Isokern Vent-Free 81036 Owner's manual

Isokern®VENT-FREE Gas Firebox
Installation, Operation, Maintenance and Owner’s Manual
Isokern Vent-Free Models 81036, 81042 & 81046
A PRODUCT OF EARTHCORE®INDUSTRIES, LLC
IMPORTANT: This manual contains assembly rules, installation steps and guidelines, use and maintenance
instructions for the Isokern Vent-Free Gas Firebox (Vent-Free Series). This manual must become the property of
and be reviewed by all current and future users of this product. It is the responsibility of the distributor, general
contractor and the installer of this product that the instructions in this manual are followed exactly and, further that
the allowed gas log appliance used in this product be installed in strict accordance with the gas log manufacturer’s
listing and explicit installation and operation instructions.
INSTALLER: Leave this manual with the appliance
CONSUMER: Retain this manual for future reference
Be Sure to Read Entire Manual Before Beginning Construction.
Contents of this manual may change without prior notification.
WARNING:
FIRE OR EXPLOSION HAZARD
Failure to follow safety warning exactly could
result in serious injury, death, or property damage.
— 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.
• Leave the building immediately.
• 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.
Issued: December 2016
Revision: 004
©2016 Earthcore Industries, LLC
THESE FIREBOXES ARE DESIGNED for USE with:
PROPANE (LP) or NATURAL GAS (NG), ONLY
THIS MANUAL CAN ONLY BE REPRODUCED IN ITS ENTIRETY
Do not install the Vent-Free Gas Firebox in a
manufactured home or mobile home or recreational
vehicle.
SBCCI NO. 9626
INTERTEK TESTING SERVICES REPORT NO. 13001A-764
ICC Report NO. ESR-2316
FOR USE ONLY WITH DECORATIVE TYPE
CERTIFIED VENT-FREE GAS LOG. DO NOT
BUILD A WOOD FIRE.

General Information...................................................... 3
Safety Instructions................................................... 4 - 5
Warnock-Hersey Listing Label ...................................... 5
Vent-Free Series 36” (81036)
Firebox Dimensions & Component List........................ 6
Vent-Free Series 42” (81042)
Firebox Dimensions & Component List........................ 7
Vent-Free Series 46” (81046)
Firebox Dimensions & Component List........................ 8
Required Clearance to Combustibles ........................... 9
Rough Framing Dimensions ......................................... 9
General Assembly Instructions....................................10
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Earthcore Industries
Vent-Free Gas Firebox 12/2016
Table of Contents
Assembly Instructions .......................................... 11 - 12
Raised & Flush Hearth Application ..............................13
Custom See-Thru Application ......................................14
Firebrick Installation.....................................................15
Access Modification:
Gas Line & Electrical Line Feed ...................................16
Clearance to Combustible Trim ....................................17
Summary .....................................................................18
Registration Card .........................................................19
Warranty ..................................................................... 20

3
Intended Use Statement
The Vent-Free Gas Firebox is a modular refractory
masonry unit designed for field assembly. The unit con-
sists of interlocking precast parts which are glued togeth-
er using Earthcore Mortar supplied with the unit. The
parts of the system are cast using a proprietary mixture
of volcanic pumice aggregate and aluminate cement.
Each piece is intended for a specific part of the enclosure
and is designed such that only one means of assembly
is possible. The system includes all the parts necessary
for the assembly of a complete masonry vent-free deco-
rative gas log enclosure.
In addition to the basic enclosure, a minimum stan-
dard one and one-eighth inch (1-1/8”) thick, high tem-
perature refractory brick is required to line the interior of
the firebox.
Vent free decorative gas log sets are supplied by oth-
ers and are limited to any listed vent-free gas-fired log
sets with heat input ratings up to 40,000 BTU/hr.
Product Description
The Vent-Free firebox has been evaluated and list-
ed by Intertek Testing Services (Warnock Hersey Inter-
national) in accordance with ANSI Z21.91 2007 and is
intended for use as a “zero clearance” rated enclosure
when used with any listed unvented or dual listed gas
log set that has a maximum input rating of 40,000 BTU/
hr. This firebox has been tested and approved in accor-
dance to ANSI Z21.97 for outdoor applications. (Physical
size limitations apply. Refer to minimum firebox require-
ments supplied with log heater.) The vent free decorative
gas logs chosen must meet the appliance manufacturer’s
minimum size dimension requirements for installation in
this enclosure.
WARNING: Any application other than the ‘intended use’
stated herein is in violation of the manufacturer’s instruc-
tions and is hereby prohibited. Such violation may cause
immediate hazard, property damage or loss of life and
will void all liabilities to the manufacturer and will void all
warranties explicit or implied.
WARNING: These models CANNOT be installed in a bed-
room unless maximum BTU rating of installed vent-free
log set is less than 10,000 BTU/hr.
Foundation Requirements
Wood floor framing systems are suitable foundations
for the Vent-Free firebox. Because the Vent-Free firebox
is listed for “zero clearance” at the unit bottom, sides,
back and top it may sit directly upon wood sub-flooring.
The Vent-Free firebox weighs approximately 750-900
lbs. (excluding gas log appliance and finish trim). Since
this weight is spread over an area of seven and one-half
square feet (7.5 sq. feet) to nine and one half square feet
Earthcore Industries
12/2016 Vent-Free Gas Firebox
General Information
(9.5 sq. feet) depending on standard unit size chosen, it
is necessary that any wood floor framing where this unit
is placed be designed to carry concentrated loading of
approximately 150 lbs/sq. foot.
Standard residential concrete slab is a suitable foun-
dation. This may be either a structural off-grade slab or a
structural slab-on-grade.
Before Beginning the Installation:
Read these instructions carefully before beginning
the installation of this Vent-Free firebox. Also read the
gas log appliance manufacturer’s literature regarding siz-
ing and suitability for installation into this enclosure prior
to installation. (Look for gas log appliance manufacturer’s
label “A.G.A. Certified Vent-Free Gas Log.”)
Since it is not possible to adequately define all instal-
lation and use circumstances in this manual be sure to
check with and strictly adhere to local building codes and
ordinances governing installation, inspection and use of
gas fired equipment. In the absence of local codes the
installation and use of this Vent-Free firebox - and the cer-
tified unvented gas log appliance placed in it - must be in
accordance with each manufacturer’s explicit installation
instructions and must conform with National Fuel Gas
Code, ANSI Z21.11.2 2013, NFPA 54.
Local building and safety codes shall govern issues
relating to the suitability of the use of unvented appli-
ances as well as to room size requirements. Prior to pur-
chase and installation it should be determined if unvented
gas log heaters are suitable to the proposed application
where health matters are concerned.
NOTE: You may need to provide combustion and ven-
tilation air from an outside source to adequately satisfy
local codes.
Non-combustible hearth extensions are not required
in front of the Vent-Free firebox. However it is the respon-
sibility of the installer to refer to the vent free gas log
manufacturer’s explicit installation instructions regarding
their requirements for non-combustible hearth exten-
sions. Requirements may vary among vent free gas log
manufacturers.
Refer to local codes governing the need for hearth
extensions for vent free gas log enclosures.
State of Massachusetts
The installation must be made by a licensed plumber
or gas fitter in the Commonwealth of Massachusetts.
Vent-free gas products are prohibited for bedroom
and bathroom installation in the Commonwealth of Mas-
sachusetts.

WARNING: This product contains or generates
chemicals known to the state of California to cause
cancer or birth defects or other reproductive harm.
IMPORTANT: Read this owner’s manual carefully
and completely before trying to assemble, operate
or service this firebox. Improper use of this firebox
can cause serious injury or death from fire, burns,
explosions and carbon monoxide poisoning.
DANGER: CARBON MONOXIDE POISONING MAY
LEAD TO DEATH!
This firebox is a unvented product and should be
installed by a qualified service person.
Propane (LP) gas and natural gas (NG) are both
colorless and odorless gases. An odor-making agent is
added to each of these gases to help you detect a gas
leak. However, the odor added to these gases can fade
and gas may be present even though no odor exists.
Carbon Monoxide Poisoning: Early signs of carbon
monoxide poisoning resemble flu symptoms, including
headaches, dizziness or nausea. If you have these signs
the fireplace may not have been installed properly, get
fresh air at once! Have the firebox inspected and serviced
by a qualified service person or your gas supplier. Some
people are more affected by carbon monoxide than
others. These include pregnant women, people with
heart or lung diseases or anemia, people at high altitude
or under the influence of alcohol. Earthcore Industries
strongly recommends the use of a carbon monoxide
detector/alarm device wherever gas fired appliances are
in use.
All parties either involved in or associated with the
installation, service and use of this firebox must read this
entire manual. Keep this manual for reference and as a
guide book to safe operation of this firebox.
WARNING:This unit is not for use with solid fuel.
1. Always check local building codes governing fireplaces
and fireplace installations. The Vent-Free Series
installation must comply with all local, regional, state and
national codes and regulations.
2. The Vent-Free Series are listed for use with the
decorative gas log appliance only.
3. For propane (LP) use do not place propane supply
tank(s) inside any structure. Locate propane supply
tank(s) outdoors.
To prevent performance problems, do not use
propane fuel tank of less than 100 lbs. capacity.
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Earthcore Industries
Vent-Free Gas Firebox 12/2016
Safety Instructions
4. Do not install the Vent-Free Gas Firebox in a
manufactured home or mobile home or recreational
vehicle.
5. This firebox reaches high temperature. Keep children
and adults away from hot surfaces to avoid burns or
clothing ignition. Firebox will remain hot for a time after
shutdown. Allow surfaces to cool before touching.
6. Turn the Vent-Free Gas Firebox off and allow to cool
before servicing. Always shut off any electricity and gas
to the Vent-Free Gas Firebox while working on it. Only a
qualified service person should install, service or repair
this firebox. Have your fireplace inspected annually by a
qualified service person.
7. Keep all combustible material, gasoline and other
flammable liquids at a safe distance from the fireplace.
Do not use the fireplace where these items are used or
stored. Decorations, clothing and other such combustible
items should not be placed on the fireplace.
8. Do not use the Vent-Free Series to cook food or burn
paper or other objects.
9. Do not use any solid fuels - wood, coal, paper,
cardboard, etc. - in this firebox. Use only the gas type
listed on the unvented gas log heater label.
10. Keep all insulation and vapor barriers a minimum
of three inches (3”) away from all Vent-Free Series and
Direct-Vent chimney components.
11. This American Gas Association fact sheet provides an
overview of the requirements for the electrical bonding
of fuel gas piping systems to the electrical grounding
system based on ANSI Z223.1/NFPA 54, National Fuel
Gas Code - 2015 (NFGC). The bonding requirements in
previous code editions, in local jurisdictions or in specific
situations, may differ.
12. Do not pack or fill required air spaces with insulation
or other material. No material is allowed in these spaces.
13. Do not use a fireplace blower insert, heat exchanger
or any other product not specified by the manufacturer
herein for use with this fireplace.
14. Do not use any Vent-Free Series decorative appliance
if any part has been under water. Immediately call a
qualified service technician to inspect the appliance and
to replace any part of the control system and any gas
control which has been under water.

5
15. The Vent-Free Series is not intended to heat an entire
home or to be used as a heat source.
16. Children and adults should be alerted to the hazards
of high surface temperature and should stay away from
this appliance to avoid burns or clothing ignition.
1 7. Young children should be carefully supervised when
they are in the same room as the appliance. Toddlers,
young children and others may be susceptible to accidental
contact burns. A physical barrier is recommended if there
are at-risk individuals in the house. To restrict access to
the fireplace, install a adjustable safety gate to keep
toddlers, young children and other at-risk individuals out
of the room and away from hot surfaces.
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Safety Instructions
Warnock Hersey Listing Label
18. Clothing or flammable material should not be placed
on or near the appliance.
19. Due to high temperatures, the appliance should
be located out of traffic and away from furniture and
draperies.
20. Installation and repair should be done by a qualified
service person.

6
Earthcore Industries
Vent-Free Gas Firebox 12/2016
Vent-Free Series 36” (81036) & Component List
37 ½”
31 ½”
43”
27 ¼”
36 ¹/8”
10 ½”
31 ½”
25 ¼”
37 ½”
34 ½”
5”
25 ¼”
43”
27 ¼”
36 1⁄8”
Front View Side View
Plan View
Component Part# Description
21 Base & Top Plate (Qty. 2)
20 Sidewall (Qty. 6)
25 Backwall (Qty. 3)
25 1/4”
43”
8”25 1/4”
10 1/2”
3”
10 1/2”
30”
NOTE: These
are inside rough
dimensions
before firebrick

7
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Vent-Free Series 42” (81042) & Component List
37 ½”
31 ½”
49”
33 ¼”
43 ¹/8”
10 ½”
31 ½”
25 ¼”
37 ½”
34 ½”
5”
25 ¼”
49”
33 ¼”
43 1⁄8”
Front View Side View
Plan View
Component Part# Description
22 Base & Top Plate (Qty. 2)
20 Sidewall (Qty. 6)
28 Backwall (Qty. 3)
25 1/4”
49”
8”25 1/4”
10 1/2”
3”
10 1/2”
36”
NOTE: These
are inside rough
dimensions
before firebrick

8
Earthcore Industries
Vent-Free Gas Firebox 12/2016
Vent-Free Series 46” (81046) & Component List
37 ½”
31 ½”
53”
37 ¼”
47 ¹/8”
10 ½”
31 ½”
25 ¼”
37 ½”
34 ½”
5”
25 ¼”
53”
37 ¼”
47 1⁄8”
Front View Side View
Plan View
Component Part# Description
23 Base & Top Plate (Qty. 2)
20 Sidewall (Qty. 6)
25 Backwall (Qty. 3)
25 1/4”
53”
8”25 1/4”
10 1/2”
3”
10 1/2”
40”
NOTE: These
are inside rough
dimensions
before firebrick

9
Clearance to Combustibles
The Vent-Free firebox may be installed at “zero clear-
ance” to plywood sheathing and to un-insulated wood
framing members at the unit bottom, sides, rear and top
when used for enclosing any listed unvented gas-fired
log set with maximum heat input ratings up to 40,000
BTU/hr. (Reference Intertek Testing Services Report No.
13001A-764.) (Figure 1)
However, when a Vent-Free firebox is to be installed
on carpeting, tile, or any combustible material other than
wood flooring or concrete, the Vent-Free firebox shall
then be installed on a metal or wood panel extending the
full width and depth of the Vent-Free firebox.
NOTE: Keep all insulation material to a minimum of three
inches (3”) away from the outside surfaces of the Vent-
Free firebox.
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Required Clearance to Combustibles & Framing Dimensions
Typical Installation Framing Dimensions (Figure2)
Vent-Free Width Height Depth
A B C
Model 36 43” 37 ½” 25 ¼”
Model 42 49” 37 ½” 25 ¼”
Model 46 53” 37 ½” 25 ¼”
NOTES:
1. “B” includes the 3” thick base plate.
2. “Raised hearth” requires additional rough opening
height at “B” equal to the height of the raised hearth
detail.
Corner Installation Framing Dimensions (Figure 3)
Vent-Free A B C
Model 36 43” 49 ¾” 32 ½”
Model 46 49” 52 ¾” 37”
Model 48 53” 54 ¾” 39½”
NOTES:
1. “B” reflects the Vent-Free Series outside center of
firebox base plate to inside corner of frame wall.
2. “C” dimension reflects the distance from the corner
of the firebox positioned 1 1/2” from frame wall to
inside corner of frame wall.
3. “D” dimension reflects the distance from the inside
frame wall perpendicular to the firebox to the inside
corner of the frame wall. (Based on 2” frame wall)
B
Framed
Opening
A
Framed
Opening
C
A
C
B
FIGURE 2
FIGURE 3
Wood Sub-Floor
Wood Floor
Joist System
FIGURE 1

10
Earthcore Industries
Vent-Free Gas Firebox 12/2016
General Assembly Instructions
When beginning the assembly process, mix the
Earthcore Mortar with clean water to a smooth, workable
texture (without lumps or dry pockets) of a “toothpaste”
consistency. This mixture is suitable for application onto
Isokern components by using a masonry grout bag
supplied with the unit.
Attention should be paid that the mortar mixture is not
too thin or runny, as this will not allow the mortar to reach
its maximum bonding strength.
Mark out the position of the base plate on the
supporting floor system. Apply a thin layer of Earthcore
Mortar to the area and set base plate in the mortar.
(Figure 4)
Earthcore Mortar is then squeezed from a grout bag
onto the contact surfaces of the Isokern components as
they are fitted together.
NOTE: It is important that a 1/2” bead of mortar is piped
onto all the components’ contact surfaces, about 1/2” in
from all edges. (Figure 5)
When setting the next component onto the mortared
contact surface of the base plate, some mortar should
squeeze out along the face of the entire joint as a sign of
complete and proper sealing of the joint.
On broader contact surfaces it is advisable to apply
several additional 1/2” beads of the Earthcore Mortar to
the area to assure proper sealing of the joint.
Properly mortared firebox and smoke dome assembly
requires approximately 100 pounds (dry measure) of
Earthcore Mortar.
Leveling and Aligning Components:
Be sure to assemble all Isokern components level
and flush with adjoining components.
Earthcore mortar is not intended to create a mortar
joint of any thickness for leveling purposes. Therefore,
leveling and alignment adjustments are made by the
use of small plastic shims supplied with the unit.
(Figure 6)
The shims can be inserted under a component to
level and align it with adjacent Isokern components. Be
sure to re-grout any and all gaps resulting from shim
insertion to maintain components to full bearing.
Broken Components:
Components can be repaired by using Earthcore
mortar along the break line as the component is set into
place. Components broken into multiple small pieces
should be discarded and replaced.
IMPORTANT:
1. Do not mix Earthcore mortar with anti-freeze agents.
2. The maximum recommended mortar joint thickness at
Isokern components is 1/4”.
Earthcore
Mortar
FIGURE 4
FIGURE 5
FIGURE 6
Earthcore
Mortar
Earthcore
Mortar

11
1. Begin assembly by setting the Vent-Free firebox’s
three inch (3”) thick base plate flat on a suitable level
surface at zero clearance. This surface can be a concrete
slab or a wood floor system capable of 150 psf loading.
The base plate can also be set on a concrete block raised
base or on a raised wood platform either of which can be
built upon a structural slab or upon a structurally suitable
wood floor system. Do not set the base plate so that it is
in span. (Figure 7)
2. Next set the first course of back wall and side walls
into place. It may be convenient to scribe the location
of the first layer of side walls and back wall on the base
plate and then to apply Earthcore Mortar to these scribed
areas on the base plate where the side walls and back
wall will sit. In this way the first layer of walls can be set
directly into grout already applied to the base plate.
Be sure to grout the vertical joints where the side
wall to back wall connect as each component is joined
to its mate. Look for mortar to squeeze out of all contact
joints as a sign of proper and complete sealing of the
joints. (Figures 8 & 9)
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Assembly Instructions
FIGURE 7
FIGURE 8
FIGURE 9
Earthcore
Mortar
Earthcore
Mortar

12
Earthcore Industries
Vent-Free Gas Firebox 12/2016
Assembly Instructions
3. Continue with the sequential assembly of the second
and third courses of the side walls and back wall by first
applying grout to the top of the previous layer, setting
the next course above into grout already applied to the
horizontal contact surface of the component below.
Again be sure to grout the vertical joints of the side wall
to back wall connection as each component is joined to
its mate. Look for some mortar to squeeze out along all
joints as a sign of proper sealing of the joint. (Figure 10)
4. Once the third, or top course of side walls and back
wall are set in place their top surfaces are to be grouted
with mortar to receive the Vent-Free firebox top plate.
Set the top plate upon the completed side wall/back wall
assembly seeing to it that the grouted contact surfaces
are properly sealed. This completes the assembly of the
Vent-Free firebox rough box components. (Figure 11)
NOTE: Make sure that the rough box assembly has
been set level and square. Adjust to level and square,
as necessary, while mortar is still wet. Make a final
inspection of all contact joints to be sure they are properly
sealed. Re-grout any and all gaps as necessary.
The manufacturer requires a minimum one and one
eighth inch (1-1/8”) thick fire brick as a liner to the inside of
the Vent-Free firebox. Thicker rated fire brick may be used
as an option. Also, the pattern for the fire brick interior
lining is not specified and is to be at owner option.
FIGURE 10
FIGURE 11

13
For a raised hearth (floor of the firebox elevated
above the room’s floor) then the Vent-Free base plate
can be set on a concrete block platform that is built up to
the desired raised hearth height on the concrete support
slab. (Figure 12)
When calculating raised hearth height, be sure to
allow for the three inch (3”) thick base plate plus the one
and one-half inch (1-1/2”) thick fire brick floor in addition
to the height of the concrete block platform. CMU used
for base plate support should be rated ASTM 90.
For a “flush hearth” (firebox floor flush with the
room’s floor) the base plate can be omitted from the
assembly and the firebox walls built directly on the
concrete support slab as long as there are no wood
underpinnings. This makes the firebox finished fire
brick floor approximately one and one-half inches (1-
1/2”) above the top of the concrete support slab. For
installation directly on a combustible floor, the base plate
must be used. (Figure 13)
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Raised and Flush Hearth Application
Standard Residential
Concrete Slab
On or Off-Grade
Base Plate
Raised Platform
FIGURE 12
FIGURE 13

Model 46 Components
14
Earthcore Industries
Vent-Free Gas Firebox 12/2016
See-Thru or two-sided Vent-Free fireboxes can be
constructed from the standard one-sided unit components
with the addition of three (3) backwall pieces.The backwalls
will be custom cut and used as the sides walls.
In this installation the standard side wall components
are eliminated and custom cut backwalls are used for the
sidewalls. The backwall components need to be cut down
the 25 ¼” and used for the sidewalls. (Figure 16)
NOTE: Two pieced of steel angle iron three inch by three
inch by one quarter inch (3” x 3” x 1/4”) cut to span the
firebox openings should be set on top of the side wall
assembly on both sides before the top plate is set into
place. (Figure 14)
Vent-Free A B
Model 36 43” 33”
Model 42 49” 39”
Model 46 53” 43”
14
Custom See-Thru Application
B
A
25 ¼”
NOTE: Two pieces of steel angle iron with measurements
of 3” x 3” x 1/4” cut to span firebox openings will be
needed to assemble the firebox. These items are not
included in the components and can be sourced locally.
FIGURE 14
FIGURE 15
Steel Angle Iron
Front View
Plan View
Component Part# Description
21 Base & Top Plate (Qty. 2)
25 Backwall (Qty. 6)
25 1/4”
43”
10 1/2”
30”
10 ½”
30”
25 ¼”
FIGURE 16
Component Part# Description
22 Base & Top Plate (Qty. 2)
25
Backwall (Qty. 6)
25 1/4”
49”
10 1/2”
30”
Component Part# Description
23 Base & Top Plate (Qty. 2)
25
Backwall (Qty. 6)
25 1/4”
53”
10 1/2”
30”
Model 36 Components
Model 42 Components
Part #25

15
Earthcore Industries
12/2016 Vent-Free Gas Firebox
15
The manufacturer requires that the fireboxes be lined
with a minimum one and one-eighth (1-1/8”) thick firebrick
for the Floor, Backwall and the Sidewalls. Thicker firebrick
may be used as an option. The pattern for the firebrick
lining is an owner option. Standard N or S type brick mortar
is suitable mortar for the firebox.
Firebrick mortar needs to be suitable to both adhere
the firebrick to the inside of the firebox and to create the
finished face joints of the brick work. Based on a history of
field applications and experience, a suitable mortar would
be as follows:
Mix:
* 1 bucket masonry mortar (S or N type)
* Up to ½ lbs Earthcore mortar (optional)
* One part Fire Clay (optional)
* Water to a sticky, toothpaste consistency
NOTE: Heat Stop orAlsey Pre-Mix Mortar are acceptable
alternatives to the Type S or N mortar.
These instructions may vary because of different
climates and conditions. The use of good masonry
practices for your area should also be considered. It takes
about 25 lbs. of mortar mix (dry measure) to firebrick line a
firebox.
Installation Instructions:
1. Wet mop the inside of the firebox with a damp sponge
to remove dust and loose particles from the interior before
firebricking.
For Best Results:
1. After wet sponged interior of firebox apply a 1/4
notch bed joint on rear sides and floor.
2. Dip each firebrick in a pale of water before applying
mortar to one side for adherence to firebox.
2. Face joint dimensions of 1/4” to 3/8” in the brick work
is recommended and has the best appearance. Other face
joint dimensions are acceptable however smaller joints
may not leave room for heat expansion of firebrick.
3. Start the firebrick at the front edge of the floor of the
Isokern firebox, proceeding inward toward the back. Let
the floor brick gap approximately 1/2” off the back wall
and side walls. This air space allows heat expansion of the
firebrick and is to be left empty of mortar. (Figure 17)
4. Next, apply firebrick to the back wall of the unit.The back
wall firebrick covers the 1/2” expansion gap left at the brick
floor along the back wall of the firebox. (Figure 18)
5. Set the side wall firebrick by starting at the front edge
of the unit’s side wall and working inward toward the back
wall firebrick. The side wall firebrick, when completed,
covers the 1/2” expansion gaps where both the floor
Firebrick Installation
firebrick and the back wall firebrick were held off the units
side walls. (Figure 19)
All required through-wall accesses (gas and air intake
supply access holes) should be drilled before the required
firebrick lining is installed. Do not cover these areas with
firebrick.
Earthcore makes no claims as to the performance of
firebrick or firebrick mortar(s). It is typical for heat stress
cracks to appear in the firebrick in fireboxes.
½“ Expansion
Gap
Fire brick floor
(built first)
½“ Expansion Gap
(No Gaps)
Firebrick Floor &
Back Wall (built first)
FIGURE 17
FIGURE 18
FIGURE 19

16
Earthcore Industries
Vent-Free Gas Firebox 12/2016
16
Access Modification
Gas Line & Electrical Line Feed
The provision for installation of a gas pipe is only for
connection to a decorative gas appliance. The decorative
gas appliance must comply with standard for Decorative
Gas Appliances for installation in Vent-Free fireboxes, ANSI
Z21.11.2 2013. The decorative gas appliance should be
installed in accordance with the National Fuel Gas Code,
ANSI Z223.1.
IMPORTANT: If a gas burning decorative appliance is
installed, look for and only use an A.G.A. Certified Vent-
Free Gas Log. Anytime a gas fired appliance is in use it is
recommended a carbon monoxide detector be installed.
Gas line for gas log sets used in the Vent Free firebox
can be routed through the side wall, back wall or floor of
the firebox by drilling an appropriately sized hole using a
masonry drill bit. (Figure 20)
Electrical Line Feed can be routed through the firebox
back wall, side walls or floor by drilling an appropriately
sized hole using a masonry drill bit.
Be sure to follow the Gas LogAppliance Manufacturer’s
explicit electrical line connection instructions for vent free
masonry fireplace installations.
NOTE: Gas Line and Electric Line must be fed through
separate access holes.
IMPORTANT: All access holes must be grouted with
mortar to seal any gaps or cracks.
Firebrick
Side
Gas or Electric
Line
Typical placement of
gas or electric line
NOTE: Fill any gaps around
line with Earthcore Mortar
FIGURE 20

17
Earthcore Industries
12/2016 Vent-Free Gas Firebox
17
Clearance to Combustible Trim
a minimum vertical distance of thirty inches (30”) from the
top of the finished fireplace opening.
IMPORTANT: Mantel height clearances may vary among
gas log appliance manufacturers. Be sure to follow the
gas log appliance manufacturer’s explicit installation
instructions for mantel height clearance requirements.
Adjoining Wall
Safe Zone
8”
24”
24”
Noncombustible
Facing Material
Horizontal
Projection from
Face of Fireplace
32"+ 28" 25" 20" 12"
Vertical Distances
to Underside of Mantel
1.5"
2.5"
6"
8"
12"+
The Vent-Free firebox is designed to be custom fin-
ished with facing trim and mantel to be at owner option.
However, all such trim material must meet standard fire-
place code requirements: non-combustible facing mate-
rial must be applied to a minimum of eight inches (8”)
beyond the sides of the finished opening of the Vent-Free
firebox and non-combustible facing material must cover
a minimum of twelve inches (12”) above the finished
opening of the installed unit. (Reference Intertek Testing
Services Report No. 13001A-764.)
Clearance to combustible trim are those distances
required to ensure that combustible mantel and facing
material will not be exposed to excessive heat while the
unit is operating. These clearances should be adequate
to prevent discoloration or warping of trim facings due to
heat. However, circumstances unique to each installation
create variables that may be beyond the scope of this
manual. Therefore be sure to follow gas log appliance
manufacturer’s explicit installation instructions re-
garding all minimum trim facing, mantel height and
side wall clearance requirements.
Interior Wall Materials
Wall materials, such as drywall, should be set flush
with the rough front face of the Vent-Free firebox. This will
allow for placement of required noncombustible surround
material in such a way that the surround material can lay
flat against the finished wall surface and also align with
the leading edge of the fire brick interior of the Vent-Free
firebox.
Trim Facings
Parts of the combustible mantel assembly located
along the sides of the firebox opening, which project more
than one and one-half inches (1-1/2”) from the face of the
firebox, shall be kept at least eight inches (8”) from the
firebox opening.
Adjoining Room Walls
Interior wall surfaces of adjoining room walls must be
at a minimum horizontal measure of twenty four inches
(24”) away from the finished opening of the Vent-Free
firebox.
Mantel and Mantel Shelf Clearance
Vent-Free firebox are subject to the same building
code safety clearances from the firebox opening as with
any fireplace opening:
Parts of the combustible mantel assembly located
above and projecting more than one and one-half inches (1-
1/2”) inches from the firebox opening shall be kept at least
twelve inches (12”) from the top of the opening.
Mantel shelves with horizontal projection of twelve
inches (12”) from the face of the fireplace must be held to
FIGURE 21
FIGURE 22

18
Earthcore Industries
Vent-Free Gas Firebox 12/2016
1. Maintenance
The Vent-Free firebox does not require any routine
maintenance procedure. However, the owner must follow
the gas log manufacturer’s explicit instructions regarding
burner limitations, burner adjustment, maintenance and
cleaning. Any and all questions and concerns regarding the
performance of gas log sets must be directed to the gas
log appliance manufacturer or the appliance manufacturer’s
agent or supplier.
2. Dual Listed Appliance
The Vent-Free firebox is certified with the use of dual-
listed unvented gas log heaters with a maximum output of
40,000 BTU’s. Do not burn any other type of vented gas
log, fire wood, paper or refuse in the Vent-Free firebox.
3. Fuel
Do not introduce any type of fuel into the Vent-Free
firebox other than the LP or Natural Gas listed for use in
the vent free gas log appliance manufacturer’s explicit
installation instructions.
Summary
4 . Electronic Equipment
Do not place electronic equipment such as television
sets, DVD players, audio equipment or computer
equipment directly above the Vent-Free firebox.
5. Structural Loads
Do not bear structural members nor set structural
loads on top of the Vent-Free firebox. The Vent-Free firebox
is designed to carry none other than its own dead weight.
CAUTION: Do not touch hot surfaces surrounding this unit
while it is in operation. Keep infants, toddlers and children
away from the Vent-Free firebox while it is in operation. Do
not leave children unattended while it is in use.

19
Earthcore Industries
12/2016 Vent-Free Gas Firebox
Registration Card
Please tear out along dashed lines and send to:
Earthcore Industries
Attn: Technical Department
6899 Phillips Industrial Blvd
Jacksonville, FL 32256
Dealer_______________________________________________________________________________________________
Date of Purchase: _____________________________ Date Of Installation: _____________________________________
Address:_____________________________________________________________________________________________
City, State, Zip: _______________________________________________________________________________________
Phone No.:___________________________________
Fireplace Size (Circle One): Vent-Free 36” (81036) Vent-Free 42” (81042) Vent-Free 46” (81046)
Fuel Type (Circle One): Natural Gas Propane
Firebox Serial Number: ________________________________________________________________________________
(Located on Rating Plate Inside Firebox)
Buyer: _______________________________________________________________________________________________
Address:_____________________________________________________________________________________________
City, State, Zip: _______________________________________________________________________________________
Phone No.:___________________________________
Installed By:__________________________________________________________________________________________
Address:_____________________________________________________________________________________________
City, State, Zip: _______________________________________________________________________________________
Phone No.:___________________________________

6899 Phillips Industrial Blvd. • Jacksonville, FL 32256 • 904.363.3417 • f: 904.363.3408 • earthcore.co
TECH1002_1216
Warranty & Disclaimer
Isokern Vent-Free Gas Firebox
Earthcore offers a lifetime warranty for all Isokern fireboxes, to be free from defects in materials
that negatively affect system performance from the date of purchase, subject to the terms and
conditions of this limited warranty.
This warranty covers only the above stated components, and NO WARRANTY, EXPRESS OR
IMPLIED, EXTENDS TO ANY OF THE HARDWARE, FOOTING, FIRE BRICK OR ACCESSORIES.
Factors beyond the manufacturer’s control affect fireplace smoking, and puffing, and Earthcore
cannot guarantee these aspects of performance.
If a component is found to be defective under the terms of this warranty the party to whom
this warranty is extended shall, notify Earthcore, 6899 Philips Industrial Blvd, Jacksonville, Florida
32256, in writing, by registered mail, within thirty (30) days following the discovery of the defect
within the lifetime warranty period. The notice shall contain (1) the date of purchase; (2) place of
purchase; (3) address of installation; (4) name, address and phone number of the owner; and (5) a
brief description of the defect.
Earthcore, or any division thereof, is not responsible for any labor costs or indirect costs incurred
for the replacement of defective components.
Earthcore is not responsible for misuse or mishandling of components. Nothing in this warranty
makes Earthcore, or any division thereof, liable in any respect for any injury or damage to the
building or structure in which the fireplace has been installed or to persons or property therein
arising out of the use, misuse, or installation of properly manufactured ISOKERN product.
EARTHCORE, OR ANY DIVISIONTHEREOF, SHALL NOT BE HELD LIABLE FOR ANY INCIDENTAL
OR CONSEQUENTIAL DAMAGES OR EXPENSES ARISING OUT OFTHE USE OFTHE FIREPLACES.
ALL SUCH DAMAGES AND EXPENSES ARE HEREBY EXCLUDED.
This warranty is null and void when the fireplace is not installed pursuant to the installation
instructions provided by Earthcore or local building codes have not been followed completely.
This warranty applies only to those fireplaces installed in the continental United States, Alaska,
and Canada. If any part of this warranty is found to be unenforceable, the remaining parts shall
remain in force and effect.
EARTHCORE HEREBY DISCLAIMS ALL GUARANTEES AND WARRANTIES, EXPRESS OR
IMPLIED, BEYOND THE WARRANTIES SET FORTH HEREIN.