Lennox G60UH Series - Gas Pressure and Flow Adjustment; Gas Flow Measurement; Gas Pressure Settings; High Altitude Pressure Adjustments

Page 31
G60UH Series
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.
TABLE 12
Gas Flow Rate (Ft.
3
/Hr.)
Seconds for 1
Revolution
Gas Meter Size
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
2 − Compare the number of seconds and the gas meter
size in table 12 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.
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.
2 − After the line pressure has been checked and ad-
justed, check the low fire and high fire manifold pres-
sures. See figures 26 and 27 for the location of the
manifold pressure adjustment screws. Low and high
fire manifold pressures are given in table 13. A natural
gas to LP/propane gas changeover kit is required to
convert the unit.
High Altitude Information
Refer to table 13 for high altitude requirements and man-
ifold pressure settings at all altitudes.
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
NOTE − A natural to L.P. propane gas changeover kit is nec-
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
TABLE 13
High Altitude Requirements / Manifold Pressure Settings
Model
Input
Size
Gas
Altitude
Manifold Pressure
at all altitudes
0 − 7500 ft.
(0 − 2285 m)
7501−10,000 ft.
(2286 − 3048 m)
Required
Conversion Kit
Pressure
Switch
Required
Conversion Kit
Pressure
Switch
Low Fire High Fire
in. w.g. kPa in. w.g. kPa
−070, −090,
−110, −135
Nat. N/A N/A 44W51 18M64 1.7 0.42 3.5 0.87
LPG 44W48 N/A 44W50 18M64 4.9 1.22 10.0 2.5
Pressure switch is factory set. No adjustment necessary. All models use the factory installed pressure switch from 0−7500 feet (0−2285 m).