Set Temperature Rise - Bryant 345MAV Installation, Start-Up, And Operating Instructions Manual

CANADA
At installation altitudes from 2000 to 4500 ft, this
furnace must be derated 5% by an authorized Gas
Conversion Station. To determine correct input rate for
altitude, see example above and use 0.95 as derate
multiplier factor.
b. Reinstall burner box cover.
NOTE: Burner box cover MUST be isntalled while clocking gas
input rate.
c. Gas valve regulator seal cap MUST be installed.
d. Turn off all other gas appliances and pilots.
e. Start furnace and let operate for 3 minutes.
f. Measure time (in sec) for gas meter test dial to complete
1 revolution.
g. Refer to Table 11 for cu ft of gas per hr.
ON/OFF SWITCH
INLET
PRESSURE TAP
Fig. 46—Redundant Automatic Gas Valve
Fig. 47—Orifice Holes
CAUTION: DO NOT redrill orifices. Improper drilling
(burrs, out-of-round holes, etc.) can cause excessive
burner noise and misdirection of burner flames. This can
result in flame impingement of burners and heat exchang-
ers causing failures.
REGULATOR
SEAL CAP
REGULATOR
ADJUSTMENT
SCREW
REGULATOR SPRING
(PROPANE - WHITE, 6 TURNS
NATURAL - SILVER, 10 TURNS)
GAS PRESSURE
REGULATOR
ADJUSTMENT
MANIFOLD
PRESSURE TAP
A03142
BURNER
ORIFICE
A93059
—40—
h. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft)
using natural gas heating value from local gas
utility/supplier.
EXAMPLE:
Btu heating input = Btu/cu ft X cu ft/hr Heating value of
gas = 975 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 70 sec
Gas rate = 103 cu ft/hr (from Table 11)
Btu heating input = 103 X 975 = 100,425 Btuh
In this example, the orifice size and manifold pressure
adjustment is within 2 percent of the furnace input rate.
B. Set Temperature Rise
CAUTION: Temperature rise must be within limits
specified on unit rating plate. Recommended operation is
at midpoint of rise or slightly above. Failure to follow this
caution may result in primary and secondary heat ex-
changers failure.
Determine and adjust air temperature rise as follows:
1. Place thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
2. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine air
temperature rise.
3. Adjust temperature rise by adjusting blower speed. Increase
blower speed to reduce temperature rise. Decrease blower
speed to increase temperature rise.
BURNER FLAME
MANIFOLD
Fig. 48—Burner Flame
TABLE 10—ALTITUDE DERATE MULTIPLIER FOR U.S.A.
ALTITUDE % OF
(FT) DERATE
0—2000 0
2001—3000 4—6
3001—4000 6—8
4001—5000 8—10
5001—6000 10—12
6001—7000 12—14
7001—8000 14—16
8001—9000 16—18
9001—10,000 18—20
* Derate multiplier factor is based on midpoint altitude for altitude range.
BURNER
A89020
DERATE MULTIPLIER
FACTOR FOR U.S.A*
1.00
0.95
0.93
0.91
0.89
0.87
0.85
0.83
0.81