User Guide

507716-01Page 46 of 58 Issue 1717
3. After a 15 second pre-purge, 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, ame sensor proves the ame, and the
combustion process continues.
6. If ame is not detected after rst ignition trial, the
ignition 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 period,
move thermostat from “Heat” to “OFF” then back to
“Heat”. Heating sequence then restarts at step 1.
Gas Pressure Adjustment
Gas Flow (Approximate)
Gas Meter Clocking Chart
Capacity
Seconds for One Revolution
Natural LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
-45 80 160 200 400
-70 55 110 136 272
-110 33 66 82 164
-135 27 54 68 136
Natural-1000 btu/cu ft LP-2500 btu/cu ft
Table 9. Gas Meter Clocking Chart
Furnace should operate at least 5 minutes before checking
gas ow. 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 Figure 68. If manifold pressure matches Table 11 and
rate is incorrect, check gas orices for proper size and
restriction. Remove temporary gas meter if installed.
NOTE: To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
When testing supply gas pressure, use the 1/8” N.P.T.
plugged tap or pressure post located on the gas valve to
facilitate test gauge connection. See Figure 69. Check
gas line pressure with unit ring at maximum rate. Low
pressure may result in erratic operation or underre. High
pressure can result in permanent damage to gas valve or
overre.
On multiple unit installations, each unit should be checked
separately, with and without other units operating. Supply
pressure must fall within range listed in Table 11.
Manifold Pressure Measurement
1. Remove the threaded plug from the outlet side of
the gas valve and install a eld provided barbed
tting. Connect to a manometer to measure manifold
pressure.
2. Start unit and allow 5 minutes for unit to reach steady
state.
3. While waiting for the unit to stabilize, observe the
ame. Flame should be stable and should not lift from
burner. Natural gas should burn blue.
4. After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
Table 11.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed tting and replace threaded plug.
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas ow rate before checking
combustion. Take combustion sample beyond the ue
outlet and compare to the tables below.
Table 10.
Capacity CO
2
% for Nat CO
2
% for L.P.
All 7.2 - 7.9 8.6 - 9.3
The maximum carbon monoxide reading should not exceed
100 ppm.
Table 11.
Manifold and Supply Line Pressure 0-10,000 ft.
Capacity Gas
Manifold Pressure in. w.g.
Supply Line Pressure
in. w.g.
0-10,000 ft.
0-4500 ft. 4501-5500 ft. 5501-6500 ft. 6501-7500 ft. 7501-10000 ft.
All Sizes
Natural 3.5 3.3 3.2 3.1 3.5 4.5 13.0
LP /
Propane
10.0 9.4 9.1 8.9 10.0 11.0 13.0
NOTE: A natural to LP propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation
instruction for the conversion procedure.