Proper Gas Flow & Combustion; Gas Meter Clocking Chart - Lennox G40UH(X) Unit Information

F− Proper Gas Flow (Approximate)
& Combustion
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time
in table 13 below. Adjust manifold pressure on gas valve to
match time needed. Manifold pressure should not exceed
values listed in table 12. If manifold pressure matches
table 12 and rate is incorrect, check gas orifices for proper
size and restriction. After furnace has operated for 15 min-
utes take a combustion sample beyond the flue outlet and
compare to table 14. The maximum carbon monoxide
reading should not exceed 100ppm.
NOTE− To obtain accurate reading, shut off all other gas
appliances connected to meter.
IMPORTANT
For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
TABLE 13

GAS METER CLOCKING CHART

Seconds for One Revolution
Natural
G40UH G40UH
Unit
1 cu ft
Dial
−45 82
−70 55
−90 41
−110 33
−135 27
−155 23
Natural−1000 btu/cu ft
LP
2 cu ft 1 cu ft 2 cu ft
Dial Dial DIAL
164 205 410
110 136 272
82 102 204
66 82 164
54 68 136
46 58 116
LP−2500 btu/cu ft
G40UH Unit CO
24A−045(X) 5.50 − 6.50
36A−045 5.80 − 6.80
24A−070 7.00 − 8.00
36A−070(X) 6.80 − 7.80
48B−070 6.80 − 7.80
36B−090 7.20 − 8.20
48B−090(X) 7.20 − 8.20
36C−110 6.50 − 7.50
48C−110 6.90 − 7.90
60C−110(X) 6.50 − 7.50
48C−135 6.70 − 7.70
60D−135 6.70 − 7.70
60D−155 6.80 − 7.80
Page 26
TABLE 14
Range Nat CO Range LP
2 2
6.80 − 7.80
6.60 − 7.60
8.00 − 9.00
7.80 − 8.80
7.80 − 8.80
7.70 − 8.70
7.70 − 8.70
7.50 − 8.50
8.50 − 9.50
7.50 − 8.50
7.60 − 8.60
7.60 − 8.60
7.80 − 8.80