Monessen Hearth PH18 User manual

652035
PH logs cover
Unvented Gas Log Heater/ Vented Decorative
Appliance Installation and Operating Instructions
Models: PH18 (for use with PH18R Log Sets)
PH24 (for use with PH24R or PH30R Log Sets)
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.
WARNINGS
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.
• 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 per-
formed by a qualied installer, service
agency or the gas supplier.
This is an unvented gas-red heater. 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.
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
CONTENTS
Carbon Monoxide Warning ........................................ 2
Important Safety Information .................................... 3
Codes ..................................................................... 4
Product Features........................................................ 5
Gas Specications ................................................. 5
Gas Pressures ....................................................... 5
Ignition Controls ..................................................... 5
Pilot/ODS ............................................................... 5
Thermal Generator ................................................. 5
Getting Started............................................................ 6
Fireplace and Hearth Dimensions............................. 7
Placement in a Fireplace with Restrictive Barrier ... 7
Adequate Combustion Ventilation Air ...................... 8
Clearances and Height Requirements...................... 9
Installation Requirements........................................ 10
Installation................................................................. 12
Installing Vented Applications .............................. 12
Damper Stop Installation ...................................... 12
Place and Secure Appliance ................................ 12
Assembly Procedure ............................................ 13
Gas Line Connection................................................ 13
Check Gas Pressure................................................. 14
Manual Control ..................................................... 14
Millivolt Control ..................................................... 14
Electrical Wiring - Millivolt....................................... 15
Optional Wall Switch or Thermostat ..................... 15
Optional Remote Receiver ................................... 16
Check System Operation ..................................... 16
Log Placement.......................................................... 17
PH18-R ................................................................ 17
PH24-R ................................................................ 19
PH30-R ................................................................ 21
Flame Appearance.................................................... 23
Millivolt Control ..................................................... 23
Manual Control ..................................................... 23
Burner Flame ....................................................... 24
Operating Instructions............................................. 25
For Your Safety Read Before Lighting ................. 26
Manual Control Lighting Instructions .................... 27
Millivolt Control Lighting Instructions .................... 28
Match Lighting Instructions .................................. 29
Cleaning and Servicing............................................ 29
Troubleshooting ....................................................... 30
Service Parts............................................................. 32
Accessories .......................................................... 38
Massachusetts Residents Only............................... 39
Warranty .................................................................... 40
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, the insert may not have been installed
properly. Get fresh air at once! Have the insert inspected and serviced by a qualied service person. Some
people are more affected by carbon monoxide than others. These include pregnant women, people with
heart or lung disease or anemia, those under the inuence of alcohol, and those at high altitudes.
Propane/LP gas and natural gas are both odorless. An odor-making agent is added to each of these gases.
The odor helps you detect a gas leak. However, the odor added to these gases can fade. Gas may be
present even though no odor exists.
Thank you and congratulations on your purchase of an Monessen Log Set.
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.
NOTE: Monessen vent ree gas logs are hand painted for
ultimate beauty and realism. As a result, some variation
in color and shading will occur from set to set. This is
intentional and designed to make each product unique,
as found in nature.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
12. Correct installation of the ceramic ber logs, proper
location of the heater, and annual cleaning are neces-
sary to avoid potential problems with sooting. Sooting,
resulting from improper installation or operation, can
settle on surfaces outside the replace. See log place-
ment instructions for proper installation.
13. 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.
14. CAUTION: Candles, incense, oil lamps, etc. produce
combustion by-products 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 reburnt in the vent-free ap-
pliance which can produce odors. It is recommended
to minimize the use of candles, incense, etc. while the
vent-free appliance is in operation.
15. This is an unvented gas-red heater. It uses air (oxy-
gen) from the room in which it is installed. Provisions
for adequate combustion and ventilation air must be
provided. Refer to Page 6.
16. 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.
17. Keep room area clear and free from combustible
materials, gasoline and other ammable vapors and
liquids.
18. Unvented gas heaters are a supplemental zone heater.
They are not intended to be a primary heating appli-
ance. Water vapor produced by an unvented heater
can create moisture problems in a home when oper-
ated for extended periods of time.
19. 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
IMPORTANT SAFETY INFORMATION
1. Due to high temperatures, the appliance should be
located out of traf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.
7. To prevent malfunction and/or sooting, an unvented
gas heater should be cleaned before use and at least
annually by a professional service person. More fre-
quent cleaning may be required due to excessive lint
from carpeting, bedding materials, etc. It is imperative
that control compartments, burners and circulating air
passageways be kept clean.
8. For propane/LP insert, do not place propane/LP supply
tank(s) inside any structure. Locate propane/LP supply
tank(s) outdoors. To prevent performance problems,
do not use propane/LP fuel tank of less than 100
lbs. capacity.
9. The installation must conform with local codes or, in the
absence of local codes, with the National Fuel Gas
Code, ANSI Z223.l/NFPA54.
10. This unit complies with ANSI Z21.11 Unvented Heat-
ers, latest edition and also complies with ANSI Z21.60
Decorative Vented Appliances for Solid Fuel Burning
Fireplaces, latest edition. State and local codes may
only allow operation of this appliance in a vented
conguration. Check your state or local codes. For
vented operation, refer to Vented Instructions in this
manual.
11. Do not install the heaters in a bathroom or bedroom.
INSTALLER
Please leave these instructions with the appliance.
OWNER
Please retain these instructions for future reference .
• 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.
WARNING

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
IMPORTANT SAFETY INFORMATION
as they are burned off 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.
20. 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. See the National Fuel Gas
Code.
21. The heater and its individual shutoff 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).
22. The heater must be isolated from the gas supply piping
system by closing its individual manual shutoff 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).
23. 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.
24. This appliance must not be used with glass doors in
the closed position. This can lead to pilot outages and
severe sooting outside the replace.
25. Never burn solid fuels in a replace where an unvented
room heater is installed.
26. Always have a replace screen in place when the ap-
pliance is in operation and , unless other provisions for
combustion air are provided, the screen shall have an
opening(s) for induction of combustion air.
WARNING
Never connect unit to private (non-utility)
gas wells. This gas is commonly known
as wellhead gas.
This appliance may be installed in an aftermarket,
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.
Nous recommandons que nos
appareils de chauffage au gaz
soient installés et entretenus par
des professionnels qui ont été
accrédités aux È.U. par le National
Fireplace Institute ® (NFI) comme
étant des spécialistes du NFI en
matièred’appareils de chauffage
au gaz.
Attention Massachusetts Residents:
This product must be installed by a licensed gas
tter.
CODES
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
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.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
PRODUCT FEATURES
GAS SPECIFICATIONS
Min.Input Max. Input
Model Fuel Control BTU/h BTU/h
PH18NM Nat. Manual 18,000 30,000
PH18NV Nat. Millivolt 26,000 30,000
PH24NM Nat. Manual 19,000 36,000
PH24NV Nat. Millivolt 24,000 36,000
PH18PM LP Manual 22,500 30,000
PH18PV LP Millivolt 24,500 30,000
PH24PM LP Manual 25,000 36,000
PH24PV LP Millivolt 29,000 36,000
GAS PRESSURES
Natural Propane (LP)
Manual Regulator Pressure 4.0" w.c. 10.0" w.c.
Millivolt Regulator Pressure 3.5" w.c. 10.0" w.c.
Millivolt Pilot Regulator 3.5" w.c. n/a
Max. Gas Inlet Pressure 10.5" w.c. 13.0" w.c.
Min. Gas Inlet Pressure 5.0" w.c. 11.0" w.c.
NOTE: An external regulator is required to reduce supply
pressure to a maximum of 13.0" w.c. for LP systems.
IGNITION CONTROLS
Piezo ignitor allows ignition of the pilot without the
use of matches or batteries.
Manual control has three (3) positions:
OFF - All gas to the gas logs is shut off at
the valve.
IGN - Valve position to light/maintain a
standing pilot.
HI/LOW - Variable position corresponding to
desired ame height.
Millivolt control has four (4) positions:
OFF - All gas to the gas logs is shut off at
the valve.
IGN - Valve position to light/maintain a
standing pilot.
ON - Valve position to turn ON/OFF log
set with remote switch/thermostat.
HI/LO - Variable position to control ame
height (heat output).
PILOT/ODS
The gas log heater is tted with a specially designed
safety pilot (ODS assembly) which senses the amount
of oxygen available in the room and shuts the gas log
heater off if the oxygen level begins to drop below
a satisfactory level. The pilot can only be relit when
adequate fresh air is available.
THERMAL GENERATOR
The millivolt gas log pilot is tted with a millivolt
(thermopile) generator to provide power for remote
activation.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
GETTING STARTED
CAUTION
• Handle the gas log burner assembly by
the burner only. Do not pick the unit up
by the burners or grate (not attached to
frame).
• Gloves are recommended when handling
ceramic ber logs to prevent skin irritation
from loose fibers. Logs are fragile —
handle with care.
MAKE SURE YOU HAVE RECEIVED ALL PARTS:
Check your packing list to verify that all listed parts have
been received. You should have the following:
•Unvented gas log burner assembly
•Plastic bag containing crushed volcanic rock
•Installation/operating instructions
•Two (2) anchoring screws
•Grate
• Ceramic ber or refractory cement logs
The millivolt controlled version of this heater is the only
style designed to be operated with optional devices for
ON/OFF functions. The following options may be used
with the millivolt controlled heater. These options are not
packaged with the log set.
• Hand held Remote with receiver
• Wall thermostat with 15' wire
• Wall switch with 15' wire
• Hand held Thermostat Remote with receiver
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 INSTALLA-
TION:
You should have the following items available before pro-
ceeding with installation:
• External regulator (for propane/LPG and 1/2 lb.
natural gas systems only)
• Piping which complies with local codes
•Sediment trap (recommended)
• Screwdriver
• Tee joint.
• Pipe sealant approved for use with propane/LPG
(Resistant to sulfur compounds)
• Drill with 5/32 bit
•Pipe wrench or appropriate size crescent wrench
set
• Manual shutoff valve
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.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
WARNING
This appliance is for installation only in a solid-fuel burning masonry or UL127 factory-built
replace, vent free appliance, or in listed ventless rebox enclosure. It has been design certied
for these installations.
Exception: DO NOT install this appliance in a factory-built replace that includes instructions
stating it has not been tested or should not be used with unvented gas logs.
FIREPLACE and HEARTH DIMENSIONS
Use manufacturer’s installation and clearance require-
ments as dened in their manual.
The PH Series unvented room heater is approved for instal-
lation into the following unvented replaces:
GCUF(32,36,42) and VFR(32,36,42) Series Fireboxes
The PH Series unvented room heater may also be installed
into a Ventless Firebox Enclosure for Gas Fired Decorative
Type Unvented Room Heaters per ANSI Z21.91b.2004,
as long as rebox hearth dimensions meet the minimum
hearth dimensions shown below.
C
A
D
B
FP2530
hearth dims
MODEL A BC D
PH18 25"
(635 mm)
13"
(330 mm)
171⁄2"
(445 mm)
17"
(432 mm)
PH24 29"
(737 mm)
13"
(330 mm)
191⁄2"
(495 mm)
17"
(432 mm)
PH30 35"
(889 mm)
13"
(330 mm)
251⁄2"
(648 mm)
17"
(432 mm)
Figure 1 -
Hearth Minimum Dimensions
FP2530
Barriers such as the bottom of a glass door
frame placed in front of a gas log set can
change the air ow characteristics of the
replace which in turn can cause the unit
to overheat and malfunction.
WARNING
IMPORTANT INFORMATION FOR THE IN-
STALLATION OF THIS GAS LOG SET
The following are guidelines for placing a gas log set in
a replace that has a restrictive barrier along the bottom
front opening of the replace. Some examples of barri-
ers are glass/screen door frames and sunken/recessed
replaces.
Height of Minimum Depth of
Restriction (x) Fireplace/Firebox
No Restriction 13"
0" to 11⁄2" 16"
Greater than 11⁄2" to 3" 16"
Greater than 3" *
*Any barrier greater than 3" placed in front of the gas log
set is not recommended by the manufacturer.
NOTE: Non combustible material such as refractory brick
may be used to line the oor of the replace in order to raise
the height of the gas log set in relation to a restrictive barrier.
If the unit is raised, the minimum height dimension listed in
the homeowner’s manual must not be exceeded.
NOTE: If the log set is equipped with a remote receiver, a
restrictive barrier may reduce the battery life by increasing
the ambient temperature inside the replace. Placement
of the receiver outside of the replace will extend the
battery life.
Figure 2 -
Reference Drawing of a Natural
Flame Log Set in an Enclosure
X
FP2794
logs in enclosure
Depth of
Fireplace/
Firebox
(Refer to
Table)
The log set should
be placed against or
as near as possible
to the rear wall of the
replace
Glass door
frames with ad-
justable louvers
should have
the louvers
fully open while
the unit is in
operation
Height of restrictive barrier
caused by glass door
frames, recessed replac-
es, etc. from the base or
bottom surface of the unit.
(Refer to Table).
FP2794
Figure 1

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
ADEQUATE COMBUSTION 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 (4.8m3per 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 m3per 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 to windows and
doors, and
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 be-
tween, 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
W
H
Counter
Fireplace
Figure 3
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.
WARNING

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
CLEARANCES and HEIGHT REQUIREMENTS
Sidewall and ceiling clearances: The sides of the re-
place opening must be at least 16" from any combustible
wall. The ceiling must be at least 42" from the top of the
replace opening.
WARNING
The dimensions shown in Figures 4 through 12 and dened in the replace manufacturer's
instructions are minimum clearances to maintain when installing this heater. Left and right
clearances are determined when facing the front of the heater.
When heater is installed into a ventless rebox, minimum clearances, as specied by the ventless
rebox manufacturer, must be met.
Follow these instructions carefully to ensure safe installation. Failure to follow instructions
exactly can create a re hazard.
16"
42"
FP1996
wall ceiling clearances
Figure 4 -
Sidewall and Ceiling Clearances
FP1996
Heat resistant material (minimum requirements)
with no wooden mantel or other combustible
projection:
To install the gas logs into a replace with no wooden
mantel, shelf or other combustible projection above the
replace opening, measure the heat resistant material
height, per Figure 5, then see TABLE A.
Heat resistant materials such as slate and marble must be
at least 1/2" thick. Sheet metal should not be installed
onto combustible material.
IMPORTANT: If you cannot meet these minimum clearanc-
es you must operate the heater with chimney ue damper
open. Refer to "Installing Vented Applications" found on
Page 12.
FP2922
heat resist material
Heat
Resistant
Material
Measure This
Distance
Heater in
Fireplace or
Firebox
FP2922
Figure 5-
Measure Heat Resistant Material
Table A -
Heat Resistant Material Requirements with No
Mantel or Combustible Projection
Heat Resistant Material PH18/24 Requirements
Measurement for Safe Installation
12" or more Hood not required
8" or less than 12" Extend resistant material to
12" or install hood. Figure 5
Less than 8" Extend heat resistant material
to at least 8" and install hood.
Figure 5. OR, extend heat
resistant material to a height
of at least 12"

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Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
INSTALLATION REQUIREMENTS
FP2923
heat resist matl w mantel
Hood
Heater in
Fireplace or
Figrebox
8" or More of Heat
Resistant Material
FP2923
Figure 6 -
Measure Heat Resistant Material for Mantel
Heat resistant material (minimum requirements) with
wooden mantel or other combustible projection:
To install the heater with a wooden mantel, shelf or other
combustible projection above, first measure the heat
resistant material shown in Figure 7, then see TABLE B.
Table B -
Heat Resistant Material Heights and Mantel Location
FP2534
Min. mantel w hood
10"
8"
6"
2¹⁄₂"
8" 14¹⁄₂" 18⁵⁄₈" 22¹⁄₂" 26"
12"
Heat
Resistant
Material
Hood
Heater in
Fireplace or
Firebox
FP2534
12”
Min.
28”
10” or Less
FP2535
min mantel no hood
Heat
Resistant
Material
Heater in
Fireplace or
Firebox
FP2535
Figure 8 -
Minimum Mantel Clearance with No Hood
Figure 7 -
Minimum Mantel Clearance with Hood
Example: The bottom of the mantel may project from the
wall a maximum of 10" at a minimum of 28"
above the opening.
Example: A mantel may project from the wall a maximum
of 21⁄2" at a minimum of 8" above the opening
and a maximum of 6" at a minimum of 141⁄2"
above the opening.
Heat Resistant
Material
Measurement
Requirements for Safe
Installation with Wooden Mantel,
Shelf or Other Combustible
Projection
12" or more Hood not required. Observe
proles (side elevations) shown in
Figure 7
8" or less than
12"
Install hood (CABR/CABL) and
observe proles show in Figure 6;
OR extend heat resistant material
to at least 12" and observe proles
shown in Figure 7
Less than 8" Extend heat resistant material to
at least 8" and install hood (CABR/
CABL) and observe proles
shown in Figure 6; OR extend
heat resistant material to at least
12" and observe proles shown in
Figure 7.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
FLOOR CLEARANCE
The gas log heater must be installed at least 5" above
any combustible ooring material, such as carpeting or
tile, which is closer than 14" to the base of the replace.
The minimum distance must be maintained from the top
surface of carpeting, tile, etc. Figure 9
OR,
5” Minimum
FP2924
min comb floor clear
Heater in Fireplace
or Firebox
Combustible
Material
FP2924
Figure 9 -
Minimum Clearance Above Combustible Flooring
14” Minimum
FP2925
min noncomb floor clear
This
Distance
May Now
be Less
than 5"
Heater in
Fireplace or
Firebox
Combustible
Material
FP2925
Figure 10 -
Minimum Clearance Above Combustible Flooring with
Noncombustible Material Installed at Base of Fireplace
The gas log heater may be installed nearer to the oor if a
minimum of 14" of noncombustible material such as slate
or marble is installed between the base of the replace and
the combustible ooring. Figure 10 NOTE: The use of a
thermostat is prohibited in vented log applications.

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
INSTALLATION
BEFORE FULLY INSTALLING THE UNIT:
•Turn OFF the gas supply to the replace or re-
box.
•Seal any fresh air vents and/or ash clean-out doors
located on the oor or wall of the replace. If left
unsealed, drafting may cause pilot outage or soot-
ing. Use a heat resistant sealant. Do not seal the
chimney ue damper.
WARNING
Before installing in a solid fuel burning
fireplace, The chimney flue and firebox
must be cleaned of soot, creosote, ashes
and loose paint by a qualified chimney
cleaner.
INSTALLING VENTED APPLICATIONS
Manual and millivolt controlled gas logs may be installed as
a vented decorative log set in compliance with ANSI Z21.60
and National Fuel Gas Code, Section 6.6 Since, the gas
logs are operated with the damper open, non-combustible
material and minimum mantel requirements do not apply.
NOTE: The use of a thermostat is prohibited in vented log
applications.
WARNING
This appliance is for installation only in a solid
fuel burning replace (masonry replace or
manufactured fireplace) with a working
ue and constructed of noncombustible
material.
Exception: DO NOT install this appliance
in a factory-built fireplace that includes
instructions stating that it has not been
tested or should not be used with unvented
gas logs. This log set may be installed as a
vented log set.
BEFORE INSTALLING THE APPLIANCE:
• Turn off gas supply to replace or rebox.
• Have the replace oor and chimney professionally
cleaned to remove ashes, soot, creosote or other
obstructions. Have this cleaning performed annually
after installation.
• Seal any fresh air vents or ash clean-out doors lo-
cated on oor or wall of replace. If not, drafting may
cause pilot outage or sooting. Use a heat-resistant
sealant. Do not seal chimney ue damper.
Install and operate the appliance as directed in this
manual.
DAMPER STOP INSTALLATION:
A damper stop must be provided with the unit. Contact your
dealer to obtain one. The damper stop must be installed as
shown in Figure 11 to prevent full closure of the replace
damper blade and provide a minimum 29 square inch ue
opening.
FP2538
damper stop
Damper
Stop
Damper
FP2538 Figure 11 -
Damper Stop Installation
(See Warning)
WARNING
The replace and gas logs function as a
system. If the replace is spilling into the
room (check with a match or a smoke stick),
reposition the damper clamp until a positive
draft is obtained by opening the damper. If
negative pressure in home prevents having
a positive draft, contact your dealer for
assistance.
PLACE AND SECURE APPLIANCE
You must secure the gas log heater to
the replace oor. If not, the entire unit
may move when you adjust the controls.
Movement of unit may cause shifting of
the gas logs which leads to sooting and
improper burning.
Special care is required if you are installing
the unit into a sunken replace. You must
raise the replace oor to allow access to
gas log controls. This will insure adequate
air ow and guard against sooting. Raise
the replace oor using noncombustible
materials, as described in Placement in a
Fireplace with Restrictive Barrier on Page
7.
WARNING

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
ASSEMBLY PROCEDURE
1. Center the gas log unit in the replace or rebox.
2. Install Grate: Insert longest middle grate bar in one of
the two square holes in control panel. Figure 12. Be sure
grate is centered. Sit horizontal bar inside two hooks
on front of control panel. Figure 12. Make certain front
feet of grate are located inside front edge of replace
or rebox.
3. Anchor holes are located on the ange of the unit. Figure
12. After centering the burner correctly, mark the hole
positions on the replace/rebox oor. Drill two (2) 5/32"
diameter holes approximately 11⁄2" deep.
4. Anchor the unit to the replace/rebox oor using the
screws provided. Figure 13.
INSTALLATION
FP2926
install grate
Screws
Hole for
Grate Bar
Middle
Grate Bar
Hooks for
Grate
Horizontal
Grate Bar
Anchor
Hole
Figure 12 -
Install Grate and Secure Heater to Floor
of Fireplace/Firebox
NOTICE: A qualied gas appliance installer must
connect the heater to the gas supply. Consult all local
codes.
IMPORTANT: Hold heater valve rmly with a wrench to
prevent movement when connecting to inlet pipe.
CONNECT THE GAS LINE
CAUTION
Use new black iron or steel pipe. Internally
tinned copper or copper tubing can be
used per National Fuel Code, section 2.6.3,
providing gas meets hydrogen sulfide
limits, and where permitted by local codes.
Gas piping system must be sized to provide
minimum inlet pressure (Listed on Data
Plate) at the maximum ow rate (BTU/Hr).
Undue pressure loss will occur if the pipe
is too small.
A manual shutoff valve must be installed
upstream of the appliance. Union tee
and plugged 1/8" NPT pressure tapping
point should be installed upstream of the
appliance. Figure 13
FP2371
gas connect
Stainless
Flexible
Tube Pipe
Possible Locations
for Pressure
Tapping Point
Gas
Supply
Inlet
To
Heater
Valve
Pipe
Coupling
Manual Shutoff
Valve
FP2371
Figure 13 -
Gas Connection
CHECK GAS TYPE: The gas supply must
be the same as stated on the heater’s rat-
ing plate. If the gas supply is different, DO
NOT INSTALL THE HEATER. Contact your
dealer for the correct model.
WARNING
Connecting directly to an unregulated pro-
pane/LPG tank can cause an explosion.
WARNING
Always use an external regulator for all propane/LPG
heaters and high pressure one to two-pound systems
only, to reduce the supply tank pressure to a maximum of
13" w.c. This is in addition to the internal regulator in the
heater valve.

14
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
INSTALLATION
CHECK GAS PRESSURE
The heater gas inlet connection is a 3/8" NPT at the valve.
All units have the inlet connection on the right side, when
you face the unit. To connect from the opposite side, route
the pipe under the rear portion of the unit.
When tightening up the joint to the valve, hold the valve
securely to prevent movement.
Test all gas joints from the gas meter to the heater valve
for leaks using a gas analyzer or soap and water solution
after completing connection. DO NOT USE AN OPEN
FLAME.
Check the gas pressure with the appliance burning and
the control set to HIGH.
MANUAL CONTROL
Figure 14
The pressure regulator is preset and locked to dis-
courage tampering. If the pressure is not as specied,
replace the regulator with the correct part from the parts
list in this manual.
Remove 1/8" NPT plug, located on side of regulator body.
Install tting and tubing to pressure gauge. After taking
pressure reading, reinstall test plug. Check for gas leaks.
MILLIVOLT CONTROL
Figure 15
The valve regulator controls the burner pressure which
should be checked at the pressure test point.
Turn captured screw counter clockwise two or thre turns
and then place tubing to pressure gauge over test point
(Use test point “OUT” closest to control knob). After tak-
ing pressure reading, be sure and turn captured screw
clockwise rmly to re-seal. Do not over torque. Check for
gas leaks.
FP2499
manual valve
NPT Test Plug
FP2499
Figure 14 -
Manual Control Pressure
Test Point Location
FP2372
millivolt valve
Test Port “Out”
FP2372
Figure 15 -
Millivolt Control Pressure
Test Point Location

15
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
The millivolt valve is a self-powered combination gas control
THAT DOES NOT REQUIRE 110 VAC TO OPERATE.
CONNECT OPTIONAL WALL SWITCH OR
THERMOSTAT(VENT FREE APPLICATIONS
ONLY)
1. Use 18 AWG, two-wire cable, 20 feet maximum length.
At one end of the cable, connect both wires to the wall
switch or thermostat. At the other end, connect one wire
to TP/TH and one wire to TH. The color of the wires
does not matter. Or you can hook the wall switch or
thermostat to wires on the unit.
ELECTRICAL WIRING - MILLIVOLT
Label all wires prior to disconnection when servicing controls.
Wiring errors can cause improper and dangerous operation.
Verify proper operation after servicing.
WARNING
FP2112
wiring diagram
12/08
Wall
Switch
On/Off Switch
On/Off
Switch
Millivolt
Valve
ODS Pilot
TH = 3
TP = 1
TP/TH = 2
ODS Pilot
Spade Terminal
Switch
Optional Wall
Switch, Remote
Receiver or
Optional T-Stat
FP2112
Figure 16 -
Wiring Diagram

16
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
CONNECT OPTIONAL REMOTE RECEIVER
Follow instructions supplied with the remote.
Connect the wires to the two .25" male connectors
located on the left side of the valve when facing the
unit (Refer to Page 18, Figure 16). Do not let wire
touch grate or burner.
NOTE: Heat reduces battery life. You can protect
the receiver and extend battery life by mounting
the receiver in a wall or other location outside the
replace.
ELECTRICAL WIRING - MILLIVOLT
CHECK SYSTEM OPERATION
The millivolt system and individual components may be
checked with a millivolt meter having a 1-1000 mV range.
Conduct each check shown in chart by connecting meter
test leads to terminals as indicated.
A. COMPLETE MILLIVOLT SYSTEM CHECK
(“A” Reading - On/Off Switch contacts CLOSED -
Control Knob “ON” - Main burner should come
ON)
a. If the reading is more than 175 millivolts and the
automatic valve still does not come on, replace the
control.
b. If the closed circuit reading (“A” reading) is less than
175 millivolts, determine cause for low reading, pro-
ceed to Section B below.
B. Thermopile Output Reading Check
(“B” Reading - On/Off Switch contacts OPEN -
Main burner OFF)
1. Check gas pressure to the unit. If gas pressure
is within minimum and maximum on data plate,
then check pilot voltage, 500 millivolts minimum.
If the minimum millivolt reading is not obtainable,
replace pilot.
Connect Switch or Meter
Check Meter Leads Thermostat Reading
Test To Test To Terminals Contacts Should Be
A Complete 2 & 3 Closed Minimum 175mV
System
B Thermopile 1 & 2 Open Minimum 500mV
Output

17
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
LOG PLACEMENT
PLACE PH18-R LOGS
1. Place Rear Log (#1) on rear support.
Figure 17.
2. Place Left Middle Log (#2) on middle
support and burner. Figure 18
3. Place Right Middle Log (#3) on middle
support. Figure 18
NOTE: Logs #1, #2 and #3 have ridges on
the bottom which secure the logs to burner
frame. After installing each log, check to be
sure it is stable.
LG1084
PH18 rear log 1
Rear Log #1
LG1084
Figure 17
LG1085
PH18 logs 2 3
Left Middle Log #2
Right Middle Log #3
LG1085 Figure 18
WARNING
The positioning of the logs are critical to the safe and clean operation of this heater. Sooting and
other problems may result if the logs are not properly and rmly positioned in the appliance.
Never add additional logs or embellishments such as pine cones, vermiculite or rock wool to
the heater. Only use the logs supplied with the unit.
Failure to position the parts in accordance with diagrams below or to use only parts specically
approved for this heater may result in property damage or personal injury.
DO NOT sprinkle
volcanic rock on the
logs or around the pilot
or the main burner. This
may cause sooting.
Only place volcanic
rock on the oor of the
replace.
During initial operation
of the new heater,
burning logs will give off
a paper burning smell
and orange ames will
be present. Simply open
the windows for a few
hours to vent the odor.
CAUTION

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PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
LOG PLACEMENT
LG1086
PH18 log 4
Front Log #4
LG1086
Figure 19
4. Place Front Log (#4) in between
burner and grate so that notched
areas t between grate supports.
Figure 19
LG1087
PH18 logs 5 6
Left Top Log #5
Right Top Log #6
LG1087
Figure 20
5. Rest Left Top Log (#5) on front
and rear log cutouts. Figure 19
6. Rest Right Top Log (#6) on front
and rear log cutouts. Figure 20

19
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
LOG PLACEMENT
WARNING
The positioning of the logs are critical to the safe and clean operation of this heater. Sooting and
other problems may result if the logs are not properly and rmly positioned in the appliance.
Never add additional logs or embellishments such as pine cones, vermiculite or rock wool to
the heater. Only use the logs supplied with the unit.
Failure to position the parts in accordance with diagrams below or to use only parts specically
approved for this heater may result in property damage or personal injury.
PLACE PH24-R LOGS
1. Place Rear Log (#1) on rear support. Figure 21
2. Place Left Middle Log (#2) on middle support and
burner. Figure 22
3. Place Right Middle Log (#3) on middle support.
Figure 22
NOTE: Logs #1, #2 and #3 have ridges on the bottom
which secure the logs to burner frame. After installing
each log, check to be sure it is stable.
LG1088
PH24 log 1
Rear Log #1
LG1088
Figure 21
LG1089
PH24 logs 2 3
Right Middle Log #3
Left Middle Log #2
LG1089
Figure 22
DO NOT sprinkle
volcanic rock on the
logs or around the pilot
or the main burner. This
may cause sooting.
Only place volcanic
rock on the oor of the
replace.
During initial operation
of the new heater,
burning logs will give off
a paper burning smell
and orange ames will
be present. Simply open
the windows for a few
hours to vent the odor.
CAUTION

20
PH Gas Logs
Monessen • PH18/24 Installation/Owner's Manual • 65D2035 • Rev G • 03/2020
LOG PLACEMENT
LG1090
PH24 log 4
Front Log #4
LG1090
Figure 23
4. Place Front Log (#4) in
between burner and grate so
that notched areas t between
grate supports. Figure 23
LG1091
PH 24 logs 5 6
Left Top Log #5 Right Top Log #6
LG1091
Figure 24
5. Rest Left Top Log (#5) on
front and rear log cutouts.
Figure 24
6. Rest Right Top Log (#6) on
front and rear log cutouts.
Figure 24