Specifications

Page 21
UNIT
FIELD PROVIDED
1/8" PRESSURE TAP
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
(REFER TO LOCAL CODES)
GAS PIPING
SUPPORT
DRIP LEG
UNIT
SUPPORT
GAS PIPING COMPONENTS
REFER TO INSTALLATION INSTRUCTIONS
FIGURE 23
VALV E
CAP HERE TO ISO
LATE VALVE
WHEN PRESSURE
TESTING LINE
B-Gas Piping
Gas supply piping must not allow more than 0.5"W.C. drop in
pressure between the gas meter and the unit. Supply gas
pipe must not be smaller than the unit gas connection. Refer
to installation instructions for details.
C-Testing Gas Piping
NOTE-In case emergency shutdown is required, turn off
the main manual shutoff valve and disconnect the main
power to the unit. These controls should be properly la
beled by the installer.
When pressure testing gas lines, the gas valve must be dis
connected and isolated. Gas valves can be damaged if sub
jected to more than 0.5 psig (14"W.C.). See figure 23.
If the test pressure is equal to or less than 0.5 psig (14"W.C.),
use the main manual shutoff valve before pressure testing to
isolate unit from gas supply.
When checking piping connection for gas leaks, use the pre
ferred means. Common kitchen detergents can cause harm
ful corrosion on various metals used in gas piping. The use of
specialty Gas Leak Detector is strongly recommended. It is
available through Lennox under part number 31B2001. See
CORP 8411-L10, for further details.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
D-Testing Gas Supply Pressure
When testing gas supply pressure, connect test gauge to the
inlet pressure tap (field provided - figure 23). Test supply gas
pressure with unit firing at maximum rate (both stages ener
gized). Make sure the reading falls within the range of the fol
lowing values. Low pressure may result in erratic operation or
underfire." High pressure can result in permanent damage to
the gas valve or overfire." For natural gas units, operating
pressure at the unit gas connection must be between
5.5"W.C. and 13.5"W.C. For L.P. gas units, operating pres
sure at the unit gas connection must be between 10.8"W.C.
and 13.5"W.C.
On multiple unit installations, each unit should be checked
separately while operating at maximum rate, with and without
the other units operating. Supply pressure must fall within the
range listed in the previous paragraph. On multiple unit instal
lations, each unit should be checked in sequence beginning
with the one closest to the supply gas main and progressing to
the one furthest from the main.
E-Check and Adjust Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move test gauge to the outlet pressure tap
located on unit gas valve GV1. See figures 20 and 21 for
location of pressure tap on the gas valve.
The manifold pressure is factory set and should not require
adjustment. WhiteRodgers gas valve is not adjustable. If
manifold pressure is incorrect and no other source of improp
er manifold pressure can be found, the valve must be re
placed. Honeywell gas valve can be adjusted from 3.0" W.C.
to 5.0" W.C. Refer to figure 20 for location of Honeywell gas
valve (manifold pressure) adjustment screw.
All gas valves are factory regulated. The gas valve should
completely and immediately cycle off in the event of gas or
power failure. The manual shutoff knob can be used to im
mediately shut off gas supply.
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.
Manifold Adjustment Procedure
1- Connect test gauge to the outlet pressure tap on the gas
valve. Start the unit (call for 2nd stage heat) and allow
five minutes for the unit to reach steady state.
2- While waiting for the unit to stabilize, notice the flame.
The flame should be stable without flashback and should
not lift from the burner heads. Natural gas should burn
basically blue with some clear streaks. L.P. gas should
burn mostly blue with some clear yellow streaks.
3- After allowing the unit to stabilize for five minutes, record
the manifold pressure and compare to the values given
for gas supply pressure (above).
CAUTION
Disconnect heating demand as soon as an accu
rate reading has been obtained.