Allied A95UH1E - Gas Pressure Adjustment; Gas Flow (Approximate); Supply Pressure Measurement; Manifold Pressure Measurement

507276-03 Page 47 of 59Issue 1621
Furnace should operate at least 5 minutes before checking
gas ow. 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 11. If manifold pressure matches Table 12 and rate
is incorrect, check gas orices 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 67. Check gas
line pressure with unit ring at maximum rate. Low pressure
may result in erratic operation or underre. High pressure
can result in permanent damage to gas valve or overre.
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 eld provided barbed tting. Connect
to a manometer to measure manifold pressure.
2. Start unit and allow 5 minutes for unit to reach steady
state.
3. While waiting for the unit to stabilize, observe the ame.
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
manifold pressure and compare to value given in Table
12.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed tting and replace threaded plug.
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Take combustion sample beyond the ue outlet
and compare to the tables below.
High Altitude Information
NOTE: In Canada, certication for installations at 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 12 for de-rate manifold values. Units
installed at altitude of 7501 - 10,000 feet require an orice
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 14 lists required pressure switch changes and orice
conversion kits at varying altitudes.
The combustion air pressure switches are factory set and
require no adjustment.
Table 12
Page 1
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*2P1013*
507280-01
*P507280-01*
TABLE 1
Manifold and Supply Line Pressure 0-10,000ft.
Unit Gas
Manifold Pressure in. wg.
Supply Line Pressure
in. w.g.
0 - 10000 ft.
0-4500 ft. 4501-5500 ft. 5501-6500 ft. 6501 - 7500ft. 7501 - 10000ft.
All Sizes
Natural 3.5 3.3 3.2 3.1 3.5 4.5 13.0
LP/propane 10.0 9.4 9.1 8.9 10.0 11.0 13.0
NOTE -
A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion
procedure.
TABLE 2
Manifold and Supply Line Pressure 0-10,000ft.
Unit Gas
Manifold Pressure in. wg.
Supply Line
Pressure
in. w.g.
0 - 10000 ft.
0-4500 ft. 4501-5500 ft. 5501-6500 ft. 6501 - 7500ft. 7501 - 10000ft.
Low
Fire
High
Fire
Low
Fire
High
Fire
Low
Fire
High
Fire
Low
Fire
High
Fire
Low
Fire
High
Fire
Min Max
All
Sizes
Natural 1.7 3.5 1.6 3.3 1.5 3.2 1.5 3.1 1.7 3.5 4.5 13.0
LP/propane 4.9 10.0 4.6 9.4 4.4 9.1 4.3 8.9 4.9 10.0 11.0 13.0
NOTE -
A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion
procedure.
Gas Pressure Adjustment
Gas Flow (Approximate)
Table 11
GAS METER CLOCKING CHART
MODEL
Seconds for One Revolution
Natural LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
-30 120 240 300 600
-45 80 160 200 400
-70 55 110 136 272
-110 33 66 82 164
-135 27 54 68 136
Natural-1000 btu/cu ft LP-2500 btu/cu ft
Table 13
Unit CO
2
% for Nat CO
2
% for L.P.
All 7.2 - 7.9 8.6 - 9.3
The maximum carbon monoxide reading should not exceed 100 ppm.