507330-01B
Page 26 of 33
Issue 1809
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. The ignition
control will then automatically repeat steps 1 through
6 after 60 minutes.
7. To interrupt the 60 minute, 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
-070
55
110
136
272
-090
41
82
102
204
-110
33
66
82
164
Natural - 1000 btu/cu ft
LP - 2500 btu/cu ft
Table 9.
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 9. If manifold pressure matches Table 10 and rate is
incorrect, check gas orifices 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
A threaded plug on the inlet side of the gas valve provides
access to the supply pressure tap. Remove the threaded
plug, install a field provided barbed fitting and connect a
manometer to measure supply pressure. See Table 10
for proper line pressure. Replace the threaded plug after
measurements have been taken.
Manifold Pressure Measurement
1. Remove the threaded plug from the outlet side of
the gas valve and install a field provided barbed
fitting. 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
flame. 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
NOTE:
Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
Manifold Pressure
Between 2000 and 7500 ft, certain units require manifold
pressure adjustments specified in Table 10. Manifold
pressure should be measured, and adjusted as required
during unit start up.
NOTE:
LP/Propane installations require a gas conversion
Orifice Kit as specified in Table 12.
Manifold Pressure and Line Pressure at Various Altitudes
Capacity
Manifold Pressure (in. w.c.)
1
Line Pressure (in. w.c.)
0 - 2000 ft.
2001 - 4500 ft.
4501 - 7500 ft.
7501 - 10000 ft.
Minimum
Max.
Nat.
Gas
LP
Gas
2
Nat.
Gas
LP
Gas
2
Nat.
Gas
LP
Gas
2
Nat.
Gas
3
LP
Gas
2
Nat.
Gas
LP
Gas
2
Nat. &
LP
070
3.5
10.0
3.2
10.0
2.8
10.0
3.5
10.0
4.5
11.0
13.0
090
3.2
10.0
2.7
9.6
110
3.5
10.0
3.0
9.6
1
Manifold pressure adjustments based on 1020 Btu/ft3 gas for natural and 2500 Btu/ft
3
gas for LP (corrected to standard conditions).
Consult local utility for actual local heating value.
2
A natural to LP/Propane gas conversion Orifice Kit is required to convert this unit. Refer to kit instructions for conversion procedure.
3
A high altitude natural Orifice Kit is required.
Table 10.
