Monessen Hearth AVFLST Series Manual

This is an unvented replace. It uses air (oxygen)
from the room in which it is installed. Provisions
for adequate combustion and ventilation air must
be provided. Refer to Page 8.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
• Do not store or use gasoline or other
ammable 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.
– Leave the building immediately.
– 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 re department.
• Installation and service must be performed
by a qualied installer, service agency or
the gas supplier.
WARNING! If the information in this manual
is not followed exactly, a re or explosion may
result causing property damage, personal
injury or loss of life.
AVFLST Vent Free See Through
Fireplace System
Installation & Operating Instructions
Models: AVFLST42NIP and AVFLST42PIP
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020

2
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
CONTENTS
Thank you and congratulations on your purchase of a Monessen replace.
PLEASE READ THE INSTALLATION AND OPERATION INSTRUCTIONS BEFORE USING THE APPLIANCE!
IMPORTANT: Read all instructions and warnings carefully before starting installation.
Failure to follow these instructions may result in a possible re hazard and will void the warranty.
STANDARD WORK CHECKLIST.................................. 3
IMPORTANT SAFETY INFORMATION ......................... 4
Building code information ............................................ 5
PRODUCT FEATURES.................................................. 6
AVFLST42 controls ..................................................... 6
Gas specications & orice size .................................. 6
Gas pressures ............................................................. 6
FIREPLACE and FRAMING DIMENSIONS .................. 7
PRE-INSTALLATION INFORMATION........................... 8
Getting started ............................................................. 8
What you will need for installation ............................... 8
Planning the installation .............................................. 8
Adequate combustion and ventilation air .................... 8
Fireplace location ........................................................ 9
Clearances and height requirements ........................ 10
FIREPLACE INSTALLATION ...................................... 12
Secure replace to framing ....................................... 12
Finishing material ...................................................... 12
Noncombustible facing installation ............................ 12
Connect the gas ........................................................ 13
Check gas pressure .................................................. 14
Gas pressures ........................................................... 14
ELECTRICAL INSTALLATION.................................... 15
Wiring junction box .................................................... 15
Wiring Requirements ................................................. 16
FINAL INSTALLATION ................................................ 18
Installation of air deection glass .............................. 18
Fireglass only placement .......................................... 18
Glass and optional stone kit placement .................... 18
OPERATING INSTRUCTIONS .................................... 19
For your safety read before lighting .......................... 19
Heat Management ..................................................... 20
Operation During a Power Outage ............................ 20
Intellire™ Plus ODS SYSTEM OPERATION............ 21
FLAME APPEARANCE & LED CONTROL................. 28
Flame appearance .................................................... 28
Check the pilot ame ................................................. 28
Check the burner ame ............................................. 28
LED Control ............................................................... 28
MAINTENANCE and CLEANING................................ 29
Cleaning and servicing .............................................. 29
Replacing top light bulb ............................................. 29
Replacing led strips ................................................... 29
Porcelain Panel Removal .......................................... 30
OPERATION AND OPTIONAL ACCESSORIES ......... 31
Operating information ................................................ 31
Optional accessories ................................................. 31
TROUBLESHOOTING................................................. 32
Intellire™ Plus ODS System ................................... 34
SERVICE PARTS......................................................... 36
LIMITED LIFETIME WARRANTY ................................ 38
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3
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
Customer:
Lot/Address:
Model (circle one): AVFLST42NIP, AVFLST42PIP
Date Installed:
Location of Fireplace:
Installer:
Dealer/Distributor Phone #
Serial #:
Comments: Further description of the issues, who is responsible (Installer/ Builder/ Other Trades, etc) and corrective
action needed _____________________________________________________________________________________
Comments Communicated to party responsible ____________________ by ______________________on ___________
(Builder / Gen. Contractor/) (Installer) (Date)
?YHW , ON F I SEY
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
4118-982A 04/20
= Contains updated information.
• Photographing the installation and copying this checklist for your file.
• That this checklist remain visible at all times on the appliance until the installation is complete.
This standard work checklist is to be used by the installer in conjunction with, not instead of, the instructions contained in this
installation manual.
WARNING! Risk of Fire or Explosion! Failure to install appliance according to these instructions could
lead to a fire or explosion.
ATTENTION INSTALLER:
Follow this Standard Work Checklist
Appliance Install (Pg. 7-12)
Verified that the chase is insulated and sealed.
Required non-combustible board is installed.
Fireplace is leveled and secured.
Adequate provisions for combustion and ventilation air have been verified.
Verified clearances to combustibles.
Gas (Pg 13-14)
Proper appliance for fuel type.
Leak check performed and inlet pressure verified.
Verified proper air shutter setting for installation type.
Electrical (Pg 15)
Unswitched power (110-120 VAC) provided to the appliance.
Switch wires properly installed.
Media & Accessories (Pg 18)
All packaging and protective materials removed (inside & outside of
appliance). Media installed correctly.
Accessories installed properly.
Finishing (Pg 10 & 12)
Verifi ed all clearances meet installation manual requirements.
Mantels and wall projections comply with installation manual requirements.
Manual bag and all of its contents are removed from inside/
under the appliance and given to party responsible for use and operation.
Started appliance and veried no gas leaks exist.
Hearth & Home Technologies recommends the following:
STANDARD WORK CHECKLIST

4
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
IMPORTANT SAFETY INFORMATION
WARNING!
• Any change to this heater or its controls can be dangerous.
• Improper installation or use of the heater can cause serious injury or death from re, burns,
explosion or carbon monoxide poisoning.
• Do not allow fans to blow directly into the replace. Avoid any drafts that alter burner ame patterns.
• Do not use a blower insert, heat exchanger insert or other accessory, not approved for use with
this heater where applicable.
INSTALLER
Please leave these instructions with the appliance.
OWNER
Please retain these instructions for future reference .
1. Due to high temperatures, the appliance should be
located out of tra󰀩c and away from furniture and
draperies.
2. Children and adults should be alerted to the hazard
of high surface temperature and should stay away
to avoid burns or clothing ignition.
3. Young children should be carefully supervised when
they are in the same room with the appliance.
4. Do not place clothing or other ammable material
on or near the appliance.
5. Any safety screen or guard removed for servicing
an appliance, must be replaced prior to operating
the heater.
6. Installation and repair should be done by a qualied
service person. To prevent malfunction and/or soot-
ing, an unvented replace should be cleaned before
use and at least annually by a professional service
person. More frequent cleaning may be required
due to excessive lint from carpeting, bedding mate-
rials, etc. It is imperative that control compartments,
burners and circulating air passageways be kept
clean.
7. WARNING! Any change to this heater or its controls
can be dangerous.
8. Unvented fireplaces are a supplemental zone
heater. They are not intended to be the primary
heating appliance.
9. CARBON MONOXIDE POISONING: Early signs of
carbon monoxide poisoning are similar to the u with
headaches, dizziness and/or nausea. If you have these
signs, obtain fresh air immediately. Have the heater
serviced as it may not be operating properly.
10. The installation must conform with local codes or, in
the absence of local codes, with the National Fuel
Gas Code, ANSI Z223.l/NFPA54.
11. This unit complies with ANSI Z21.11.2:19 Unvented
Heaters.
12. Do not install the heaters in a bathroom or bedroom.
13. Proper location of the heater, and annual cleaning are
necessary to avoid potential problems with sooting.
Sooting, resulting from improper installation or opera-
tion, can settle on surfaces outside the replace.
14. Avoid any drafts that alter burner ame patterns. Do not
allow fans to blow directly into replace. Do not place
a blower inside burn area of rebox. Ceiling fans may
create drafts that alter burner ame patterns. Sooting
and improper burning will occur.
15. Caution: Candles, incense, oil lamps, etc. produce
combustion byproducts including soot. Vent-free
appliances will not lter or clean soot produced by
these types of products. In addition, the smoke and/or
aromatics (scents) may be re-burned in the vent-free
appliance which can produce odors. It is recommended
to minimize the use of candles, incense, etc. while the
vent-free appliance is in operation.
16. This is an unvented replace. It uses air (oxygen) from
the room in which it is installed. Provisions for adequate
combustion and ventilation air must be provided. Refer
to Page 8.
17. This heater shall not be installed in a room or space
unless the required volume of indoor combustion air is
provided by the method described in the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, the International
Fuel Gas Code or applicable local codes.
18. Keep room area clear and free from combustible mate-
rials, gasoline and other ammable vapors and liquids.
19. Unvented replaces emit moisture into the living area.
In most homes of average construction, this does not
pose a problem. In houses of extremely tight con-
struction, additional mechanical ventilation is recom-
mended.
20. During manufacturing, fabricating and shipping, various
components of this appliance are treated with certain
oils, lms or bonding agents. These chemicals are not
harmful but may produce annoying smoke and smells

5
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
IMPORTANT SAFETY INFORMATION
as they are burned o󰀨 during the initial operation of the
appliance; possibly causing headaches or eye or lung
irritation. This is a normal and temporary occurrence.
The initial break-in operation should last two to three
hours with the burner at the highest setting. Provide
maximum ventilation by opening windows or doors to
allow odors to dissipate. Any odors remaining after this
initial break-in period will be slight and will disappear
with continued use.
21. Input ratings are shown in BTU per hour and are for
elevations up to 2,000 feet. For elevations above 2,000
feet, input ratings should be reduced 4 percent for each
1,000 feet above sea level. Refer to the National Fuel
Gas Code.
22. 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 psig (3.5 kPa).
23. The appliance must be isolated from gas supply piping
system by closing its equipment shuto󰀨 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).
24. Do not use this room heater if any part has been under
water. Immediately call a qualied service technician
to inspect the room heater and to replace any part of
the control system and any gas control which has been
under water.
25. Never burn solid fuels in a replace where a unvented
room heater is installed.
BUILDING CODE INFORMATION
Adhere to all local codes or, in their absence, the latest
edition of THE NATIONAL FUEL GAS CODE ANSI Z223.1
or NFPA54 which can be obtained from:
American National Standards Institute, Inc.
1430 Broadway
New York, NY 10018
or
National Fire Protection Association, Inc.
Batterymarch Park
Quincy, MA 02269
This appliance may be installed in an after-
market, permanently located, manufactured
(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.
WARNING: This product and the
fuels used to operate this product (liquid
propane or natural gas), and the products
of combustion of such fuels, can expose
you to chemicals including benzene, which
is known to the State of California to cause
cancer and reproductive harm. For more
information go to: www.P65Warnings.
ca.gov.

6
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
PRODUCT FEATURES
NOTE: For LP models an external regulator is required
to reduce supply pressure to a maximum of 13" w.c.
GAS SPECIFICATIONS & ORIFICE SIZE
AVFLST42 CONTROLS
MODEL FUEL
MAX. INPUT
(BTU/h)
MIN. INPUT
(BTU/h)
ORIFICE
SIZE
AVFLST42NIP N AT. 37,000 24,500 2.20 mm
AVFLST42PIP L P. 36,000 28,500 #55
GAS PRESSURES
NATURAL PROPANE (LP)
Inlet Minimum 5.0" w.c. 11.0" w.c.
Inlet Maximum 10.5" w.c. 13.0" w.c.
Regulator Pressure
Setting
3.5" w.c. 10" w.c.
Pilot Regulator 3.5" w.c. —
Control Module
Thermocouple Module
Aux Module
LED Switches
Figure 1. AVFLST42 Controls (Control Access Door Shown Open)

7
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
FIREPLACE AND FRAMING DIMENSIONS
13⁄"
[333mm]
32"
[813mm]
43"
[1092mm]
48½"
[1232mm]
39¾"
[1010mm]
37½"
[953mm]
6⁄"
[154mm]
28"
[711mm]
15⁄"
[386mm]
½"[13mm]
or
⁄"[16mm]
½"[13mm]
or
⁄"[16mm]
33 ½" *
[851mm]
Minimum rough
opening depth
for 5/8" wall thickness
12"
[305mm]
Interior wall
installation
Exterior wall
installation
Minimum Rough
Framing Width
44"
[1118mm]
44"
[1118mm]
Wall cover
thickness
Wall cover
thickness
Minimum rough
opening depth
for 5/8" wall thickness
14⁄"
[378mm]
Minimum
Rough
Framing
Height
32"
[813mm]
*NOTE: The AVFLST42 unit must be raised at least 1.5 inches above the top surface of the nished oor when
using the AVFL42WFBT-A or AVFL42WCSS-A wide contemporary face.
Figure 2. Fireplace dimensions
Figure 3. Framing dimensions with outdoor kit installed (AVFLSTSSODK)

8
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
GETTING STARTED
Check to verify that all listed parts have been received.
You should have the following:
• One (1) Unvented replace
• Two (2) Anchoring screws
• One (1)Installation/operating instructions
• Two (2) 5" noncombustible board
• Two (2) 2" x 32" deector glass
• Two (2) Bags reglass
• One (1) 90 watt bulb
• One (1) RC300 remote control
Carefully inspect the contents for shipping damage. If any
parts are missing or damaged, immediately inform the
dealer from whom you purchased the appliance. Do not
attempt to install any part of the appliance unless you
have all parts in good condition.
WHAT YOU WILL NEED FOR INSTALLATION
You must have the following items available before pro-
ceeding with installation:
• External regulator (for propane/LPG only)
• Manual shuto󰀨 valve
• Piping which complies with local codes
• Sediment trap
• Phillips head screwdriver
• Tee joint.
• Pipe sealant approved for use with propane/LPG
(Resistant to sulfur compounds)
• Pipe wrench
PRE-INSTALLATION INFORMATION
PLANNING THE INSTALLATION
In planning the installation for the replace it is necessary
to determine where the unit is to be installed and whether
optional accessories are desired. Gas supply piping should
also be planned. The following steps represent the normal
sequence of installation. Each installation is unique, how-
ever, and might require a di󰀨erent sequence.
1. Position fireplace in desired location. Refer to the
Fireplace and Framing Dimensions (page 7, Figures 2
and 3,) Fireplace Location (page 9, Figure 5) and
Clearances and Height Requirements (page 10, Figures
6 and 7.)
NOTE: Be sure all cardboard packing material has been
removed from under the unit.
2. Install following the instructions found in this manual.
3. Field wire main power supply to junction box. Refer to
the Electrical Installation section (page 15). (Electrical
connections should only be performed by an experi-
enced, licensed certied service person).
4. Plumb gas line. Refer to the Connect the Gas (page
13, Figure 10) section found in this manual. (Gas
connections should only be performed by an experi-
enced, licensed/certied service person).
5. Complete nish wall material and/or surround.
ADEQUATE COMBUSTION AND
VENTILATION AIR
This heater shall not be installed in a conned space or
unusually tight construction unless provisions are provided
for adequate combustion and ventilation air.
The National Fuel Gas Code, (ANSI Z223.1/NFPA54),
denes a conned space as a space whose volume is less
than 50 cubic feet per 1,000 BTU per hour (4.8m3 per kw)
of the aggregate input rating of all appliances installed in
that space, and an unconned space as a space whose
volume is not less than 50 cubic feet per 1,000 BTU per
hour (4.8 m3 per kw) of the aggregate input rating of all
appliances installed in that space. Rooms communicating
directly with the space in which the appliances are installed,
through openings not furnished with doors, are considered
a part of a conned space.
Unusually tight construction is dened as construction
where:
a. Walls and ceilings exposed to the outside atmosphere
have a continuous water vapor retarder with a rating of
1 perm (6 x 1011 kg per pa/sec-m2) or less with openings
gasketed or sealed, and
b. Weather stripping has been added on openable win-
dows and doors, and
WARNING!
Do not install the heater:
•Where curtains, furniture, clothing, or
other ammable objects are less than 36"
from the front of the heater.
• In high tra󰀩c areas.
• In windy or drafty areas.

9
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
PRE-INSTALLATION INFORMATION
FP3029
c. Caulking or sealants are applied to areas such as joints
around window and door frames, between sole plates
and oors, between wall-ceiling joints, between wall
panels, at penetrations for plumbing, electrical and gas
lines and other openings.
The following formula can be used to determine the maxi-
mum heater rating per the denition of unconned space:
BTU/Hr = (L1+ L2) Ft x (W) Ft x (H) Ft
50
Consider two connecting rooms with an open area
between, with the following dimensions:
L1 = 151/2 Ft., L2 = 12 Ft., W = 12 Ft., H = 8 Ft.
BTU/Hr = (151/2 + 12) x (12) x (8)
50
If there were a door between the two rooms the calculation
would be based only on the room with the heater.
BTU/Hr = (151/2) x (12) x (8)
50
FIREPLACE LOCATION
This unvented replace requires no outside venting and
burns cleanly and e󰀩ciency. As a zero-clearance unvented
replace, it can be installed recessed into any wall that is
accessible to a gas line, except in a bedroom or bathroom.
Carefully select the best location for installation of your
unvented replace. The following factors should be taken
into consideration.
• Clearance to side wall, ceiling, woodwork and window
or other combustibles. Refer to Clearance and Height
Requirements section on Page 10. Minimum clear-
ances to combustibles must be maintained.
• Location must not be a󰀨ected by drafts caused by
kitchen exhaust fans, ceiling fans, return air registers
for forced air furnaces / air conditioners, windows or
doors.
• Installation must provide adequate ventilation and
combustion air.
• DO NOT INSTALL THIS MODEL IN A BEDROOM
OR BATHROOM.
• Location should be out of high tra󰀩c areas and
away from furniture and draperies due to heat from
rebox.
• Never obstruct the front opening of the unvented re-
place or restrict the ow of combustion and ventilation
air.
• Minimize modications to existing construction. Refer
to Figure 5 below for location suggestions.
• Do not install in the vicinity where gasoline or other
ammable liquids may be stored. The unvented re-
box must be kept clear and free from the combustible
materials.
WARNING!
If the area in which the heater may be operated
does not meet the required volume for indoor
combustion air, combustion and ventilation
air shall be provided by one of the methods
described in the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, the International Fuel Gas
Code or applicable local codes.
W
H
Counter
Fireplace
Figure 4.
Fireplace locations
Indoor application
Exterior wall application
with AVFLSTSSODK installed
Figure 5. Possible Fireplace Locations

10
AVFLST Vent Free Fireplace
Monessen • AVFLST42 Installation Instructions • 4118-900 Rev. B • 05/2020
PRE-INSTALLATION INFORMATION
CLEARANCES AND HEIGHT
REQUIREMENTS
Ensure that minimum clearances shown in Figures 6 and
7 are maintained. Left and right clearances are determined
when facing the front of the rebox.
Follow these instructions carefully to ensure safe instal-
lation. Failure to follow these requirements may create a
re hazard.
Sidewall Clearances — The clearance from the inside of
the appliance to any combustible adjacent wall should not
be less than 6". Figure 6
Ceiling Clearance — The ceiling must be at least 36" from
the rebox opening. Figure 6
WARNING!
The dimensions shown in Figures 6 and 7
are minimum clearances to maintain when
installing this heater. Left and right clearances
are determined when facing the front of the
heater.
Follow these instructions carefully to ensure
safe installation. Failure to follow instructions
exactly can create a re hazard.
Floor Clearance — The replace may be installed directly
on a combustible oor or a raised platform of an appropriate
height. Do not place replace on carpeting, vinyl, tile or
other soft oor coverings. It may, however, be placed on at
wood, plywood, particle board or other hard surfaces. Be
sure replace rests on a solid continuous oor or platform
with appropriate framing for support so that no cold air can
enter from under the rebox. See note below regarding
oor installation with wide contemporary faces.
Mantel clearances — Must meet the clearance require-
ments detailed in Figures 6 and 7.
36"Minimum
From Opening
12"Max.
Depth
21/2"Max
Depth
18"Min.
From Opening
28"Min.
From Opening
6"Min.
FP3006
mantel clearances
Figure 6. Sidewall and Ceiling Clearances
FP3006
Figure 7. Mantel Clearances
23"
28"
12"
6"
21/2"
mantel clearances
18"
Top of Fireplace
Opening
FP3007
SIDE VIEW
Wall
Insulation
Board
Stud
Stando󰀨
6"
5"
3"4¹⁄₂"45°
1"
3¹⁄₂"
FP3008
mantel leg
1¹⁄₂"
2¹⁄₂"
Fireplace
Opening
FP3008
TOP VIEW
Mantel Clearances shown apply to both sides
of the See Through Unit.