Bryant 312AAV User Manual
Page 23
NOTE: Component test feature will not operate if any thermostat
signal is present at the control.
Component test sequence is as follows:
a. Momentarily short (jumper) TEST/TWIN and Com-24v
terminals until LED goes off.
b. LED will display previous status code 4 times.
c. Inducer motor starts on high-speed and continues to run
until Step H of component test sequence.
d. Hot surface igniter is energized for 15 sec., then de-
energized.
e. Blower motor operates on LO-HEAT speed for 10 sec.
f. Blower motor operates on HI-HEAT speed for 10 sec.
g. Blower motor operates on COOL speed for 10 sec.
h. Inducer motor goes to low-speed for 10 sec., then stops.
3. Operate Furnace: Follow procedures on operating instruc-
tions label attached to furnace.
4. Furnace Restart: With the furnace operating, set the
thermostat below room temperature and observe that the
furnace goes off. Set the thermostat above room tempera-
ture and observe that the furnace restarts.
IV. ADJUSTMENTS
1. Set gas input rate
Furnace gas input rate on rating plate is for installations at
altitudes up to 2000 ft. Furnace input rate must be within ±2
percent of furnace rating plate input.
In the U.S.A., the input rating for altitudes above 2,000 ft.
must be reduced by 4
for each 1,000 ft. above sea level.
In Canada, input rating must be reduced by 10
for altitudes of 2,000 ft. to 4,500 ft. above sea level.
4. Determine natural gas orifice size and manifold pressure for
correct input.
a. Obtain average yearly gas heat value (at installed alti-
tude) from local gas supplier.
b. Obtain average yearly gas specific gravity from local gas
supplier.
c. Verify furnace model. Table 9 may only be used for
model 312AAV furnaces.
d. Find installation altitude in Table 9.
NOTE: For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 9.
e. Find closest natural gas heat value and specific gravity in
Table 9.
f. Follow heat value and specific gravity lines to point of
intersection to find orifice size and low-and high-heat
manifold pressure settings for proper operation.
g. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE. ALWAYS CHECK AND
VERIFY.
EXAMPLE: (0–2000 ft altitude)
Heating value = 975 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 43*
Manifold pressure: 3.6-in. wc for high-heat
1.6-in. wc for low-heat
* Furnace is shipped with No. 43 orifices. In this example
all main burner orifices are the correct size and do not need
to be changed to obtain proper input rate.
5. Adjust manifold pressure to obtain input rate.
a. Remove regulator seal caps that conceal adjustment
screws for low-and high-heat gas valve pressure regula-
tors. (See Fig.32)
b. Move setup switch LHT on control to ON position. (See
Fig. 22). This keeps furnace locked in low-heat opera-
tion.
c. Jumper R and W/W1 thermostat connections on control
to start furnace.
d. Turn low-heat adjusting screw (5/64 hex Allen wrench)
counterclockwise (out) to decrease input rate or clock-
wise (in) to increase input rate.
NOTE: DO NOT set low-heat manifold pressure less than 1.3–in
wc or more than 1.7–in. wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
CAUTION: DO NOT bottom out gas valve regulator
adjusting screw. This can result in unregulated manifold
pressure and result in excess overfire and heat exchanger
failures.
NOTE: If orifice hole appears damaged or it is suspected to have
been redrilled, check orifice hole with a numbered drill bit of
correct size. Never redrill an orifice. A burr-free and squarely
aligned orifice hole is essential for proper flame characteristics.
TABLE 9–MODEL 312AAV GAS ORIFICE SIZE* AND MANIFOLD PRESSURES FOR GAS INPUT RATE (CONTINUED)
(TABULATED DATA BASED ON 22,000 BTUH HIGH-HEAT/14,500 BTUH FOR LOW-HEAT PER BURNER,
DERATED 4 PERCENT FOR EACH 1000 FT ABOVE SEA LEVEL)
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
Only
9001
to
10,000
575
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.4/1.5
44
3.5/1.5
600
46
3.6/1.6
46
3.7/1.6
45
3.7/1.6
45
3.8/1.7
44
3.2/1.4
625
47
3.8/1.6
46
3.5/1.5
46
3.6/1.6
46
3.7/1.6
46
3.8/1.7
650
47
3.5/1.5
47
3.6/1.6
47
3.7/1.6
46
3.4/1.5
46
3.5/1.5
675
48
3.7/1.6
48
3.8/1.7
47
3.5/1.5
47
3.6/1.6
47
3.7/1.6
700
48
3.4/1.5
48
3.6/1.5
48
3.7/1.6
48
3.8/1.6
47
3.4/1.5
725
49
3.8/1.6
48
3.3/1.4
48
3.4/1.5
48
3.5/1.4
48
3.6/1.6
750
49
3.5/1.5
49
3.6/1.6
49
3.8/1.6
48
3.3/1.4
48
3.4/1.5
775
49
3.3/1.4
49
3.4/1.5
49
3.5/1.5
49
3.6/1.6
49
3.7/1.6
* Orifice numbers (43) shown in shading are factory installed.
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