Monessen Hearth DFX24C Manual



Installation & Operating Instructions


334051
VFS DBX cover
       



 
     

 
  
  

     


  

     
    


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 

33D4047 1/11 Rev. 7





DFX & DBX Series Vent Free Fireplaces 
 
 
 
Gas Pressures .......................................................... 5
Gas Specications .................................................... 5
Ignition Controls ....................................................... 5
Pilot .......................................................................... 5
Thermal Generator ................................................... 5
Fireplace and Framing Dimensions .......................... 6
 
What You Will Need .................................................. 7
General Fireplace Installation ................................... 7
 
Fireplace Location .................................................... 8
Clearances ............................................................... 9
Fireplace Installation .............................................. 10
Secure Heater to Floor or Hearth ........................... 11
 
 
Manual Control ....................................................... 13
Thermostat Control ................................................. 13
Millivolt Control ....................................................... 13
 
Connect Optional Wall Switch ................................ 14
Connect Remote Receiver ..................................... 15
Check System Operation ....................................... 15
 
Screen Removal ..................................................... 16
Canopy Installation ................................................. 16
Log Placement ....................................................... 17
Rock Wool Placement ............................................ 18
 
Pilot Flame ............................................................. 19
Burner Flame Appearance ..................................... 0
 
For Your Safety Read Before Lighting .................... 1
Manual Control Lighting Instructions ...................... 
Thermostatic Control Lighting Instructions ............. 3
MilliVolt Control Lighting Instructions ...................... 4
Match Lighting Instructions ..................................... 5
 
Cleaning and Servicing .......................................... 5
 
 
Firebox ................................................................... 7
DFX4C Millivolt & Manual Control Burner ........... 8
DFX3C Millivolt Burner ......................................... 9
DBX4C T-Stat Burner ........................................... 30
 
Forced Air Kit .......................................................... 31
Optional Brick ......................................................... 3
Optional Trim .......................................................... 3
Trim Installation ...................................................... 33
 








 3
DFX & DBX Series Vent Free Fireplaces


 
 

 

 


Please leave these instructions with the appliance.

Please retain these instructions for future reference .
1. Due to high temperatures, the appliance should be
located out of trafc and away from furniture and
draperies.
. 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 frequent 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.    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.
9. The installation must conform with local codes or, in
the absence of local codes, with the  

10. Do not install the DFX model in a bathroom or bedroom.
The DBX model may be installed in a bedroom, but
not in a bathroom.
11. 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. Refer to log
placement instructions for proper installation.
1. 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.
13.  Candles, incense, oil lamps, etc. produce
combustion byproducts including soot. Vent-free appli-
ances will not lter or clean soot produced by these
types of products. In addition, the smoke and/or aro-
matics (scents) may be reburnt in the vent-free appli-
ance which can produce odors. It is recommended to
minimize the use of candles, incense, etc. while the
vent-free appliance is in operation.
14. This is an unvented gas-fired heater. It uses air
(oxygen) from the room in which it is installed. Provi-
sions for adequate combustion and ventilation air must
be provided. Refer to 
15. 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 
  , the 
 or applicable local codes.
16. Keep room area clear and free from combustible
materials, gasoline and other ammable vapors and
liquids.
17. Unvented gas heaters are a supplemental zone heater.
They are not intended to be the primary heating appli-
ance.
18. Unvented gas heaters emit moisture into the living
area. In most homes of average construction, this
does not pose a problem. In houses of extremely
tight construction, additional mechanical ventilation is
recommended.
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
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.

4
DFX & DBX Series Vent Free Fireplaces 
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.
0. Input ratings are shown in BTU per hour and are for
elevations up to ,000 feet. For elevations above ,000
feet, input ratings should be reduced 4 percent for each
1,000 feet above sea level. Refer to the National Fuel
Gas Code.
1. 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 pres-
sures in excess of 1/ psig (3.5 kPa).
. The appliance must be isolated from gas supply piping
system by closing its equipment shutoff valve during
any pressure testing of the gas supply piping system
at test pressures equal to or less than 1/ psig (3.5
kPa).
3. 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.
4. Never burn solid fuels in a replace where a unvented
room heater is installed.
5. Always have a replace screen in place when the
appliance is in operation and, unless other provisions
for combustion air are provided, the screen must have
an opening(s) for induction of combustion air.
    
  



      



Adhere to all local codes or, in their absence, the latest
edition of THE NATIONAL FUEL GAS CODE ANSI Z3.1
or NFPA54 which can be obtained from:

1430 Broadway
New York, NY 10018
or

Batterymarch Park
Quincy, MA 069

 5
DFX & DBX Series Vent Free Fireplaces

This vent-free replace must be mounted on the oor or
on the optional replace hearth.

This unvented gas heater requires no outside venting and
burns cleanly with high heating efciency.
This zero-clearance unvented gas heater can be installed
against (or recessed into) any wall that is accessible to a
gas line.
FP2507
VFS DBX controls
Piezo
Ignition
Fireplace
Screen
Control
Knob
Figure 1 -
Unvented Gas Heater
(Control Access Door Shown Open)
On/Off Switch FP507


    
Regulator Pressure Nat. 4.0” w.c. 3.5” w.c.
Pilot Regulator Nat. n/a 3.5” w.c.
Max. Inlet Pressure Nat. 10.5” w.c. 10.5” w.c.
Min. Inlet Pressure Nat. 5.0” w.c. 5” w.c.
Regulator Pressure LP 10.0” w.c. 10.0” w.c.
Max. Inlet Pressure LP 13.0” w.c. 13.0” w.c.
Min. Inlet Pressure LP 11.0” w.c. 11.0” w.c.

      
4DFXNMC Nat. Manual ,000 15,000
4DFXPMC LP Manual ,000 17,000
4DFXNVC Nat. Millivolt ,000 17,000
4DFXPVC LP Millivolt ,000 17,000
3DFXNVC Nat. Millivolt 6,000 0,000
3DFXPVC LP Millivolt 6,000 0,000
DBX4NTC Nat. T-Stat 10,000 --
DBX4PTC LP T-Stat 10,000 --

 For LP models an external regulator is required
to reduce supply pressure to a maximum of 13" w.c.

Piezo ignitor allows ignition of the pilot without the use of
matches or batteries.

 - All gas to the gas logs is shut off at the
valve.
 - Valve position to light/maintain a standing
pilot.
 - Valve position to turn ON/OFF log set with
remote switch/thermostat.
 - Variable position to control ame height
(heat output). Both front and rear burners
are in operation to provide realistic glow
and yellow ame.

 - All gas to the gas logs is shut off at the
valve.
 - Valve position to light/maintain a standing
pilot.
 - Variable position corresponding to desired
temperature.

The gas log heater is tted with a specially designed safety
pilot light 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.

The millivolt gas log pilot is tted with a millivolt generator
to provide power for remote activation.

6
DFX & DBX Series Vent Free Fireplaces
O - Min. Rough Opening Width
Min. Rough
Opening
Depth
1/2”
or 5/8”
Min. Rough
Opening
Height
L
334051
VFS DBX dims
A
B
C
D
H
E
F
G
J
P
S
R
Q
S
I
N
M
K

Figure 2 -
Fireplace and Framing Dimensions
  
A 4Z\x" (6 mm) 3" (813 mm)
B Z\x" (57 mm) 8C\v" (730 mm)
C 6Z\x" (673 mm) 30" (76 mm)
D 14" (356 mm) 1C\v" (553 mm)
E 17" (43 mm) 0Z\v" (514 mm)
F 4B\," (118 mm) 4C\v" (11 mm)
G 4M\," (14 mm) 5" (17 mm)
H 11M\," (30 mm) 13C\," (340 mm)
I 1" (5 mm) 1B\," (41 mm)
J 10Z\x" (67 mm) 1" (305 mm)
K 9" (9 mm) 10B\," (70 mm)
L 13Z\," (333 mm) 17Z\x" (445 mm)
M 1" (533 mm) 7" (686 mm)

N 6C\v" (680 mm) 30Z\v" (768 mm)
O 4C\v" (69 mm) 3Z\x" (86 mm)
P 10Z\x" (67 mm) 1Z\v" (311 mm)
Q 4Z\x" (1080 mm) 53C\v" (136 mm)
R 1" (533 mm) 6C\v" (680 mm)
S 30" (76 mm) 38" (965 mm)

 7
DFX & DBX Series Vent Free Fireplaces

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 heater • Trim kit
• Two () 90°-angle brackets • Ceramic ber logs
• Installation/operating instructions
• Canopy and three (3) screws
• Two () anchoring screws • Four (4) black screws
Millivolt controlled heater designed to be operated with
optional devices for ON/OFF functions.
• Hand held Remote with receiver
• Wall T-stat with 0' wire
• Wall switch with 0' wire
• Hand held Thermostat Remote w/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.


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 shutoff valve
• Piping which complies with local codes
• Sediment trap
• Phillips head screwdriver
• Tee joint.
• Pipe sealant approved for use with propane/LPG
• Pipe wrench
(Resistant to sulfur compounds)

 


 

      

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 different sequence.
1. Position replace in desired location. Refer to the 
 and and  
, and   sections found in this
manual.
 Be sure all packing material has been removed
from underside the unit.
. Install canopy and logs per instructions found in this
manual. The canopy MUST be installed for safe opera-
tion of the unit.
3. Field wire main power supply to units with fan kit. Refer
to the  found in this manual. (Electrical
connections should only be performed by an experi-
enced, licensed certied tradesman).
4. Install optional ON/OFF kit on units with millivolt control.
Refer to the installation instructions included with the
kit and also refer to the  section found
in this manual.
5. Plumb gas line. Refer to the  sec-
tion found in this
manual. (Gas connections should only be performed
by an experienced,
licensed/certied tradesman).
6. Complete nish wall material and/or surround.


 


 
 

        


      
      National
Fuel Gas Code, ANSI Z223.1/NFPA 54 
International Fuel Gas Code  


8
DFX & DBX Series Vent Free Fireplaces 

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 “Clear-
ances” section on . Minimum clearances to combustibles 
• Location must not be affected 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.
• 
• Location should be out of high trafc areas and away from furniture and draperies due to
heat from rebox.
• Never obstruct the front opening of the unvented replace or restrict the ow of combustion
and ventilation air.
• Minimize modications to existing construction. below for location sugges-
tions.
• Do not install in the vicinity where gasoline or other ammable liquids may be stored. The
unvented rebox must be kept clear and free from the combustible materials.
FP2440
fireplace locations
Figure 3 -
Possible Fireplace Locations
FP440

 9
DFX & DBX Series Vent Free Fireplaces

Ensure that minimum clearances shown in are maintained. Left and right clearances
are determined when facing the front of the rebox.
Follow these instructions carefully to ensure safe installation. Failure to follow these requirements
may create a re hazard.
 — The clearance from the inside of the appliance to any combustible adjacent
wall should not be less than 9" for the DBX4C/DFX4C and DFX3C. 
— The ceiling must be at least 4" from the top of the rebox opening. 
— The appliance may be placed against a combustible back wall.
— 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 and so that no cold
air can enter from under the rebox.
— The canopy supplied with the unit must be installed. If a combustible mantel
is installed. It must meet the clearance requirements detailed in 
9"
Minimum
9"
Minimum
42" Minimum
FP2441
sidewall clg clear
FP441
Figure 4 -
Sidewall and Ceiling Clearances
256O”
12”
10”
19”
FP2508
VFS DBX mantel clearances
Canopy
FP508
Figure 5 -
Mantel Clearances

    Figures 4 and 5    





10 
DFX & DBX Series Vent Free Fireplaces 
If unit is to be “built in”, replace framing can be built before
or after the appliance is set in place. 

    
Construct replace framing following
 for replace dimensions. The framing
headers may rest directly on top of the rebox.
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 and so that no cold air can
enter from under the rebox.
Anchor replace to the side framing members using nail-
ing anges.
K
J
FP2445
opening size
   
J 6C\v" 6C\v" 31Z\v"
(680 mm) (680 mm) (800 mm)
K 5" 5" 3ZC\zn"
(635 mm) (635 mm) (833 mm)
FP445
Figure 6 -
Custom Cabinet
When finishing a custom cabinet, mantel or other built-in
enclosure, the opening size to accommodate the replace with
trim installed is as follows:

    
 

1. Bend out the nailing anges located on each side of the
rebox.
. Slide the rebox into prepared framing or position rebox
in its nal position and frame later.
3. Level the rebox by checking the top edge of the rebox.
Shim if necessary.
4. Anchor rebox to the side framing members using 8d
nails or other suitable fasteners. 
5. The canopy must be installed for safe operation of
the heater.     for canopy installation
details.
FP2509
nailing flanges
Nail Sides
Through Nailing
Flanges
FP509
Figure 7 -
Nailing Flanges