Bryant CONDENSING GAS FURNACE 350MAV, Installation, Start-Up, And Operating Instructions Manual

Page: 44 / 52

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.
WARNING: Disconnect 115-v electrical power before
changing speed tap. Failure to follow this warning could
result in personal injury.
4. To change blower motor speed selections for heating mode,
remove blower motor lead from control center HEAT
terminal. (See Fig. 31.) Select desired blower motor speed
lead from 1 of the other motor leads and relocate it to HEAT
TABLE 10—MODEL 350MAV ORIFICE SIZE AND MANIFOLD PRESSURE FOR CORRECT INPUT
FOR USE WITH 140 SIZE FURNACES ONLY
(TABULATED DATA BASED ON 23,000 BTUH PER BURNER, DERATED 2 PERCENT FOR EACH 1000 FT ABOVE SEA LEVEL)
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(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.
and
Canada
0
to
2000
0%
derate
850 41 3.6 41 3.7 41 3.8 40 3.6 40 3.8
875 42 3.8 41 3.5 41 3.6 41 3.7 41 3.8
900 42 3.5 42 3.7 42 3.8 41 3.5 41 3.6
925 42 3.4 42 3.5 42 3.6 42 3.7 42 3.8
950 42 3.2 42 3.3 42 3.4 42 3.5 42 3.6
975 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
1000 43 3.5 43 3.6 43 3.7 42 3.2 42 3.3
1025 43 3.3 43 3.4 43 3.6 43 3.7 43 3.8
1050 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
1075 44 3.5 44 3.6 43 3.2 43 3.3 43 3.4
1100 44 3.3 44 3.4 44 3.5 43 3.2 43 3.3
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(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.
and
Canada
Altitudes
2001 to
3000
or
Canada
Altitudes
2001 to
4500
5%
derate
775 41 3.7 41 3.8 40 3.6 40 3.7 39 3.6
800 42 3.8 41 3.6 41 3.7 41 3.8 40 3.6
825 42 3.6 42 3.7 41 3.5 41 3.6 41 3.7
850 42 3.4 42 3.5 42 3.6 42 3.7 41 3.5
875 42 3.2 42 3.3 42 3.4 42 3.5 42 3.6
900 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
925 43 3.5 43 3.6 43 3.7 42 3.2 42 3.3
950 43 3.3 43 3.4 43 3.5 43 3.7 43 3.8
975 43 3.1 43 3.3 43 3.4 43 3.5 43 3.6
1000 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
1025 43 2.8 43 2.9 43 3.0 43 3.1 43 3.2
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(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
3001
to
4000
7%
derate
750 41 3.6 41 3.8 40 3.6 40 3.7 40 3.8
775 42 3.8 41 3.5 41 3.6 41 3.7 40 3.6
800 42 3.5 42 3.7 42 3.8 41 3.5 41 3.6
825 42 3.3 42 3.4 42 3.6 42 3.7 42 3.8
850 43 3.8 42 3.2 42 3.4 42 3.5 42 3.6
875 43 3.6 43 3.7 42 3.2 42 3.3 42 3.4
900 43 3.4 43 3.5 43 3.6 43 3.8 42 3.2
925 43 3.2 43 3.3 43 3.5 43 3.6 43 3.7
950 43 3.1 43 3.2 43 3.3 43 3.4 43 3.5
975 43 2.9 43 3.0 43 3.1 43 3.2 43 3.3
1000 43 2.8 43 2.9 43 3.0 43 3.0 43 3.1
* Orifice numbers 43 are factory installed.
Percents of derate are based on midpoints of U.S. altitude ranges.
—44—