Gas Pressure Measurement; Proper Combustion; High Altitude - Lennox ML196UHE Installation Instructions Manual

Unit Start-Up
Gas Flow (Approximate)
TABLE 12
GAS METER CLOCKING CHART
Seconds For One Revolution
ML196UHE Natural
Unit
1 cu ft
Dial
-030 120
-045 80
-070 55
-090 41
-110 33
-135 27
Natural-1000 btu/cu ft LP-2500 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. 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 61. 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 pres-
sure must fall within range listed in TABLE 13.
Check Manifold Pressure
After supply pressure has been checked and adjusted,
check manifold pressure. Move pressure gauge to outlet
pressure tap located on unit gas valve (GV1). Checks of
manifold pressure are made as verification of proper reg-
ulator adjustment.
IMPORTANT
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
LP/Propane
2 cu ft 1 cu ft 2 cu ft
Dial Dial Dial
240 300 600
160 200 400
110 136 272
82 102 204
66 82 164
54 68 136
Follow the steps below. Gas manifold Kit 10L34 provides
additional components if needed.
1 - Connect the test gauge positive side "+" to manifold
pressure tap on gas valve.
2 - Tee into the gas valve regulator vent hose and
connect to test gauge negative "-".
3 - Start unit and let run for 5 minutes to allow for steady
state conditions.
4 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
TABLE 13.
5 - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
replace pressure tap plug.
6 - Start unit and perform leak check. Seal leaks if found.
Supply Line and Manifold Pressure (inches w.c.)
Unit
All
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 table below. The maximum carbon
monoxide reading should not exceed 100 ppm.
ML196UHE Unit
-030
-045
-070
-090
-110
-135
High Altitude Information
NOTE - In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local
authorities.
Units may be installed at altitudes up to 10,000 ft. above
sea level. See TABLE 16 for de-rate manifold values. Units
installed at altitude of 7501 - 10,000 feet require an orifice
change. Units installed at altitude of 4501 - 10,000 feet
require a pressure switch change which can be ordered
separately. TABLE 16 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
Fuel
Pressure
Nat 3.5
10.0
TABLE 14
CO2% Nat
7.5- 8.5
Line Pressure
4.5 - 10.5
11.0 - 13.0
CO2% LP
8.2 - 9.5