Other Unit Adjustmens; Service - Lennox MERIT Series Installation Instructions Manual

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 front of
the burner box.
Pressure Switch
The pressure switch is located in the heating compartment
on the cold end header box. This switch checks for proper
combustion air inducer operation before allowing ignition
trial. The switch is factory-set and must not be adjusted.
Temperature Rise
After the furnace has been started and supply and return
air temperatures have been allowed to stabilize, check the
temperature rise. If necessary, adjust the blower speed
to maintain the temperature rise within the range shown
on the unit nameplate. Increase the blower speed to de-
crease the temperature. Decrease the blower speed to
increase the temperature rise. Failure to adjust the tem-
perature rise may cause erratic limit operation.
Fan Control
The fan on time of 30 seconds is not adjustable. The fan
off delay (amount of time that the blower operates after
the heat demand has been satisfied) may be adjusted by
changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan off
setting of 120 seconds. The fan off delay affects comfort
and is adjustable to satisfy individual applications. Adjust
the fan off delay to achieve a supply air temperature be-
tween 90° and 110°F at the moment that the blower is
deenergized. Longer off delay settings provide lower re-
turn air temperatures; shorter settings provide higher re-
turn air temperatures. See figure 56.
Electrical
1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace
operating).
3 - Check amp-draw on the blower motor.
Motor Nameplate__________Actual__________
HEAT FAN OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
60 Second
off Time
Blower Speeds
Follow the steps below to change the blower speeds.
1 - Turn off electrical power to furnace.
2 - Remove blower access panel.
3 - Disconnect existing speed tap at integrated control
speed terminal.
See unit Product Specifications Bulletin for indoor
blower data.
NOTE - Termination of any unused motor leads
must be insulated.
4 - Place unused blower speed tap on integrated control
"PARK" terminal or insulate.
5 - Refer to blower speed selection chart on unit wiring
diagram for desired heating or cooling speed.
6 - Connect selected speed tap at integrated control
speed terminal.
7 - Resecure blower access panel.
8 - Turn on electrical power to furnace.
9 - Recheck temperature rise
.

Service

. ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could result in
dangerous operation, serious injury, death or property
damage.
Improper servicing could result in dangerous operation,
serious injury, death, or property damage. Before
servicing, disconnect all electrical power to furnace.
When servicing controls, label all wires prior to
disconnecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
Page 43
NO JUMPER
achieve desired setting.
90 Second 120 Second
off Time off Time
FIGURE 56
WARNING
180 Second
off Time