Page 5
506373−01 11/2011
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
in.wg.
Unit
Natural Gas
Propane (LP)
Gas
1st
Stage
+
0.2
2nd
Stage
+
0.3
1st
Stage
+
0.2
2nd
Stage
+
0.3
036, 048, 060, 072
Std./Med./High Heat
NA 3.5 NA 10.5
036, 048, 060, 072
Dual Heat
1.7 3.5 5.1 10.5
092− 360 1.6 3.7 5.5 10.5
Gas Heat Operation
See the operating instruction plate on the unit for details.
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.
TABLE 4
GAS METER CLOCKING CHART
Unit
Input
Rate
(Btuh)
Seconds for One Revolution
Natural LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
65,000 55 111 138 277
78,000 46 92 115 231
105,000 34 69 86 171
125,000 29 58 72 144
130,000 28 55 69 138
150,000 24 48 60 120
169,000 21 43 53 107
180,000 20 40 50 100
240,000 15 30 38 75
260,000 14 28 35 69
360,000 10 20 30 50
480,000 8 15 19 38
Natural−1000 btu/cu ft LP−2500 btu/cu ft
Note: Table assumes standard temperature (60°F), pressure
(30in.Hg.), and fuel heating values (Btuh/Ft.
3
). Apply pressure
corrections in altitudes above 2000 ft.
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