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915SB: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
53
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked in the
Start-up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes
air-circulating blower motor, if furnace overheats. By using this
method to check the temperature limit control, it can be established
that the limit is functioning properly and that the limit will operate
if there is a restricted return-air supply or motor failure. If the limit
control does not function during this test, the cause must be
determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of cardboard or sheet
metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re-light when furnace cools down.
2. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115-v power to furnace.
b. Disconnect inducer motor lead wires from wire harness.
c. Turn on 115-v power to furnace.
d. Set thermostat to “call for heat” and wait 1 minute. When low
pressure switch is functioning properly, hot surface igniter
should
NOT
glow and control diagnostic light flashes a status
code 31. If hot surface igniter glows when inducer motor is
disconnected, shut down furnace immediately.
e. Determine reason low pressure switch did not function properly
and correct condition.
f. Turn off 115-v power to furnace.
g. Reconnect inducer motor wires, replace door, and turn on 115-v
power.
h. Blower will run for 90 sec before beginning the call for heat
again.
i. Furnace should ignite normally.
Checklist
1. Put away tools and instruments. Clean up debris.
2. Verify that the jumper is removed from the TEST/TWIN terminal.
Verify that there is nothing plugged into the PLT connector. (Note:
If there is a jumper connector plugged into PLT, remove it and
discard.) See
.
3. Verify that the Blower/Heat Off Delay jumpers are set as desired.
See
.
4. Verify that there are no unsealed openings in the blower shelf or
casing.
5. Verify that the blower (lower door in upflow position) and control
(“Main” or upper door in upflow position) doors are properly
installed.
6. Verify that the Status LED glows. If not, check that the power
supply is energized and that the blower door is secure. See
to interpret diagnostic codes.
7. Cycle test furnace with room thermostat to be sure that it operates
properly with the room thermostat. Check all modes including
Heat, Cool and Fan.
8. Check operation of accessories per manufacturer’s instructions.
9. Review Owner’s Manual with owner.
10. Attach entire literature packet to furnace.
Table 21 – Orifice Size and Manifold Pressure (in. w.c.) for Gas
Input Rate
40,000 BTUH to 140,000 BTUH
A11253A
(Continued) -Orifice Size and Manifold Pressure (in. w.c.)
for Gas Input Rate (Cont.)
40,000 BTUH to 140,000 BTUH
A11253B
S
A
G
L
A
R
U
T
A
N
F
O
Y
T
I
V
A
R
G
C
I
F
I
C
E
P
S
S
A
G
.
G
V
A
HEAT VALUE
0.58
0.60
0.62
0.64
AT ALTITUDE
Orifice
Manifold
Orifice
Manifold
Orifice
Manifold
Orifice
Manifold
(Btu/cu ft)
No.
Pressure
No.
Pressure
No.
Pressure
No.
Pressure
900
43
3.8
42
3.2
42
3.3
42
3.4
0
925
43
3.6
43
3.7
43
3.8
42
3.2
(0)
950
43
3.4
43
3.5
43
3.6
43
3.7
975
44
3.7
44
3.8
43
3.4
43
3.6
to
1000
44
3.5
44
3.6
44
3.8
43
3.4
1025
44
3.3
44
3.5
44
3.6
44
3.7
2000
1050
44
3.2
44
3.3
44
3.4
44
3.5
(610)
1075
45
3.7
45
3.8
44
3.3
44
3.4
1100
46
3.7
46
3.8
45
3.8
44
3.2
U.S.A.
800
42
3.4
42
3.5
42
3.6
42
3.7
2001 (611)
825
43
3.8
42
3.3
42
3.4
42
3.5
to
850
43
3.6
43
3.7
42
3.2
42
3.3
3000 (914)
875
43
3.4
43
3.5
43
3.7
43
3.8
900
44
3.7
44
3.8
43
3.5
43
3.6
Canada
925
44
3.5
44
3.6
44
3.8
43
3.4
2001 (611)
950
44
3.3
44
3.4
44
3.6
44
3.7
to
975
44
3.2
44
3.3
44
3.4
44
3.5
4500 (1372)
1000
44
3.0
44
3.1
44
3.2
44
3.3
775
42
3.3
42
3.4
42
3.5
42
3.6
3001
800
43
3.8
42
3.2
42
3.3
42
3.4
(915)
825
43
3.6
43
3.7
43
3.8
42
3.2
850
44
3.8
43
3.5
43
3.6
43
3.7
875
44
3.6
44
3.7
43
3.4
43
3.5
4000
900
44
3.4
44
3.5
44
3.7
44
3.8
(1219)
925
44
3.2
44
3.4
44
3.5
44
3.6
950
44
3.1
44
3.2
44
3.3
44
3.4
750
42
3.3
42
3.4
42
3.5
42
3.6
4001
775
43
3.7
43
3.8
42
3.3
42
3.4
(1220)
800
43
3.5
43
3.6
43
3.7
43
3.8
825
44
3.8
43
3.4
43
3.5
43
3.6
850
44
3.5
44
3.7
44
3.8
43
3.4
5000
875
44
3.3
44
3.5
44
3.6
44
3.7
(1524)
900
44
3.2
44
3.3
44
3.4
44
3.5
925
44
3.0
44
3.1
44
3.2
44
3.3
725
42
3.2
42
3.3
42
3.4
42
3.5
5001
750
43
3.7
43
3.8
42
3.2
42
3.3
(1525)
775
43
3.4
43
3.5
43
3.7
43
3.8
800
44
3.7
44
3.8
43
3.4
43
3.5
825
44
3.5
44
3.6
44
3.7
44
3.8
6000
850
44
3.3
44
3.4
44
3.5
44
3.6
(1829)
875
44
3.1
44
3.2
44
3.3
44
3.4
900
44
2.9
44
3.0
44
3.1
44
3.2
675
42
3.4
42
3.5
42
3.6
42
3.8
6001
700
42
3.2
42
3.3
42
3.4
42
3.5
(1830)
725
43
3.6
43
3.7
43
3.8
42
3.3
750
43
3.4
43
3.5
43
3.6
43
3.7
775
44
3.6
44
3.7
43
3.4
43
3.5
7000
800
44
3.4
44
3.5
44
3.6
44
3.7
(2133)
825
44
3.2
44
3.3
44
3.4
44
3.5
850
44
3.0
44
3.1
44
3.2
44
3.3
to
to
to
to
ALTITUDE
RANGE
ft (m)
U
.S
.A
.
an
d
C
an
ad
a
SINGLE
-
STAGE FURNACE
(TABULATED DATA BASED ON 20,000 BTUH PER BURNER, DERATED 2%/1000 FT (305M) ABOVE SEA LEVEL)
U
.S.A
.
O
n
ly
U.
S
.A
.
O
n
ly
U.
S
.A
.
O
n
ly
U
.S.A
.
O
nly
U
.S.A
.
a
nd
C
a
na
da
S
A
G
L
A
R
U
T
A
N
F
O
Y
T
I
V
A
R
G
C
I
F
I
C
E
P
S
S
A
G
.
G
V
A
HEAT VALUE
0.58
0.60
0.62
0.64
AT ALTITUDE
Orifice
Manifold
Orifice
Manifold
Orifice
Manifold
Orifice
Manifold
(Btu/cu ft)
No.
Pressure
No.
Pressure
No.
Pressure
No.
Pressure
ALTITUDE
RANGE
ft (m)
SINGLE
-
STAGE FURNACE
(TABULATED DATA BASED ON 20,000 BTUH PER BURNER, DERATED 2%/1000 FT (305M) ABOVE SEA LEVEL)
650
42
3.4
42
3.5
42
3.6
42
3.7
7001
675
43
3.8
42
3.2
42
3.3
42
3.4
(2134)
700
43
3.5
43
3.7
43
3.8
42
3.2
725
44
3.8
43
3.4
43
3.5
43
3.6
750
44
3.5
44
3.7
44
3.8
43
3.4
8000
775
44
3.3
44
3.4
44
3.5
44
3.7
(2438)
800
44
3.1
44
3.2
44
3.3
44
3.4
825
44
2.9
44
3.0
44
3.1
44
3.2
625
42
3.4
42
3.5
42
3.6
42
3.7
8001
650
43
3.8
42
3.2
42
3.3
42
3.4
(2439)
675
43
3.5
43
3.6
43
3.7
42
3.2
700
44
3.7
43
3.4
43
3.5
43
3.6
725
44
3.5
44
3.6
44
3.7
44
3.8
9000
750
44
3.3
44
3.4
44
3.5
44
3.6
(2743)
775
44
3.0
44
3.2
44
3.3
44
3.4
9001
600
42
3.3
42
3.4
42
3.6
42
3.7
(2744)
625
43
3.7
42
3.2
42
3.3
42
3.4
650
43
3.5
43
3.6
43
3.7
43
3.8
675
44
3.7
44
3.8
43
3.4
43
3.5
10000
700
44
3.4
44
3.5
44
3.7
44
3.8
(3048)
725
44
3.2
44
3.3
44
3.4
44
3.5
* Orifice numbers shown in
BOLD
are factory-installed.
to
to
to
U.
S
.A.
On
ly
U.
S
.A.
On
ly
U.
S
.A.
On
ly