V-System Service Checks - Lennox LDT Series Information

V- SYSTEMS SERVICE CHECKS
A-Heating System Service Checks
All LDT units are ETL/CSA design certified without
modification.
Before checking piping, check with gas company or
authorities having jurisdiction for local code requirements.
Refer to the LDT Installation, Operation and Maintenance
instruction for more information.
1-Gas Piping
Gas supply piping must not allow more than 0.5"W.C.
(124.3 Pa) 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.
2-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
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. (3481 Pa)].
See figure 28.
When checking piping connection for gas leaks, use the
preferred means. Common kitchen detergents can cause
harmful corrosion on various metals used in gas piping.
The use of specialty Gas Leak Detector is strongly
recommended. It is available through 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.
GAS PIPING COMPONENTS
REFER TO INSTALLATION INSTRUCTIONS
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
(REFER TO LOCAL CODES)
GAS PIPING
FIGURE 28
3-Testing Gas Supply Pressure
When testing gas supply pressure, connect test gauge to
the inlet pressure tap located on unit gas valve GV1 and or
GV3. Test supply gas pressure with unit firing at maximum
rate (both stages energized). Make sure the reading falls
VALVE
CAP HERE
UNIT
TO ISOLATE
VALVE WHEN
PRESSURE
TESTING
LINE
ROOF
MOUNTING
FRAME
DRIP LEG
SUPPORT
within the range of the following values. Low pressure may
result in erratic operation or "underfire." High pressure can
result in permanent damage to the gas valve or "overfire.".
See table 12 for supply pressures.
On multiple unit installations, each unit should be checked
separately while operating at maximum rate, beginning
with the one closest to the supply gas main and progressing
to the one furthest from the main. Multiple units should also
be tested with and without the other units operating. Supply
pressure must fall within the range listed in the previous
paragraph.
4-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 and or GV3. See figure
27 for location of pressure tap on the gas valve.
The manifold pressure is factory set and should not require
adjustment. If manifold pressure is incorrect and no other
source of improper manifold pressure can be found, the
valve must be replaced. See figure 27 for location of 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
immediately shut off gas supply.
For safety, connect a shut‐off valve between the manometer
and the gas tap to permit shut off of gas pressure to the
Manifold Adjustment Procedure
1- Connect test gauge to the outlet pressure tap on the
gas valve. Start the unit (call for second 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 in table 12.
Disconnect heating demand as soon as an
accurate reading has been obtained.
Page 34
CAUTION
manometer.
CAUTION