Lennox G50UH Series User Manual

Page 27
G50UH Series
8 − Honeywell VR8205 Gas Valve with ON/OFF Switch −
Move gas valve switch to ON. See figure 27.
Honeywell VR8205 Gas Valve with Control Knob −
Turn knob on gas valve counterclockwise
to ON.
Do not force. See figure 28.
White Rodgers 36G Gas Valve − Move gas valve
switch to ON. See figure 29.
9 − Replace the upper access panel.
10− Turn on all electrical power to to the unit.
11− Set the thermostat to desired setting.
NOTE − When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12− If the appliance will not operate, follow the instructions
Turning Off Gas to Unit" and the gas supplier.
Turning Off Gas to Unit
1 − Set the thermostat to the lowest setting.
2 − Turn off all electrical power to the unit if service is to be
performed.
3 − Remove the upper access panel.
4 − Honeywell VR8205 Gas Valve with ON/OFF Switch −
Move gas valve switch to OFF. See figure 27.
Honeywell VR8205 Gas Valve with Control Knob −
Turn knob on gas valve clockwise
to OFF. Do not
force. See figure 28.
White Rodgers 36G Gas Valve − Move gas valve
switch to OFF. See figure 29.
5 − Replace the upper access panel.
Heating Sequence Of Operation
1 − When thermostat calls for heat, combustion air inducer
starts.
2 − Combustion air pressure switch proves combustion air
inducer operation. 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.
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 (WATCHGUARD"
flame failure mode). The ignition control will then auto-
matically repeat steps 3, 4, 5, and 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)
1 − Operate unit at least 15 minutes before checking gas
flow. Determine the time in seconds for one revolu-
tions of gas through the meter. A portable LP gas me-
ter (17Y44) is available for LP applications.
2 − Compare the number of seconds and the gas meter
size in table 10 to determine the gas flow rate. Multiply
the gas flow rate by the heating value to determine the
unit input rate. If manifold pressure is correct and the
unit input rate is incorrect, check gas orifices for proper
size and restriction.
3 − Remove temporary gas meter if installed.
NOTE − To obtain accurate reading, shut off all other gas
appliances connected to meter.
TABLE 10
Gas Flow Rate (Ft.
3
/Hr.)
Seconds for 1
Gas Meter Size
Seconds
for
1
Revolution
1/2 cu ft Dial 1 cu ft Dial
10 180 360
12 150 300
14 129 257
16 113 225
18 100 200
20 90 180
22 82 164
24 75 150
26 69 138
28 64 129
30 60 120
32 56 113
34 53 106
36 50 100
38 47 95
40 45 90
42 43 86
44 41 82
46 39 78
48 38 75
50 36 72
52 35 69
54 33 67
56 32 64
58 31 62
60 30 60
Gas Pressure
1 − Check the gas line pressure with the unit firing at maxi-
mum rate. A minimum of 4.5 in. w.c. for natural gas or
11.0 in. w.c. for LP/propane gas should be maintained.

Lennox G50UH Series Specifications

General

Brand	Lennox
Model	G50UH Series
Category	Furnace
Language	English