Table of Contents
Advertisement
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 lock out? If the unit locks
out again, call the service technician to inspect the unit
for blockages.
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
See Figure 27
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 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, 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.
1
ON
OFF
Demand
CAI
Ignitor
Gas Valve
Indoor Blower
Blower on time will be 45 seconds after gas valve is energized. Blower off time will depend on "OFF TIME" Setting.
507332-02G / 31-5000663
15
Ignitor Warm-up
Pre-Purge
Figure 27. Heating Sequence of Operation
Gas Pressure Adjustment
Gas Flow (Approximate)
Capacity
-045
-070
-090
-110
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 14 above. If manifold pressure matches Table 17
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 17
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.
35
39
80
Blower
Trial for
"On" Delay
Ignition
Issue 2209
Gas Meter Clocking Chart
Seconds for One Revolution
Natural
1 cu ft
2 cu ft
Dial
Dial
80
160
55
110
41
82
33
66
Natural - 1000 btu/cu ft
Table 14.
LP
1 cu ft
2 cu ft
Dial
Dial
200
400
136
272
102
204
82
164
LP - 2500 btu/cu ft
5 SEC
Post
Purge
Page 27 of 35
Advertisement
Table of Contents
