Page 44
Unit Start-Up
Gas Flow (Approximate)
TABLE 12
GAS METER CLOCKING CHART
ML196UHE
Unit
Seconds For One Revolution
Natural LP/Propane
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
-030 120 240 300 600
-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
Furnace should operate at least 5 minutes before check-
ing gas ow. 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 orices for proper size
and restriction. Remove temporary gas meter if installed.
NOTE - To obtain accurate reading, shut o 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 gure 61. Check
gas line pressure with unit ring at maximum rate. Low
pressure may result in erratic operation or underre. High
pressure can result in permanent damage to gas valve or
overre.
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 verication of proper reg-
ulator adjustment.
IMPORTANT
For safety, connect a shut-o valve between the
manometer and the gas tap to permit shut o of gas
pressure to the manometer.
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 o 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.
TABLE 13
Supply Line and Manifold Pressure (inches w.c.)
Unit Fuel
Manifold
Pressure
Line Pressure
All Nat 3.5 4.5 - 10.5
All LP/Propane 10.0
11.0 - 13.0
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas ow rate before checking com-
bustion. Take combustion sample beyond the ue outlet
and compare to the table below. The maximum carbon
monoxide reading should not exceed 100 ppm.
TABLE 14
ML196UHE Unit CO2% Nat CO2% LP
-030
7.5- 8.5 8.2 - 9.5
-045
-070
-090
-110
-135
High Altitude Information
NOTE - In Canada, certication 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 orice
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.
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