Iv-Heating System Service Checks - Lennox ML193DFE 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 ML193DFE 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 0.5psig (14" W.C.). See FIGURE
52.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
FIGURE 52
CAP
FURNACE
ISOLATE
GAS VALVE
Page 40
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.
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
D-Testing Gas Supply Pressure
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 51. 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 19.
E-Check Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move pressure gauge to outlet pres-
sure tap located on unit gas valve (GV1).
Checks of manifold pressure are made as verification of
proper regulator adjustment.
CAUTION
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
Follow the steps below and use FIGURE 53 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
replace pressure tap plug.
6 - Start unit and perform leak check. Seal leaks if
found.