Two Stage Gas Valve Adjustment; Gas Heat Operation; Proper Gas Flow - Lennox LGH 036 Installation Instructions Manual

Two−Stage Gas Valve Adjustment
Gas manifold pressures should match pressures shown
in table 3. On two stage gas valves, initiate a W2
thermostat demand to check high fire pressure before low
fire pressure. With high fire operating, reduce the
thermostat demand to W1 and check the low fire
pressure. Refer to the Unit Controller manual to initiate a
thermostat demand.
IMPORTANT − Do not set low fire pressure lower than
the certified minimum input rating listed in table 3.
TABLE 3
MANIFOLD INPUT PRESSURES
Unit
Stage
+ 0.2
036, 048, 060, 072
Std./Med./High Heat
036, 048, 060, 072
Dual Heat
092− 360

Gas Heat Operation

See the operating instruction plate on the unit for details.
in.wg.
Propane (LP)
Natural Gas
Gas
1st 2nd 1st
Stage Stage
+ 0.3 + 0.2
NA 3.5 NA
1.7 3.5 5.1
1.6 3.7 5.5
Proper Gas Flow (Approximate)
1− Operate unit at least 15 minutes before checking gas
flow. Determine the time in seconds for two
revolutions of gas through the meter. (Two
revolutions assures a more accurate time.) A
portable LP gas meter (17Y44) is available for LP
applications.
2− Divide the number of seconds by two and
compare to the time in table 4. If manifold pressure is
correct and 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 METER CLOCKING CHART
2nd
Stage
Unit
+ 0.3
Input
Rate
10.5
(Btuh)
10.5
65,000
78,000
10.5
105,000
125,000
130,000
150,000
169,000
180,000
240,000
260,000
360,000
480,000
Natural−1000 btu/cu ft
Note: Table assumes standard temperature (60°F), pressure
(30in.Hg.), and fuel heating values (Btuh/Ft.
corrections in altitudes above 2000 ft.
Page 5
TABLE 4
Seconds for One Revolution
Natural
1 cu ft 2 cu ft 1 cu ft
Dial Dial Dial
55 111 138
46 92 115
34 69
29 58
28 55
24 48
21 43
20 40
15 30
14 28
10 20
8 15
LP−2500 btu/cu ft
506373−01
LP
2 cu ft
Dial
277
231
86 171
72 144
69 138
60 120
53 107
50 100
38 75
35 69
30 50
19 38
3
). Apply pressure
11/2011