Appliance Application Requirements; Additional Venting Requirements - International comfort products N8MSN Installation Instructions Manual

APPLIANCE APPLICATION REQUIREMENTS

Appliance operation has a significant impact on the
performance of the venting system. If the appliances are
sized, installed, adjusted, and operated properly, the venting
system and/or the appliances should not suffer from
condensation and corrosion. The venting system and all
appliances shall be installed in accordance with applicable
listings, standards, and codes.
The furnace should be sized to provide 100 percent of the
design heating load requirement plus any margin that occurs
because of furnace model size capacity increments. Heating
load estimates can be made using approved methods
available from Air Conditioning Contractors of America
(Manual J); American Society of Heating, Refrigerating, and
Air−Conditioning Engineers; or other approved engineering
methods. Excessive oversizing of the furnace could cause
the furnace and/or vent to fail prematurely.
When a metal vent or metal liner is used, the vent must be in
good condition and be installed in accordance with the vent
manufacturer's instructions.
To prevent condensation in the furnace and vent system, the
following precautions must be observed:
1. The return−air temperature must be at least 60_F
(16_C) db except for brief periods of time during warm−
up from setback at no lower than 55_F (13_C) db or
during initial start−up from a standby condition.
2. Adjust the gas input rate per the installation instruc-
tions. Low gas input rate causes low vent gas temper-
atures, causing condensation and corrosion in the fur-
nace and/or venting system. Derating is permitted only
for altitudes above 2000 ft. (610 M).
3. Adjust the air temperature rise to the midpoint of the
rise range or slightly above. Low air temperature rise
can cause low vent gas temperature and potential for
condensation problems.
4. Set thermostat heat anticipator or cycle rate to reduce
short cycling.
Table 8— EXTERIOR MASONRY CHIMNEY FAN + NAT
INSTALLATIONS WITH TYPE−B DOUBLE WALL VENT
CONNECTORS ENFPA & AGA Combined Appliance
Maximum Input
Rating in Thousands of Btuh per Hour
INTERNAL AREA OF CHIMNEY
VENT HEIGHT
FT. (M)
12
(7741)
6 (1.8) 74
8 (2.4) 80
10 (3.0) 84
15 (4.5) NR
20 (6.0) NR
30 (9.1) NR
26
SQ. IN. (SQ. MM)
19 28 38
(12258) (18064) (24516)
119 178 257
130 193 279
138 207 299
152 233 334
NR 250 368
NR NR 404
Table 9—Minimum Allowable Input Rating of Space−Heat-
ing Appliance in Thousands of Btuh per Hour
INTERNAL AREA OF CHIMNEY
VENT HEIGHT
FT. (M)
12
(7741)
Local 99% Winter Design Temperature: 17 to 26 degrees F
6
0
8
52
10
NR
15
NR
20
NR
30
NR
Local 99% Winter Design Temperature: 5 to 16 degrees F*
6
NR
8
NR
10
NR
15
NR
20
NR
30
NR
Local 99% Winter Design Temperature: -10 to 4 degrees F*
6
NR
8
NR
10
NR
15
NR
20
NR
30
NR
Local 99% Winter Design Temperature: -11
Not recommended for any vent configuration.
*The 99.6% heating db temperatures found in the 1997 or 2001 ASHRAE
Fundamentals Handbook, Climatic Design Information chapter, Table 1A
(United States) and 2A (Canada) or the 2005 ASHRAE Fundamentals hand­
book, Climatic Design Information chapter, and the CD-ROM included with
the 2005 ASHRAE Fundamentals Handbook.
Air for combustion must not be contaminated by halogen
compounds which include chlorides, fluorides, bromides, and
iodides. These compounds are found in many common home
products such as detergent, paint, glue, aerosol spray,
bleach, cleaning solvent, salt, and air freshener, and can
cause corrosion of furnaces and vents. Avoid using such
products in the combustion−air supply. Furnace use during
construction of the building could cause the furnace to be
exposed to halogen compounds, causing premature failure of
the furnace or venting system due to corrosion.
Vent dampers on any appliance connected to the common
vent can cause condensation and corrosion in the venting
system. Do not use vent dampers on appliances common
vented with this furnace.

ADDITIONAL VENTING REQUIREMENTS

A 4−in. (102 mm) round vent elbow is supplied with the
furnace. A 5−in. (127 mm) or 6−in. (152 mm) vent connector
may be required for some model furnaces. A field−supplied
4−in. (102 mm) to 5−in. (127 mm) or 4−in. (102 mm) to 6−in.
(152 mm) sheet metal increaser fitting is required when 5−in.
(127 mm) or 6−in. (152 mm) vent connector is used. See
Figure 28 − Figure 40 Venting Orientation for approved vent
configurations.
NOTE: Vent connector length for connector sizing starts at
furnace vent elbow. The 4−in. (102 mm) vent elbow is
shipped for upflow configuration and may be rotated for other
positions. Remove the 3 screws that secure vent elbow to
furnace, rotate furnace vent elbow to position desired,
reinstall screws. The factory−supplied vent elbow does NOT
count as part of the number of vent connector elbows.
SQ. IN. (SQ. MM)
19 28 38
(12258) 18064) (24516)
55 99 141
74 111 154
90 125 169
NR 167 212
NR 212 258
NR NR 362
78 121 166
94 135 182
111 149 198
NR 193 247
NR NR 293
NR NR 377
NR 145 196
NR 159 213
NR 175 231
NR NR 283
NR NR 333
NR NR NR
_F (16_C)
or
lower
441 01 1402 02