Allied A96US2V - Gas Pressure Adjustment and Proper Combustion; Gas Pressure Adjustment

507404-02Page 64 of 80 Issue 1448
Gas Pressure Adjustment
Gas Flow (Approximate)
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 13. If manifold pressure matches Table 15 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
An inlet pressure post on the inlet side of the gas valve
provides access to the supply pressure. See Figure 66.
Back out the 3/32 Hex screw one turn, connect a piece
of 5/16” tubing and connect to a manometer to measure
supply pressure.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to re-tighten
the 3/32 Hex screw.
Table 13
For proper furnace operation the minimum gas supply
pressure is 4.5” w.c and the maximum gas supply pressure is
10.5” w.c for natural gas. The minimum gas supply pressure
is 10” w.c. and the maximum gas supply pressure is 13” w.c.
for LP/propane gas.
Manifold Pressure Measurement
1. A manifold presssure post located on the gas valve
provides access to the manifold pressure. See Figure
66. Back out the 3/32 Hex screw one turn, connect a
piece of 5/16” tubing and connect to a manometer to
measure supply 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
14.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to re-tighten
the 3/32 Hex screw.
Table 14
A95US2V
Natujreal to LP/
Propane
High Altitude
Natural Burner
Orice Kit
High Altitude
LP/Propane Burner
Orice Kit
High Altitude Pressure switch
0 - 7500 ft
(0 - 2286m)
7501 - 10000 ft
(2286 - 3048m)
7501 - 10000 ft
(2286 - 3048m)
4501 - 7500 ft
(1371 - 2286m)
7501 - 10000 ft
(2286 - 3048m)
045
*78W94 *51W01 *78W97
93W81 93W84
070 11X65 98W79
090 11X72 11X65
110 93W80 93W85
135 93W83 93W85
Conversion kit fan Pressure Switch Requirements at Varing Altitudes
*Conversion Requires installation of a gas valve manifold spring which is provided with the gas conversion kit.
Preasure switch is factory set. No adjustment necessary. All models use the factory-installed pressure switch from 0-4500 feet (0-1370 m).
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. The maximum carbon
monoxide reading should not exceed 50 ppm.