Lennox Allied Air A95UH1D Installation Instructions Manual page 47

Gas Pressure Adjustment
Gas Flow (Approximate)
Seconds for One Revolution
Natural
Capacity
1 cu ft
Dial
-045 80
-070 55
-090 41
-110 33
-135 27
Natural - 1000 btu/cu ft
Table 10. Gas Meter Clocking Chart
Furnace should operate at least 5 minutes before checking
gas flow. Determine time in seconds for two revolutions of
gas through the meter. (Two revolutions assures a more
accurate time.) Divide by two and compare to time in Table
10. If manifold pressure matches Table 12 and rate is
incorrect, check gas orifices for proper size and restriction.
Remove temporary gas meter if installed.
NOTE: To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
When testing supply gas pressure, use the 1/8" N.P.T.
plugged tap or pressure post located on the gas valve to
facilitate test gauge connection. See Figure 69. Check
gas line pressure with unit firing at maximum rate. Low
pressure may result in erratic operation or underfire. High
pressure can result in permanent damage to gas valve or
overfire.
On multiple unit installations, each unit should be checked
separately, with and without other units operating. Supply
pressure must fall within range listed in Table 12.
Manifold Pressure Measurement
1. Remove the threaded plug from the outlet side of
the gas valve and install a field provided barbed
fitting. Connect to a manometer to measure manifold
pressure.
Capacity Gas
Natural
All
LP / Propane
NOTE: A natural to LP propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation
instruction for the conversion procedure.
507270-03
LP
2 cu ft 1 cu ft 2 cu ft
Dial Dial
160 200
110 136
82 102
66 82
54 68
LP - 2500 btu/cu ft
Manifold and Supply Line Pressure 0 - 10,000 ft.
Manifold Pressure in. w.g.
4,501 - 5,500
0 - 4,500 ft.
ft.
3.5 3.3
10. 9.4
2. Start unit and allow 5 minutes for unit to reach steady
state.
3. While waiting for the unit to stabilize, observe the
flame. Flame should be stable and should not lift from
burner. Natural gas should burn blue.
4. After allowing unit to stabilize for 5 minutes, record
Dial
manifold pressure and compare to value given in
400
Table 12.
272
NOTE: Shut unit off and remove manometer as soon
204
as an accurate reading has been obtained. Take care
to remove barbed fitting and replace threaded plug.
164
136
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Take combustion sample beyond the flue
outlet and compare to the tables below.
Capacity
All
The maximum carbon monoxide reading should not exceed
100 ppm.
High Altitude Information
NOTE: In
elevations over 4500 feet (1371 m) is the jurisdiction of
local authorities.
Units may be installed at altitudes up to 10,000 ft. above
sea level. See Table 11 for derate manifold values. Units
installed at altitude of 7501 - 10,000 feet require an orifice
change. Units installed at altitudes of 4,501 - 10,000 feet
(1371 -3048 m) may require a pressure switch change
which can be ordered separately.
Table 13 lists required pressure switch changes and orifice
conversion kits at varying altitudes.
The combustion air pressure switches are factory set and
require no adjustment.
5,501 - 6,500 6,501 - 7,500
ft. ft.
3.2 3.1
9.1 8.9
Table 12.
Issue 1917
CO % for Nat
2
7.2 - 7.9
Table 11.
Canada, certification
Supply Line Pressure
7,501 -
10,000 ft.
3.5
10.0
CO % for L.P.
2
8.6 - 9.3
for installations at
in. w.g.
0 - 10,000 ft.
4.5 13.0
11.0 13.0
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