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NBST27 Unvented Gas Log Set
WARNING
This appliance is for installation only in a solid-fuel
burning masonry or UL127 factory-built fireplace,
vent free appliance, or in listed ventless firebox
enclosure. It has been design certified for these
installations.
Exception: DO NOT install this appliance in a factory-
built fireplace that includes instructions stating
it has not been tested or should not be used with
unvented gas logs.
Use the fireplace manufacturer's installation and clear-
ance requirements as defined in their manual.
The NBST27 unvented room heater is approved for installa-
tion into the following unvented fireboxes: LSTF36, LPF36,
LRF36, LLF36
The NBST27 unvented room heater may also be installed
into a Ventless Firebox Enclosure for Gas Fired Decorative
Type Unvented Room Heaters per IAS Requirement No.
2-97 ANSI Z21.91-2001 (typically referred to as a "Univer-
sal Firebox"), as long as firebox hearth dimensions meet
the minimum hearth dimensions shown below.
21¹⁄₂"
32"
Figure 1 -
Hearth Minimum Dimensions for Solid Fuel Burning Fire-
places and UL127 Factory Built Fireplaces
FP2361
fireplace dims
WARNING
Barriers such as the bottom of a glass door frame
placed in front of a gas log set can change the air
flow characteristics of the fireplace which in turn can
cause the unit to overheat and malfunction.
6
Monessen • NBST27 Gas Log Set Installation/Owner's Manual • 81D3032 • Rev A • 08/16
FIREPLACE AND HEARTH DIMENSIONS
PLACEMENT IN FIREPLACE WITH A
RESTRICTIVE BARRIER
The following are guidelines for placing a gas log set in a
fireplace that has a restrictive barrier along the bottom front
opening of the fireplace. Some examples of barriers are
glass/screen door frames and sunken/recessed fireplaces.
Height of Restriction
No Restriction
Greater than 1
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 floor of the fireplace 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 fireplace. Placement
of the receiver outside of the fireplace will extend the
battery life.
Glass door
frames with
adjustable
louvers should
have the louvers
fully open while
the unit is in
operation
21¹⁄₂"
Height of restrictive barrier
caused by glass door frames,
recessed fireplaces, etc. from the
base or bottom surface of the unit.
(Refer to Table)
Figure 2 -
Reference Drawing of NBST27 Log Set in an Enclosure
Minimum Depth of
(x)
0" to 1
⁄
"
1
2
⁄
" to 3"
1
2
X
FP2362
fireplace barrier
Fireplace/Firebox
21
⁄
""
1
2
25
⁄
"
1
4
27
⁄
"
1
4
*
Refer to
Table
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