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4 - Move gas valve switch to
OFF.
5 - Replace the access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped breaker?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the internal manual shut‐off valve open?
9 - Is the unit ignition system in lockout? If the unit locks
out again, inspect the unit for blockages.
Heating Sequence Of Operation
1 - When thermostat calls for heat, combustion air inducer
starts.
2 - Combustion air pressure switch proves blower opera
tion. Switch is factory set and requires no adjustment.
3 - After a 15-second prepurge, the hot surface ignitor en
ergizes.
4 - After a 20-second ignitor warm-up period, the gas
valve solenoid opens. A 4-second trial for ignition peri
od begins.”
5 - Gas is ignited, flame sensor proves the flame, and the
combustion process continues.
6 - If flame is not detected after first ignition trial, the igni
tion control will repeat steps 3 and 4 four more times
before locking out the gas valve. The ignition control
will then automatically repeat steps 1 through 6 after 60
minutes. To interrupt the 60-minute lockout period,
move thermostat from “Heat” to “OFF” then back to
“Heat”. Heating sequence then restarts at step 1.
Gas Pressure Adjustment
Gas Flow (Approximate)
TABLE 15
GAS METER CLOCKING CHART
95AF2
Unit
Seconds for One Revolution
Natural
LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
DIAL
-045
80
160
200
400
-070
55
110
136
272
-090
41
82
102
204
-110
33
66
82
164
-135
27
54
68
136
Natural-1000 btu/cu ft LP-2500 btu/cu ft
Furnace should operate at least 5 minutes before checking
gas flow. Determine time in seconds for
two
revolutions of
gas through the meter. (Two revolutions assures a more
accurate time.)
Divide by two
and compare to time in table
15. If manifold pressure matches table 17 and rate is incor
rect, check gas orifices for proper size and restriction. Re
move temporary gas meter if installed.
NOTE
- To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
An inlet post located on the gas valve provides access to
the supply pressure. See figure 57. Back out the 3/32 hex
screw one turn, connect a piece of 5/16 tubing and connect
to a manometer to measure supply pressure. See table 17
for supply line pressure.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply pres
sure must fall within range listed in table 17.
Manifold Pressure Measurement
NOTE - Order pressure test adapter kit (10L34) to facilitate
manifold pressure measurement.
A manifold pressure post located on the gas valve provides
access to the manifold pressure. See figure 57. Back out
the 3/32 hex screw one turn, connect a piece of 5/16 tubing
and connect to a manometer to measure manifold pres
sure.
To correctly measure manifold pressure, the differential
pressure between the positive gas manifold and the nega
tive burner box must be considered.
1 - Connect the test gauge positive side “+“ to manifold
pressure tap on gas valve as noted above.
2 - Tee into the gas valve regulator vent hose and con
nect to test gauge negative “-”.
3 - Ignite unit on low fire and let run for 5 minutes to allow
for steady state conditions.
4 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
17.
5 - If necessary, make adjustments. Figure 57 shows
location of high fire and low fire adjustment screws.
6 - Repeat steps 3, 4 and 5 on high fire. See values in
table 17.
NOTE
- Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Re-start unit and
check gas valve for gas leaks.
