Table of Contents
Advertisement
10 - Is pressure switch closed? Obstructed flue will
cause unit to shut off at pressure switch. Check flue
and outlet for blockages.
11 - Are flame rollout switches tripped? If flame rollout
switches are tripped, call the service technician for
inspection.
Heating Sequence Of Operation (follow steps below)
1 - When thermostat calls for heat, combustion air
blower starts.
2 - Combustion air pressure switch proves blower
operation. Switch is factory-set and requires no
adjustment.
3 - After a 15-second prepurge, the hot surface ignitor
energizes.
4 - After a 20-second ignitor warm-up period, the gas
valve solenoid opens. A 4-second trial for ignition
period 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
ignition control will repeat steps 3 and 4 four
more times before locking out the gas valve
("WATCHGUARD" flame failure mode). The ignition
control will then automatically repeat steps 1 through
6 after 60 minutes.
7 - To interrupt the 60-minute "WATCHGUARD" 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 8
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
Unit
1 cu ft
Dial
-040
90
-060
60
-080
45
-100
36
Natural-1000 btu/cu ft LP/Propane - 2500 btu/cu ft
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time in
TABLE 8. Remove temporary gas meter if installed.
NOTE - To obtain accurate reading, shut off all other gas
appliances connected to meter.Supply Pressure Mea-
surement
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 9.
Check Manifold Pressure
1 - Remove the threaded plug from the outlet side of
the gas valve and install a field-provided barbed
fitting. Connect measuring device "+" connection to
barbed fitting to measure manifold pressure.
LP/Propane
2 cu ft
1 cu ft
Dial
Dial
180
n/a
120
150
90
112
72
n/a
Start unit and allow 5 minutes for unit to reach
steady state.
2- After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
TABLE 9. Make manifold adjustment if necessary
3 - Shut unit off and remove manometer as soon as an
accurate reading has been obtained.
4 - Restart unit and check for any gas leaks. Seal any
leaks if found.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
Supply Line and Manifold Pressure (inches w.c.)
Altitude
ft
0-4500 ft
4501-
7500 ft
Proper Combustion & LP/Propane Conversion Kis
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. Take combustion sample beyond the flue outlet
2 cu ft
and compare to the table below.
Dial
n/a
300
Unit
224
n/a
-040
-060
-080
-100
High Altitude
Units may be installed at altitudes up to 7,500 ft. above
sea level. See Table 9 for de-rate manifold values. Units
installed at altitude of 4501 - 7,500 feet require a pressure
switch change which can be ordered separately. Table 11
lists pressure switch requirements at high altitude. The
combustion air pressure switch is factory-set and requires
no adjustment.
Page 26
IMPORTANT
TABLE 9
Natuarl
Unit
Manifold
Supply
-040
1.6-2.2
-060
-080
3.0-3.8
-100
4.5-10.5
-040
1.4-2.0
-060
2.5-3.3
-080
-100
TABLE 10
CO2% Nat
CO2% LP
N/A
7.5 - 9.0
6.5 - 7.5
7.5 - 9.0
N/A
LP/Propane
Manifold Supply
N/A
N/A
11.0-
3.4-3.8
13.0
N/A
N/A
N/A
N/A
11.0-
2.5-3.3
13.0
N/A
N/A
N/A
N/A
LP
Conversion
Kit
N/A
20P40
20P41
N/A
Hide quick links:
Advertisement
Table of Contents
