Lennox G32V Series Service Literature page 48

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.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
E−Testing Gas Supply Pressure
When testing supply gas pressure, connect test gauge to
inlet pressure tap (field provided). Check gas line pressure
with unit firing at maximum rate or high fire. Low pressure
may result in erratic operation or underfire. High pressure
can result in permanent damage to gas valve or overfire.
For G32V units, operating pressure at unit gas connection
must be between 4.5" W.C. and 13.0" W.C.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply pres-
sure must fall within range listed in previous paragraph.
F−Check Manifold Pressure
IMPORTANT
WhiteRodgers valve is NOT adjustable on low
fire. Do not attempt to adjust low fire on White-
Rodgers valve.
Manifold Operating Pressure is the manifold pressure mea-
sured during normal operation (sensing burner box pres-
sure). Manifold Absolute Pressure is the manifold pressure
measured when the gas valve regulator is operating at fac-
tory preset level (sensing atmospheric pressure).
After line pressure has been checked and adjusted, check
manifold absolute pressure. Move pressure gauge to outlet
pressure tap located on unit gas valve (GV1). Checks of
manifold absolute pressure are made as verification of proper
regulator adjustment.
Manifold operating pressure for the G32V can be measured
at any time the gas valve is open and is supplying gas to the
unit. For natural gas units, normal manifold absolute pressure
for high fire is 3.5 in. W.C. (see figure 30 for changes due to
burner box pressure). and 1.7 in. W.C. for low fire. For pro-
pane units, normal manifold absolute pressure for high fire is
7.5 in. W.C. and 3.5 in. W.C for low fire. See tale below.
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.
The gas valve is factory set and should not require adjust-
ment. Also, gas valve regulation varies with burner box
pressure (figure 30).
*Manifold Absolute Pressure Measurement and Adjustment
1 − Connect test gauge to outlet tap on gas valve.
2 − Disconnect pressure sensing hose from gas valve
and plug hose. Leave hose barb on valve open to at-
mosphere. See figure 52.
3 − Start unit on high fire and allow 5 minutes for unit to
reach steady state.
MANIFOLD CHECK
(G32V−75 SHOWN)
CONNECT C.A.B. HOSE TO +" SIDE OF SWITCH.
CONNECT BURNER BOX HOSE TO −" SIDE OF SWITCH.
4 − While waiting for the unit to stabilize, notice the flame.
Flame should be stable and should not lift from burner.
Natural gas should burn blue.
5 − After allowing unit to stabilize for 5 minutes, record
manifold pressure. Manifold pressure should read
3.5"W.C. + or − 0.3 W.C. for natural gas units and 7.5"
W.C + or − 0.3" W.C for propane gas units. Regulator
cap must be installed when reading pressures.
NOTE−Shut unit off and remove manometer as soon as
an accurate reading has been obtained. Take care to re-
place pressure tap plug.
NOTE−During this test procedure, the unit will be overfir-
ing:
D Operate unit only long enough to obtain accurate read-
ing to prevent overheating heat exchanger.
D Attempts to clock gas valve during this procedure will
be inaccurate. Measure gas flow rate only during nor-
mal unit operation.
6 − When test is complete remove obstruction from hose
and return hose to gas valve barb.
Fire and explosion hazard.
These instructions MUST be followed exactly.
Can cause a fire or explosion resulting in property
damage, personal injury or loss of life.
G− Proper 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 33 below.
NOTE−To obtain accurate reading, shutoff all other gas
appliances connected to meter.
Page 48
BURNER
SENSING
GAS VALVE
FIGURE 52
WARNING
HOSE
BARB
BOX
HOSE
GAS
VALVE
SENSING
HOSE