Lennox Allied Air A96UHMV, Installation Instructions Manual

Page: 51 / 66

506550-01 Page 51 of 66 Issue 1230
Manifold Pressure Measurement
To correctly measure manifold pressure, the differential
pressure between the positive gas manifold and the negative
burner box must be considered. Use pressure test adapter
kit (available as part 10L34) to assist in measurement.
1. Remove the threaded plug from the outlet side of the
gas valve and install a field provided barbed fitting.
Connect test gauge “+” connection to barbed fitting to
measure manifold pressure.
2. Tee into the gas valve regulator vent hose and connect
test gauge “-” connection.
3. Start unit on low heat (35% rate) and allow 5 minutes
for unit to reach steady state.
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 and compare to value given in Table
24.
6. Repeat steps 3, 4 and 5 on HIGH HEAT.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
DO NOT attempt to make adjustments to the gas valve.
CAUTION
Other Unit Adjustments
Primary Limit
The primary limit is located on the heating compartment
vestibule panel. This limit is factory set and requires no
adjustment.
Flame Rollout Switches (Two)
These manually reset switches are located on the inside of
the burner box. If tripped, check for adequate combustion
air before resetting.
Pressure Switches (Two)
The pressure switches are located on the cold end header
box. These switches check for proper combustion air inducer
operation before allowing ignition trial. The switches are
factory set and require no adjustment.
Temperature Rise
After the furnace has been started and supply and return air
temperatures have been allowed to stabilize, check the
temperature rise with the unit operating at 100 percent firing
rate. If necessary, adjust the blower speed to maintain the
temperture rise within the range shown on the unit
nameplate. Increase the blower speed to decrease the
temperature. Decrease the blower speed to increase the
temperature. Decrease the blower speed to increase the
temperature rise. Failure to adjust the temperature rise may
cause erratic limit operation.
Thermostat Heat Anticipation
Set the heat anticipator setting (if adjustable) according to
the amp draw listed on the wiring diagram that is attached
to the unit.
Electronic Ignition
The integrated control has a feature that serves as an
automatic reset device for ignition control lockout caused
by ignition failure. This type of lockout is usually due to low
gas line pressure. After one hour of continuous thermostat
demand for heat, the control will break and remake
thermostat demand to the furnace and automatically reset
the control to begin the ignition sequence.
Exhaust and Air Intake Pipe
1. Check exhaust and air intake connections for tightness
and to make sure there is not blockage.
2. Are pressure switches closed? Obstructed exhaust pipe
will cause unit to shut off at pressure switches. Check
termination for blockages.
3. Reset manual flame rollout switches on burner box
cover.
Conversion Kit Requirements and Manifold Test Pressures
Table 24
NOTE: The values given in table 23 are measurements only. The gas valve should not be adjusted.