Bryant 333JAV Installation, Start-Up, And Operating Instructions Manual page 24

TABLE 13—ALTITUDE DERATE MULTIPLER FOR U.S.A.
ALTITUDE PERCENT OF
(FT) DERATE
0—2000 0
2001—3000 8—12
3001—4000 12—16
4001—5000 16—20
5001—6000 20—24
6001—7000 24—28
7001—8000 18—32
8001—9000 32—36
9001—10,000 36—40
* Derate multiplier factor is based on midpoint altitude for altitude range.
c. Obtain yearly gas heat value average for local gas
supply.
NOTE: Be sure heating value of gas used for calculations is
correct for your altitude. Consult local gas utility for altitude
adjustment of gas heating value.
d. Check and verify orifice size in furnace. NEVER AS-
SUME THE ORIFICE SIZE. ALWAYS CHECK AND
VERIFY.
e. Turn off all other gas appliances and pilots.
f. Move setup switch SW-2 to ON position. (See Fig. 18.)
This keeps furnace locked in low-heat operation.
g. Jumper R to W/W1.
h. Let furnace run for 3 minutes in low-heat operation.
i. Measure time (in sec) for gas meter to complete 1
revolution. Note reading.
j. Refer to Table 12 for cubic ft of gas per hr.
k. Multiply gas rate cu ft/hr by heating value (Btu/cu ft).
l. Move setup switch SW-2 to OFF position and jumper R
and W2 thermostat connections. (See Fig. 18.) This keeps
furnace locked in high-heat operation. Repeat items h
through k for high-heat operation.
EXAMPLE: (High-heat operation at 0 2000 ft altitude)
Furnace input from rating plate is 85,000 Btuh
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 1050 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 90 sec
Gas rate = 80 cu ft/hr (from Table 12) Btu heating input =
1050 X 80 = 84,000 Btuh In this example, the orifice size
and manifold pressure adjustment is within ±2 percent of
the furnace input rate.
NOTE: Measured gas inputs (high heat and low heat) must be
within ±2 percent of that stated on furnace rating plate when
installed at sea level or derated per that stated above when installed
at higher altitudes.
m. Remove jumper across R, W/W1, and W2 thermostat
connections to terminate call for heat.
5. Set air temperature rises.
Place SW-2 in ON position. Jumper R to W/W1 and W2 to check
high-gas heat temperature rise. To check low-gas heat temperature
rise, remove jumper to W2. Determine air temperature rises for
both high and low heat. Do not exceed temperature rise ranges
specified on unit rating plate for high and low heat.
a. Place duct thermometers in return and supply ducts as
near furnace as possible. Be sure thermometers do not
see heat exchangers so that radiant heat will not affect
thermometer readings. This is particularly important
with straight run ducts.
DERATE MULTIPLIER
FACTOR FOR U.S.A.*
1.00
0.90
0.86
0.82
0.78
0.74
0.70
0.66
0.62
—24—
ON/OFF
SWITCH
INLET
PRESSURE
TAP
MANIFOLD
PRESSURE
Fig. 22—Redundant Automatic Gas Control Valve
BURNER FLAME
MANIFOLD
Fig. 23—Burner Flame
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine
temperature rise.
If the temperature rise is outside this range, first check:
(1.) Gas input for low- and high-heat operation.
(2.) Derate for altitude if applicable.
(3.) Return and supply ducts for excessive restrictions
causing static pressures greater than 0.70-in. wc.
c. Adjust air temperature rise by adjusting airflow. Move
the RED jumper wire on the airflow selector control to
MID, HI, or M-HI for mid-point of the air temperature
rise range, high end of the rise range, or in-between,
respectively. The single RED jumper selection is used
for both high- and low-heat rises. Power need not be
reset after making this selection.
LOW-FIRE
ADJUSTMENT
ALLEN SCREW
(UNDER CAP)
HIGH-FIRE
ADJUSTMENT
ALLEN SCREW
(UNDER CAP)
TAP
A97358
BURNER
A89020