Bryant 310A Installation, Start--Up, Operating, And Service And Maintenance page 28

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 instructions.
Low gas input rate causes low vent gas temperatures, caus-
ing condensation and corrosion in the furnace and/or vent-
ing 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.
Exterior Masonry Chimney FAN + NAT
Installations with Type- -B Double- -Wall Vent
Connectors ENFPA & AGA
Table A—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
Table B—Minimum Allowable Input Rating of
Space- -Heating 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
handbook, Climatic Design Information chapter, and the CD ---ROM in-
cluded with the 2005 ASHRAE Fundamentals Handbook.
28
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
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