Iv-Heating System Service Checks - Lennox ML196UHE Series Unit Information

IV-HEATING SYSTEM SERVICE CHECKS

A-C.S.A. Certification
All units are C.S.A. design certified without modifications.
Refer to the ML196UHE Operation and Installation In-
struction Manual Information.
B-Gas Piping
IMPORTANT
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet. The flexible connector can then
be added between the black iron pipe and the gas
supply line.
WARNING
Do not over torque (800 in-lbs) or under torque (350
in-lbs) when attaching the gas piping to the gas
valve.
Gas supply piping should not allow more than 0.5"W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection.
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
C-Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn off the
main shut-off valve and disconnect the main power
to unit. These controls should be properly labeled
by the installer.
When pressure testing gas lines, the gas valve must be
disconnected and isolated. Gas valves can be damaged if
subjected to more than 0.5 psig (14" W.C.). See FIGURE
56.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
FIGURE 56
When checking piping connections for gas leaks, use
preferred means. Kitchen detergents can cause harmful
corrosion corrosion on various metals used in gas piping.
Use of a specialty Gas Leak Detector is strongly recom-
mended. It is available through Lennox under part number
31B2001. See Corp. 8411-L10, for further details.
CAP
FURNACE
ISOLATE
GAS VALVE
Page 44
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
D-Testing Gas Supply Pressure
Gas Flow (Approximate)
TABLE 17
GAS METER CLOCKING CHART
Seconds for One Revolution
ML196
Natural
Unit
1 cu ft Dial 2 cu ft Dial 1 cu ft Dial 2 cu ft Dial
-030 120
-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 17. If manifold pressure matches TABLE 19 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 located on the gas valve to facilitate test
gauge connection. See FIGURE 55. Check gas line pres-
sure 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 other units operating. Supply
pressure must fall within range listed in TABLE 19.
Manifold Pressure Measurement
Follow the steps below and use FIGURE 57 as a refer-
ence. Gas manifold Kit 10L34 provides additional compo-
nents 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 19.
5 - 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.
6 - Start unit and perform leak check. Seal leaks if
found.
LP/Propane
240 300 600
160 200 400
110 136 272
82 102 204
66 82 164
54 68 136
LP-2500 btu/cu ft