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10- Turn on all electrical power to to the unit.
11- Set the thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 11 may
need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the instructions
"Turning Off Gas to Unit" and call your service techni
cian or gas supplier.
Turning Off Gas to Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
3 - Remove the upper access panel.
4 - Move the gas valve switch to the OFF position.
5 - Replace the upper access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the gas valve turned on?
9 - Is the unit ignition system in lock out? If the unit locks out
again, inspect the unit for blockages.
10 - Is blower harness connected to integrated control? Fur
nace will not operate unless harness is connected.
C-Safety or Emergency Shutdown
Turn off unit power. Close manual and main gas valves.
D-Extended Period Shutdown
Turn off thermostat or set to "UNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guaran
tee no gas leak into combustion chamber. Turn off power to
unit. All access panels and covers must be in place and se
cured.
V-HEATING SYSTEM SERVICE CHECKS
A-CSA Certification
All units are CSA design certified without modifications. Re
fer to the SLP99DFV Installation Instruction.
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 sub
jected to more than 0.5psig (14" W.C.). See figure 48.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
CAP
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.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
D- Proper Gas Flow (Approximate)
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
SLP99
Unit
1 cu ft
Dial
-70
55
-90
41
-110
33
-135
27
Natural-1000 btu/cu ft
Page 56
FURNACE
ISOLATE
GAS VALVE
FIGURE 48
TABLE 28
LP
2 cu ft
1 cu ft
Dial
Dial
110
136
82
102
66
82
54
68
LP-2500 btu/cu ft
2 cu ft
DIAL
272
204
164
136
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