Heating System Service Checks; C.s.a. Certification; Gas Piping; Testing Gas Piping - Lennox ML193UHE Series Manual

IV-HEATING SYSTEM SERVICE CHECKS
A-C.S.A. Certification
All units are C.S.A. design certified without modifications.
Refer to the ML193UHE Operation and Installation Instruc­
tion Manual Information.
B-Gas Piping
CAUTION
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 dis­
connected and isolated. Gas valves can be damaged if
subjected to more than 0.5psig (14" W.C.). See figure 54.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
CAP
FIGURE 54
When checking piping connections for gas leaks, use pre­
ferred means. Kitchen detergents can cause harmful corro­
sion on various metals used in gas piping. Use of a specialty
Gas Leak Detector is strongly recommended. It is available
through Lennox under part number 31B2001. See Corp.
8411-L10, for further details.
D-Testing Gas Supply Pressure
Gas Flow (Approximate)
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 16 below. If manifold pressure matches table 18
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 53. 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 18.
Manifold Pressure Measurement
Follow the steps below and use figure 55 as a reference. Gas
manifold Kit 10L34 provides additional components if need­
FURNACE
ed.
1 - Connect the test gauge positive side "+" to manifold
ISOLATE
GAS VALVE
2 - Tee into the gas valve regulator vent hose and connect
3 - Start unit and let run for 5 minutes to allow for steady
4 - After allowing unit to stabilize for 5 minutes, record
5 - Shut unit off and remove manometer as soon as an ac­
6 - Start unit and perform leak check. Seal leaks if found.
Page 40
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
TABLE 16
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
ML193
Unit
1 cu ft 2 cu ft
Dial Dial
-030 120 240
-045 80 160
-070 55 110
-090 41
-110 33
Natural-1000 btu/cu ft
pressure tap on gas valve.
to test gauge negative "-".
state conditions.
manifold pressure and compare to value given in table
18.
curate reading has been obtained. Take care to re­
place pressure tap plug.
LP
1 cu ft 2 cu ft
Dial DIAL
300 600
200 400
136 272
82 102 204
66 82 164
LP-2500 btu/cu ft