Gas Pressure Measurement; Proper Combustion; High Altitude - Lennox EL195UHE Elite Series Installation Instructions Manual

Gas Pressure Adjustment
Gas Flow (Approximate)
TABLE 12
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
EL195
Unit
1 cu ft
Dial
−045 80
−070 55
−090 41
−110 33
−135 27
Natural−1000 btu/cu ft
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time
in table 12 below. If manifold pressure matches table 13
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 65. Check gas
line pressure with unit firing at maximum rate. Low pres-
sure may result in erratic operation or underfire. High pres-
sure can result in permanent damage to gas valve or over-
fire.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply pres-
sure must fall within range listed in table 13.
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 pres-
sure.
2 − Start unit and allow 5 minutes for unit to reach steady
state.
LP
2 cu ft 1 cu ft 2 cu ft
Dial Dial DIAL
160 200 400
110 136 272
82 102 204
66 82 164
54 68 136
LP−2500 btu/cu ft
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
13.
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.
Supply Line and Manifold Pressure (inches w.c.)
Unit Fuel
All Nat
All LP/Propane

Proper Combustion

Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. Take combustion sample beyond the flue outlet
and compare to the tables below.
EL195
Unit
−045
−070
−090
−110
−135
The maximum carbon monoxide reading should not exceed 50 ppm.
High Altitude Information
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
EL195UHE units require no manifold pressure adjust-
ments for operation at altitudes up to 10,000 feet (3048 m).
Units installed at altitude of 4501 − 10,000 feet (1373 to
3048 m) may require a pressure switch change which can
be ordered separately. Table 15 lists conversion kit and
pressure switch requirements at varying altitudes.
The combustion air pressure switch is factory−set and re-
quires no adjustment.
Page 44
TABLE 13
Manifold
Line Pressure
Pressure
3.5 4.5 − 10.5
10.0 11.0 − 13.0
TABLE 14
CO % CO %
2 For Nat 2
7.2 − 8.2 8.6 − 9.6
For LP