Iv-Heating System Service Checks - Lennox SL280UHNV Series Manual

MANIFOLD PRESSURE ADJUSTMENT
(TURN CCW TO INCREASE PRESSURE)
NEGATIVE AIR
PRESSURE PORT
INLET
SUPPLY
PRESSURE
TAP
GAS VALVE SHOWN IN THE ON POSITION
FIGURE 16
8 - Move switch on gas valve to ON. Do not force. See
Figure 16.
9 - Replace the access panel.
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.
Turning Off Gas To Unit
1 - Set thermostat to lowest setting.
2 - Turn off all electrical power to unit if service is to be
performed.
3 - Remove access panel.
4 - Move switch on valve to OFF. Do not force.
5 - Replace 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 or tripped circuit breaker?
5 - Is the fi lter dirty or plugged? Dirty or plugged fi lters
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 internal manual shut-off valve open?
9 - Is the unit ignition system in lock out? If the unit locks
out again, call the service technician to inspect the
unit for blockages.
GAS VALVE
POSITIVE AIR
PRESSURE PORT
MANIFOLD
PRESSURE TAP
10 - Is pressure switch closed? Obstructed fl ue will
cause unit to shut off at pressure switch. Check fl ue
and outlet for blockages.
11 - Are fl ame rollout switches tripped? If fl ame rollout
switches are tripped, call the service technician for
inspection.
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
OUTLET
all gas valves (both internal and external to unit) to guar-
antee no gas leak into combustion chamber. Turn off pow-
er to unit. All access panels and covers must be in place
and secured.

IV-Heating System Service Checks

A-CSA Certifi cation
All units are CSA design certifi ed without modifi cations.
Refer to the SL280UHNV Installation Instruction.
B-Gas Piping
If a fl exible 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.
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 liquefi ed petroleum gases.
C-Testing Gas Piping
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.
Page 31
CAUTION
WARNING
IMPORTANT