If the furnace control CPU selects high-heat operation, the
inducer motor IDM remains running at high-speed, and the
high-heat pressure switch relay HPSR is de-energized to
close the NC contact. When sufficient pressure is available
the high-heat pressure switch HPS closes, and the high-heat
gas valve solenoid GV-HI is energized. The furnace control
CPU begins a 15-second prepurge period after the low-heat
pressure switch LPS closes. If the high-heat pressure switch
HPS fails to close and the low-heat pressure switch LPS
closes, the furnace will operate at low-heat gas flow rate
until the high-heat pressure switch closes for a maximum of
2 minutes after ignition.
2. Igniter Warm-Up-At end of the inducer prepurge period,
the Hot Surface Igniter HSI is energized for a 17-sec igniter
warm-up period.
3. Trial-For-Ignition Sequence-When the igniter warm-up
period is completed the main gas valve relay contacts GVR
close to energize the gas valve GV, the gas valve opens. The
gas valve GV permits gas flow to the burners where it is
ignited by the Hot Surface Igniter HSI. Five seconds after
the GVR closes, a 2-second flame period begins. The HSI
igniter will remain energized until the flame is sensed or
until the 2-second flame proving period begins.
TABLE 10—MODEL 352MAV ORIFICE SIZE AND HIGH/LOW-HEAT MANIFOLD PRESSURE FOR CORRECT INPUT
FOR USE WITH 060 THROUGH 120 SIZE FURNACES ONLY
(TABULATED DATA BASED ON 20,000/13,000 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
43
3.7/1.5
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
42
3.4/1.4
875
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/12.6
42
3.2/1.4
900
44
3.7/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
925
44
3.5/1.5
44
3.7/1.6
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
950
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.6
44
3.8/1.6
975
44
3.2/1.3
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
1000
45
3.7/1.6
45
3.8/1.6
44
3.2/1.4
44
3.4/1.4
44
3.5/1.5
1025
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
44
3.2/1.3
44
3.3/1.4
1050
45
3.3/1.4
45
3.4/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
1075
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
1100
47
3.6/1.5
47
3.7/1.6
45
3.2/1.4
45
3.4/1.4
45
3.5/1.5
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
2000
to
4500
5%
derate
775
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
42
3.4/1.4
42
3.5/1.5
800
43
3.5/1.5
43
3.7/1.5
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
825
44
3.8/1.6
43
3.4/1.5
43
3.6/1.5
43
3.7/1.5
43
3.8/1.6
850
44
3.6/1.5
44
3.7/1.6
44
3.8/1.6
43
3.5/1.5
43
3.6/1.5
875
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.6
43
3.4/1.4
900
44
3.2/1.4
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
925
45
3.7/1.5
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.4/1.5
950
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
44
3.3/1.4
975
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
45
3.8/1.6
1000
47
3.7/1.6
45
3.2/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
1025
47
3.6/1.5
47
3.7/1.6
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
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
43
3.7/1.6
43
3.8/1.6
42
3.3/1.4
42
3.4/1.4
42
3.5/1.5
775
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/1.6
42
3.2/1.4
800
44
3.7/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
825
44
3.5/1.5
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
850
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.7/1.5
44
3.8/1.6
875
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.5/1.5
44
3.6/1.5
900
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
44
3.3/1.4
44
3.4/1.4
925
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
44
3.2/1.3
950
45
3.2/1.4
45
3.3/1.4
45
3.4/1.5
45
3.5/1.5
45
3.7/1.5
975
47
3.6/1.5
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
1000
47
3.5/1.5
47
3.6/1.5
45
3.7/1.6
45
3.2/1.4
45
3.3/1.4
* Orifice numbers shown in shading are factory installed.
NOTE: Percents of derate are based on midpoints of U.S. altitude ranges.
—41—
Summary of Contents for CONDENSING GAS FURNACE 352MAV
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