508189-01
Issue 2116
Page 23 of 42
Manifold Pressure Measurement
After line pressure has been checked and adjusted, check
manifold pressure. Checks of manifold pressure are made
as verification of proper regulator adjustment. Manifold
pressure for the 80G2DFE can be measured at any time
the gas valve is open and is supplying gas to the unit.
NOTE:
Pressure test adapter kit (10L34) is available from
Allied Air to facilitate manifold pressure measurement.
NOTE:
The gas valve is factory set and should not require
adjustment. All gas valves are factory regulated.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
IMPORTANT
1.
Connect test gauge to manifold pressure post (Figure
2.
Ignite unit on low fire and let run for 5 minutes to allow
for steady state conditions.
3.
After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
4.
If necessary, make adjustments. Figure 13 shows
location of high fire and low fire adjustment screw.
5.
Repeat steps 2, 3 and 4 on high fire.
6.
Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
replace pressure tap plug.
7.
Start unit and perform leak check. Seal leaks if found.
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
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.
Capacity
Seconds for One Revolution
Natural
LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
-70
55
110
136
272
-90
41
82
102
204
Natural-1000 btu/cu ft LP-2500 btu/cu ft
Table 10. Gas Meter Clocking Chart
For safety, shut unit off and remove manometer as soon
as an accurate reading has been obtained. Take care to
replace pressure tap plug.
IMPORTANT
Proper Combustion
Furnace should operate a minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Table 11 shows acceptable combustion for
all 80G2DFE models.
The maximum carbon monoxide
reading should not exceed 100 ppm.
Capacity
CO
2
% for Nat
CO
2
% for LP
High Fire
6.0 - 7.5
7.0 - 8.5
Low Fire
5.0 - 6.5
5.8 - 7.3
Table 11.
High Altitude
The manifold pressure may require adjustment and
combustion air pressure switch may need replacing to
ensure proper combustion at higher altitudes. Refer to
Table 12 for manifold pressure and Table 13 for pressure
switch change and gas conversion kits.
