40-1/4 (1022) 40-1/4 (1022)

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

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 The Glass Enclosure Panel

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.

DETAILED INSTALLATION STEPS

Step 1. FRAMING

Frame the appliance as illustrated in Figures

12 and 13 on Pages 11 and 12 (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.

Iftheapplianceistobeelevated aboveﬂoorlevel,

asolidcontinuousplatformmustbeconstructed

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.

Securetheﬁreplacetothesideframingmembers

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.

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" materials 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" and

5/8" 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

(Page 27).

Step 9. INSTALL VOLCANIC STONE, GLOWING

EMBERS, AND LOGS (Page 28).

Step 10. INSTALLING GLASS DOOR

ASSEMBLY (Page 32).

Step 11. BURNER ADJUSTMENTS (Page

32): Adjust burner to ensure proper ﬂame

appearance.

Step 12. HOOD INSTALLATION (Page 34).

Step 13. ATTACHING SAFETY-IN-OPERATION

WARNINGS (Page 35).

IMPORTANT!

Bend up the appropriate header spacing top

standoffs before installing the ﬁreplace.

Figure 11 - Unit Secured to Framing by

Nailing Flange

NOTE:Thenailingﬂanges,combustiblemembers,

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.

Combustibleframing maybein directcontactwith

thenailingﬂangesandmaybelocatedcloserthan

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.

Side

Framing

Unit Nailing Flange

(No clearance to

combustible framing

is required)

Header Spacing Top Standoffs

(two pairs on front edge of firebox top)

Lift up outer pair for

1/2” finish materials Lift up inner pair for

5/8” finish materials

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Model A B C D E

MPDT33 33-1/4 33-1/4 --- 37-3/4 12-7/8

845 845 --- 959 327

MPDR33 in. 33-1/4 33-1/4 19-5/8 --- 12-7/8

mm 845 845 498 --- 327

MPD35 in. 35-1/4 35-1/4 21-11/16 39-3/4 16

mm 895 895 551 1010 406

MPD40 in. 40-1/4 40-1/4 26-11/16 44-3/4 16

mm 1022 1022 678 1137 406

MPD45 in. 45-1/4 40-1/4 26-11/16 44-3/4 16

mm 1149 1022 678 1137 406

(178)

5-1/8 12-1/8

(308)

10-1/2

(267)

VENT FRAMING:

TOP VENT WITH ONE

90°ELBOW

VENT FRAMING:

REAR VENT WITH

NO ELBOWS

Framing should be

constructed of 2x4

or larger lumber.

Inches (mm)

(130)

(308)

(178)

1/2 A

5-1/8 12-1/8

Dimension “E” is the required framing depth when the

finish material (drywall) thickness is 1/2 in. (13mm).

Top View

Concentric Flue:

Flue

4-1/2” (114 mm);

Combustion Air

7-1/2” (190 mm).

See Notes [1] and [2].

Rear/Side

Framing

Spacers

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.

F (rear vent

models only)

N1/2 (13)

1-5/8 (42)

Gas Inlet (either

side and bottom)

Electrical Inlet

2-3/4" x 2"

(70 x 51 mm)

Cover Plate

with Knockout

Right Side View

See Note [2].

6 (152)

1-3/8 (35)

Optional Electrical Inlet

Knockout requiring a

Field-Provided Junction

Box (either side)

Front View 3 (76)

Header

Spacing

Top

Standoffs

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" x 10-1/2" (267 mm x 267 mm) inside dimensions, about this center mark (see Figure 20).

Notes

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.

Thermal Efﬁciency (%)

Fireplace

Model

Natural Gas Propane

AFUE EnerGuide

(P4) AFUE EnerGuide

(P4)

MPDT33 62 45 64 49

MPDR33 61 53 64 55

MPD35 62 53 60 55

MPD40 67 59 67 60

MPD45 67 59 67 59 Based on CSA P. 4.1-09

Figure 12 - Fireplace and Framing Speciﬁcations

Framing

Model A B C D E F G H J K L M N

MPD33 in. 33-1/8 30-1/8 17 27-1/2 33-1/8 19-5/8 21-1/2 10-3/4 6-13/16 38-11/32 2-3/4 13

mm 841 765 432 699 841 498 546 273 173 76 212 70 330

MPD35 in. 35-1/8 32-1/8 19 29-1/2 35-1/8 21-11/16 24-7/8 12-7/16 9 3 9 3 16

mm 892 816 483 749 892 551 632 316 220 76 220 76 406

MPD40 in. 40-1/8 37-1/8 24 34-1/2 40-1/8 26-11/16 29-7/8 14-15/16 9 3 9 3 16

mm 1019 943 610 876 1019 678 759 379 220 76 220 76 406

MPD45 in. 40-1/8 37-1/8 24 39-1/2 45-1/8 26-11/16 34-7/8 17-7/16 9 3 9 3 16

mm 1146 943 610 1003 1146 678 886 443 220 76 220 76 406

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

FIREPLACE FRAMING SPECIFICATIONS

Schedule 40 Pipe

Length (feet)

Natural

Gas

Propane

Gas

0-10 1/2" 3/8"

10-40 1/2" 1/2"

40-100 1/2" 1/2"

100-150 3/4" 1/2"

150-200 3/4" 1/2"

Table 6 - Schedule 40 Black Iron Pipe -

Inside Diameter

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/CGA-B149.1

- latest edition (Canada).

Step 2. ROUTING GAS LINE

Route a 1/2" (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 factory-equipped with a ﬂexible gas line

connector and 1/2" shutoff valve. (See Step

7 on Page 26).

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.

Figure 13 - Corner Framing with Horizontal Termination

Also see Figure 12.

Figure 14 - Route Gas Line

(76 mm)

Left Side Front

Corner of Fireplace

Framing

6-1/2"

(152 mm)

Pipe Coupling

(Recommended)

NOTE:

• Rear Vent Applications in Corner Installations: The horizontal vent length

(from ato 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.

Notes:

• All appliances are factory-equipped with

a ﬂexible gas line connector and 1/2 inch

shutoff valve (see Figure 47 on Page 27).

• See Massachusetts Requirements onPage

4foradditionalrequirementsforinstallations

in the state of Massachusetts in the USA.

• The gas supply line should Not be connected

to the appliance until Step 7 (Page 26).

• A pipe joint compound rated for gas should be

usedonthethreadedjoints.Ensurepropane

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 ofcial 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.

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

(178 mm)

MPD and MPDR units

MPD and MPDT units

Framing

Model A B C D E F

MPDT33

MPDR33 in. 33-1/8 48-1/2 34-5/16 17-3/16 24-1/4 5

mm 841 1232 872 437 616 127

MPD35 in. 35-1/8 57-1/2 40-5/8 19-3/16 28-3/4 6-1/8

mm 892 1461 1032 487 730 156

MPD40 in. 40-1/8 61-3/16 43-11/32 19-3/16 30-11/16 7-7/8

mm 1019 1554 1101 487 779 200

MPD45 in. 45-1/8 66-3/8 46-15/16 19-3/16 33-3/16 9-3/4

mm 1146 1686 1192 487 843 248

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Use only approved vent components (see

Approved Vent Components on Page 2).

These ﬁreplaces must be vented directly

to the outside.

The vent system may not service multiple

appliances, and must never be connected to

a ﬂue serving a separate solid fuel burning

appliance. The vent pipe is tested to be run

insideanenclosed wall (suchasachase). There

isnorequirementforinspectionopeningsinthe

enclosingwallatanyofthejointsintheventpipe.

Step 3. PREPARING APPLIANCE VENT

COLLAR (MPD35/-40/-45 models with

combined top/rear vent)

Each of the unit’s two vent collars are sealed

with a cover plate and a seal plate and gasket.

The cover, and seal plate and gasket must be

removedfrom thevent collarbeing used. Refer

to Figure 15 for top vent usage and Figure 16

for rear, and the following steps to prepare the

appropriate collar for use.

From the vent collar being used, remove the four

screws securing the vent seal plate and gasket.

Remove and discard the seal plate and gasket.

When the top vent collar is being used, from

inside the ﬁrebox, loosen the two screws in the

keyhole slots of the cover plate and remove the

remaining two cover plate securing screws.

Remove and discard the cover plate. Reinstall

and securely tighten all four screws.

When the rear vent collar is being used, from

inside the ﬁrebox, remove the two screws

securing the lintel to the rear wall of the ﬁrebox,

then remove the lintel. Remove the four cover

plate securing screws. Remove and discard

the cover plate.

Reinstall and securely tighten all four cover

plate screws. Re-secure the lintel to the rear

wall of the ﬁrebox.

Figure 15 - Top vent seal and cover plate

removal - MPD35/40/45 series models

(combined top and rear vent units)

Step 4. INSTALLING VENT SYSTEM

These instructions should be used as a

guideline and do not supersede local codes

in any way. Install venting according to local

codes,theseinstructions,thecurrentNational

Fuel Gas Code (ANSI-Z223.1) in the USA or

the current standards of CAN/CGA-B149.1

in Canada.

Ensure clearances are in accordance with

local installation codes and the requirements

of the gas supplier.

Dégagement conforme aux codes d'installa-

tionlocaux etauxexigences dufoumisseunde

gaz.

Select Venting System - Horizontal or Vertical

Withtheappliancesecuredinframing,determine

ventroutingandidentifytheexteriortermination

location. The following sections describe

vertical (roof) and horizontal (exterior wall)

vent applications. Refer to the section relating

to your installation. A list of approved venting

components are shown on Pages 36 and 37.

U-SHAPED VENT

RESTRICTOR

APPLIANCE REAR

VENT OUTLET

A vent restrictor may be needed when

horzontally terminating the vent system from

the rear of the appliance (when using the

appliance rear vent), install vent restrictor in

the rear vent of the fireplace outlet on

MPD35/40/45 series models, in any

installation that has a vertical vent run in

excess of three feet (0.914 meters).

INNER FIREPLACE

COLLAR

If needed, install the restrictor orientated as

shown, either from inside or outside the unit,

in the inner fireplace collar.

Figure 16 - Rear vent seal and cover plate

removal - MPD35/40/45 series models

(combined top and rear vent units)

Figure 18 -Vent restrictor installation -

Rear vent

KNOCKOUT

GASKET

FIREBOX TOP

CABINET TOP

VENT

COVER PLATE

TOP VENT

TOP VENT SEAL AND COVER PLATE REMOVAL

WHEN USING THE TOP VENT

COVER PLATE

SECURING SCREWS

CROSS SECTION

(INSIDE UNIT)

(OUTSIDE UNIT)

KNOCKOUT

CAP AND

GASKET

CROSS SECTION

REAR VENT

COVER PLATE

SECURING SCREWS

CABINET BACK

(INSIDE UNIT) (OUTSIDE UNIT)

REAR VENT SEAL AND COVER PLATE REMOVAL

WHEN USING THE REAR VENT

Figure 17 - Vent restrictor installation -

Top vent

Aventrestrictormaybe needed when vertically

terminating the vent system above the roof

(whenusingthe appliancetopvent),installvent

restrictor in the top vent of the ﬁreplace outlet

on MPD35/40/45 and MPDT33 series models.

If needed, install the restrictor orientated as

shown, either from inside or outside the unit,

in the inner ﬁreplace collar.

U-Shaped Vent

Restrictor

Inner Fireplace

Collar Appliance Top

Vent Outlet

Installation of Vent Restrictor

A vent restrictor may be needed with this

appliance, install vent restrictor (provided)

in the appliance top ﬂue outlet as shown in

Figure 17 (MPDT33, MPD35, MPD40 and

MPD45) or rear ﬂue outlet as shown in Figure

18 (MPD35, MPD40 and MPD45). It is held in

place by friction, only.

NOTE: The vent restrictor is included in the

rebox.

WARNING

Failure to reinstall and securely

tightencover plate screws could

resultinleakageofﬂueproducts

into the living space. Vent cover

plate and vent seal cap must

remain securely installed on

unused vent collar. Failure to

do so could result in leakage of

ﬂue products into living space.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

NOTE: Convert inches into metric equivalent

measurement, as follows:

Millimeters (mm) = Inches x 25.4

Centimeters (cm) = Inches x 2.54

Meters (M) = Inches x .0254

SV4.5FA or

SV4.5FB Flashing

AND SV4.5SC

Storm Collar

SV4.5VF

Firestop/Spacer*

1 in (25.4 mm)

Minimum

Clearance to

Combustibles

SV4.5CGV-1

Termination

SV4.5L6/12/24/36/48

Vent Sections

*When using Secure Flex,

use Firestop/Spacer

SF4.5VF.

Max. 40 ft

(12.2 m)

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5.4573.0100001

957.0200002

5.01578.0010001

5152.1110002

5.91526.1210003

1257.1020002

5.22578.1001001

5.52521.2120003

5.13526.2030003

5.43578.2000101

5.73521.3111003

5.34526.3021003

5457.3002002

5.64578.3000011

5.94521.4102003

1552.4100012

5.55526.4012003

7557.4001102

6652.5022004

5.76526.5003003

9657.5000202

2761030

5.37521.6100203

5.97526.6010203

1857.6000112

095.7021014

5.19526.7002013

3957.7000022

6981012

5.79521.8100023

2015.8200024

5.301526.8000303

80191003

4115.9020024

71157.9105006

5.811578.9110305

6215.01001304

5.031578.01101305

53152.11006006

8315.11000404

5.931526.11000033

5.241578.11100405

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5.451578.21110035

5.061573.31020035

5.271573.41000505

77157.41100506

38152.51010506

6815.51000044

5.091578.51100045

5.691573.61010045

5.502521.71011507

70252.71000606

5.112526.71100607

5.712521.81010607

5.922521.91001607

5.232573.91000055

73257.91100056

5.142521.02000707

6425.02100708

25212010708

46222001708

67232000808

97252.32000066

5.082573.32100809

5.382526.32100067

5.982521.42010067

5.103521.52001067

5.013578.52000909

5135.621009001

5.523521.72000077

0335.72100078

63382010078

54357.82000 01001

5.943521.921

00 01011

27313000088

5.673573.13100089

5.973526.13000 11011

5.814578.43000099

32452.531000901

56457.83000

0010

Model Effective Length

SV4.5L6 4-1/2"

SV4.5L12 10-1/2"

SV4.5L24 22-1/2"

SV4.5L36 34-1/2"

SV4.5L48 46 1/2"

Table 8 - Effective Vent Length

Figure 19

Table 7: Vent Section Length

VERTICAL TERMINATION SYSTEMS (ROOF)

See Figure 19 and Figures 27 through 29

on Page 17 and their associated Vertical

VentTables,which illustratethevarious vertical

venting conﬁgurations that are possible for

use with these appliances. Secure Vent®pipe

applicationsareshownintheseFigures;Secure

Flex®pipe may also be used. A Vertical Vent

Table summarizeseach system’sminimumand

maximum vertical and horizontal length values

that can be used to design and install the vent

components in a variety of applications.

Both these vertical vent systems terminate

through the roof. The minimum vent height

abovetheroofand/oradjacentwallsisspeciﬁed

in ANSI Z223.1 (In Canada, the current CAN/

CGA-B149.1installationcode)bymajorbuilding

codes. Always consult your local codes for

speciﬁcrequirements.Ageneralguideto follow

istheGasVentRule(refertoFigure5onPage 6).

Vertical (Straight) Installation

(Figure 19)

Determinethenumber of straightventsections

required. 4-1/2" (114 mm), 10-1/2" (267 mm),

22-1/2" (572 mm), 34-1/2" (876 mm) and 46

1/2"(1181mm)netsectionlengthsareavailable

(see Tables on this page and Pages 36 and

37 - Vent Sections). Plan the vent lengths so

that a joint does not occur at the intersection of

ceiling or roof joists. Refer to the Vent Section

Length Chart.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Figure 20

Figure 22

Figure 21

Support the vertical portion of the venting

system every 8 feet (2.4m) above the ﬁreplace

ventoutlet.Onemethodofsupportisbyutilizing

ﬁeld provided support straps (conventional

plumber's tape). Secure the plumber's tape

to the framing members with nails or screws.

Loop the tape around the vent, securing the

ends of the tape to the framing. If desired,

sheet metal screws #6 x 1/2" length may be

used to secure the support straps to the vent

pipe. See Figure 22.

Vertical (Offset) Installation

Analyze the vent routing and determine the

quantities of vent sections and number of

elbowsrequired.RefertoVerticalVent Figures

and Tables on Page 17 to select the type of

vertical installation desired. Vent sections are

available in net lengths of 4-1/2" (114 mm),

10-1/2" (267 mm), 22-1/2" (572 mm), 34-1/2"

(876 mm) and 46 1/2" (1181 mm). Refer to the

Vent Section Length Chart on Page 14 for an

aidinselectinglengthcombinations.Elbowsare

available in 90° and 45° conﬁgurations. Refer

to Figure 23 for the SV4.5E45 and SV4.5E90

elbow dimensional speciﬁcations.

Where required, a telescopic vent section

(SV4.5LA) may be used to provide the installer

with an option in installing in tight and conﬁned

spaces or where the vent run made up of ﬁxed

length pieces develops a joint in a undesirable

location, or will not build up to the required

length. The SV4.5LA Telescopic Vent Section

has an effective length of from 1 1/2" (38 mm)

to 7 1/2" (191 mm). The SV4.5LA is ﬁtted with

a locking inclined channel end (identical to a

normalventsectioncomponent)andaplainend

with 3 pilot holes. Slip the plain end over the

locking channel end of a standard SV4.5 vent

component the required distance and secure

with three screws.

Maintain a minimum 1" (25 mm) clearance to

combustible materials for all vertical elements.

Clearances for all horizontal elements are 3"

(76 mm) on top, 1" (25 mm) on sides and 1"

(25 mm) on the bottom.

A. 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" x 10-1/2" (267 mm x 267

mm)inside dimensions,about thiscenter mark

(Figure 20).

B. Attach vent components to appliance

- Secure Vent®SV4.5 direct vent system

components are unitized concentric pipe

components featuring positive twist lock

connections (see Figure 19). All of the

appliances covered in this document are ﬁtted

with collars having locking inclined channels.

Thedimpledendoftheventcomponentsﬁtover

the appliance collar to create the positive twist

lock connection.To attach a vent component to

the appliance collar, align the dimpled end over

the collar, adjusting the radial alignment until

the four locking dimples are aligned with the

inlet of the four inclined channels on the collar

(refer to Figure 21). Push the vent component

againstthecollaruntilitfullyengages,thentwist

the component clockwise, running the dimples

down and along the incline channels until they

seat at the end of the channels. The unitized

design of the Secure Vent®components will

engage and seal both the inner and outer pipe

withouttheneedforsealantorscrews.Ifdesired

a #6 x 1/2" screw may be used at the joint, but

it is not required as the pipe will securely lock

when twisted.

NOTE: An elbow may also be attached to the

appliance collar. Attach in the same manner as

you would a vent section.

C. Attach vent components to each other

- Other vent sections may be added to the

previously installed section in accordance with

the requirements of the vertical vent ﬁgures

and tables. To add another vent component

to a length of vent run, align the dimpled end

over the inclined channel end of the previously

installed section, adjusting the radial alignment

until the four locking dimples are aligned with

the inlets of the four incline channels of the

previous section.

Push the vent component against the previous

section until it fully engages, then twist the

componentclockwiserunningthedimplesdown

and along the incline channels until they seat at

the end of the channels.This seating position

is indicated by the alignment of the arrow and

dimple as shown in Figure 21.

D. Install ﬁrestop/spacer at ceiling - When

usingSecureVent,useSV4.5VFﬁrestop/spacer

at ceiling joists; when using Secure Flex®, use

SF4.5VF ﬁrestop/spacer. If there is living space

abovetheceilinglevel,theﬁrestop/spacer must

be installed on the bottom side of the ceiling.

If attic space is above the ceiling, the ﬁrestop/

spacer must be installed on the top side of

the joist. Route the vent sections through the

framed opening and secure the ﬁrestop/spacer

with 8d nails or other appropriate fasteners at

each corner.

Remember to maintain 1" (25 mm) clearance

to combustibles, framing members, and attic

or ceiling insulation when running vertical

chimney sections. Attic insulation shield

(96K94) may be used to obtain the required

clearances indicated here. See installation

accessoriestableonPages36and37.Thegap

between the vent pipe and a vertical ﬁrestop

canbesealedwithnon-combustiblecaulking.

E. Support the vertical vent run sections -

NOTE: Proper venting support is very important.

Blocking

Support Straps

(Plumber's tape)

8 feet (2.4 m)

Maximum

1/2 inch (12.7

mm) minimum

clearance to

combustibles

Align the dimple (four places) of

the upper vent section with the

opening of the locking incline

channel on the lower vent section

or appliance collar. Twist vent

component clockwise to engage

and seal until arrow and dimple

align.

Dimple

Locking Incline

Channel

Connected Vent

Sections Arrow

Arrow

Appliance Collar or

Vent Section

Min. 10-1/2"

(267 mm)

Min. 10-1/2"

(267 mm)

Roof

Framing

Ceiling

Framing

Plumb

Bob

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Figure 24

Figure 26

Figure 25

If the vent system extends more than 5' (1.5

m) above the roof ﬂashing, stabilizers may be

necessary. Additional screws may be used at

section joints for added stability. Guide wires

may be attached to the joint for additional sup-

port on multiple joint conﬁgurations.

G.Continueinstallationofhorizontal/inclined

sections - Continue with the installation of the

straight vent sections in horizontal/inclined run

as described in Step C. Install support straps

every 5 ft (1.52 m) along horizontal/inclined

vent runs using conventional plumber’s tape.

Itisveryimportantthatthe horizontal/inclined

run be maintained in a straight (no dips),

slightly elevated plane. The recommended

incline is approximately 1/4" per foot (20 mm

permeter)horizontal,inadirectionawayfrom

the ﬁreplace. The rise per foot run ratios that

are smaller are acceptable all the way down

to at or near level. Use a carpenter’s level to

measure from a constant surface and adjust

the support straps as necessary.

It is important to maintain the required

clearances to combustibles: 1" (25 mm) at all

sides for all vertical runs; and 3" (76 mm) at

the top, 1" (25 mm) at sides, and 1" (25 mm)

at the bottom for all horizontal/inclined runs.

H. Frame roof opening - Identify location for

vent at the roof. Cut and/or frame opening per

Roof Framing Chart and Figure 24.

F.Changeventdirectiontohorizontal/inclined

run - At transition from or to a horizontal/

inclinedrun,installtheSV4.5E45andSV4.5E90

elbows in the same manner as the straight vent

sections. The elbows feature a twist section to

allow them to be routed about the center axis

of their initial collar section to align with the

required direction of the next vent run element.

Twist elbow sections in a clockwise direction

only so as to avoid the possiblity of unlocking

anyofthepreviouslyconnectedventsections.

See Figure 23.

Figure 23

SV4.5E90

(90

Elbow)

8-1/8"

(206 mm)

Swivel Joint

(360

swivel)

4-13/16"

(122 mm)

SV4.5E45

(45

Elbow)

Swivel Joint

(360

swivel)

Storm

Collar

K. Install the vertical termination - The ﬁnal

step involves installation of the SV4.5CGV-1

Vertical Termination. Extend the vent sections

to the height as shown in the "Vertical vent

terminationsection"onPage 6.TheSV4.5CGV-1

Vertical Termination (Figure 26) installs in the

exact same fashion as any other Secure Vent®

section. Align the termination over the end of

the previously installed section, adjusting the

radial alignment until the four locking dimples

of the termination are aligned with the inlets of

thefourinclinechannelsofthelastventsection.

Pushtheterminationdownuntilitfullyengages,

thentwisttheterminationclockwiserunningthe

dimples down and along the incline channels

until they seat at the end of the channels.

I. Install the roof ﬂashing - Extend the vent

sections through the roof structure. Install the

roof ﬂashing over the vent section and posi-

tion such that the vent column rises vertically

(use carpenters level) (Figure 25 ). Nail along

perimetertosecure ﬂashing oradjustrooﬁngto

overlap the ﬂashing edges at top and sides only

andtrimwherenecessary.Seal thetopandboth

sides of the ﬂashing with waterproof caulking.

J. Install the storm collar - Install the storm

collar, supplied with theﬂashing, overthe vent/

ﬂashingjoint.See Figure 25.Loosenthestorm

collar screw. Slide collar down until it meets

the top of the ﬂashing. Tighten the adjusting

screw. Apply non-combustible caulking or

mastic around the circumference of the joint

to provide a water tight seal.

Pitch C D

0/12 10-1/2"

(267 mm)

10-1/2"

(267 mm)

6/12 10-1/2"

(267 mm)

12"

(305 mm)

12/12 10-1/2"

(267 mm)

17-3/4"

(451 mm)

Framing Dimensions for Roof

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Figure 28 - Rear Vent - ONE 90-DEGREE ELBOW

Figure 27 - Top Vent - STRAIGHT

Figure 29 - Top Vent - TWO 90-DEGREE ELBOWS

VERTICAL VENT FIGURES/TABLES

NOTE: Secure Vent®(rigid vent pipe) is shown

in the ﬁgures; Secure Flex®(ﬂexible vent pipe)

may also be used.

NOTE: It is very important that the horizontal/

inclined run be maintained in a straight (no

dips), slightly elevated plane.The recommended

incline is approximately 1/4" per foot (20 mm

per meter) horizontal, in a direction away from

the ﬁreplace. The rise per foot run ratios that

are smaller are acceptable all the way down to

at or near level.

NOTE:SV4.5VF (Secure Vent),SF4.5VF (Secure

Flex®) ﬁrestop/spacer must be used anytime

vent pipe passes through a combustible ﬂoor

or ceiling. SV4.5HF (Secure Vent), SF4.5HF

(Secure Flex®)ﬁrestop/spacer must be used

anytime vent pipe passesthrough a combustible

wall.

NOTE: Two 45 degree elbows may be used in

place of one 90 degree elbow. The same rise

to run ratios, as shown in the venting ﬁgures

for 90 elbows, must be followed if 45 degree

elbows are used.

NOTE: An elbow is acceptable as 1 foot of

vertical rise, except where an elbow is the

only vertical component in the system. (See

Figure 36 on Page 21).

A Vent Restrictor, as shown in Figure 17 on

Page 13, must be used in this application.

This table shows a 1 (V) to 2 (H) ratio.

For every 1 foot of (V) vertical, you are

allowed 2 feet of (H) horizontal run, up

to a maximum horizontal run of 8 feet.

Example: If 8 feet of (H) horizontal vent

run is needed, then 4 feet minimum (V)

vertical vent will be required.

TABLE A

H Maximum V Minimum

feet feet

2(0.610) 1(0.305)

4(1.219) 2(0.610)

6(1.829) 3(0.914)

8(2.438) 4(1.219)

V + H = 40 feet (12.2 meters) Max.

H = 8 feet (2.4 meters) Max.

Ratio V to H ratio is 1:2

(meters) (meters)

Example: If 20 feet of (H) horizontal vent

run is needed, then 4 feet minimum of

(V) vertical vent will be required.

This table shows a 1 (V) to 5 (H) ratio.

For every 1 foot of (V) vertical, you are

allowed 5 feet of (H) horizontal run, up

to a maximum horizontal run of 20 feet.

An elbow isacceptable as 1 foot ofvertical

rise except where an elbow is the only

vertical component in the system. See

Figure 36.

NOTE: Install the U-shaped vent

restrictor in any vent run with more

than 8 ft of vertical rise (See Page 13).

TABLE B

H Maximum V Minimum

feet (meters) feet

5(1.524) Elbow Only

5(1.524) 1(0.305)

10 (3.048) 2(0.610)

15 (4.572) 3(0.914)

20 (6.096) 4(1.219)

V + V1+ H = 40 feet (12.2 m) Max.

H = 20 feet (6.096 meters) Max.

(meters)

WARNING

Under no circumstances, may separate sections of concentric ﬂexible vent

pipe be joined together.

Max. 40 ft

(12.2 m)

*When using

Secure Flex, use

Ceiling Firestop/

Spacer SF4.5VF.

Ceiling

Firestop/

Spacer

SV4.5VF*

Ceiling

Firestop/Spacer

SV4.5VF*

*When using Secure Flex, use

Ceiling Firestop/Spacer

SF4.5VF.

Ceiling

Firestop/Spacer

SV4.5VF*

Wall

Firestop/Spacer

SV4.5HF**

*When using Secure Flex, use

Ceiling Firestop/Spacer SF4.5VF.

**When using Secure Flex, use

Wall Firestop/Spacer SF4.5HF.

NOTE: Install the U-shaped vent restrictor in

any vent run with more than 8 ft of vertical rise

(See Page 13).

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

TABLE C

H+H1Maximum HMaximum V Minimum

feet feet feet

5(1.524) 2(0.610) 1(0.305)

10 (3.048) 4(1.219) 2(0.610)

15 (4.572) 6(1.829) 3(0.914)

20 (6.096) 8(2.438) 4(1.219)

V + V1+ H + H1= 40 feet (12.2 m) Max

H = 8 feet (2.438 meters) Max.

H + H1= 20 feet (6.096 meters) Max.

(meters) (meters)

(meters)

Example: If 20 feet of (H) horizontal vent run is needed,

then 4 feet minimum of (V) vertical vent will be required.

This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of

(V) vertical, you are allowed 5 feet of (H) horizontal run, up

to a maximum horizontal run of 20 feet.

NOTE: Install the U-shaped vent restrictor in any vent run

with more than 8 ft of vertical rise (See Page 13).

TABLE D

H +H1Maximum V Minimum

feet feet

5(1.524) Elbow Only

5(1.524) 1(0.305)

10 (3.048) 2(0.610)

15 (4.572) 3(0.914)

20 (6.096) 4(1.219)

H + H1= 20 feet (6.096 m) Max.

V + V1+ H + H1= 40 ft. (12.192 m) Max.

(meters) (meters)

Example: If 20 feet of (H) horizontal vent run is needed, then 4 feet

minimum of (V) vertical vent will be required.

This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of (V) vertical,

you are allowed 5 feet of (H) horizontal run, up to a maximum

horizontal run of 20 feet.

An elbow is acceptable as 1 foot of vertical rise except where an

elbow is the only vertical component in the system. See Figure 36.

NOTE: Install the U-shaped vent restrictor in any vent run with more

than 8 ft of vertical rise (See Page 13).

VERTICAL VENT FIGURES/TABLES

(continued)

Figure 30 - Rear Vent - THREE ELBOWS

Figure 31: Top Vent - THREE ELBOWS

Ceiling

Firestop/Spacer

SV4.5VF*

Wall

Firestop/Spacer

SV4.5HF**

*When using Secure Flex, use

Ceiling Firestop/Spacer SF4.5VF.

**When using Secure Flex, use

Wall Firestop/Spacer SF4.5HF.

Ceiling

Firestop/Spacer

SV4.5VF*

Ceiling

Firestop/Spacer

SV4.5VF* Wall

Firestop/Spacer

SV4.5HF**

*When using Secure Flex, use

Ceiling Firestop/Spacer SF4.5VF.

**When using Secure Flex, use

Wall Firestop/Spacer SF4.5HF.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Figure 32 - Typical Horizontal Vent Installation

Vertical

Rise

SV4.5E90

Elbow

Horizontal / Inclined Run SV4.5HT-2

Termination

Firestop/Spacer

SV4.5L6/12/24/36/48

Vent Sections

Support bracket spacing

every 5 ft (1.52 m)

See Figure 24 on Page 15 for

vertical vent section support.

SV4.5HT-2

Termination

Support

Brackets

Building

Support

Framing

Ceiling

Fireplace

Exterior

Wall

Exterior

Wall

TYPICAL HORIZONTAL VENT INSTALLATION

HORIZONTAL(OUTSIDEWALL)TERMINATION

SYSTEM

Figure 32, and Figures 35 to 41 on Pages

21 to 23 and their associated Horizontal

Vent Table illustrate the various horizontal

venting conﬁgurations that are possible for

use with these appliances. Secure Vent®pipe

applicationsare shownin these ﬁgures;Secure

Flex®pipe may also be used. A Horizontal Vent

Tablesummarizeseachsystem’sminimumand

maximum vertical and horizontal length values

that can be used to design and install the vent

componentsin avariety ofapplications. Bothof

thesehorizontalventsystemsterminatethrough

an outside wall. Building Codes limit or prohibit

terminating in speciﬁc areas. Refer to Figure 7

on Page 7 for location guidelines.

Secure Vent SV4.5 direct vent system compon-

ents are unitized concentric pipe components

featuring positive twist lock connection, (refer

to Figure 21 on Page 15). All of the appliances

covered in this document are ﬁtted with collars

having locking inclined channels. The dimpled

end ofthe vent componentsﬁt over theappliance

collarto createthe positivetwist lockconnection.

A. Plan the vent run - Analyze the vent routing

and determinethe typesandquantities ofsections

required 4-1/2" (114 mm), 10-1/2" (267 mm),

22-1/2" (572 mm), 34-1/2" (876 mm) and 46-1/2".

(1181 mm) net section lengths are available. It is

recommended that you plan the venting so that a

jointdoesnotoccurintheceilingorroofjoists.Allow

for elbows as indicated in Figure 23 on Page 16.

Maintain a minimum 1" (25 mm) clearance to

combustiblesontheverticalsections.Clearances

for the horizontal runs are; 3" (76 mm) on top, 1"

(25 mm) on sides, and 1" (25 mm) at the bottom.

B. Frame exterior wall opening - Locate the

center of the vent outlet on the exterior wall

according to the dimensions shown in Figure

12 on Page 11. Cut and/or frame an opening,

10-1/2" x 12-1/8" (267 mm x 308 mm) inside

dimensions, about this center.

C. Frame ceiling opening - If the vertical route

isto penetratea ceiling,use plumbline tolocate

thecenterabovetheappliance.Cutand/orframe

an opening, 10-1/2" x 10-1/2" (267 mm x 267

mm)insidedimensions,aboutthiscenter(refer

to Figure 20 on Page 15).

D. Attach vent components to appliance - To

attach a vent component to the appliance collar,

alignthedimpledendoverthecollar,adjustingthe

radialalignmentuntilthe fourlockingdimplesare

aligned with the inlets of the four incline channels

on the collar (refer to Figure 21 on Page 15).

Push the vent component against the collar

until it fully engages, then twist the component

clockwise, running the dimples down and along

the incline channels until they seat at the end of

the channels. The unitized design of the Secure

Vent components will engage and seal both the

inner and outer pipe elements with the same

procedure. Sealant and securing screws are

not required.

NOTE: An elbow may also be attached to the

appliance collar. Attach in the same manner as

you would a vent section.

E. Attach vent components to each other

- Other vent sections may be added to the

previously installed section in accordance with

the requirements of the vent tables. To add

another vent component to a length of vent run,

align the dimpled end of thecomponent over the

inclined channel end of the previously installed

section, adjusting the radial alignment until the

fourlockingdimplesarealignedwiththeinletsof

thefourincline channelsoftheprevioussection.

Push the vent component against the previous

section until it fully engages, then twist the

componentclockwiserunningthedimplesdown

and along the incline channels until they seat at

the end of the channels.This seating position

is indicated by the alignment of the arrow and

dimple as shown in Figure 21 on Page 15.

F. Install ﬁrestop/spacer at ceiling - When

usingSecureVent,useSV4.5VFﬁrestop/spacer

at ceiling joists; when using Secure Flex®, use

SF4.5VF ﬁrestop/spacer. If there is living space

abovetheceilinglevel,theﬁrestop/spacermust

be installed on the bottom side of the ceiling.

If attic space is above the ceiling, the ﬁrestop/

spacer must be installed on the top side of

the joist. Route the vent sections through the

framed opening and secure the ﬁrestop/spacer

with 8d nails or other appropriate fasteners at

each corner.

Remember to maintain 1" (25 mm) clearance

to combustibles, framing members, and attic

or ceiling insulation when running vertical

chimney sections.

G. Support the vertical run sections - On the

vertical run, support the venting system every

8 feet (2.4m) above the ﬁreplace vent outlet

with ﬁeld provided support straps (Plumber's

tape). Attach the straps to the vent pipe and

secure to the framing members with nails or

screws. See Figure 22 on Page 15.

H.Changeventdirection- At transitionfromor

toahorizontal/inclinedrun,installtheSV4.5E45

and SV4.5E90 elbows in the same manner as

thestraight ventsections. The elbowsfeature a

twist section to allow them to be routed about

the center axis of their initial collar section to

align with the required direction of the next

vent run element. Twist elbow sections in a

clockwise direction only so as to avoid the

possiblity of unlocking any of the previously

connected vent sections. See Figure 23 on

Page 16.

I.Continue installationofhorizontal/inclined

sections - Continue with the installation of the

straightventsectionsin horizontal/inclinedrun

as described in Step E. Install support straps

every 5 ft. (1.52 m) along horizontal/inclined

vent runs using conventional plumber’s tape.

See Figure 32,It is very important that the

horizontal/inclined run be maintained in a

straight (no dips), slightly elevated plane.

The recommended incline is approximately

1/4" per foot (20 mm per meter) horizontal,

in a direction away from the ﬁreplace. The

rise per foot run ratios that are smaller are

acceptable all the way down to at or near level.

Use a carpenter’s level to measure from a

constant surface and adjust the support straps

as necessary.

It is important to maintain the required

clearances to combustibles: 1" (25 mm) at all

sides for all vertical runs; and 3" (76 mm) at

the top, 1" (25 mm) at sides, and 1" (25 mm)

at the bottom for all horizontal/inclined runs.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

Figure 33 - Installing the Square Horizontal Termination (SV4.5HT-2)

Figure 34 - Venting Connection and Exterior Wall Recessing of the Horizontal Square

Termination (SV4.5HT-2)

J. Assemble vent run to exterior wall - If not

previously measured, locate the center of the

vent at the exterior wall. Prepare an opening as

described in Step B. Assemble the vent system

topointwhere theterminusof the lastsectionis

within7"(178mm)to11-1/4"(286mm)inboard

of the exterior surface to which the SV4.5 HT

termination is to be attached, see Figure 34.

If the terminus of the last section is not within

this distance, use the telescopic vent section

SV4.5LA, as the last vent section. For wall

thicknesses greater than that shown in Figure

34, refer to Table 9 on Page 21. This table lists

the additional venting components needed (in

addition to the termination and adaptor) for a

particular range of wall thicknesses.

K. Attach termination adaptor - Attach

the adaptor (SV4.5RCH, provided with the

termination) to the vent section or telescoping

ventsection),elboworappliancecollarasshown

in Figure 33 in the same manner as any SV4.5

vent component (refer to Step E).

L. Install Firestop/Spacer at exterior wall

- When using the square termination, install

SV4.5HF (Secure Vent®), SF4.5HF (Secure

Flex®) Firestop/Spacer over the opening at the

exterior side of the framing, long side up, with

the 3 inch spacer clearance at the top as shown

in Figure 33, and nail into place (the Firestop/

Spacer may also be installed over the opening

at the interior side of the framing).

M. Install the desired termination

1.Install thesquaretermination (SV4.5HT-2

or SV4.5HTSS) - For the last step , from

outside the exterior wall, slide the collars of

the termination onto the adaptor (the outer

over the outer and the inner inside the inner)

until the termination seats against the exterior

wall surface to which it will be attached. Orient

the housing of the termination with the arrow

pointed upwards. Secure the termination to

the exterior wall. The horizontal termination

must not be recessed into the exterior wall

or siding by more than the 1-1/4" (32 mm) as

shown in Figure 34.

SVHRK Snorkel Cap - The snorkel cap is

designed to be ﬁtted into a basement window

box. The SVHRK cap is for use with ex vent.

The vertical distance between the inlet and

outlet of the cap is 28" (711 mm).

IMPORTANT: The vent termination is hot

while in operation and for a period of

time following the use of the ﬁreplace.

To prevent contact with hot surfaces,

we recommend the use of a Termination

Guard. See Page 36. This can be

purchased at your local dealer.

SV4.5HT-2

Termination

10-1/2”

(267mm)

7”

(178)

5-1/8”

(130 mm)

12-1/8”

(308 mm)

NOTE: Centerline of Vent Piping is NOT

the Same as the Centerline of the

Framed Opening.

6 to 48” Vent Section,

Telescopic vent section,

Elbow or Appliance Collar Base of Appliance

3”

(76 mm)

1”

(25.4 mm)

Adaptor

SV4.5RCH

Horizontal terminations have been designed to perform in a wide range of weather

conditions. Our terminations meet or exceed industry standards.

When selecting the locations of your horizontal terminations, do not place the termination

where water from eaves and adjoining rooﬂines may create a heavy ﬂow of cascading water

onto the termination cap. If the cap must be placed where the possibility of cascading water

exists, it is the responsibility of the builder to direct the water away from the termination

cap by using gutters or other means.

Take care to carefully follow the installation instructions for the termination, including the

use of silicone caulking where required.

Siding

Stucco

1-1/4" Maximum Recess of

the Square Termination into

Exterior Finishing Material

Exterior Surface of

Framing

6” to 9-1/4”

(152 to 235 mm)**

Exterior Surface of Siding

Interior Surface of

Finished Wall

Maximum wall thickness

10” (254 mm)**

SV4.5HT-2

Square Termination

Maximum Extent of

Vent Run Sections

Relative to Exterior

Surface of Framing

Last Vent Section. Use

Telescopic Vent

Section (SV4.5LA), If

Necessary

Adaptor

SV4.5RCH

SV4.5HT-2

Square Termination

Venting Connection and Exterior Wall Recessing of the

Horizontal Square Termination (SV4.5HT-2).

*Use silicone caulking to seal

the top and sides of the

termination, up to the

underlayment, stucco, or

masonry wall surface.

**For thicknesses greater

than 10” see Table 8.

*Caulk

**Forthicknessesgreaterthan

10" (254mm) see Table 9.

To help minimize water inﬁl-

tration it is recommended that

the Firestop/Spacer (SV4.5HF)

be installed on the exterior

side of the wall.

SeeFigure 12 onPage 10 forMin.

Distance to Base of Appliance.

NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS

H Maximum V Minimum

feet feet

5(1.524) 1(0.305)

10 (3.048) 2(0.610)

15 (4.572) 3(0.914)

20 (6.096) 4(1.219)

V + H = 40 feet (12.2 m) Max.

H = 20 ft. (6.096 m) Max.

TABLE G

(meters) (meters)

TABLE F

H Maximum V Minimum

feet feet

3(0.914) Elbow Only

(meters) (meters)

Example: If 20 feet of (H)

horizontal ventrun isneeded, then

4 feetminimum of (V)vertical vent

will be required.

This table shows a 1 (V) to 5

(H) ratio. For every 1 foot of

(V) vertical, you are allowed 5

feet of (H) horizontal run, up

to a maximum horizontal run

of 20 feet.

Figure 36 - Top Vent - ONE 90-DEGREE ELBOW -

ELBOW CONNECTION AT APPLIANCE

Figure 37 - Top Vent - ONE 90-DEGREE ELBOW -

ELBOW CONNECTION NOT DIRECTLY AT APPLIANCE

Square termination (SV4.5HT-2) shown.

See Table 9 as an aid in venting component selection for a particular range of

exterior wall thicknesses.

Square termination (SV4.5HT-2) shown.

See Table 9 as an aid in venting component selection for a particular range of

exterior wall thicknesses.

NOTE: Install the U-shaped vent restrictor in any vent run with more

than 8 ft of vertical rise (See Page 13).

Venting Components Required for Various Exterior Wall Thick-

nesses, when using Typical Termination Kits

Vent Components Required Exterior Wall Thickness - in. (mm)

Termination Kit Only 6 to 9-1/4 (152 to 235)

Termination Kit and 6" Vent

Section (SV4.5L6) 10-3/4 to 14 (2733 to 356)

Termination Kit and 12"

Vent Section (SV4.5L12) 16-3/4 to 20 (426 to 508)

Termination Kit and

Telescopic Section

(SV4.5L12)

11-3/4 to 20 (299 to 508)

Table 9 NOTE: See Figure 34 showing wall thickness range

when using SV4.5HT-2 termination kit.

HORIZONTAL VENT FIGURES/TABLES

NOTE: Secure Vent®components (rigid vent pipe and terminal) are

shown in the ﬁgures; Secure Flex®components (ﬂexible vent pipe and

terminal) may also be used.

NOTE: Two 45 degree elbows may be used in place of one 90 degree

elbow. The same rise to run ratios, as shown in the venting ﬁgures for

90 elbows, must be followed if 45 degree elbows are used.

NOTE: It is very important that the horizontal/inclined run be maintained

in a straight (no dips), slightly elevated plane. The recommended

incline is approximately 1/4" per foot (20 mm per meter) horizontal,

in a direction away from the ﬁreplace. The rise per foot run ratios that

are smaller are acceptable all the way down to at or near level.

NOTE: SV4.5VF (Secure Vent®), SF4.5VF (Secure Flex) ﬁrestop/spacer

must be used anytime vent pipe passes through a combustible ﬂoor or

ceiling. SV4.5HF (Secure Vent), SF4.5HF (Secure Flex) ﬁrestop/spacer

must be used anytime vent pipe passes through a combustible wall.

Figure 35 - Rear Vent - NO ELBOWS

WARNING

Under no circumstances, may separate sections of

concentric ﬂexible vent pipe be joined together.

H = 28 in. (711 mm) Maximum.

7 in

(178 mm)

Wall Firestop/

Spacer

SV4.5HF**

**When using Secure Flex, use

Wall Firestop/Spacer SF4.5HF.

Ceiling

Firestop/

Spacer

SV4.5VF*

Wall Firestop/

Spacer SV4.5HF**

*When using Secure Flex, use

Ceiling Firestop/Spacer SF4.5VF.

**When using Secure Flex, use

Wall Firestop/Spacer SF4.5HF.

Wall Firestop/

Spacer

SV4.5HF**

**When using Secure

Flex, use Wall Firestop/

Spacer SF4.5HF.

Only the square termination (SV4.5HT-2) may be used.

See Table 9 as an aid in venting component selection for a particular

range of exterior wall thicknesses.

NOTE: Install the U-shaped vent

restrictor in any vent run with

more than 8 ft of vertical rise

(See Page 13).

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