Allied Air Enterprises WARM AIR GAS FURNACE 92G1UH - Manual (Page 43)

506724-01 Page 43 of 57 Issue 1108
Gas Pressure Adjustment
Gas Flow (Approximate)
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 9. If manifold pressure matches Table 10 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 56. 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 units operating. Supply pressure
must fall within range listed in table 10.
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.
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
manifold pressure and compare to value given in Table
9.
NOTE: Shut unit off and remove manometer as soon as
an accurate reading has been obtained. Take care to remove
barbed fitting 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 flue outlet
and compare to the tables below.
High Altitude Information
NOTE: In Canada, certification for installations at elevations
over 4500 feet (1372 m) is the jurisdiction of local authorities.
Units installed at altitudes of 4,501 - 10,000 feet (1373 -
3048 m) may require a pressure switch change which can
be ordered separately.
Table 12 lists required pressure switch changes and orifice
conversion kits at varying altitudes.
The combustion air pressure switches are factory set and
require no adjustment.
TABLE 9
GAS METER CLOCKING CHART
Unit
Seconds for One Revolution
Natural LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
DIAL
−045 80 160 200 400
−070 55 110 136 272
−090 41 82 102 204
−110 33 66 82 164
−135 27 54 68 136
Natural−1000 btu/cu ft LP−2500 btu/cu ft
TABLE 10
Supply Line and Manifold Pressure (inches w.c.)
Unit Fuel
Manifold
Pressure
Line Pressure
All Nat. Gas 3.5 4.5 − 10.5
All L.P. Gas 10.0 11.0 − 13.0
NOTE − A natural to L.P. propane gas changeover kit is nec-
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
TABLE 11
Unit CO
2
% For Nat CO
2
%
For L.P.
7.2 − 7.9 8.6 − 9.3
The maximum carbon monoxide reading should not exceed 50 ppm.
All