Lennox MERIT Series Installation Instructions Manual page 15

The ML180UHE series units are classified as fan-assisted
Category I furnaces when vertically vented according to
the latest edition of National Fuel Gas Code (NFPA 54 /
ANSI Z223.1) in the USA. A fan-assisted Category I fur-
nace is an appliance equipped with an integral mechan-
ical means to either draw or force combustion products
through the combustion chamber and/or heat exchanger.
The ML180UHE is not approved for use with horizontal
venting.
NOTE - Use these instructions as a guide. They do not
supersede local codes. This furnace must be vented ac-
cording to all local codes these installation instructions,
and the provided venting tables in these instructions
The venting tables in this manual were extracted from the
National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are
provided as a guide for proper vent installation. Proper
application, termination, construction and location of vents
must conform to local codes having jurisdiction. In the ab-
sence of local codes, the NFGC serves as the defining
document.
Use self-drilling sheet metal screws or a mechanical fas-
tener to firmly secure the vent pipe to the round collar of
the flue transition. If self-drilling screws are used to attach
the vent pipe, it is recommended that three be used. Drive
one self-drilling screw through the front and one through
each side of the vent pipe and collar. See figure 23.
Install the first vent connector elbow at a minimum of six
inches (152 mm) from the furnace vent outlet. See figure
23.
Venting Using a Masonry Chimney
The following additional requirements apply when a lined
masonry chimney is used to vent this furnace. Masonry
chimneys used to vent Category I central furnaces must
be either tile-lined or lined with a listed metal
VENT PIPE
(min. 6" length)
FLUE TRANSITION
COLLAR
VENT CONNECTION UPFLOW AND HORIZONTAL POSITION
"DISCONNECTED VENT"
WARNING
STICKER
lining system or dedicated gas vent. Unlined masonry
chimneys are prohibited. See figures 24 and 25 for com-
mon venting.
A chimney with one or more sides exposed to the outside
of the structure is considered to be an exterior chimney.
An exterior masonry chimney that is not tile-lined must be
lined with B1 vent or a listed insulated flexible metal vent.
An exterior tile-lined chimney that is sealed and capped
may be lined with a listed uninsulated flexible metal vent.
If the existing chimney will not accommodate a listed met-
al liner, either the chimney must be rebuilt to accommo-
date one of these liners or an alternate approved venting
method must be found.
Insulation for the flexible vent pipe must be an encapsu-
lated fiberglass sleeve recommended by the flexible vent
pipe manufacturer. See figure 24. Refer to the tables and
the venting information contained in these instructions to
properly size and install the venting system.
Once the venting system is installed, attach the
"Disconnected Vent" warning sticker to a visible area
of the plenum near the vent pipe. See figure 23. The
warning sticker is provided in the bag assembly. Order
Kit 66W04 for additional stickers.
Asphyxiation hazard. The exhaust vent for this furnace
must be securely connected to the furnace flue transition
at all times..
"DISCONNECTED VENT"
WARNING
STICKER
VENT PIPE
(min. 6" length)
Figure 23
Page 15
IMPORTANT
WARNING
TRANSITION
FLUE
COLLAR